Build on wgpu 30

Two majors, and the renderer is under everything else that is left to extract, so it goes before the slices that would otherwise be written twice. `image` 0.25.6 -> 0.25.10 rides along; `winit` stays on 0.30.12, since 0.31 is only a prerelease. What the API asked for: - An instance now takes the display it will present on, and GLES on Wayland needs it -- so the window the surface is made from is handed over with it. - `get_current_texture` returns a `CurrentSurfaceTexture` rather than a `Result`, which replaces an `unwrap` that would have panicked on a resize or an occluded window: reconfigure when the surface is outdated, lost or suboptimal, and skip the frame when there is nothing to draw into. - Presenting moved to the queue, after `pre_present_notify` as before. - Bind group layouts and vertex buffer layouts are sparse now, so a pipeline states `Some(layout)` per slot. Verified with the three render checks and `tests/draw_cost.rs`: identical pictures, and 33.6/167/587/2855 us per frame at 8/64/256/1024 layers against 33.3/161/588/2903 on wgpu 28. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Draw the glyph atlas as an array texture and images with their own bind groups + primitive rendering overhaul
2026-09-13 18:57:52 -04:00 · 2026-09-13 18:56:59 -04:00 · 2026-09-13 03:39:23 -04:00
25 changed files with 1627 additions and 1112 deletions
@@ -234,18 +234,18 @@ dependencies = [
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+ "skrifa",
 ]
 [[package]]
@@ -2275,9 +2252,9 @@ dependencies = [
 [[package]]
 name = "ravif"
-version = "0.12.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef69c1990ceef18a116855938e74793a5f7496ee907562bd0857b6ac734ab285"
+checksum = "e52310197d971b0f5be7fe6b57530dcd27beb35c1b013f29d66c1ad73fbbcc45"
 dependencies = [
 "avif-serialize",
 "imgref",
@@ -2294,6 +2271,18 @@ version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "20675572f6f24e9e76ef639bc5552774ed45f1c30e2951e1e99c59888861c539"
 [[package]]
 name = "raw-window-metal"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "40d213455a5f1dc59214213c7330e074ddf8114c9a42411eb890c767357ce135"
 dependencies = [
 "objc2 0.6.4",
 "objc2-core-foundation",
 "objc2-foundation 0.3.2",
 "objc2-quartz-core 0.3.2",
 ]
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -2314,16 +2303,6 @@ dependencies = [
 "crossbeam-utils",
 ]
 [[package]]
 name = "read-fonts"
 version = "0.36.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5eaa2941a4c05443ee3a7b26ab076a553c343ad5995230cc2b1d3e993bdc6345"
 dependencies = [
 "bytemuck",
 "font-types 0.10.1",
 ]
 [[package]]
 name = "read-fonts"
 version = "0.41.0"
@@ -2331,7 +2310,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "046a7d674daf459825b32f5062056d6882db0d2f5a479fbd76ccfc870ac18709"
 dependencies = [
 "bytemuck",
- "font-types 0.12.4",
+ "font-types",
 "once_cell",
 ]
@@ -2506,16 +2485,6 @@ dependencies = [
 "quote",
 ]
 [[package]]
 name = "skrifa"
 version = "0.39.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c9eb0b904a04d09bd68c65d946617b8ff733009999050f3b851c32fb3cfb60e"
 dependencies = [
 "bytemuck",
 "read-fonts 0.36.0",
 ]
 [[package]]
 name = "skrifa"
 version = "0.44.0"
@@ -2523,7 +2492,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "819ab7d62b1d3e72d9d9dea5650bac30424f9111364bb94928dbf5ecad1baa68"
 dependencies = [
 "bytemuck",
- "read-fonts 0.41.0",
+ "read-fonts",
 ]
 [[package]]
@@ -2583,9 +2552,9 @@ dependencies = [
 [[package]]
 name = "spirv"
-version = "0.3.0+sdk-1.3.268.0"
+version = "0.4.0+sdk-1.4.341.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eda41003dc44290527a59b13432d4a0379379fa074b70174882adfbdfd917844"
+checksum = "d9571ea910ebd84c86af4b3ed27f9dbdc6ad06f17c5f96146b2b671e2976744f"
 dependencies = [
 "bitflags 2.10.0",
 ]
@@ -2614,7 +2583,7 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c2499c2d826531388872b2268718aed907a39bd785ab0dcfe57fab26283f92e"
 dependencies = [
- "skrifa 0.39.0",
+ "skrifa",
 "yazi",
 "zeno",
 ]
@@ -2703,16 +2672,16 @@ dependencies = [
 [[package]]
 name = "tiff"
-version = "0.10.3"
+version = "0.11.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af9605de7fee8d9551863fd692cce7637f548dbd9db9180fcc07ccc6d26c336f"
+checksum = "b63feaf3343d35b6ca4d50483f94843803b0f51634937cc2ec519fc32232bc52"
 dependencies = [
 "fax",
 "flate2",
 "half",
 "quick-error",
 "weezl",
- "zune-jpeg 0.4.21",
+ "zune-jpeg",
 ]
 [[package]]
@@ -2885,9 +2854,9 @@ dependencies = [
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d759f433fa64a2d763d1340820e46e111a7a5ab75f993d1852d70b03dbb80fd"
+checksum = "aecb87a33d3b0c5e3b7aa46336eaf486cffafbd281b195e4c8b80d50df2351bf"
 dependencies = [
 "cfg-if",
 "once_cell",
@@ -2898,22 +2867,19 @@ dependencies = [
 [[package]]
 name = "wasm-bindgen-futures"
-version = "0.4.56"
+version = "0.4.78"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "836d9622d604feee9e5de25ac10e3ea5f2d65b41eac0d9ce72eb5deae707ce7c"
+checksum = "6ef4c5d3d2cdf5c54f4231181768f5510842e350db025faf1f7163b1030ed928"
 dependencies = [
 "cfg-if",
 "js-sys",
 "once_cell",
 "wasm-bindgen",
 "web-sys",
 ]
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48cb0d2638f8baedbc542ed444afc0644a29166f1595371af4fecf8ce1e7eeb3"
+checksum = "a690d511e3c1a8b3a55e33511e3c2c00c78415cd23650f32b808627f5696b9ed"
 dependencies = [
 "quote",
 "wasm-bindgen-macro-support",
@@ -2921,22 +2887,22 @@ dependencies = [
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cefb59d5cd5f92d9dcf80e4683949f15ca4b511f4ac0a6e14d4e1ac60c6ecd40"
+checksum = "411e4887f0071ef2d2164a9d5fdf2d20efbef78fccd3a78b0c10a1dc5295e48a"
 dependencies = [
 "bumpalo",
 "proc-macro2",
 "quote",
- "syn 2.0.113",
+ "syn 3.0.5",
 "wasm-bindgen-shared",
 ]
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbc538057e648b67f72a982e708d485b2efa771e1ac05fec311f9f63e5800db4"
+checksum = "81941cd78d0c92026c33e5e01312845a4cb1e9af3407f9134b100dd03144103e"
 dependencies = [
 "unicode-ident",
 ]
@@ -3052,9 +3018,9 @@ dependencies = [
 [[package]]
 name = "web-sys"
-version = "0.3.83"
+version = "0.3.105"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b32828d774c412041098d182a8b38b16ea816958e07cf40eec2bc080ae137ac"
+checksum = "9fbddc4a036f00ec4f18c83445bd3115cb306a91da554919a099d9222fe4a7f8"
 dependencies = [
 "js-sys",
 "wasm-bindgen",
@@ -3078,9 +3044,9 @@ checksum = "a28ac98ddc8b9274cb41bb4d9d4d5c425b6020c50c46f25559911905610b4a88"
 [[package]]
 name = "wgpu"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f9cb534d5ffd109c7d1135f34cdae29e60eab94855a625dcfe1705f8bc7ad79f"
+checksum = "527ccdf43dd5b2e8676eed9984ce00e2bbb0a1b85b70c1969dcb6cd2eb55ab9e"
 dependencies = [
 "arrayvec",
 "bitflags 2.10.0",
@@ -3088,7 +3054,7 @@ dependencies = [
 "cfg-if",
 "cfg_aliases",
 "document-features",
- "hashbrown 0.16.1",
+ "hashbrown 0.17.1",
 "js-sys",
 "log",
 "naga",
@@ -3108,9 +3074,9 @@ dependencies = [
 [[package]]
 name = "wgpu-core"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8bb4c8b5db5f00e56f1f08869d870a0dff7c8bc7ebc01091fec140b0cf0211a9"
+checksum = "14c018fce9b6270aa203c2fdd56f3cce996713534bd757e4ea58c8560b121f14"
 dependencies = [
 "arrayvec",
 "bit-set",
@@ -3119,10 +3085,11 @@ dependencies = [
 "bytemuck",
 "cfg_aliases",
 "document-features",
- "hashbrown 0.16.1",
+ "hashbrown 0.17.1",
 "indexmap",
 "log",
 "naga",
 "naga-types",
 "once_cell",
 "parking_lot",
 "portable-atomic",
@@ -3135,66 +3102,70 @@ dependencies = [
 "wgpu-core-deps-emscripten",
 "wgpu-core-deps-windows-linux-android",
 "wgpu-hal",
 "wgpu-naga-bridge",
 "wgpu-types",
 ]
 [[package]]
 name = "wgpu-core-deps-apple"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "87b7b696b918f337c486bf93142454080a32a37832ba8a31e4f48221890047da"
+checksum = "061f3d319a40d39d00b1ecc2c33b89fe21d4e6fe01859df3500a3a8ecccd6b68"
 dependencies = [
 "wgpu-hal",
 ]
 [[package]]
 name = "wgpu-core-deps-emscripten"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34b251c331f84feac147de3c4aa3aa45112622a95dd7ee1b74384fa0458dbd79"
+checksum = "d98b86cf4abf524a902dd35f18ca6a3f08fc2ae9847c8f10b48e30491b1f0b86"
 dependencies = [
 "wgpu-hal",
 ]
 [[package]]
 name = "wgpu-core-deps-windows-linux-android"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68ca976e72b2c9964eb243e281f6ce7f14a514e409920920dcda12ae40febaae"
+checksum = "7586165fd5f6d881cb9ce4bb71f40d6caab2c0f1837e3fc1d9788a197fb6004f"
 dependencies = [
 "wgpu-hal",
 ]
 [[package]]
 name = "wgpu-hal"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "293080d77fdd14d6b08a67c5487dfddbf874534bb7921526db56a7b75d7e3bef"
+checksum = "b6b7fb58561a792bc237628ba0792e332de418fefe145f13b5ed8201e6d52f58"
 dependencies = [
 "android_system_properties",
 "arrayvec",
 "ash",
 "bit-set",
 "bitflags 2.10.0",
- "block",
+ "block2 0.6.2",
 "bytemuck",
 "cfg-if",
 "cfg_aliases",
 "core-graphics-types 0.2.0",
 "glow",
 "glutin_wgl_sys",
 "gpu-allocator",
- "gpu-descriptor",
+ "hashbrown 0.17.1",
 "hashbrown 0.16.1",
 "js-sys",
 "khronos-egl",
 "libc",
 "libloading",
 "log",
 "metal",
 "naga",
 "naga-types",
 "ndk-sys",
- "objc",
+ "objc2 0.6.4",
 "objc2-core-foundation",
 "objc2-core-graphics",
 "objc2-foundation 0.3.2",
 "objc2-metal 0.3.2",
 "objc2-quartz-core 0.3.2",
 "once_cell",
 "ordered-float",
 "parking_lot",
@@ -3203,26 +3174,44 @@ dependencies = [
 "profiling",
 "range-alloc",
 "raw-window-handle",
 "raw-window-metal",
 "renderdoc-sys",
 "smallvec",
 "static_assertions",
 "thiserror 2.0.17",
 "wasm-bindgen",
 "wayland-sys",
 "web-sys",
 "wgpu-naga-bridge",
 "wgpu-types",
 "windows",
 "windows-core",
 "windows-result",
 ]
 [[package]]
 name = "wgpu-naga-bridge"
 version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d2f62e73117bb7a62bfd9c5a5841438a823f6566c6442a808ee269d2d055c081"
 dependencies = [
 "naga",
 "wgpu-types",
 ]
 [[package]]
 name = "wgpu-types"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e18308757e594ed2cd27dddbb16a139c42a683819d32a2e0b1b0167552f5840c"
+checksum = "99dad6f1fbdbbdb4c278a6508b059d44688f5cebddf78d005a46a31340269286"
 dependencies = [
 "bitflags 2.10.0",
 "bytemuck",
 "js-sys",
 "log",
 "naga-types",
 "raw-window-handle",
 "static_assertions",
 "web-sys",
 ]
@@ -3586,12 +3575,12 @@ dependencies = [
 "android-activity",
 "atomic-waker",
 "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
 "bytemuck",
 "calloop",
 "cfg_aliases",
 "concurrent-queue",
- "core-foundation 0.9.4",
+ "core-foundation",
 "core-graphics",
 "cursor-icon",
 "dpi",
@@ -3858,12 +3847,6 @@ dependencies = [
 "syn 3.0.5",
 ]
 [[package]]
 name = "zune-core"
 version = "0.4.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f423a2c17029964870cfaabb1f13dfab7d092a62a29a89264f4d36990ca414a"
 [[package]]
 name = "zune-core"
 version = "0.5.0"
@@ -3879,20 +3862,11 @@ dependencies = [
 "simd-adler32",
 ]
 [[package]]
 name = "zune-jpeg"
 version = "0.4.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "29ce2c8a9384ad323cf564b67da86e21d3cfdff87908bc1223ed5c99bc792713"
 dependencies = [
 "zune-core 0.4.12",
 ]
 [[package]]
 name = "zune-jpeg"
 version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e35aee689668bf9bd6f6f3a6c60bb29ba1244b3b43adfd50edd554a371da37d5"
 dependencies = [
- "zune-core 0.5.0",
+ "zune-core",
 ]
@@ -29,9 +29,9 @@ edition = "2024"
 [workspace.dependencies]
 pollster = "0.4.0"
 winit = "0.30.12"
-wgpu = "28.0.0"
+wgpu = "30.0.1"
 bytemuck = "1.23.1"
-image = "0.25.6"
+image = "0.25.10"
 parley = "0.11.1"
 swash = "0.2.10"
 fxhash = "0.2.1"
@@ -1,7 +1,7 @@
 use std::ops::{Index, IndexMut};
 use crate::{
-    render::{MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst, Primitives},
+    render::{LayerDraws, MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst},
    util::to_mut,
 };
@@ -39,7 +39,7 @@ struct Child {
    tail: usize,
 }
-pub type PrimitiveLayers = Layers<Primitives>;
+pub type DrawLayers = Layers<LayerDraws>;
 impl<T: Default> Layers<T> {
    pub fn new() -> Layers<T> {
@@ -119,7 +119,7 @@ impl<T: Default> Layers<T> {
    }
 }
-impl PrimitiveLayers {
+impl DrawLayers {
    pub fn write<P: Primitive>(
        &mut self,
        layer: LayerId,
@@ -1,6 +1,5 @@
 use crate::{
-    Align, GlyphAtlas, GlyphEntry, GlyphKey, PlacedGlyph, RegionAlign, Textures, UiColor,
