iris: a phone-shaped desktop window, driven by the same touch recordings

Layer 2 of docs/RUST.md's "Three test layers":

    ./run-headless.sh phone --phone --shot /tmp/p.png -- -p transcript-fixture

opens `transcript-fixture`'s screen -- the same fixture and the same
fold the headless tests and the Android bench use -- in a window at the
phone's own 1080x2424 and `content_scale` 2.55, and screenshots it. 15
seconds, warm. `--replay FILE` drives one of the `.touch` recordings
into it and writes `<shot>-before.png` too, so "the list moved" is two
pictures: the flick carries it back about seven turns of the fixture.

Two things this needed.

**The desktop backend now lays out in physical pixels with a density,
exactly as Android does** (`default::content_scale`, overridable with
`IRIS_SCALE`, which is how `--phone` hands it the phone's). It used to
divide winit's coordinates into a separate "logical" space, which left
`UiRenderState::resize` (physical, from `WindowEvent::Resized`) and the
window uniform (logical) disagreeing on any display whose scale factor
is not 1.0, and rasterised glyphs at one resolution to show them at
another. At 1.0 -- every display here -- the numbers are unchanged, and
the `tabs` screenshot is identical.

**`rig-input`'s `replay-touch`** puts a gesture on screen. This
machine's compositor has no pointer to move: sway runs on the headless
backend with no input devices, so `swaymsg seat - cursor press` reports
success and `swaymsg -t get_seats` shows `capabilities: 0`. wlroots 0.19
dropped `WLR_HEADLESS_INPUTS` and ydotool's uinput device would be
ignored by a compositor not reading libinput, so the virtual-pointer
protocol is what is left. It parses the *same* `TouchScript` the
harness does, so one recording drives both layers.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

iris/Cargo.lock

@@ -965,9 +965,9 @@ dependencies = [
 
 [[package]]
 name = "dlib"
-version = "0.5.2"
+version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "330c60081dcc4c72131f8eb70510f1ac07223e5d4163db481a04a0befcffa412"
+checksum = "ab8ecd87370524b461f8557c119c405552c396ed91fc0a8eec68679eab26f94a"
 dependencies = [
  "libloading",
 ]
@@ -2875,9 +2875,9 @@ checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
 
 [[package]]
 name = "quick-xml"
-version = "0.38.4"
+version = "0.41.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b66c2058c55a409d601666cffe35f04333cf1013010882cec174a7467cd4e21c"
+checksum = "e660451e55124f798a69a5af3f49ccfbefbd41910eefd25caf2393e1f3473ec1"
 dependencies = [
  "memchr",
 ]
@@ -3058,6 +3058,15 @@ version = "0.8.52"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0c6a884d2998352bb4daf0183589aec883f16a6da1f4dde84d8e2e9a5409a1ce"
 
