From 3cb18ac5c28fc8f38418e18168cc472890943136 Mon Sep 17 00:00:00 2001 From: iris <2+iris@noreply.localhost> Date: Sun, 6 Sep 2026 19:41:40 -0400 Subject: [PATCH] iris: a one-layer glyph atlas is a GL_TEXTURE_2D, so every glyph drew as a box The emulator was blamed for two days for what is iris's own defect on any GL adapter. `GpuTextures::new` created the atlas `texture_2d_array` with one layer; wgpu-hal picks the GL target from the descriptor alone (`gles::Texture::get_info_from_desc`, `(false, 1) => TEXTURE_2D`), so the shader's `sampler2DArray` was handed a `GL_TEXTURE_2D`, the unit was incomplete, every `textureSample` returned (0,0,0,1), and `draw_glyph`'s `color.a *= texel.a` painted the whole glyph quad. `MIN_ARRAY_LAYERS = 2`, with the account at `create_array_texture` and a `debug_assert!` there. Vulkan -- the phone's build and the desktop's default backend -- was never affected. `force-gles` now switches the desktop backend too, so the GLES path is reproducible on a machine with a real GPU in seconds rather than only through an APK: that is how this was found, with two shader probes showing the sample was exactly (0,0,0,1). --- docs/IRIS_TODO.md | 25 ++++++++------- docs/RUST.md | 55 +++++++++++++++++++++++++++++++++ iris/Cargo.toml | 6 +++- iris/core/src/render/texture.rs | 25 ++++++++++++++- iris/src/default/render.rs | 11 ++++++- 5 files changed, 108 insertions(+), 14 deletions(-) diff --git a/docs/IRIS_TODO.md b/docs/IRIS_TODO.md index 366e429..da62fa6 100644 --- a/docs/IRIS_TODO.md +++ b/docs/IRIS_TODO.md @@ -609,17 +609,20 @@ agent ticks it here with the evidence. format rather than the palette -- but it makes the desktop build useless as a colour reference, which is exactly what P1a needed it for when the emulator could not draw glyphs. -- [ ] **The emulator cannot draw iris's glyphs.** Under `-gpu host` with - Vulkan disabled (Mesa 26.2.2 / virgl -- what `emu` does on this - machine) every character renders as a solid filled box: the atlas - sample's alpha reads 1, which is what an incomplete GL texture returns - (0,0,0,1). Not new (`20303e0` does it too) and not the platform's - (Compose draws text perfectly on the same AVD in the same minute). - Enabling host Vulkan still dies at boot in gfxstream, and - `EMU_GPU=software` gives SwiftShader Vulkan on which iris **SIGSEGVs - in `surface_changed`**. Either of the last two would restore - appearance testing on Android; today it has to be done on the desktop - backend or on Iris's phone. +- [x] **Every glyph was a solid box on the GLES backend -- iris's bug, + not the emulator's.** Fixed 2026-09-06. The atlas is one + `texture_2d_array` and `GpuTextures::new` created it with **one + layer**; wgpu-hal picks the GL target from the descriptor + (`(false, 1) => TEXTURE_2D`), so under GLES that array was a + `GL_TEXTURE_2D` bound to the shader's `sampler2DArray`, the unit was + incomplete, every `textureSample` returned (0,0,0,1), and + `draw_glyph`'s `color.a *= texel.a` filled the quad. `MIN_ARRAY_LAYERS + = 2` in `iris/core/src/render/texture.rs`, with a `debug_assert!` at + `create_array_texture`. Vulkan (the phone, the desktop's default + backend) was never affected. Reproduce the class in seconds without an + emulator: `iris`'s `force-gles` feature now switches the **desktop** + backend too -- `./run-headless.sh transcript --shot /tmp/x.png -- -p + transcript-ui --features iris/force-gles`. ## Build (for the port) diff --git a/docs/RUST.md b/docs/RUST.md index be2062c..ea46277 100644 --- a/docs/RUST.md +++ b/docs/RUST.md @@ -5600,6 +5600,61 @@ device. transcript-ui -p desktop-app -p tabs-ui --all-targets` warning-free; `cargo test` 85 (iris, +4) + 13 (iris-core) + 31 (transcript-ui, +11) + 123 (client-core). + **2026-09-06, after P1a: "the emulator cannot draw iris's glyphs" + was iris's bug, not the emulator's.