+    Align, GlyphAtlas, GlyphEntry, GlyphKey, PlacedGlyph, RegionAlign, UiColor, util::Vec2,
    util::Vec2,
 };
 use parley::{
    Alignment, AlignmentOptions, FontContext, FontFamily, FontFamilyName, GenericFamily, Layout,
@@ -159,7 +158,7 @@ impl TextBuffer {
 }
 impl TextData {
-    pub fn place(&mut self, buffer: &TextBuffer, textures: &mut Textures) -> Vec<PlacedGlyph> {
+    pub fn place(&mut self, buffer: &TextBuffer) -> Vec<PlacedGlyph> {
        let mut placed = Vec::new();
        for line in buffer.layout.lines() {
            for item in line.items() {
@@ -185,17 +184,14 @@ impl TextData {
                        subpixel,
                        coords: coords_hash,
                    };
-                    let Some(entry) = self.glyph_entry(
+                    let Some(entry) = self.glyph_entry(GlyphRaster {
                        GlyphRaster {
                        key,
                        font: font_ref,
                        font_size,
                        coords,
                        subpixel,
                        glyph_id: glyph.id,
-                        },
+                    }) else {
                        textures,
                    ) else {
                        continue;
                    };
                    placed.push(PlacedGlyph {
@@ -211,11 +207,7 @@ impl TextData {
        placed
    }
-    fn glyph_entry(
+    fn glyph_entry(&mut self, glyph: GlyphRaster<'_>) -> Option<GlyphEntry> {
        &mut self,
        glyph: GlyphRaster<'_>,
        textures: &mut Textures,
    ) -> Option<GlyphEntry> {
        if let Some(entry) = self.atlas.get(&glyph.key) {
            return entry;
        }
@@ -237,7 +229,7 @@ impl TextData {
        .render(&mut scaler, glyph.glyph_id as u16);
        if let Some(image) = image {
-            self.atlas.insert(glyph.key, &image, textures)
+            self.atlas.insert(glyph.key, &image)
        } else {
            self.atlas.insert_empty(glyph.key);
            None
@@ -278,10 +270,9 @@ impl TextData {
        buffer: &mut TextBuffer,
        attrs: &TextAttrs,
        width: Option<f32>,
        textures: &mut Textures,
    ) -> RenderedText {
        buffer.shape(self, attrs, width);
-        let glyphs = self.place(buffer, textures);
+        let glyphs = self.place(buffer);
        RenderedText {
            glyphs,
            size: buffer.size(),
@@ -1,7 +1,4 @@
-use crate::{
+use crate::util::{RefCounter, Vec2};
    render::TexturePrimitive,
    util::{RefCounter, Vec2},
 };
 use image::{DynamicImage, GenericImageView};
 use std::{
    ops::Index,
@@ -10,7 +7,7 @@ use std::{
 #[derive(Debug, Clone)]
 pub struct TextureHandle {
-    inner: TexturePrimitive,
+    slot: u32,
    size: Vec2,
    counter: RefCounter,
    send: Sender<u32>,
@@ -31,6 +28,8 @@ pub enum TextureUpdate<'a> {
    Set(u32, &'a DynamicImage),
    Patch(u32, PatchRect, &'a DynamicImage),
    Free(u32),
    /// Added and freed before the renderer drained either update. It still has
    /// to push a slot to stay lined up with `images`; `Free` then empties it.
    PushFree,
    SetFree,
 }
@@ -64,14 +63,8 @@ impl Textures {
    pub fn add(&mut self, image: impl Into<DynamicImage>) -> TextureHandle {
        let image = image.into();
        let size = image.dimensions().into();
        let view_idx = self.push(image);
        // 0 == default in renderer; TODO: actually create samplers here
        let sampler_idx = 0;
        TextureHandle {
-            inner: TexturePrimitive {
+            slot: self.push(image),
                view_idx,
                sampler_idx,
            },
            size,
            counter: RefCounter::new(),
            send: self.send.clone(),
@@ -92,15 +85,20 @@ impl Textures {
    }
    pub fn image_mut(&mut self, handle: &TextureHandle) -> &mut DynamicImage {
-        self.images[handle.inner.view_idx as usize]
+        self.images[handle.slot as usize]
            .as_mut()
            .expect("texture was freed while still held")
    }
    /// Queue an upload of just `rect`, after writing it with `image_mut`.
    pub fn patch(&mut self, handle: &TextureHandle, rect: PatchRect) {
-        self.updates
+        self.updates.push(Update::Patch(handle.slot, rect));
-            .push(Update::Patch(handle.inner.view_idx, rect));
+    }
    /// How many textures are live, which is what a ui can ask; the renderer's
    /// copies follow from the updates it drains.
    pub fn count(&self) -> usize {
        self.images.iter().flatten().count()
    }
    pub fn free(&mut self) {
@@ -131,8 +129,9 @@ impl Textures {
 }
 impl TextureHandle {
-    pub fn primitive(&self) -> TexturePrimitive {
+    /// Index into `Textures`, and into the renderer's parallel slots.
-        self.inner
+    pub fn slot(&self) -> u32 {
        self.slot
    }
    pub fn size(&self) -> Vec2 {
        self.size
@@ -142,7 +141,7 @@ impl TextureHandle {
 impl Drop for TextureHandle {
    fn drop(&mut self) {
        if self.counter.drop() {
-            let _ = self.send.send(self.inner.view_idx);
+            let _ = self.send.send(self.slot);
        }
    }
 }
@@ -151,7 +150,7 @@ impl Index<&TextureHandle> for Textures {
    type Output = DynamicImage;
    fn index(&self, index: &TextureHandle) -> &Self::Output {
-        self.images[index.inner.view_idx as usize].as_ref().unwrap()
+        self.images[index.slot as usize].as_ref().unwrap()
    }
 }
@@ -1,11 +1,12 @@
 use crate::{
-    PatchRect, TextureHandle, Textures,
+    PatchRect,
    util::{HashMap, Vec2},
 };
 use image::RgbaImage;
 use swash::scale::image::{Content, Image};
-const PAGE: u32 = 1024;
+/// Side of one page, and so of every layer of `render::page`'s array texture.
 pub(crate) const PAGE: u32 = 1024;
 /// Transparent margin kept around every glyph, so that sampling one cannot
 /// pick up its neighbour along a shared edge.
@@ -35,8 +36,8 @@ pub struct GlyphEntry {
    pub width: u32,
    pub height: u32,
    pub is_colored: bool,
-    pub view_idx: u32,
+    /// Which atlas array layer this glyph is on.
-    pub sampler_idx: u32,
+    pub layer: u32,
 }
 impl GlyphEntry {
@@ -48,18 +49,26 @@ impl GlyphEntry {
 }
 struct Page {
-    handle: TextureHandle,
+    image: RgbaImage,
    x: u32,
    y: u32,
    shelf_height: u32,
 }
 /// A rectangle of one page the renderer has not uploaded yet.
 #[derive(Clone, Copy)]
 pub struct PageUpload {
    pub layer: u32,
    pub rect: PatchRect,
 }
 #[derive(Default)]
 pub struct GlyphAtlas {
    pages: Vec<Page>,
    /// `None` for a glyph that rasterised to nothing -- a space, say. Cached
    /// too, so it is not re-rasterised on every layout.
    entries: HashMap<GlyphKey, Option<GlyphEntry>>,
    uploads: Vec<PageUpload>,
 }
 impl GlyphAtlas {
@@ -67,12 +76,7 @@ impl GlyphAtlas {
        self.entries.get(key).copied()
    }
-    pub fn insert(
+    pub fn insert(&mut self, key: GlyphKey, image: &Image) -> Option<GlyphEntry> {
        &mut self,
        key: GlyphKey,
        image: &Image,
        textures: &mut Textures,
    ) -> Option<GlyphEntry> {
        let w = image.placement.width;
        let h = image.placement.height;
        if w == 0 || h == 0 {
@@ -94,23 +98,11 @@ impl GlyphAtlas {
            return None;
        }
-        let (page_idx, x, y) = self.allocate(w, h, textures);
+        let upload = self.allocate(w, h);
-        let page = &self.pages[page_idx];
+        let PatchRect { x, y, .. } = upload.rect;
        write_glyph(&mut self.pages[upload.layer as usize].image, image, x, y);
        self.uploads.push(upload);
        let img = textures.image_mut(&page.handle);
        let rgba = img.as_mut_rgba8().expect("atlas page is rgba8");
        write_glyph(rgba, image, x, y);
        let handle = page.handle.clone();
        let rect = PatchRect {
            x,
            y,
            width: w,
            height: h,
        };
        textures.patch(&handle, rect);
        let page = &self.pages[page_idx];
        let scale = 1.0 / PAGE as f32;
        let entry = GlyphEntry {
            uv_min: Vec2::new(x as f32 * scale, y as f32 * scale),
@@ -120,39 +112,60 @@ impl GlyphAtlas {
            width: w,
            height: h,
            is_colored: matches!(image.content, Content::Color),
-            view_idx: page.handle.primitive().view_idx,
+            layer: upload.layer,
            sampler_idx: page.handle.primitive().sampler_idx,
        };
        self.entries.insert(key, Some(entry));
        Some(entry)
    }
-    fn allocate(&mut self, w: u32, h: u32, textures: &mut Textures) -> (usize, u32, u32) {
+    /// Reserves room for a `w` by `h` glyph, adding a page if none has it.
    fn allocate(&mut self, w: u32, h: u32) -> PageUpload {
        let rect = |x, y| PatchRect {
            x,
            y,
            width: w,
            height: h,
        };
        if let Some((i, (x, y))) = self
            .pages
            .iter_mut()
            .enumerate()
            .find_map(|(i, page)| page.allocate(w, h).map(|position| (i, position)))
        {
-            return (i, x, y);
+            return PageUpload {
                layer: i as u32,
                rect: rect(x, y),
            };
        }
        let handle = textures.add(RgbaImage::new(PAGE, PAGE));
        self.pages.push(Page {
-            handle,
+            image: RgbaImage::new(PAGE, PAGE),
            x: PAD + w + PAD,
            y: PAD,
            shelf_height: h + PAD,
        });
-        (self.pages.len() - 1, PAD, PAD)
+        PageUpload {
            layer: self.pages.len() as u32 - 1,
            rect: rect(PAD, PAD),
        }
    }
    /// Drains what has been written since the last call, for the renderer to
    /// upload. A new page needs nothing more: wgpu leaves the rest of a fresh
    /// layer transparent, which is what an atlas wants.
    pub fn uploads(&mut self) -> impl Iterator<Item = (PageUpload, &RgbaImage)> {
        let pages = &self.pages;
        self.uploads
            .drain(..)
            .map(|upload| (upload, &pages[upload.layer as usize].image))
    }
    pub fn insert_empty(&mut self, key: GlyphKey) {
        self.entries.insert(key, None);
    }
-    pub fn page_count(&self) -> usize {
+    pub fn page_count(&self) -> u32 {
-        self.pages.len()
+        self.pages.len() as u32
    }
    pub fn glyph_count(&self) -> usize {
@@ -12,20 +12,16 @@ pub struct WindowUniform {
 #[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct PrimitiveInstance {
    pub region: UiRegion,
    pub binding: u32,
    pub idx: u32,
    pub mask_idx: MaskIdx,
 }
 impl PrimitiveInstance {
-    const ATTRIBS: [VertexAttribute; 7] = vertex_attr_array![
+    const ATTRIBS: [VertexAttribute; 5] = vertex_attr_array![
        0 => Float32x2,
        1 => Float32x2,
        2 => Float32x2,
        3 => Float32x2,
        4 => Uint32,
        5 => Uint32,
        6 => Uint32,
    ];
    pub fn desc() -> VertexBufferLayout<'static> {
@@ -1,8 +1,6 @@
 use std::num::NonZero;
 use crate::{
    UiData, UiRenderState,
-    render::{data::PrimitiveInstance, texture::GpuTextures, util::ArrBuf},
+    render::{data::PrimitiveInstance, util::ArrBuf},
    util::{HashMap, Vec2},
 };
 use data::WindowUniform;
@@ -13,6 +11,7 @@ use wgpu::{
 mod atlas;
 mod data;
 mod page;
 mod primitive;
 mod texture;
 mod util;
@@ -21,42 +20,63 @@ pub use atlas::*;
 pub use data::{Mask, MaskIdx};
 pub use primitive::*;
-const SHAPE_SHADER: &str = include_str!("./shader.wgsl");
+const PRELUDE: &str = include_str!("./shader/prelude.wgsl");
 pub struct UiRenderNode {
-    uniform_group: BindGroup,
+    shared_layout: BindGroupLayout,
-    primitive_layout: BindGroupLayout,
+    shared_group: BindGroup,
-    rsc_layout: BindGroupLayout,
+    format: TextureFormat,
    rsc_group: BindGroup,
-    pipeline: RenderPipeline,
+    /// One per registered primitive, in id order.
    primitives: Vec<PrimitivePipeline>,
    layers: HashMap<usize, RenderLayer>,
    active: Vec<usize>,
    window_buffer: Buffer,
    textures: GpuTextures,
    masks: ArrBuf<Mask>,
 }
 struct RenderLayer {
    /// One per registered primitive, `None` where this layer draws none.