+[[package]]
+name = "rig-input"
+version = "0.1.0"
+dependencies = [
+ "iris",
+ "wayland-client",
+ "wayland-protocols-wlr",
+]
+
 [[package]]
 name = "ring"
 version = "0.17.14"
@@ -3906,9 +3915,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-backend"
-version = "0.3.12"
+version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fee64194ccd96bf648f42a65a7e589547096dfa702f7cadef84347b66ad164f9"
+checksum = "38a91b4eaddff87b1cd1074985e3713da4af2c49742d1b356b2c01670a67a078"
 dependencies = [
  "cc",
  "downcast-rs",
@@ -3920,9 +3929,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-client"
-version = "0.31.12"
+version = "0.31.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b8e6faa537fbb6c186cb9f1d41f2f811a4120d1b57ec61f50da451a0c5122bec"
+checksum = "e3c36a0f861ad76d0901f2800b46321410d9f73f2ea88aac0650d86c32688073"
 dependencies = [
  "bitflags 2.10.0",
  "rustix 1.1.3",
@@ -3954,9 +3963,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-protocols"
-version = "0.32.10"
+version = "0.32.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "baeda9ffbcfc8cd6ddaade385eaf2393bd2115a69523c735f12242353c3df4f3"
+checksum = "23d0c813de3daa2ed6520af85a3bd49b0e722a3078506899aa9686fea58dc4b6"
 dependencies = [
  "bitflags 2.10.0",
  "wayland-backend",
@@ -3979,9 +3988,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-protocols-wlr"
-version = "0.3.10"
+version = "0.3.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e9597cdf02cf0c34cd5823786dce6b5ae8598f05c2daf5621b6e178d4f7345f3"
+checksum = "eb04e52f7836d7c7976c78ca0250d61e33873c34156a2a1fc9474828ec268234"
 dependencies = [
  "bitflags 2.10.0",
  "wayland-backend",
@@ -3992,9 +4001,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-scanner"
-version = "0.31.8"
+version = "0.31.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5423e94b6a63e68e439803a3e153a9252d5ead12fd853334e2ad33997e3889e3"
+checksum = "338e30461b3a2b67d70eb30a6d89f8e0c93a833e07d2ae89085cd070c4a00ac0"
 dependencies = [
  "proc-macro2",
  "quick-xml",
@@ -4003,9 +4012,9 @@ dependencies = [
 
 [[package]]
 name = "wayland-sys"
-version = "0.31.8"
+version = "0.31.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e6dbfc3ac5ef974c92a2235805cc0114033018ae1290a72e474aa8b28cbbdfd"
+checksum = "d8eab23fefc9e41f8e841df4a9c707e8a8c4ed26e944ef69297184de2785e3be"
 dependencies = [
  "dlib",
  "log",

iris/Cargo.toml

@@ -89,7 +89,15 @@ name = "message_list"
 harness = false
 
 [workspace]
-members = ["core", "macro", "tabs-ui", "transcript-ui", "transcript-fixture", "desktop-app"]
+members = [
+    "core",
+    "macro",
+    "tabs-ui",
+    "transcript-ui",
+    "transcript-fixture",
+    "rig-input",
+    "desktop-app",
+]
 # android-app pulls in android-view, which needs the NDK sysroot to link
 # -- excluded so `cargo build --workspace --all-targets` on the host stays
 # buildable. Cross-compile it from its own directory (its own single-crate

iris/rig-input/Cargo.toml

@@ -0,0 +1,32 @@
+[package]
+name = "rig-input"
+version.workspace = true
+edition.workspace = true
+
+# Layer 2's input half (docs/RUST.md's "Three test layers"): replays one
+# of the `.touch` files the headless tests use into whatever window is
+# under a Wayland compositor, so the *same recording* drives the
+# assertion layer and the layer a person looks at.
+#
+# It exists because this machine's compositor has no pointer to move.
+# `run-headless.sh` starts sway on the headless backend with no input
+# devices at all (`WLR_LIBINPUT_NO_DEVICES=1`, `LIBSEAT_BACKEND=noop`),
+# so `swaymsg seat - cursor press` reports success and nothing reaches
+# the client -- `swaymsg -t get_seats` shows `capabilities: 0`. wlroots
+# 0.19 dropped `WLR_HEADLESS_INPUTS`, and ydotool's uinput device would
+# be ignored by a compositor that is not reading libinput. The
+# virtual-pointer protocol is what is left, and it is a client protocol,
+# so it needs no devices and no root.
+
+# Named for what it does rather than for the crate, since the crate may
+# grow a keyboard replay beside it.
+[[bin]]
+name = "replay-touch"
+path = "src/main.rs"
+
+[dependencies]
+# `TouchScript` -- the same parser the harness uses, so a file that
+# replays here and one that replays headless can never disagree.
+iris = { path = ".." }
+wayland-client = "0.31.15"
+wayland-protocols-wlr = { version = "0.3.12", features = ["client"] }