** The finding recorded in the + box above -- that every glyph is a solid filled box under `-gpu + host` GLES and that this is what an incomplete GL texture returns + -- had the mechanism right and the attribution wrong. It is a real + defect on **any** adapter that is GL rather than Vulkan. + - **Reproduced off the emulator entirely**, which is what made it + cheap: `default/render.rs` now honours the same `force-gles` + feature `android/render.rs` did, so + `./run-headless.sh transcript --shot /tmp/x.png -- -p + transcript-ui --features iris/force-gles` draws the boxes on this + machine's own GPU in seconds. Two shader probes then said what + the sample was: `return vec4(texel.rgb, 1.0)` drew black boxes and + `return vec4(texel.a, texel.a, texel.a, 1.0)` drew white ones, so + the atlas sample was exactly (0, 0, 0, 1) -- GL's answer for an + **incomplete texture unit**, and not the null texture (which is + zeroed, alpha 0). + - **Root cause: the glyph atlas array was created with one layer.** + `GpuTextures::new` started `array_capacity` at 1 and `grow_array` + only doubles once a page needs a layer past it, so the ordinary + case -- one atlas page -- is a one-layer array. wgpu-hal picks the + GL texture target from the descriptor alone + (`gles::Texture::get_info_from_desc`: `(false, 1) => TEXTURE_2D`), + so that array is created as a `GL_TEXTURE_2D` and then bound to + the shader's `sampler2DArray`. wgpu has a name for this + (`log_failing_target_heuristics`, its issues #1614/#1574); the + result is an incomplete unit, `texel.a == 1`, and `draw_glyph`'s + `color.a *= texel.a` paints the whole glyph quad. + - **Fix**: `MIN_ARRAY_LAYERS = 2` in + `iris/core/src/render/texture.rs` -- the array is never created + with fewer, with the account at `create_array_texture` and a + `debug_assert!` there so a future capacity arithmetic change fails + at the mistake rather than as boxes on a screen. Cost: one page of + texture memory, which the next atlas page uses anyway. + - **Not a regression from `3e72a4e..20303e0`, and the bisect was not + run.** The defect is a function of the layer count, not of any + commit in that range: it has been there since the atlas became a + `texture_2d_array` (TEXTURES.md, 2026-09-04) and it reproduces at + HEAD and disappears at HEAD with the one-line capacity change. The + claimed "visible text at `3e72a4e`" is a misreading of its own + evidence -- `/tmp/final-typing.png`, the screenshot that entry + cites, is boxes; what the agent read was the `iris text render: + chars=5 glyphs=5` log line, which reports what **parley shaped**, + not what reached the screen. The earlier genuinely-good emulator + shots (`/tmp/after3.png`, 2026-09-05 19:56) predate the APK being + built with `force-gles` at all, so they were the Vulkan path. + - **The phone build is not affected and does not need withdrawing.** + `android-app/build-apk.sh`'s default features are deliberately + without `force-gles` (`d73db97`'s comment), so a phone build takes + `Backends::PRIMARY` -> Vulkan, where a one-layer array is an + ordinary one-layer array and glyphs draw correctly -- which is + also what Iris's phone reports have shown all along. The fix + matters for any device that falls back to GLES, which is why it is + not just an emulator convenience. + - [ ] **P1b — tool-call cards and grouping.