    primitives: Vec<Option<ListBuffers>>,
 }
 /// What draws one registered primitive.
 struct PrimitivePipeline {
    data_layout: BindGroupLayout,
    pipeline: RenderPipeline,
    render: Box<dyn PrimitiveRender>,
 }
 /// One list's vertex buffer and the data its shader reads.
 struct ListBuffers {
    instance: ArrBuf<PrimitiveInstance>,
-    primitives: PrimitiveBuffers,
+    data: ArrBuf<u8>,
-    primitive_group: BindGroup,
+    group: Option<BindGroup>,
    /// What the primitive asked to keep per instance, if anything.
    bindings: Vec<u32>,
 }
 impl UiRenderNode {
    pub fn draw<'a>(&'a self, pass: &mut RenderPass<'a>) {
-        pass.set_pipeline(&self.pipeline);
+        pass.set_bind_group(0, &self.shared_group, &[]);
        pass.set_bind_group(0, &self.uniform_group, &[]);
        pass.set_bind_group(2, &self.rsc_group, &[]);
        for i in &self.active {
            let layer = &self.layers[i];
-            if layer.instance.len() == 0 {
+            for (id, list) in layer.primitives.iter().enumerate() {
-                continue;
+                let Some(list) = list else { continue };
                let Some(group) = &list.group else { continue };
                let primitive = &self.primitives[id];
                pass.set_pipeline(&primitive.pipeline);
                pass.set_bind_group(1, group, &[]);
                pass.set_vertex_buffer(0, list.instance.buffer.slice(..));
                primitive.render.draw(
                    pass,
                    ListDraw {
                        instances: list.instance.len() as u32,
                        bindings: &list.bindings,
                    },
                );
            }
            pass.set_bind_group(1, &layer.primitive_group, &[]);
            pass.set_vertex_buffer(0, layer.instance.buffer.slice(..));
            pass.draw(0..4, 0..layer.instance.len() as u32);
        }
    }
@@ -67,55 +87,56 @@ impl UiRenderNode {
        ui: &mut UiData,
        ui_render: &mut UiRenderState,
    ) {
        // Before the layers: each list is given its pipeline's data layout.
        self.build_pipelines(device, queue, &ui.primitives);
        self.active.clear();
-        for (i, primitives) in ui_render.layers.iter_mut() {
+        for (i, draws) in ui_render.layers.iter_mut() {
            self.active.push(i);
-            for change in primitives.apply_free() {
+            for change in draws.apply_free() {
                if let Some(inst) = ui_render.active.get_mut(&change.id) {
                    for h in &mut inst.primitives {
-                        if h.layer == i && h.inst_idx == change.old {
+                        if h.layer == i && h.kind == change.kind && h.inst_idx == change.old {
                            h.inst_idx = change.new;
                            break;
                        }
                    }
                }
            }
-            let rlayer = self.layers.entry(i).or_insert_with(|| {
+            let rlayer = self.layers.entry(i).or_insert_with(RenderLayer::new);
-                let primitives = PrimitiveBuffers::new(device);
+            if draws.updated {
-                let primitive_group =
+                let lists = draws.primitives();
-                    Self::primitive_group(device, &self.primitive_layout, primitives.buffers());
+                // The zip would otherwise skip a list with no pipeline.
-                RenderLayer {
+                assert!(lists.len() <= self.primitives.len());
-                    instance: ArrBuf::new(
+                rlayer.primitives.resize_with(lists.len(), || None);
-                        device,
+                for ((buffers, list), primitive) in rlayer
-                        BufferUsages::VERTEX | BufferUsages::COPY_DST,
+                    .primitives
-                        "instance",
+                    .iter_mut()
-                    ),
+                    .zip(lists)
-                    primitives,
+                    .zip(&self.primitives)
-                    primitive_group,
+                {
                    let Some(list) = list else {
                        continue;
                    };
                    buffers
                        .get_or_insert_with(|| ListBuffers::new(device))
                        .update(device, queue, primitive, list);
                }
-            });
+                draws.updated = false;
            if primitives.updated {
                rlayer
                    .instance
                    .update(device, queue, primitives.instances());
                rlayer.primitives.update(device, queue, primitives.data());
                rlayer.primitive_group = Self::primitive_group(
                    device,
                    &self.primitive_layout,
                    rlayer.primitives.buffers(),
                );
                primitives.updated = false;
            }
        }
-        let mut changed = false;
+        for primitive in &mut self.primitives {
-        changed |= self.textures.update(&mut ui.textures);
+            primitive.render.update(ui);
        }
        if ui.masks.changed {
            ui.masks.changed = false;
-            self.masks.update(device, queue, &ui.masks[..]);
+            if self.masks.update(device, queue, &ui.masks[..]) {
-            changed = true;
+                self.shared_group = Self::shared_group(
                    device,
                    &self.shared_layout,
                    &self.window_buffer,
                    &self.masks,
                );
            }
        if changed {
            self.rsc_group = Self::rsc_group(device, &self.rsc_layout, &self.textures, &self.masks);
        }
    }
@@ -128,17 +149,7 @@ impl UiRenderNode {
        queue.write_buffer(&self.window_buffer, 0, bytemuck::cast_slice(slice));
    }
-    pub fn new(
+    pub fn new(device: &Device, config: &SurfaceConfiguration) -> Self {
        device: &Device,
        queue: &Queue,
        config: &SurfaceConfiguration,
        limits: UiLimits,
    ) -> Self {
        let shader = device.create_shader_module(ShaderModuleDescriptor {
            label: Some("UI Shape Shader"),
            source: ShaderSource::Wgsl(SHAPE_SHADER.into()),
        });
        let window_uniform = WindowUniform {
            width: config.width as f32,
            height: config.height as f32,
@@ -149,67 +160,73 @@ impl UiRenderNode {
            usage: BufferUsages::UNIFORM | BufferUsages::COPY_DST,
        });
-        let uniform_layout = device.create_bind_group_layout(&BindGroupLayoutDescriptor {
+        let shared_layout = Self::shared_layout(device);
            entries: &[BindGroupLayoutEntry {
                binding: 0,
                visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Uniform,
                    has_dynamic_offset: false,
                    min_binding_size: None,
                },
                count: None,
            }],
            label: Some("window"),
        });
        let uniform_group = Self::bind_group_0(device, &uniform_layout, &window_buffer);
        let primitive_layout = device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &core::array::from_fn::<_, { PrimitiveBuffers::LEN }, _>(|i| {
                BindGroupLayoutEntry {
                    binding: i as u32,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: BufferBindingType::Storage { read_only: true },
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                }
            }),
            label: Some("primitive"),
        });
        let tex_manager = GpuTextures::new(device, queue);
        let masks = ArrBuf::new(
            device,
            BufferUsages::STORAGE | BufferUsages::COPY_DST,
            "ui masks",
        );
        let shared_group = Self::shared_group(device, &shared_layout, &window_buffer, &masks);
-        let rsc_layout = Self::rsc_layout(device, &limits);
+        Self {
-        let rsc_group = Self::rsc_group(device, &rsc_layout, &tex_manager, &masks);
+            shared_layout,
            shared_group,
            format: config.format,
            primitives: Vec::new(),
            window_buffer,
            layers: HashMap::default(),
            active: Vec::new(),
            masks,
        }
    }
-        let pipeline_layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
+    /// Compiles a pipeline for every primitive registered since the last call.
-            label: Some("UI Shape Pipeline Layout"),
+    /// Sources only ever arrive at the end, so an id keeps its pipeline.
-            bind_group_layouts: &[&uniform_layout, &primitive_layout, &rsc_layout],
+    fn build_pipelines(&mut self, device: &Device, queue: &Queue, registry: &PrimitiveRegistry) {
        for source in &registry.sources()[self.primitives.len()..] {
            let render = (source.render)(device, queue);
            let data_layout = Self::data_layout(device, source.stride);
            let mut groups = vec![Some(&self.shared_layout), Some(&data_layout)];
            groups.extend(render.layout().map(Some));
            let layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
                label: Some(source.label),
                bind_group_layouts: &groups,
                immediate_size: 0,
            });
-        let pipeline = device.create_render_pipeline(&RenderPipelineDescriptor {
+            let pipeline = Self::pipeline(device, &layout, self.format, source.wgsl, source.label);
-            label: Some("UI Shape Pipeline"),
+            self.primitives.push(PrimitivePipeline {
-            layout: Some(&pipeline_layout),
+                data_layout,
                pipeline,
                render,
            });
        }
    }
    fn pipeline(
        device: &Device,
        layout: &PipelineLayout,
        format: TextureFormat,
        wgsl: &str,
        label: &str,
    ) -> RenderPipeline {
        let module = device.create_shader_module(ShaderModuleDescriptor {
            label: Some(label),
            source: ShaderSource::Wgsl(format!("{PRELUDE}\n{wgsl}").into()),
        });
        device.create_render_pipeline(&RenderPipelineDescriptor {
            label: Some(label),
            layout: Some(layout),
            vertex: VertexState {
-                module: &shader,
+                module: &module,
                entry_point: Some("vs_main"),
-                buffers: &[PrimitiveInstance::desc()],
+                buffers: &[Some(PrimitiveInstance::desc())],
                compilation_options: Default::default(),
            },
            fragment: Some(FragmentState {
-                module: &shader,
+                module: &module,
                entry_point: Some("fs_main"),
                targets: &[Some(ColorTargetState {
-                    format: config.format,
+                    format,
                    blend: Some(BlendState::ALPHA_BLENDING),
                    write_mask: ColorWrites::ALL,
                })],
@@ -232,90 +249,42 @@ impl UiRenderNode {
            },
            multiview_mask: None,
            cache: None,
        });
        Self {
            uniform_group,
            primitive_layout,
            rsc_layout,
            rsc_group,
            pipeline,
            window_buffer,
            layers: HashMap::default(),
            active: Vec::new(),
            textures: tex_manager,
            masks,
        }
    }
    fn bind_group_0(
        device: &Device,
        layout: &BindGroupLayout,
        window_buffer: &Buffer,
    ) -> BindGroup {
        device.create_bind_group(&BindGroupDescriptor {
            layout,
            entries: &[BindGroupEntry {
                binding: 0,
                resource: window_buffer.as_entire_binding(),
            }],
            label: Some("ui window"),
        })
    }
-    fn primitive_group(
+    /// What every draw in the ui is given: the window and the masks.
-        device: &Device,
+    fn shared_layout(device: &Device) -> BindGroupLayout {
        layout: &BindGroupLayout,
        buffers: [(u32, &Buffer); PrimitiveBuffers::LEN],
    ) -> BindGroup {
        device.create_bind_group(&BindGroupDescriptor {
            layout,
            entries: &buffers.map(|(binding, buf)| BindGroupEntry {
                binding,
                resource: buf.as_entire_binding(),
            }),
            label: Some("ui primitives"),
        })
    }
    fn rsc_layout(device: &Device, limits: &UiLimits) -> BindGroupLayout {
        device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &[
                BindGroupLayoutEntry {
                    binding: 0,
-                    visibility: ShaderStages::FRAGMENT,
+                    visibility: ShaderStages::VERTEX | ShaderStages::FRAGMENT,
-                    ty: BindingType::Texture {
+                    ty: BindingType::Buffer {
-                        sample_type: TextureSampleType::Float { filterable: false },
+                        ty: BufferBindingType::Uniform,
-                        view_dimension: TextureViewDimension::D2,
+                        has_dynamic_offset: false,
-                        multisampled: false,
+                        min_binding_size: BufferSize::new(size_of::<WindowUniform>() as u64),
                    },
-                    count: Some(NonZero::new(limits.max_textures).unwrap()),
+                    count: None,
                },
                BindGroupLayoutEntry {
                    binding: 1,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Sampler(SamplerBindingType::NonFiltering),
                    count: Some(NonZero::new(limits.max_samplers).unwrap()),
                },
                BindGroupLayoutEntry {
                    binding: 2,
                    visibility: ShaderStages::FRAGMENT,
                    ty: BindingType::Buffer {
                        ty: BufferBindingType::Storage { read_only: true },
                        has_dynamic_offset: false,
-                        min_binding_size: None,
+                        min_binding_size: BufferSize::new(size_of::<Mask>() as u64),
                    },
                    count: None,
                },
            ],
-            label: Some("ui rsc"),
+            label: Some("ui shared"),
        })
    }
-    fn rsc_group(
+    fn shared_group(
        device: &Device,
        layout: &BindGroupLayout,
-        tex_manager: &GpuTextures,
+        window: &Buffer,
        masks: &ArrBuf<Mask>,
    ) -> BindGroup {
        device.create_bind_group(&BindGroupDescriptor {
@@ -323,45 +292,85 @@ impl UiRenderNode {
            entries: &[
                BindGroupEntry {
                    binding: 0,
-                    resource: BindingResource::TextureViewArray(&tex_manager.views()),
+                    resource: window.as_entire_binding(),
                },
                BindGroupEntry {
                    binding: 1,
                    resource: BindingResource::SamplerArray(&tex_manager.samplers()),
                },
                BindGroupEntry {
                    binding: 2,
                    resource: masks.buffer.as_entire_binding(),
                },
            ],
-            label: Some("ui rsc"),
+            label: Some("ui shared"),
        })
    }
-    pub fn view_count(&self) -> usize {
+    /// Layout for a list of one primitive's data. Every size in the ui is
-        self.textures.view_count()
+    /// stated, so "is the buffer big enough for one entry?" is answered when
    /// the bind group is made; a `None` size is wgpu's to check on every draw.