iris/rig-input/src/main.rs

@@ -0,0 +1,164 @@
+//! Replays a `.touch` file into the compositor as a left-button drag --
+//! see this crate's `Cargo.toml` for why it exists rather than
+//! `swaymsg seat - cursor`.
+//!
+//!     WAYLAND_DISPLAY=… replay-touch WIDTH HEIGHT FILE
+//!
+//! `WIDTH`/`HEIGHT` are the output's own size, because the virtual
+//! pointer protocol positions absolutely against an extent rather than
+//! in pixels; passing the output size makes a script's coordinates mean
+//! the same pixels they mean in the headless tests.
+//!
+//! Replayed in real time (the sleeps between samples are the gaps in the
+//! file), because winit has no timestamp on a pointer event and dates
+//! each one when it arrives -- so a 20ms flick has to actually take
+//! 20ms here, unlike layer 1 where the sample carries its own time.
+
+use iris::harness::{TouchAction, TouchScript};
+use std::time::Duration;
+use wayland_client::protocol::wl_pointer::ButtonState;
+use wayland_client::protocol::{wl_registry, wl_seat};
+use wayland_client::{Connection, Dispatch, QueueHandle, delegate_noop};
+use wayland_protocols_wlr::virtual_pointer::v1::client::{
+    zwlr_virtual_pointer_manager_v1::ZwlrVirtualPointerManagerV1,
+    zwlr_virtual_pointer_v1::ZwlrVirtualPointerV1,
+};
+
+/// `linux/input-event-codes.h`. The protocol takes the kernel's own
+/// button code, not a wayland enum.
+const BTN_LEFT: u32 = 0x110;
+
+/// How long the pointer sits at the gesture's first position before the
+/// script starts -- see the comment at the pre-step in `main`.
+const SETTLE: Duration = Duration::from_millis(200);
+
+#[derive(Default)]
+struct Globals {
+    seat: Option<wl_seat::WlSeat>,
+    manager: Option<ZwlrVirtualPointerManagerV1>,
+}
+
+impl Dispatch<wl_registry::WlRegistry, ()> for Globals {
+    fn event(
+        state: &mut Self,
+        registry: &wl_registry::WlRegistry,
+        event: wl_registry::Event,
+        _: &(),
+        _: &Connection,
+        qh: &QueueHandle<Self>,
+    ) {
+        let wl_registry::Event::Global {
+            name,
+            interface,
+            version,
+        } = event
+        else {
+            return;
+        };
+        match interface.as_str() {
+            "wl_seat" => {
+                state.seat = Some(registry.bind(name, version.min(7), qh, ()));
+            }
+            "zwlr_virtual_pointer_manager_v1" => {
+                state.manager = Some(registry.bind(name, version.min(2), qh, ()));
+            }
+            _ => {}
+        }
+    }
+}
+
+delegate_noop!(Globals: ignore wl_seat::WlSeat);
+delegate_noop!(Globals: ZwlrVirtualPointerManagerV1);
+delegate_noop!(Globals: ZwlrVirtualPointerV1);
+
+fn main() {
+    let args: Vec<String> = std::env::args().skip(1).collect();
+    let [width, height, path] = args.as_slice() else {
+        eprintln!("usage: replay-touch WIDTH HEIGHT FILE");
+        std::process::exit(2);
+    };
+    let (width, height) = (parse(width, "WIDTH"), parse(height, "HEIGHT"));
+    let text = std::fs::read_to_string(path)
+        .unwrap_or_else(|e| fail(&format!("could not read {path}: {e}")));
+    let script = TouchScript::parse(&text).unwrap_or_else(|e| fail(&e));
+
+    let conn = Connection::connect_to_env().unwrap_or_else(|e| {
+        fail(&format!(
+            "no wayland display ({e}); is WAYLAND_DISPLAY set?"
+        ))
+    });
+    let mut queue = conn.new_event_queue();
+    let qh = queue.handle();
+    let display = conn.display();
+    display.get_registry(&qh, ());
+    let mut globals = Globals::default();
+    queue
+        .roundtrip(&mut globals)
+        .unwrap_or_else(|e| fail(&format!("wayland roundtrip failed: {e}")));
+
+    let manager = globals.manager.as_ref().unwrap_or_else(|| {