** `ToolRows.kt`/ `ToolInput.kt`'s cards: a collapsed row per call with name and a one-line summary, expand to input and output, runs of diff --git a/iris/Cargo.toml b/iris/Cargo.toml index 061cc10..40e9c6f 100644 --- a/iris/Cargo.toml +++ b/iris/Cargo.toml @@ -66,7 +66,11 @@ send_wrapper = "0.6.0" # default) or virgl's GLES path, without a second env-var plumbing path that # nothing on this machine can hand to an already-launched Android process # (there is no `am start` environment and no system-property reader here to -# add one). Android-only; `android/render.rs` is the only reader. +# add one). Read by `android/render.rs` and, so the GLES path can be +# reproduced on a machine with a real GPU rather than only in the emulator, +# by `default/render.rs`: +# ./run-headless.sh transcript --shot /tmp/x.png -- -p transcript-ui \ +# --features iris/force-gles force-gles = [] [dev-dependencies] diff --git a/iris/core/src/render/texture.rs b/iris/core/src/render/texture.rs index 03fe4dd..9fac2e4 100644 --- a/iris/core/src/render/texture.rs +++ b/iris/core/src/render/texture.rs @@ -5,6 +5,10 @@ use crate::{PatchRect, TextureKind, TextureUpdate, Textures}; use super::atlas::PAGE; +/// The fewest layers the glyph atlas array is ever created with. Two, not +/// one, for the GLES reason written on `create_array_texture`. +const MIN_ARRAY_LAYERS: u32 = 2; + /// What one texture slot is, GPU-side. Parallel to `Textures`' own slot /// numbering (`TextureKind`'s `Image`/`Page`), so a slot's index means the /// same thing on both sides without a second map to keep in sync. @@ -360,7 +364,26 @@ impl GpuTextures { }) } + /// The atlas is sampled as a `texture_2d_array`, and **a one-layer + /// array is not one on the GLES backend**: wgpu-hal picks the GL + /// texture target from the descriptor alone + /// (`gles::Texture::get_info_from_desc`, `(false, 1) => TEXTURE_2D`), + /// so a capacity of 1 creates a `GL_TEXTURE_2D` and binds it to the + /// shader's `sampler2DArray`. GL then treats that unit as incomplete + /// and every `textureSample` returns (0, 0, 0, 1) -- which, through + /// `draw_glyph`'s `color.a *= texel.a`, draws every glyph as a solid + /// filled box. That was iris's appearance on the emulator's GLES for + /// two days (RUST.md, "the emulator cannot draw iris's glyphs"), and + /// it is a real defect on any device whose adapter is GL rather than + /// Vulkan, not an emulator artifact. So the array never has fewer than + /// `MIN_ARRAY_LAYERS` layers; the second layer costs one page of + /// texture memory and is used by the next atlas page anyway. fn create_array_texture(device: &Device, capacity: u32) -> Texture { + debug_assert!( + capacity >= MIN_ARRAY_LAYERS, + "glyph atlas array asked for {capacity} layers; fewer than {MIN_ARRAY_LAYERS} is a \ + GL_TEXTURE_2D on the GLES backend and draws every glyph as a box" + ); device.create_texture(&TextureDescriptor { label: Some("glyph atlas array"), size: Extent3d { @@ -382,7 +405,7 @@ impl GpuTextures { pub fn new(device: &Device, queue: &Queue) -> Self { let sampler = default_sampler(device); let null_view = null_texture_view(device); - let array_capacity = 1; + let array_capacity = MIN_ARRAY_LAYERS; let array_texture = Self::create_array_texture(device, array_capacity); let array_view = array_texture.create_view(&TextureViewDescriptor { dimension: Some(TextureViewDimension::D2Array), diff --git a/iris/src/default/render.rs b/iris/src/default/render.rs index 2306da1..d0cc245 100644 --- a/iris/src/default/render.rs +++ b/iris/src/default/render.rs @@ -85,7 +85,16 @@ impl UiRenderer { let size = window.inner_size(); let instance = Instance::new(&InstanceDescriptor { - backends: Backends::PRIMARY, + // `force-gles` on the desktop too, not just on Android: the + // GLES backend has behaviour of its own (a one-layer array + // texture is a `GL_TEXTURE_2D` -- see + // `GpuTextures::create_array_texture`), and a machine with a + // real GPU is where that is cheap to reproduce and screenshot. + backends: if cfg!(feature = "force-gles") { + Backends::GL + } else { + Backends::PRIMARY + }, ..Default::default() });