    fn data_layout(device: &Device, stride: u64) -> BindGroupLayout {
        device.create_bind_group_layout(&BindGroupLayoutDescriptor {
            entries: &[BindGroupLayoutEntry {
                binding: 0,
                visibility: ShaderStages::FRAGMENT,
                ty: BindingType::Buffer {
                    ty: BufferBindingType::Storage { read_only: true },
                    has_dynamic_offset: false,
                    min_binding_size: BufferSize::new(stride),
                },
                count: None,
            }],
            label: Some("ui primitive data"),
        })
    }
 }
-pub struct UiLimits {
+impl RenderLayer {
-    max_textures: u32,
+    fn new() -> Self {
    max_samplers: u32,
 }
 impl Default for UiLimits {
    fn default() -> Self {
        Self {
-            max_textures: 100000,
+            primitives: Vec::new(),
            max_samplers: 1000,
        }
    }
 }
-impl UiLimits {
+impl ListBuffers {
-    pub fn max_binding_array_elements_per_shader_stage(&self) -> u32 {
+    fn new(device: &Device) -> Self {
-        self.max_textures + self.max_samplers
+        Self {
            instance: ArrBuf::new(
                device,
                BufferUsages::VERTEX | BufferUsages::COPY_DST,
                "instance",
            ),
            data: ArrBuf::new(
                device,
                BufferUsages::STORAGE | BufferUsages::COPY_DST,
                "primitive data",
            ),
            group: None,
            bindings: Vec::new(),
        }
-    pub fn max_binding_array_sampler_elements_per_shader_stage(&self) -> u32 {
+    }
-        self.max_samplers
+
    fn update(
        &mut self,
        device: &Device,
        queue: &Queue,
        primitive: &PrimitivePipeline,
        list: &InstanceList,
    ) {
        self.bindings.clear();
        primitive.render.instance_bindings(list, &mut self.bindings);
        self.instance.update(device, queue, list.instances());
        let resized = self.data.update(device, queue, list.data());
        if list.instances().is_empty() {
            self.group = None;
        } else if resized || self.group.is_none() {
            self.group = Some(device.create_bind_group(&BindGroupDescriptor {
                layout: &primitive.data_layout,
                entries: &[BindGroupEntry {
                    binding: 0,
                    resource: self.data.buffer.as_entire_binding(),
                }],
                label: Some("ui primitive data"),
            }));
        }
    }
 }
@@ -0,0 +1,156 @@
 use wgpu::*;
 use crate::{GlyphAtlas, UiData};
 use super::{
    atlas::PAGE,
    primitive::{ListDraw, PrimitiveRender},
    texture::{default_sampler, sampled_group, sampled_layout, write_region},
 };
 /// Draws glyphs from the atlas, which it owns: one array texture bound once
 /// for a whole list, since every glyph in it reads the same pages.
 pub struct GlyphRender {
    pages: GpuPages,
    layout: BindGroupLayout,
    sampler: Sampler,
 }
 impl GlyphRender {
    pub fn new(device: &Device, queue: &Queue) -> Self {
        let layout = sampled_layout(device, TextureViewDimension::D2Array, "ui atlas");
        let sampler = default_sampler(device);
        Self {
            pages: GpuPages::new(device, queue, &layout, &sampler),
            layout,
            sampler,
        }
    }
 }
 impl PrimitiveRender for GlyphRender {
    fn layout(&self) -> Option<&BindGroupLayout> {
        Some(&self.layout)
    }
    fn update(&mut self, ui: &mut UiData) {
        self.pages
            .update(&mut ui.text.atlas, &self.layout, &self.sampler);
    }
    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
        pass.set_bind_group(2, self.pages.group(), &[]);
        pass.draw(0..4, 0..list.instances);
    }
 }
 /// The glyph atlas on the GPU: one array texture whose layers are the pages
 /// `GlyphAtlas` packs.
 ///
 /// One array rather than a texture per page because a layer index is ordinary
 /// Vulkan 1.0 / GLES sampling, where a `binding_array` would need
 /// `VK_EXT_descriptor_indexing`, which a real share of Android GPUs lack.
 pub struct GpuPages {
    device: Device,
    queue: Queue,
    texture: Texture,
    group: BindGroup,
 }
 impl GpuPages {
    pub fn new(
        device: &Device,
        queue: &Queue,
        layout: &BindGroupLayout,
        sampler: &Sampler,
    ) -> Self {
        let texture = create_array(device, 1);
        Self {
            device: device.clone(),
            queue: queue.clone(),
            group: atlas_group(device, layout, &texture, sampler),
            texture,
        }
    }
    pub fn update(&mut self, atlas: &mut GlyphAtlas, layout: &BindGroupLayout, sampler: &Sampler) {
        if atlas.page_count() > self.texture.depth_or_array_layers() {
            self.grow(atlas.page_count(), layout, sampler);
        }
        for (upload, page) in atlas.uploads() {
            let dst = TexelCopyTextureInfo {
                texture: &self.texture,
                mip_level: 0,
                origin: Origin3d {
                    x: upload.rect.x,
                    y: upload.rect.y,
                    z: upload.layer,
                },
                aspect: TextureAspect::All,
            };
            write_region(&self.queue, dst, page, upload.rect);
        }
    }
    pub fn group(&self) -> &BindGroup {
        &self.group
    }
    /// Doubles until `needed` fits and copies the old layers across GPU side.
    /// The new texture stales the group, so that is rebuilt here.
    fn grow(&mut self, needed: u32, layout: &BindGroupLayout, sampler: &Sampler) {
        let old = self.texture.depth_or_array_layers();
        let mut layers = old;
        while layers < needed {
            layers *= 2;
        }
        let texture = create_array(&self.device, layers);
        let mut encoder = self
            .device
            .create_command_encoder(&CommandEncoderDescriptor {
                label: Some("atlas grow"),
            });
        encoder.copy_texture_to_texture(
            self.texture.as_image_copy(),
            texture.as_image_copy(),
            Extent3d {
                width: PAGE,
                height: PAGE,
                depth_or_array_layers: old,
            },
        );
        self.queue.submit(std::iter::once(encoder.finish()));
        self.group = atlas_group(&self.device, layout, &texture, sampler);
        self.texture = texture;
    }
 }
 fn atlas_group(
    device: &Device,
    layout: &BindGroupLayout,
    texture: &Texture,
    sampler: &Sampler,
 ) -> BindGroup {
    let view = texture.create_view(&TextureViewDescriptor {
        dimension: Some(TextureViewDimension::D2Array),
        ..Default::default()
    });
    sampled_group(device, layout, &view, sampler, "ui atlas")
 }
 fn create_array(device: &Device, layers: u32) -> Texture {
    device.create_texture(&TextureDescriptor {
        label: Some("glyph atlas"),
        size: Extent3d {
            width: PAGE,
            height: PAGE,
            depth_or_array_layers: layers,
        },
        mip_level_count: 1,
        sample_count: 1,
        dimension: TextureDimension::D2,
        format: TextureFormat::Rgba8Unorm,
        usage: TextureUsages::TEXTURE_BINDING | TextureUsages::COPY_DST | TextureUsages::COPY_SRC,
        view_formats: &[],
    })
 }
@@ -1,115 +1,247 @@
-use std::ops::{Deref, DerefMut};
+use std::{any::TypeId, marker::PhantomData};
 use crate::{
-    Color, UiRegion, WidgetId,
+    Color, TextureHandle, UiData, UiRegion, WidgetId,
    render::{
        ArrBuf,
        data::{MaskIdx, PrimitiveInstance},
        page::GlyphRender,
        texture::ImageRender,
    },
-    util::Vec2,
+    util::{HashMap, Vec2},
 };
 use bytemuck::Pod;
-use wgpu::*;
+use wgpu::{BindGroupLayout, Device, Queue, RenderPass};
-pub struct Primitives {
+/// One instance of a primitive, laid out as the struct its shader reads.
 ///
 /// The type carries its own shader, so drawing one is all the wiring it needs:
 /// its list, free list, buffers and pipeline follow from being registered.
 pub trait Primitive: Pod + 'static {
    /// Compiled after `prelude.wgsl`, which states what it declares and what
    /// it is given.
    const WGSL: &'static str;
    /// Made once, the first time the renderer sees this primitive. It owns
    /// whatever the shader samples and records the primitive's own draws; the
    /// default owns nothing and draws every instance in one call.
    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender>
    where
        Self: Sized,
    {
        let _ = (device, queue);
        Box::new(Instanced)
    }
 }
 /// The renderer's half of a primitive: what it samples, what it uploads, and
 /// what draws it records.
 ///
 /// Everything a draw shares -- the pipeline, the window and masks, the list's
 /// own data and instance buffer -- is set before this is called. What is left
 /// is what only this primitive knows: its group 2, and how many draws its
 /// instances are.
 pub trait PrimitiveRender {
    /// The layout its shader reads at group 2. `None` for a primitive whose
    /// shader samples nothing, whose pipeline then has no group 2 at all.
    fn layout(&self) -> Option<&BindGroupLayout> {
        None
    }
    /// Uploads whatever this primitive owns, once a frame, before any draw.
    fn update(&mut self, ui: &mut UiData) {
        let _ = ui;
    }
    /// Keeps what the primitive needs per instance at draw time, read from
    /// the list's own data. A primitive that binds nothing per instance --
    /// most of them -- leaves this empty and draws in one call.
    fn instance_bindings(&self, list: &InstanceList, out: &mut Vec<u32>) {
        let _ = (list, out);
    }
    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>);
 }
 /// What a `PrimitiveRender` draws: this list's instances, and whatever
 /// `instance_bindings` kept for them.
 pub struct ListDraw<'a> {
    pub instances: u32,
    pub bindings: &'a [u32],
 }
 /// The default: nothing sampled, every instance in one call.
 pub struct Instanced;
 impl PrimitiveRender for Instanced {
    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
        pass.draw(0..4, 0..list.instances);
    }
 }
 /// Which registered primitive an instance is.
 pub struct PrimitiveKind<P> {
    id: u32,
    _p: PhantomData<fn(P)>,
 }
 impl<P> PrimitiveKind<P> {
    fn new(id: u32) -> Self {
        Self {
            id,
            _p: PhantomData,
        }
    }
 }
 impl<P> Clone for PrimitiveKind<P> {
    fn clone(&self) -> Self {
        *self
    }
 }
 impl<P> Copy for PrimitiveKind<P> {}
 /// Every primitive a ui can draw, in the order they were first drawn.
 #[derive(Default)]
 pub struct PrimitiveRegistry {
    kinds: Vec<PrimitiveSource>,
    ids: HashMap<TypeId, u32>,
 }
 pub struct PrimitiveSource {
    pub wgsl: &'static str,
    pub label: &'static str,
    /// Size of one instance's entry, stated as the data binding's minimum.
    pub stride: u64,
    pub render: fn(&Device, &Queue) -> Box<dyn PrimitiveRender>,
 }
 impl PrimitiveRegistry {
    /// Registers `P` if this is the first time it has been drawn.
    pub fn kind<P: Primitive>(&mut self) -> PrimitiveKind<P> {
        let Self { kinds, ids } = self;
        let id = *ids.entry(TypeId::of::<P>()).or_insert_with(|| {
            kinds.push(PrimitiveSource {
                wgsl: P::WGSL,
                label: std::any::type_name::<P>(),
                stride: size_of::<P>() as u64,
                render: P::render,
            });
            kinds.len() as u32 - 1
        });
        PrimitiveKind::new(id)
    }
    pub fn sources(&self) -> &[PrimitiveSource] {
        &self.kinds
    }
 }
 /// One registered primitive's instances in one layer. Everything per-instance
 /// rides here, so it stays in step through a `swap_remove`.
 pub struct InstanceList {
    instances: Vec<PrimitiveInstance>,
    /// The widget each instance belongs to, for renumbering its handles.
    assoc: Vec<WidgetId>,
    data: PrimitiveData,
    free: Vec<usize>,
    /// `stride` bytes of the primitive's own data per instance.
    data: Vec<u8>,
    /// From the type the list was made for, so a write is never checked.
    stride: usize,
 }
 impl InstanceList {
    fn new<P: Primitive>() -> Self {
        Self {
            instances: Vec::new(),
            assoc: Vec::new(),
            free: Vec::new(),
            data: Vec::new(),
            stride: size_of::<P>(),
        }
    }
    pub fn instances(&self) -> &[PrimitiveInstance] {
        &self.instances
    }
    pub fn data(&self) -> &[u8] {
        &self.data
    }
    pub fn stride(&self) -> usize {
        self.stride
    }
    fn push(&mut self, id: WidgetId, inst: PrimitiveInstance, data: &[u8]) -> usize {
        if let Some(i) = self.free.pop() {
            self.instances[i] = inst;
            self.assoc[i] = id;
            self.data[i * self.stride..][..self.stride].copy_from_slice(data);
            i
        } else {
            let i = self.instances.len();
            self.instances.push(inst);
            self.assoc.push(id);
            self.data.extend_from_slice(data);
            i
        }
    }
    fn free(&mut self, i: usize) -> MaskIdx {
        self.free.push(i);
        self.instances[i].mask_idx
    }
    fn apply_free(&mut self, kind: u32) -> impl Iterator<Item = PrimitiveChange> {
        self.free.sort_by(|a, b| b.cmp(a));
        let instances = &mut self.instances;
        let assoc = &mut self.assoc;
        let data = &mut self.data;
        let stride = self.stride;
        self.free.drain(..).filter_map(move |i| {
            instances.swap_remove(i);
            assoc.swap_remove(i);
            let last = instances.len();
            data.copy_within(last * stride..(last + 1) * stride, i * stride);
            data.truncate(last * stride);
            if i == last {
                return None;
            }
            let id = assoc[i];
            Some(PrimitiveChange {
                id,
                kind,
                old: last,
                new: i,
            })
        })
    }
 }
 /// Everything one layer draws, one list per registered primitive.
 pub struct LayerDraws {
    /// `None` until this layer draws that primitive, because only the write
    /// knows the type the list is for.
    primitives: Vec<Option<InstanceList>>,
    pub updated: bool,
 }
-impl Default for Primitives {
+impl Default for LayerDraws {
    fn default() -> Self {
        Self {
-            instances: Default::default(),
+            primitives: Vec::new(),
            assoc: Default::default(),
            data: Default::default(),
            free: Vec::new(),
            updated: true,
        }
    }
 }
-pub trait Primitive: Pod {
+impl LayerDraws {
    const BINDING: u32;
    fn vec(data: &mut PrimitiveData) -> &mut PrimitiveVec<Self>;
 }
 macro_rules! primitives {
    ($($name:ident: $ty:ty => $binding:expr,)*) => {
        #[derive(Default)]
        pub struct PrimitiveData {
            $(pub(crate) $name: PrimitiveVec<$ty>,)*
        }
        pub struct PrimitiveBuffers {
            $($name: ArrBuf<$ty>,)*
        }
        impl PrimitiveBuffers {
            pub fn update(&mut self, device: &Device, queue: &Queue, data: &PrimitiveData) {
                $(self.$name.update(device, queue, &data.$name);)*
            }
        }
        impl PrimitiveBuffers {
            pub const LEN: usize = primitives!(@count $($name)*);
            pub fn buffers(&self) -> [(u32, &Buffer); Self::LEN] {
                [
                    $((<$ty>::BINDING, &self.$name.buffer),)*
                ]
            }
            pub fn new(device: &Device) -> Self {
                Self {
                    $($name: ArrBuf::new(
                        device,
                        BufferUsages::STORAGE | BufferUsages::COPY_DST,
                        stringify!($name),
                    ),)*
                }
            }
        }
        impl PrimitiveData {
            pub fn clear(&mut self) {
                $(self.$name.clear();)*
            }
            pub fn free(&mut self, binding: u32, idx: usize) {
                match binding {
                    $(<$ty>::BINDING => self.$name.free(idx),)*
                    _ => unreachable!()
                }
            }
        }
        $(
            unsafe impl bytemuck::Pod for $ty {}
            unsafe impl bytemuck::Zeroable for $ty {}
            impl Primitive for $ty {
                const BINDING: u32 = $binding;
                fn vec(data: &mut PrimitiveData) -> &mut PrimitiveVec<Self> {
                    &mut data.$name
                }
            }
        )*
    };
    (@count $t1:tt $($t:tt)+) => { 1 + primitives!(@count $($t)+) };
    (@count $t:tt) => { 1 };
 }
 pub struct PrimitiveInst<P> {
    pub id: WidgetId,
    pub primitive: P,
    pub region: UiRegion,
    pub mask_idx: MaskIdx,
 }
 impl Primitives {
    pub fn write<P: Primitive>(
        &mut self,
        layer: usize,
        PrimitiveInst {
            kind,
            id,
            primitive,
            region,
@@ -117,65 +249,67 @@ impl Primitives {
        }: PrimitiveInst<P>,
    ) -> PrimitiveHandle {
        self.updated = true;
-        let vec = P::vec(&mut self.data);
+        // Grown on first use rather than sized from the registry, which a
-        let i = vec.add(primitive);
+        // layer cannot see.
-        let inst = PrimitiveInstance {
+        if self.primitives.len() <= kind.id as usize {
-            region,
+            self.primitives.resize_with(kind.id as usize + 1, || None);
-            idx: i as u32,
+        }
-            mask_idx,
+        let inst_idx = self.primitives[kind.id as usize]
-            binding: P::BINDING,
+            .get_or_insert_with(InstanceList::new::<P>)
-        };
+            .push(
-        let inst_i = if let Some(i) = self.free.pop() {
+                id,
-            self.instances[i] = inst;
+                PrimitiveInstance { region, mask_idx },
-            self.assoc[i] = id;
+                bytemuck::bytes_of(&primitive),
-            i
+            );
-        } else {
+        PrimitiveHandle {
-            let i = self.instances.len();
+            layer,
-            self.instances.push(inst);
+            kind: kind.id,
-            self.assoc.push(id);
+            inst_idx,
-            i
+        }
        };
        PrimitiveHandle::new::<P>(layer, inst_i, i)
    }
-    /// returns (old index, new index)
+    pub fn primitives(&self) -> &[Option<InstanceList>] {
-    pub fn apply_free(&mut self) -> impl Iterator<Item = PrimitiveChange> {
+        &self.primitives
        self.free.sort_by(|a, b| b.cmp(a));
        self.free.drain(..).filter_map(|i| {
            self.instances.swap_remove(i);
            self.assoc.swap_remove(i);
            if i == self.instances.len() {
                return None;
    }
-            let id = self.assoc[i];
+
-            let old = self.instances.len();
+    pub fn apply_free(&mut self) -> impl Iterator<Item = PrimitiveChange> {
-            Some(PrimitiveChange { id, old, new: i })
+        self.primitives
-        })
+            .iter_mut()
            .enumerate()
            .filter_map(|(kind, list)| Some((kind as u32, list.as_mut()?)))
            .flat_map(|(kind, list)| list.apply_free(kind))
    }
    pub fn free(&mut self, h: &PrimitiveHandle) -> MaskIdx {
        self.updated = true;
-        self.data.free(h.binding, h.data_idx);
+        self.list(h).free(h.inst_idx)
        self.free.push(h.inst_idx);
        self.instances[h.inst_idx].mask_idx
    }
    pub fn data(&self) -> &PrimitiveData {
        &self.data
    }
    pub fn instances(&self) -> &Vec<PrimitiveInstance> {
        &self.instances
    }
    pub fn region_mut(&mut self, h: &PrimitiveHandle) -> &mut UiRegion {
        self.updated = true;
-        &mut self.instances[h.inst_idx].region
+        &mut self.list(h).instances[h.inst_idx].region
    }
    /// A handle is only ever made by `write`, which is what created the list.
    fn list(&mut self, h: &PrimitiveHandle) -> &mut InstanceList {
        self.primitives[h.kind as usize]
            .as_mut()
            .expect("handle names a primitive this layer never drew")
    }
 }
 pub struct PrimitiveInst<P> {
    pub kind: PrimitiveKind<P>,
    pub id: WidgetId,
    pub primitive: P,
    pub region: UiRegion,
    pub mask_idx: MaskIdx,
 }
 pub struct PrimitiveChange {
    pub id: WidgetId,
    /// Which registered primitive's list moved, since they index separately.
    pub kind: u32,
    pub old: usize,
    pub new: usize,
 }
@@ -183,30 +317,12 @@ pub struct PrimitiveChange {
 #[derive(Debug)]
 pub struct PrimitiveHandle {
    pub layer: usize,
    pub kind: u32,
    pub inst_idx: usize,
    pub data_idx: usize,
    pub binding: u32,
 }
 impl PrimitiveHandle {
    fn new<P: Primitive>(layer: usize, inst_idx: usize, data_idx: usize) -> Self {
        Self {
            layer,
            inst_idx,
            data_idx,
            binding: P::BINDING,
        }
    }
 }
 primitives!(
    rects: RectPrimitive => 0,
    textures: TexturePrimitive => 1,
    glyphs: GlyphPrimitive => 2,
 );
 #[repr(C)]
-#[derive(Copy, Clone)]
+#[derive(Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct RectPrimitive {
    pub color: Color<u8>,
    pub radius: f32,
@@ -214,6 +330,10 @@ pub struct RectPrimitive {
    pub inner_radius: f32,
 }
 impl Primitive for RectPrimitive {
    const WGSL: &'static str = include_str!("shader/rect.wgsl");
 }
 impl RectPrimitive {
    pub fn color(color: Color<u8>) -> Self {
        Self {
@@ -225,71 +345,51 @@ impl RectPrimitive {
    }
 }
-#[repr(C)]
+/// `color` is multiplied by the atlas alpha for a mask glyph; a colour glyph
-#[derive(Debug, Copy, Clone)]
+/// takes the texel unchanged, which `GlyphEntry::IS_COLORED` selects.
-pub struct TexturePrimitive {
+#[repr(C, align(8))]
    pub view_idx: u32,
    pub sampler_idx: u32,
 }
 #[repr(C)]
 #[derive(Debug, Copy, Clone)]
 pub struct GlyphPrimitive {
    pub uv_min: Vec2,
    pub uv_max: Vec2,
-    pub view_idx: u32,
+    /// Which atlas array layer this glyph is on.
-    pub sampler_idx: u32,
+    pub layer: u32,
    pub color: Color<u8>,
    pub flags: u32,
 }
-pub struct PrimitiveVec<T> {
+// Manual rather than derived: the align(8) leaves four bytes of padding, which
-    vec: Vec<T>,
+// is how WGSL lays the struct out.
-    free: Vec<usize>,
+unsafe impl bytemuck::Pod for GlyphPrimitive {}
 unsafe impl bytemuck::Zeroable for GlyphPrimitive {}
 impl Primitive for GlyphPrimitive {
    const WGSL: &'static str = include_str!("shader/glyph.wgsl");
    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender> {
        Box::new(GlyphRender::new(device, queue))
    }
 }
-impl<T> PrimitiveVec<T> {
+/// One drawn image. Its shader reads nothing per instance; the slot names the
-    pub fn new() -> Self {
+/// texture to bind for it.
 #[repr(C)]
 #[derive(Debug, Copy, Clone, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct TexturePrimitive {
    pub slot: u32,
 }
 impl Primitive for TexturePrimitive {
    const WGSL: &'static str = include_str!("shader/texture.wgsl");
    fn render(device: &Device, queue: &Queue) -> Box<dyn PrimitiveRender> {
        Box::new(ImageRender::new(device, queue))
    }
 }
 impl From<&TextureHandle> for TexturePrimitive {
    fn from(handle: &TextureHandle) -> Self {
        Self {
-            vec: Vec::new(),
+            slot: handle.slot(),
            free: Vec::new(),
        }
    }
    pub fn add(&mut self, t: T) -> usize {
        if let Some(i) = self.free.pop() {
            self.vec[i] = t;
            i
        } else {
            let i = self.vec.len();
            self.vec.push(t);
            i
        }
    }
    pub fn free(&mut self, i: usize) {
        self.free.push(i);
    }
    pub fn clear(&mut self) {
        self.free.clear();
        self.vec.clear();
    }
 }
 impl<T> Default for PrimitiveVec<T> {
    fn default() -> Self {
        Self::new()
    }
 }
 impl<T> Deref for PrimitiveVec<T> {
    type Target = Vec<T>;
    fn deref(&self) -> &Self::Target {
        &self.vec
    }
 }
 impl<T> DerefMut for PrimitiveVec<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.vec
    }
 }
@@ -1,204 +0,0 @@
 const RECT: u32 = 0u;
 const TEXTURE: u32 = 1u;
 const GLYPH: u32 = 2u;
@group(0) @binding(0)
 var<uniform> window: WindowUniform;
@group(1) @binding(RECT)
 var<storage> rects: array<Rect>;
@group(1) @binding(TEXTURE)
 var<storage> textures: array<TextureInfo>;
@group(1) @binding(GLYPH)
 var<storage> glyphs: array<GlyphInfo>;
 struct Rect {
    color: u32,
    radius: f32,
    thickness: f32,
    inner_radius: f32,
 }
 struct TextureInfo {
    view_idx: u32,
    sampler_idx: u32,
 }
 struct GlyphInfo {
    uv_min: vec2<f32>,
    uv_max: vec2<f32>,
    view_idx: u32,
    sampler_idx: u32,
    color: u32,
    flags: u32,
 }
 struct Mask {
    x: UiSpan,
    y: UiSpan,
 }
 struct UiSpan {
    start: UiScalar,
    end: UiScalar,
 }
 struct UiScalar {
    rel: f32,
    abs: f32,
 }
 struct UiVec2 {
    rel: vec2<f32>,
    abs: vec2<f32>,
 }
@group(2) @binding(0)
 var views: binding_array<texture_2d<f32>>;
@group(2) @binding(1)
 var samplers: binding_array<sampler>;
@group(2) @binding(2)
 var<storage> masks: array<Mask>;
 struct WindowUniform {
    dim: vec2<f32>,
 };
 struct InstanceInput {
    @location(0) x_start: vec2<f32>,
    @location(1) x_end: vec2<f32>,
    @location(2) y_start: vec2<f32>,
    @location(3) y_end: vec2<f32>,
    @location(4) binding: u32,
    @location(5) idx: u32,
    @location(6) mask_idx: u32,
 }
 struct VertexOutput {
    @location(0) top_left: vec2<f32>,
    @location(1) bot_right: vec2<f32>,
    @location(2) uv: vec2<f32>,
    @location(3) binding: u32,
    @location(4) idx: u32,
    @location(5) mask_idx: u32,
    @builtin(position) clip_position: vec4<f32>,
 };
 struct Region {
    pos: vec2<f32>,
    uv: vec2<f32>,
    top_left: vec2<f32>,
    bot_right: vec2<f32>,
 }
@vertex
 fn vs_main(
    @builtin(vertex_index) vi: u32,
    in: InstanceInput,
 ) -> VertexOutput {
    var out: VertexOutput;
    let top_left_rel = vec2(in.x_start.x, in.y_start.x);
    let top_left_abs = vec2(in.x_start.y, in.y_start.y);
    let bot_right_rel = vec2(in.x_end.x, in.y_end.x);
    let bot_right_abs = vec2(in.x_end.y, in.y_end.y);
    let top_left = floor(top_left_rel * window.dim) + floor(top_left_abs);
    let bot_right = floor(bot_right_rel * window.dim) + floor(bot_right_abs);
    let size = bot_right - top_left;
    let uv = vec2<f32>(
        f32(vi % 2u),
        f32(vi / 2u)
    );
    let pos = (top_left + uv * size) / window.dim * 2.0 - 1.0;
    out.clip_position = vec4<f32>(pos.x, -pos.y, 0.0, 1.0);
    out.uv = uv;
    out.binding = in.binding;
    out.idx = in.idx;
    out.top_left = top_left;
    out.bot_right = bot_right;
    out.mask_idx = in.mask_idx;
    return out;
 }
@fragment
 fn fs_main(
    in: VertexOutput
 ) -> @location(0) vec4<f32> {
    let pos = in.clip_position.xy;
    let region = Region(pos, in.uv, in.top_left, in.bot_right);
    let i = in.idx;
    var color: vec4<f32>;
    switch in.binding {
        case RECT: {
            color = draw_rounded_rect(region, rects[i]);
        }
        case TEXTURE: {
            color = draw_texture(region, textures[i]);
        }
        case GLYPH: {
            color = draw_glyph(region, glyphs[i]);
        }
        default: {
            color = vec4(1.0, 0.0, 1.0, 1.0);
        }
    }
    if in.mask_idx != 4294967295u {
        let mask = masks[in.mask_idx];
        let tl = UiVec2(vec2(mask.x.start.rel, mask.y.start.rel), vec2(mask.x.start.abs, mask.y.start.abs));
        let br = UiVec2(vec2(mask.x.end.rel, mask.y.end.rel), vec2(mask.x.end.abs, mask.y.end.abs));
        let top_left = floor(tl.rel * window.dim) + floor(tl.abs);
        let bot_right = floor(br.rel * window.dim) + floor(br.abs);
        if pos.x < top_left.x || pos.x > bot_right.x || pos.y < top_left.y || pos.y > bot_right.y {
            color *= 0.0;
        }
    }
    return color;
 }
 // TODO: this seems really inefficient (per frag indexing)?
 fn draw_texture(region: Region, info: TextureInfo) -> vec4<f32> {
    return textureSample(views[info.view_idx], samplers[info.sampler_idx], region.uv);
 }
 fn draw_glyph(region: Region, g: GlyphInfo) -> vec4<f32> {
    let uv = mix(g.uv_min, g.uv_max, region.uv);
    let texel = textureSample(views[g.view_idx], samplers[g.sampler_idx], uv);
    if (g.flags & 1u) != 0u {
        return texel;
    }
    var color = unpack4x8unorm(g.color);
    color.a *= texel.a;
    return color;
 }
 fn draw_rounded_rect(region: Region, rect: Rect) -> vec4<f32> {
    var color = unpack4x8unorm(rect.color);
    let edge = 0.5;
    let size = region.bot_right - region.top_left;
    let corner = size / 2.0;
    let center = region.top_left + corner;
    let dist = distance_from_rect(region.pos, center, corner, rect.radius);
    color.a *= 1.0 - smoothstep(-min(edge, rect.radius), edge, dist);
    if rect.thickness > 0.0 {
        let dist2 = distance_from_rect(region.pos, center, corner - rect.thickness, rect.inner_radius);
        color.a *= smoothstep(-min(edge, rect.inner_radius), edge, dist2);
    }
    return color;
 }
 fn distance_from_rect(pixel_pos: vec2<f32>, rect_center: vec2<f32>, rect_corner: vec2<f32>, radius: f32) -> f32 {
    // vec from center to pixel
    let p = pixel_pos - rect_center;
    // vec from inner rect corner to pixel
    let q = abs(p) - (rect_corner - radius);
    return length(max(q, vec2(0.0))) - radius;
 }
@@ -0,0 +1,33 @@
 // Matches `GlyphEntry::IS_COLORED`.
 const COLORED: u32 = 1u;
 // The glyph atlas, whose array layers are its pages.
@group(2) @binding(0)
 var atlas: texture_2d_array<f32>;
@group(2) @binding(1)
 var samp: sampler;
 struct GlyphInfo {
    uv_min: vec2<f32>,
    uv_max: vec2<f32>,
    // Which layer of the atlas array this glyph's page is.
    layer: u32,
    color: u32,
    flags: u32,
 }
@group(1) @binding(0)
 var<storage> glyphs: array<GlyphInfo>;
@fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let g = glyphs[in.idx];
    let uv = mix(g.uv_min, g.uv_max, in.uv);
    let texel = textureSample(atlas, samp, uv, i32(g.layer));
    if (g.flags & COLORED) != 0u {
        return masked(in, texel);
    }
    var color = unpack4x8unorm(g.color);
    color.a *= texel.a;
    return masked(in, color);
 }
@@ -0,0 +1,96 @@
 // Prepended to every primitive's shader, which declares its own instance data
 // as `var<storage> <name>: array<T>` at group 1 binding 0, and an `fs_main`
 // shading one instance of it. What it samples, if anything, is bound at group
 // 2: the texture at binding 0 and the sampler at binding 1.
@group(0) @binding(0)
 var<uniform> window: WindowUniform;
@group(0) @binding(1)
 var<storage> masks: array<Mask>;
 struct WindowUniform {
    dim: vec2<f32>,
 };
 struct Mask {
    x: UiSpan,
    y: UiSpan,
 }
 struct UiSpan {
    start: UiScalar,
    end: UiScalar,
 }
 struct UiScalar {
    rel: f32,
    abs: f32,
 }
 struct InstanceInput {
    @location(0) x_start: vec2<f32>,
    @location(1) x_end: vec2<f32>,
    @location(2) y_start: vec2<f32>,
    @location(3) y_end: vec2<f32>,
    @location(4) mask_idx: u32,
 }
 struct VertexOutput {
    @location(0) top_left: vec2<f32>,
    @location(1) bot_right: vec2<f32>,
    @location(2) uv: vec2<f32>,
    @location(3) @interpolate(flat) mask_idx: u32,
    @location(4) @interpolate(flat) idx: u32,
    @builtin(position) clip_position: vec4<f32>,
 };
@vertex
 fn vs_main(
    @builtin(vertex_index) vi: u32,
    @builtin(instance_index) ii: u32,
    in: InstanceInput,
 ) -> VertexOutput {
    var out: VertexOutput;
    let top_left_rel = vec2(in.x_start.x, in.y_start.x);
    let top_left_abs = vec2(in.x_start.y, in.y_start.y);
    let bot_right_rel = vec2(in.x_end.x, in.y_end.x);
    let bot_right_abs = vec2(in.x_end.y, in.y_end.y);
    let top_left = floor(top_left_rel * window.dim) + floor(top_left_abs);
    let bot_right = floor(bot_right_rel * window.dim) + floor(bot_right_abs);
    let size = bot_right - top_left;
    let uv = vec2<f32>(
        f32(vi % 2u),
        f32(vi / 2u)
    );
    let pos = (top_left + uv * size) / window.dim * 2.0 - 1.0;
    out.clip_position = vec4<f32>(pos.x, -pos.y, 0.0, 1.0);
    out.uv = uv;
    out.top_left = top_left;
    out.bot_right = bot_right;
    out.mask_idx = in.mask_idx;
    out.idx = ii;
    return out;
 }
 fn masked(in: VertexOutput, color: vec4<f32>) -> vec4<f32> {
    if in.mask_idx == 4294967295u {
        return color;
    }
    let mask = masks[in.mask_idx];
    let tl = vec2(mask.x.start.rel, mask.y.start.rel);
    let tl_abs = vec2(mask.x.start.abs, mask.y.start.abs);
    let br = vec2(mask.x.end.rel, mask.y.end.rel);
    let br_abs = vec2(mask.x.end.abs, mask.y.end.abs);
    let top_left = floor(tl * window.dim) + floor(tl_abs);
    let bot_right = floor(br * window.dim) + floor(br_abs);
    let pos = in.clip_position.xy;
    if pos.x < top_left.x || pos.x > bot_right.x || pos.y < top_left.y || pos.y > bot_right.y {
        return color * 0.0;
    }
    return color;
 }
@@ -0,0 +1,39 @@
 struct Rect {
    color: u32,
    radius: f32,
    thickness: f32,
    inner_radius: f32,
 }
@group(1) @binding(0)
 var<storage> rects: array<Rect>;
@fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    let rect = rects[in.idx];
    var color = unpack4x8unorm(rect.color);
    let edge = 0.5;
    let size = in.bot_right - in.top_left;
    let corner = size / 2.0;
    let center = in.top_left + corner;
    let pos = in.clip_position.xy;
    let dist = distance_from_rect(pos, center, corner, rect.radius);
    color.a *= 1.0 - smoothstep(-min(edge, rect.radius), edge, dist);
    if rect.thickness > 0.0 {
        let dist2 = distance_from_rect(pos, center, corner - rect.thickness, rect.inner_radius);
        color.a *= smoothstep(-min(edge, rect.inner_radius), edge, dist2);
    }
    return masked(in, color);
 }
 fn distance_from_rect(pixel_pos: vec2<f32>, rect_center: vec2<f32>, rect_corner: vec2<f32>, radius: f32) -> f32 {
    // vec from center to pixel
    let p = pixel_pos - rect_center;
    // vec from inner rect corner to pixel
    let q = abs(p) - (rect_corner - radius);
    return length(max(q, vec2(0.0))) - radius;
 }
@@ -0,0 +1,10 @@
 // The image this instance draws, bound for it alone.
@group(2) @binding(0)
 var image: texture_2d<f32>;
@group(2) @binding(1)
 var samp: sampler;
@fragment
 fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
    return masked(in, textureSample(image, samp, in.uv));
 }
@@ -1,119 +1,119 @@
-use image::{DynamicImage, EncodableLayout, GenericImageView};
+use image::{DynamicImage, EncodableLayout, GenericImageView, RgbaImage};
 use wgpu::{util::DeviceExt, *};
-use crate::{PatchRect, TextureUpdate, Textures};
+use crate::{
    PatchRect, TextureUpdate, Textures, UiData,
    render::{
        TexturePrimitive,
        primitive::{ListDraw, PrimitiveRender},
    },
 };
 /// Draws standalone images, which it owns. Each is its own texture, so each
 /// instance binds its own and is a draw of its own.
 pub struct ImageRender {
    textures: GpuTextures,
    layout: BindGroupLayout,
    sampler: Sampler,
 }
 impl ImageRender {
    pub fn new(device: &Device, queue: &Queue) -> Self {
        Self {
            textures: GpuTextures::new(device, queue),
            layout: sampled_layout(device, TextureViewDimension::D2, "ui image"),
            sampler: default_sampler(device),
        }
    }
 }
 impl PrimitiveRender for ImageRender {
    fn layout(&self) -> Option<&BindGroupLayout> {
        Some(&self.layout)
    }
    fn update(&mut self, ui: &mut UiData) {
        self.textures
            .update(&mut ui.textures, &self.layout, &self.sampler);
    }
    fn instance_bindings(&self, list: &super::InstanceList, out: &mut Vec<u32>) {
        let slots = list
            .data()
            .chunks_exact(list.stride())
            .map(|data| bytemuck::pod_read_unaligned::<TexturePrimitive>(data).slot);
        out.extend(slots);
    }
    fn draw<'a>(&'a self, pass: &mut RenderPass<'a>, list: ListDraw<'a>) {
        for (i, &slot) in list.bindings.iter().enumerate() {
            let Some(image) = self.textures.group(slot) else {
                continue;
            };
            pass.set_bind_group(2, image, &[]);
            pass.draw(0..4, i as u32..i as u32 + 1);
        }
    }
 }
 /// The standalone images a ui draws, each its own texture and bind group --
 /// unlike the glyph atlas in `super::page`, which is one array they share.
 pub struct GpuTextures {
    device: Device,
    queue: Queue,
-    /// Parallel to `views`; patches require textures rather than views.
+    slots: Vec<Option<ImageGpu>>,
-    textures: Vec<Option<Texture>>,
+}
-    views: Vec<TextureView>,
+
-    view_count: usize,
+struct ImageGpu {
-    samplers: Vec<Sampler>,
+    /// Kept for `patch`, which needs the texture rather than the view.
-    null_view: TextureView,
+    texture: Texture,
-    no_views: Vec<TextureView>,
+    group: BindGroup,
 }
 impl GpuTextures {
-    pub fn update(&mut self, textures: &mut Textures) -> bool {
+    pub fn new(device: &Device, queue: &Queue) -> Self {
-        let mut bindings_changed = false;
+        Self {
            device: device.clone(),
            queue: queue.clone(),
            slots: Vec::new(),
        }
    }
    pub fn update(&mut self, textures: &mut Textures, layout: &BindGroupLayout, sampler: &Sampler) {
        for update in textures.updates() {
-            bindings_changed |= match update {
+            match update {
                TextureUpdate::Push(image) => {
-                    self.push(image);
+                    let image = self.create(image, layout, sampler);
-                    true
+                    self.slots.push(Some(image));
                }
                TextureUpdate::Set(i, image) => {
-                    self.set(i, image);
+                    let image = self.create(image, layout, sampler);
-                    true
+                    self.slots[i as usize] = Some(image);
                }
-                TextureUpdate::Patch(i, rect, image) => {
+                TextureUpdate::Patch(i, rect, image) => self.patch(i, rect, image),
-                    self.patch(i, rect, image);
+                TextureUpdate::PushFree => self.slots.push(None),
-                    false
+                TextureUpdate::SetFree => {}
                TextureUpdate::Free(i) => self.slots[i as usize] = None,
            }
                TextureUpdate::SetFree => {
                    self.view_count += 1;
                    true
        }
                TextureUpdate::Free(i) => {
                    self.free(i);
                    true
                }
                TextureUpdate::PushFree => {
                    self.push_free();
                    true
                }
            };
        }
        bindings_changed
    }
    fn set(&mut self, i: u32, image: &DynamicImage) {
        self.view_count += 1;
        let (texture, view) = self.create(image);
        self.textures[i as usize] = Some(texture);
        self.views[i as usize] = view;
    }
    fn free(&mut self, i: u32) {
        self.view_count -= 1;
        self.textures[i as usize] = None;
        self.views[i as usize] = self.null_view.clone();
    }
    fn push(&mut self, image: &DynamicImage) {
        self.view_count += 1;
        let (texture, view) = self.create(image);
        self.textures.push(Some(texture));
        self.views.push(view);
    }
    fn push_free(&mut self) {
        self.view_count += 1;
        self.textures.push(None);
        self.views.push(self.null_view.clone());
    }
-    fn patch(&mut self, i: u32, rect: PatchRect, image: &DynamicImage) {
+    pub fn group(&self, slot: u32) -> Option<&BindGroup> {
-        let Some(texture) = &self.textures[i as usize] else {
+        self.slots.get(slot as usize)?.as_ref().map(|i| &i.group)
            return;
        };
        if rect.width == 0 || rect.height == 0 {
            return;
        }
        // `write_texture` requires tightly packed rows, unlike the atlas image.
        let sub = image
            .view(rect.x, rect.y, rect.width, rect.height)
            .to_image();
        self.queue.write_texture(
            TexelCopyTextureInfo {
                texture,
                mip_level: 0,
                origin: Origin3d {
                    x: rect.x,
                    y: rect.y,
                    z: 0,
                },
                aspect: TextureAspect::All,
            },
            sub.as_bytes(),
            TexelCopyBufferLayout {
                offset: 0,
                bytes_per_row: Some(rect.width * 4),
                rows_per_image: Some(rect.height),
            },
            Extent3d {
                width: rect.width,
                height: rect.height,
                depth_or_array_layers: 1,
            },
        );
    }
-    fn create(&self, image: &DynamicImage) -> (Texture, TextureView) {
+    fn create(
-        let image = image.to_rgba8();
+        &self,
-        let (width, height) = image.dimensions();
+        image: &DynamicImage,
        layout: &BindGroupLayout,
        sampler: &Sampler,
    ) -> ImageGpu {
        let rgba = image.to_rgba8();
        let (width, height) = rgba.dimensions();
        let texture = self.device.create_texture_with_data(
            &self.queue,
            &TextureDescriptor {
-                label: None,
+                label: Some("image"),
                size: Extent3d {
                    width,
                    height,
@@ -127,63 +127,115 @@ impl GpuTextures {
                view_formats: &[],
            },
            wgt::TextureDataOrder::MipMajor,
-            image.as_bytes(),
+            rgba.as_bytes(),
        );
        let view = texture.create_view(&TextureViewDescriptor::default());
-        (texture, view)
+        let group = sampled_group(&self.device, layout, &view, sampler, "ui image");
        ImageGpu { texture, group }
    }
-    pub fn new(device: &Device, queue: &Queue) -> Self {
+    fn patch(&mut self, i: u32, rect: PatchRect, image: &DynamicImage) {
-        let null_view = null_texture_view(device);
+        let Some(Some(slot)) = self.slots.get(i as usize) else {
-        Self {
+            return;
-            device: device.clone(),
+        };
-            queue: queue.clone(),
+        let dst = TexelCopyTextureInfo {
-            textures: Vec::new(),
+            texture: &slot.texture,
-            views: Vec::new(),
+            mip_level: 0,
-            samplers: vec![default_sampler(device)],
+            origin: Origin3d {
-            no_views: vec![null_view.clone()],
+                x: rect.x,
-            null_view,
+                y: rect.y,
-            view_count: 0,
+                z: 0,
            },
            aspect: TextureAspect::All,
        };
        match image.as_rgba8() {
            Some(rgba) => write_region(&self.queue, dst, rgba, rect),
            // The texture is rgba8, so any other layout has to be converted --
            // and converting the rectangle is cheaper than the whole image.
            None => {
                let sub = image
                    .view(rect.x, rect.y, rect.width, rect.height)
                    .to_image();
                write_region(&self.queue, dst, &sub, PatchRect { x: 0, y: 0, ..rect });
            }
        }
    }
 }
-    pub fn views(&self) -> Vec<&TextureView> {
+pub fn write_region(queue: &Queue, dst: TexelCopyTextureInfo, src: &RgbaImage, rect: PatchRect) {
-        if self.views.is_empty() {
+    if rect.width == 0 || rect.height == 0 {
-            &self.no_views
+        return;
        } else {
            &self.views
    }
-        .iter()
+    let stride = src.width() * 4;
-        .by_ref()
+    queue.write_texture(
-        .collect()
+        dst,
-    }
+        src.as_bytes(),
-
+        TexelCopyBufferLayout {
-    pub fn samplers(&self) -> Vec<&Sampler> {
+            offset: (rect.y * stride + rect.x * 4) as u64,
-        self.samplers.iter().by_ref().collect()
+            bytes_per_row: Some(stride),
-    }
+            rows_per_image: Some(rect.height),
-
+        },
-    pub fn view_count(&self) -> usize {
+        Extent3d {
-        self.view_count
+            width: rect.width,
-    }
+            height: rect.height,
 }
 pub fn null_texture_view(device: &Device) -> TextureView {
    device
        .create_texture(&TextureDescriptor {
            label: Some("null"),
            size: Extent3d {
                width: 1,
                height: 1,
            depth_or_array_layers: 1,
        },
-            mip_level_count: 1,
+    );
-            sample_count: 1,
+}
-            dimension: TextureDimension::D2,
+
-            format: TextureFormat::Rgba8Unorm,
+/// What a primitive that samples binds: a texture, and the sampler that reads
-            usage: TextureUsages::TEXTURE_BINDING,
+/// it.
-            view_formats: &[],
+pub fn sampled_group(
    device: &Device,
    layout: &BindGroupLayout,
    view: &TextureView,
    sampler: &Sampler,
    label: &'static str,
 ) -> BindGroup {
    device.create_bind_group(&BindGroupDescriptor {
        layout,
        entries: &[
            BindGroupEntry {
                binding: 0,
                resource: BindingResource::TextureView(view),
            },
            BindGroupEntry {
                binding: 1,
                resource: BindingResource::Sampler(sampler),
            },
        ],
        label: Some(label),
    })
 }
 /// The layout for one of those. The dimension differs -- the atlas is an
 /// array of pages and an image is not -- and nothing else does.
 pub fn sampled_layout(
    device: &Device,
    dimension: TextureViewDimension,
    label: &'static str,
 ) -> BindGroupLayout {
    device.create_bind_group_layout(&BindGroupLayoutDescriptor {
        entries: &[
            BindGroupLayoutEntry {
                binding: 0,
                visibility: ShaderStages::FRAGMENT,
                ty: BindingType::Texture {
                    sample_type: TextureSampleType::Float { filterable: false },
                    view_dimension: dimension,
                    multisampled: false,
                },
                count: None,
            },
            BindGroupLayoutEntry {
                binding: 1,
                visibility: ShaderStages::FRAGMENT,
                ty: BindingType::Sampler(SamplerBindingType::NonFiltering),
                count: None,
            },
        ],
        label: Some(label),
    })
        .create_view(&TextureViewDescriptor::default())
 }
 pub fn default_sampler(device: &Device) -> Sampler {
@@ -21,17 +21,25 @@ impl<T: Pod> ArrBuf<T> {
            _pd: PhantomData,
        }
    }
-    pub fn update(&mut self, device: &Device, queue: &Queue, data: &[T]) {
+    /// Returns whether the `Buffer` was recreated, which stales any cached
-        if self.len != data.len() {
+    /// `BindGroup` holding it.
    pub fn update(&mut self, device: &Device, queue: &Queue, data: &[T]) -> bool {
        let resized = self.len != data.len();
        if resized {
            self.len = data.len();
            self.buffer =
                Self::init_buf(device, std::mem::size_of_val(data), self.usage, self.label);
        }
        queue.write_buffer(&self.buffer, 0, bytemuck::cast_slice(data));
        resized
    }
    pub fn len(&self) -> usize {
        self.len
    }
    fn init_buf(device: &Device, size: usize, usage: BufferUsages, label: &'static str) -> Buffer {
        let mut size = size as u64;
        if usage.contains(BufferUsages::STORAGE) {
            // A binding cannot be empty or under the layout's minimum.
            size = size.max(std::mem::size_of::<T>() as u64);
        }
        device.create_buffer(&BufferDescriptor {
@@ -41,8 +49,4 @@ impl<T: Pod> ArrBuf<T> {
            usage,
        })
    }
    #[allow(clippy::len_without_is_empty)]
    pub fn len(&self) -> usize {
        self.len
    }
 }
@@ -1,4 +1,6 @@
-use crate::{Mask, TextData, Textures, WeakWidget, WidgetId, Widgets, util::TrackedArena};
+use crate::{
    Mask, PrimitiveRegistry, TextData, Textures, WeakWidget, WidgetId, Widgets, util::TrackedArena,
 };
 mod active;
 mod cache;
@@ -7,13 +9,15 @@ mod render_state;
 mod size;
 pub use active::*;
-pub use painter::Painter;
+pub use painter::{Painter, PrimitiveLike};
 pub use render_state::*;
 pub use size::*;
 #[derive(Default)]
 pub struct UiData {
    pub widgets: Widgets,
    /// Every primitive this ui can draw.
    pub primitives: PrimitiveRegistry,
    pub textures: Textures,
    pub text: TextData,
    pub masks: TrackedArena<Mask, u32>,
@@ -1,7 +1,10 @@
 use crate::{
    Axis, Len, RenderedText, Size, SizeCtx, StrongWidget, TextAttrs, TextBuffer, TextData,
    TextureHandle, UiRegion, UiRenderState, UiRsc, UiScalar, UiVec2, Widget, WidgetId,
-    render::{GlyphPrimitive, Mask, MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst},
+    render::{
        GlyphPrimitive, Mask, MaskIdx, Primitive, PrimitiveHandle, PrimitiveInst, PrimitiveKind,
        TexturePrimitive,
    },
    util::Vec2,
 };
@@ -21,15 +24,26 @@ pub struct Painter<'a> {
 impl<'a> Painter<'a> {
    fn primitive_at<P: Primitive>(&mut self, primitive: P, region: UiRegion) {
        let kind = self.rsc.ui_mut().primitives.kind::<P>();
        self.write(kind, primitive, region);
    }
    /// Takes the kind, for a caller writing many of one primitive.
    fn write<P: Primitive>(&mut self, kind: PrimitiveKind<P>, primitive: P, region: UiRegion) {
        let h = self.state.layers.write(
            self.layer,
            PrimitiveInst {
                kind,
                id: self.id,
                primitive,
                region,
                mask_idx: self.mask,
            },
        );
        self.push_primitive(h);
    }
    fn push_primitive(&mut self, h: PrimitiveHandle) {
        if self.mask != MaskIdx::NONE {
            // TODO: I have no clue if this works at all :joy:
            self.rsc.ui_mut().masks.push_ref(self.mask);
@@ -38,11 +52,13 @@ impl<'a> Painter<'a> {
    }
    /// Writes a primitive to be rendered
-    pub fn primitive<P: Primitive>(&mut self, primitive: P) {
+    pub fn primitive(&mut self, primitive: impl PrimitiveLike) {
        let primitive = primitive.into_primitive(self);
        self.primitive_at(primitive, self.region)
    }
-    pub fn primitive_within<P: Primitive>(&mut self, primitive: P, region: UiRegion) {
+    pub fn primitive_within(&mut self, primitive: impl PrimitiveLike, region: UiRegion) {
        let primitive = primitive.into_primitive(self);
        self.primitive_at(primitive, region.within(&self.region));
    }
@@ -75,21 +91,6 @@ impl<'a> Painter<'a> {
        );
    }
    pub fn texture_within(&mut self, handle: &TextureHandle, region: UiRegion) {
        self.textures.push(handle.clone());
        self.primitive_at(handle.primitive(), region.within(&self.region));
    }
    pub fn texture(&mut self, handle: &TextureHandle) {
        self.textures.push(handle.clone());
        self.primitive(handle.primitive());
    }
    pub fn texture_at(&mut self, handle: &TextureHandle, region: UiRegion) {
        self.textures.push(handle.clone());
        self.primitive_at(handle.primitive(), region);
    }
    pub fn render_text(
        &mut self,
        buffer: &mut TextBuffer,
@@ -97,10 +98,12 @@ impl<'a> Painter<'a> {
        width: Option<f32>,
    ) -> RenderedText {
        let ui = self.rsc.ui_mut();
-        ui.text.render(buffer, attrs, width, &mut ui.textures)
+        ui.text.render(buffer, attrs, width)
    }
    // TODO: merge the text methods into the primitive ones.
    pub fn glyphs(&mut self, text: &RenderedText, origin: UiRegion) {
        let kind = self.rsc.ui_mut().primitives.kind::<GlyphPrimitive>();
        for glyph in text.glyphs.iter() {
            let mut region = origin;
            region.x.end = region.x.start;
@@ -108,12 +111,12 @@ impl<'a> Painter<'a> {
            let mut region = region.offset(UiVec2::abs(glyph.offset));
            region.x.end = region.x.start + UiScalar::abs(glyph.entry.width as f32);
            region.y.end = region.y.start + UiScalar::abs(glyph.entry.height as f32);
-            self.primitive_at(
+            self.write(
                kind,
                GlyphPrimitive {
                    uv_min: glyph.entry.uv_min,
                    uv_max: glyph.entry.uv_max,
-                    view_idx: glyph.entry.view_idx,
+                    layer: glyph.entry.layer,
                    sampler_idx: glyph.entry.sampler_idx,
                    color: text.color,
                    flags: glyph.entry.flags(),
                },
@@ -169,3 +172,28 @@ impl<'a> Painter<'a> {
        self.state.size_ctx(self.id, self.region.size(), self.rsc)
    }
 }
 /// What `Painter::primitive` takes: a primitive, or something that yields one
 /// and does whatever else drawing it needs.
 pub trait PrimitiveLike {
    type Primitive: Primitive;
    fn into_primitive(self, painter: &mut Painter) -> Self::Primitive;
 }
 impl<P: Primitive> PrimitiveLike for P {
    type Primitive = P;
    fn into_primitive(self, _: &mut Painter) -> P {
        self
    }
 }
 impl PrimitiveLike for &TextureHandle {
    type Primitive = TexturePrimitive;
    /// Retains a share of the handle, so the slot the primitive names cannot
    /// be freed and reused while it is still drawn.
    fn into_primitive(self, painter: &mut Painter) -> TexturePrimitive {
        painter.textures.push(self.clone());
        self.into()
    }
 }
@@ -1,13 +1,13 @@
 use crate::{
-    ActiveData, Axis, IdLike, MaskIdx, Painter, PixelRegion, PrimitiveLayers, SizeCtx,
+    ActiveData, Axis, DrawLayers, IdLike, MaskIdx, Painter, PixelRegion, SizeCtx, StrongWidget,
-    StrongWidget, UiRegion, UiRsc, UiVec2, WidgetId, Widgets,
+    UiRegion, UiRsc, UiVec2, WidgetId, Widgets,
    ui::cache::Cache,
    util::{HashMap, HashSet, Vec2, forget_ref},
 };
 pub struct UiRenderState {
    pub active: HashMap<WidgetId, ActiveData>,
-    pub layers: PrimitiveLayers,
+    pub layers: DrawLayers,
    pub(super) output_size: Vec2,
    pub cache: Cache,
@@ -243,14 +243,14 @@ impl UiRenderState {
    }
    pub fn debug_layers(&self) {
-        for ((idx, depth), primitives) in self.layers.iter_depth() {
+        for ((idx, depth), draws) in self.layers.iter_depth() {
            let indent = " ".repeat(depth * 2);
-            let len = primitives.instances().len();
+            let counts: Vec<String> = draws
-            print!("{indent}{idx}: {len} primitives");
+                .primitives()
-            if len >= 1 {
+                .iter()
-                print!(" ({})", primitives.instances()[0].binding);
+                .map(|l| l.as_ref().map_or(0, |l| l.instances().len()).to_string())
-            }
+                .collect();
-            println!();
+            println!("{indent}{idx}: [{}]", counts.join(", "));
        }
    }
@@ -308,7 +308,6 @@ impl UiRenderState {
            source,
            cache: &mut self.cache,
            text: &mut ui.text,
            textures: &mut ui.textures,
            widgets: &ui.widgets,
            outer,
            output_size: self.output_size,
@@ -1,11 +1,10 @@
 use crate::{
-    Axis, AxisT, IdLike, Len, RenderedText, Size, TextAttrs, TextBuffer, TextData, Textures,
+    Axis, AxisT, IdLike, Len, RenderedText, Size, TextAttrs, TextBuffer, TextData, UiVec2,
-    UiVec2, WidgetAxisFns, WidgetId, Widgets, XAxis, YAxis, ui::cache::Cache, util::Vec2,
+    WidgetAxisFns, WidgetId, Widgets, XAxis, YAxis, ui::cache::Cache, util::Vec2,
 };
 pub struct SizeCtx<'a> {
    pub text: &'a mut TextData,
    pub textures: &'a mut Textures,
    pub(super) source: WidgetId,
    pub(super) widgets: &'a Widgets,
    pub(super) cache: &'a mut Cache,
@@ -33,7 +32,6 @@ impl SizeCtx<'_> {
            .get_dyn_dynamic(id)
            .desired_len::<A>(&mut SizeCtx {
                text: self.text,
                textures: self.textures,
                source: self.source,
                widgets: self.widgets,
                cache: self.cache,
@@ -82,7 +80,7 @@ impl SizeCtx<'_> {
        attrs: &TextAttrs,
        width: Option<f32>,
    ) -> RenderedText {
-        self.text.render(buffer, attrs, width, self.textures)
+        self.text.render(buffer, attrs, width)
    }
    pub fn label(&self, id: WidgetId) -> &String {
@@ -212,10 +212,10 @@ impl DefaultAppState for Client {
        render: &mut UiRenderState,
    ) {
        let new = format!(
-            "widgets: {}\nactive: {}\nviews: {}",
+            "widgets: {}\nactive: {}\ntextures: {}",
            rsc.widgets().len(),
            render.active_widgets(),
-            self.ui_state.renderer.ui.view_count(),
+            rsc.ui().textures.count(),
        );
        if new != *rsc.widgets()[self.info].content {
            *rsc.widgets_mut()[self.info].content = new;
@@ -1,4 +1,4 @@
-use iris_core::{UiData, UiLimits, UiRenderNode, UiRenderState};
+use iris_core::{UiData, UiRenderNode, UiRenderState};
 use pollster::FutureExt;
 use std::sync::Arc;
 use wgpu::*;
@@ -22,7 +22,23 @@ impl UiRenderer {
    }
    pub fn draw(&mut self) {
-        let output = self.surface.get_current_texture().unwrap();
+        let output = match self.surface.get_current_texture() {
            CurrentSurfaceTexture::Success(texture) => texture,
            // Still drawable; the surface has just changed under us, and
            // reconfiguring is what the next frame wants rather than this one.
            CurrentSurfaceTexture::Suboptimal(texture) => {
                self.surface.configure(&self.device, &self.config);
                texture
            }
            CurrentSurfaceTexture::Outdated | CurrentSurfaceTexture::Lost => {
                self.surface.configure(&self.device, &self.config);
                return;
            }
            // Nothing to draw into this frame.
            CurrentSurfaceTexture::Timeout
            | CurrentSurfaceTexture::Occluded
            | CurrentSurfaceTexture::Validation => return,
        };
        let view = output
            .texture
            .create_view(&TextureViewDescriptor::default());
@@ -46,7 +62,7 @@ impl UiRenderer {
        self.queue.submit(std::iter::once(encoder.finish()));
        self.window.pre_present_notify();
-        output.present();
+        self.queue.present(output);
    }
    pub fn resize(&mut self, size: &PhysicalSize<u32>) {
@@ -65,9 +81,12 @@ impl UiRenderer {
    pub fn new(window: Arc<Window>) -> Self {
        let size = window.inner_size();
-        let instance = Instance::new(&InstanceDescriptor {
+        // The display handle is what GLES needs to present on Wayland, and it
        // has to be the one the surface is made from.
        let instance = Instance::new(InstanceDescriptor {
            backends: Backends::PRIMARY,
-            ..Default::default()
+            display: Some(Box::new(window.clone())),
            ..InstanceDescriptor::new_without_display_handle()
        });
        let surface = instance
@@ -79,22 +98,14 @@ impl UiRenderer {
                power_preference: PowerPreference::default(),
                compatible_surface: Some(&surface),
                force_fallback_adapter: false,
                apply_limit_buckets: false,
            })
            .block_on()
            .expect("Could not get adapter!");
        let ui_limits = UiLimits::default();
        let (device, queue) = adapter
            .request_device(&DeviceDescriptor {
                required_features: Features::TEXTURE_BINDING_ARRAY
                    | Features::PARTIALLY_BOUND_BINDING_ARRAY
                    | Features::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING,
                required_limits: Limits {
                    max_binding_array_elements_per_shader_stage: ui_limits
                        .max_binding_array_elements_per_shader_stage(),
                    max_binding_array_sampler_elements_per_shader_stage: ui_limits
                        .max_binding_array_sampler_elements_per_shader_stage(),
                    max_buffer_size: 1 << 30,
                    ..Default::default()
                },
@@ -114,6 +125,7 @@ impl UiRenderer {
        let config = SurfaceConfiguration {
            usage: TextureUsages::RENDER_ATTACHMENT,
            format: surface_format,
            color_space: SurfaceColorSpace::Auto,
            width: size.width,
            height: size.height,
            present_mode: PresentMode::AutoVsync,
@@ -126,7 +138,7 @@ impl UiRenderer {
        let encoder = Self::create_encoder(&device);
-        let ui = UiRenderNode::new(&device, &queue, &config, ui_limits);
+        let ui = UiRenderNode::new(&device, &config);
        Self {
            surface,
@@ -7,7 +7,7 @@ pub struct Image {
 impl Widget for Image {
    fn draw(&mut self, painter: &mut Painter) {
-        painter.texture(&self.handle);
+        painter.primitive(&self.handle);
    }
    fn desired_width(&mut self, _: &mut SizeCtx) -> Len {
@@ -0,0 +1,206 @@
 //! What one frame of `UiRenderNode::draw` costs on the CPU, against the number
 //! of layers it walks. Recording only: the pass is built and dropped without
 //! being submitted, so this is the loop's cost and not the GPU's.
 //!
 //!     cargo test --release --test draw_cost -- --ignored --nocapture
 //!
 //! **Read the instruction count, not the clock.** Wall time here swings by 2x
 //! between runs of one binary on this machine -- more under `cargo test` than
 //! run directly -- while instructions retired are stable to 0.1%:
 //!
 //!     perf stat -e instructions:u target/release/.../draw_cost-* --ignored
 //!
 //! Measured that way on 2026-09-13, drawing each primitive through its own
 //! `PrimitiveRender` rather than a match in the renderer costs **6
 //! instructions per list drawn**, which is 0.1% of a frame at both 256 and
 //! 1024 layers. Recording one list into the pass costs wgpu ~5,400.
 //!
 //! The instance is leaked on purpose. Dropping the last one makes the Vulkan
 //! loader unload Mesa's ICD, which faults when a thread that touched Vulkan
 //! exits -- and libtest runs every test on a spawned thread.
 use std::time::Instant;
 use iris::prelude::*;
 use iris_core::{
    GlyphPrimitive, MaskIdx, PrimitiveInst, RectPrimitive, TextureHandle, TexturePrimitive, UiData,
    UiRegion, UiRenderNode, UiRenderState,
 };
 use wgpu::{Color as GpuColor, *};
 const SIZE: u32 = 1024;
 const FRAMES: u32 = 200;
 /// Reported as the best of this many batches. The mean moves by 15% between
 /// runs on this machine, which is more than the thing being measured.
 const BATCHES: u32 = 8;
 fn gpu() -> Option<(Device, Queue)> {
    // Probed rather than assumed: this machine's Vulkan device comes and goes,
    // and GL is what is left when it is gone.
    let all = Instance::new(InstanceDescriptor::new_without_display_handle());
    let instance = match pollster::block_on(all.request_adapter(&RequestAdapterOptions::default()))
    {
        Ok(_) => all,
        Err(_) => Instance::new(InstanceDescriptor {
            backends: Backends::GL,
            ..InstanceDescriptor::new_without_display_handle()
        }),
    };
    // Leaked rather than dropped: see the note at the top of the file.
    let instance: &'static Instance = Box::leak(Box::new(instance));
    let adapter =
        pollster::block_on(instance.request_adapter(&RequestAdapterOptions::default())).ok()?;
    println!("adapter: {:?}", adapter.get_info());
    pollster::block_on(adapter.request_device(&DeviceDescriptor::default())).ok()
 }
 fn config(format: TextureFormat) -> SurfaceConfiguration {
    SurfaceConfiguration {
        usage: TextureUsages::RENDER_ATTACHMENT,
        format,
        color_space: SurfaceColorSpace::Auto,
        width: SIZE,
        height: SIZE,
        present_mode: PresentMode::Fifo,
        desired_maximum_frame_latency: 2,
        alpha_mode: CompositeAlphaMode::Auto,
        view_formats: vec![],
    }
 }
 /// Every layer draws all three primitives, so the renderer takes a different
 /// path for each list it walks -- which is the case a single-primitive layer
 /// would never exercise. Images are bound per instance, so there are few.
 fn fill(
    ui: &mut UiData,
    render: &mut UiRenderState,
    layers: usize,
    per_layer: usize,
 ) -> Vec<TextureHandle> {
    let rect = ui.primitives.kind::<RectPrimitive>();
    let glyph = ui.primitives.kind::<GlyphPrimitive>();
    let texture = ui.primitives.kind::<TexturePrimitive>();
    let id = ui.widgets.add_strong(Rect::new(UiColor::WHITE)).id();
    let handles: Vec<_> = (0..4)
        .map(|_| ui.textures.add(image::RgbaImage::new(4, 4)))
        .collect();
    let mut layer = 0;
    for _ in 0..layers {
        for _ in 0..per_layer {
            render.layers.write(
                layer,
                PrimitiveInst {
                    kind: rect,
                    id,
                    primitive: RectPrimitive::color(UiColor::WHITE),
                    region: UiRegion::FULL,
                    mask_idx: MaskIdx::NONE,
                },
            );
            render.layers.write(
                layer,
                PrimitiveInst {
                    kind: glyph,
                    id,
                    primitive: GlyphPrimitive {
                        uv_min: vec2(0.0, 0.0),
                        uv_max: vec2(1.0, 1.0),
                        layer: 0,
                        color: UiColor::WHITE,
                        flags: 0,
                    },
                    region: UiRegion::FULL,
                    mask_idx: MaskIdx::NONE,
                },
            );
        }
        for h in &handles[..2] {
            render.layers.write(
                layer,
                PrimitiveInst {
                    kind: texture,
                    id,
                    primitive: TexturePrimitive::from(h),
                    region: UiRegion::FULL,
                    mask_idx: MaskIdx::NONE,
                },
            );
        }
        layer = render.layers.next(layer);
    }
    handles
 }
 fn frame_cost(device: &Device, queue: &Queue, layers: usize, per_layer: usize) -> f64 {
    let format = TextureFormat::Bgra8Unorm;
    let mut node = UiRenderNode::new(device, &config(format));
    let mut ui = UiData::default();
    let mut render = UiRenderState::new();
    let _handles = fill(&mut ui, &mut render, layers, per_layer);
    node.update(device, queue, &mut ui, &mut render);
    let target = device.create_texture(&TextureDescriptor {
        label: Some("draw cost"),
        size: Extent3d {
            width: SIZE,
            height: SIZE,
            depth_or_array_layers: 1,
        },
        mip_level_count: 1,
        sample_count: 1,
        dimension: TextureDimension::D2,
        format,
        usage: TextureUsages::RENDER_ATTACHMENT,
        view_formats: &[],
    });
    let view = target.create_view(&TextureViewDescriptor::default());
    let record = |frames: u32| {
        let start = Instant::now();
        for _ in 0..frames {
            let mut encoder = device.create_command_encoder(&CommandEncoderDescriptor::default());
            {
                let pass = &mut encoder.begin_render_pass(&RenderPassDescriptor {
                    color_attachments: &[Some(RenderPassColorAttachment {
                        view: &view,
                        resolve_target: None,
                        ops: Operations {
                            load: LoadOp::Clear(GpuColor::BLACK),
                            store: StoreOp::Store,
                        },
                        depth_slice: None,
                    })],
                    ..Default::default()
                });
                node.draw(pass);
            }
            drop(encoder.finish());
        }
        start.elapsed().as_secs_f64() / frames as f64
    };
    record(FRAMES / 4);
    (0..BATCHES)
        .map(|_| record(FRAMES))
        .fold(f64::MAX, f64::min)
 }
 #[test]
 #[ignore = "measurement, not a check"]
 fn draw_cost_by_layer_count() {
    let Some((device, queue)) = gpu() else {
        panic!("no wgpu device; see the this-machine-graphics notes");
    };
    println!(
        "layers, each 8 rects + 8 glyphs + 2 images: us/frame (us per layer), best of {BATCHES}"
    );
    let base = frame_cost(&device, &queue, 1, 8) * 1e6;
    for layers in [8, 64, 256, 1024] {
        let per_frame = frame_cost(&device, &queue, layers, 8) * 1e6;
        // Net of the empty pass, which is the same in any version of this.
        println!(
            "{layers:>5}: {per_frame:8.1} us ({:.3} us)",
            (per_frame - base).max(0.0) / layers as f64
        );
    }
 }