+        fail(
+            "this compositor does not offer zwlr_virtual_pointer_manager_v1, so a pointer cannot \
+             be synthesised; sway and every wlroots compositor do",
+        )
+    });
+    let pointer = manager.create_virtual_pointer(globals.seat.as_ref(), &qh, ());
+
+    // Put the pointer where the gesture starts and let the compositor
+    // settle before anything is pressed. Without this the press is
+    // dropped: sway has just learned about this pointer, and a button
+    // sent in the same breath as the motion that first puts it over a
+    // window arrives before there is a focused surface to send it to --
+    // winit sees `CursorEntered`, the moves and the *release*, never the
+    // press, so the gesture reads as a hover and nothing scrolls. Found
+    // by printing winit's own events; the settle is what fixed it.
+    if let Some(first) = script.samples.first() {
+        pointer.motion_absolute(0, first.pos.x as u32, first.pos.y as u32, width, height);
+        pointer.frame();
+        conn.flush()
+            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
+        std::thread::sleep(SETTLE);
+    }
+
+    let mut previous = 0;
+    for sample in &script.samples {
+        std::thread::sleep(Duration::from_millis(sample.t_ms - previous));
+        previous = sample.t_ms;
+        let t = sample.t_ms as u32;
+        pointer.motion_absolute(t, sample.pos.x as u32, sample.pos.y as u32, width, height);
+        // One frame per sample, so the compositor delivers them as
+        // separate pointer frames rather than coalescing the whole
+        // gesture -- the shape the file recorded is the point.
+        pointer.frame();
+        // The button goes in a frame of its own, *after* the motion has
+        // been committed. Sent in the same frame as the motion that
+        // first puts the pointer over the window, sway drops it: the
+        // client sees `CursorEntered` and the moves but never a
+        // `MouseInput { state: Pressed }`, so the whole gesture reads as
+        // a hover and nothing scrolls. Found exactly that way, by
+        // printing winit's events.
+        let state = match sample.action {
+            TouchAction::Down => Some(ButtonState::Pressed),
+            TouchAction::Up | TouchAction::Cancel => Some(ButtonState::Released),
+            TouchAction::Move => None,
+        };
+        if let Some(state) = state {
+            pointer.button(t, BTN_LEFT, state);
+            pointer.frame();
+        }
+        conn.flush()
+            .unwrap_or_else(|e| fail(&format!("flush: {e}")));
+    }
+    pointer.destroy();
+    conn.flush().ok();
+}
+
+fn parse(text: &str, what: &str) -> u32 {
+    text.parse()
+        .unwrap_or_else(|_| fail(&format!("{what} is not a whole number: {text:?}")))
+}
+
+fn fail(message: &str) -> ! {
+    eprintln!("replay-touch: {message}");
+    std::process::exit(1);
+}

iris/run-headless.sh

@@ -3,6 +3,25 @@
 #
 #   ./run-headless.sh tabs [-- cargo args]
 #   ./run-headless.sh tabs --shot /tmp/tabs.png --seconds 4
+#   ./run-headless.sh phone --phone --shot /tmp/p.png -- -p transcript-fixture
+#   ./run-headless.sh phone --phone --replay transcript-fixture/touch/flick-120hz.touch \
+#       --shot /tmp/p.png -- -p transcript-fixture
+#
+# `--phone` is layer 2 of docs/RUST.md's "Three test layers": the output
+# and the window take Iris's phone's own size and density (1080x2424 at
+# `content_scale` 2.55, from docs/bench/iris-phone-v2-2026-09-06.md,
+# carried in `transcript_fixture::PHONE_*`), and `IRIS_SCALE` hands that
+# density to iris the way `DisplayMetrics.density` does on Android
+# (`iris::default::content_scale`). So a screenshot from here and one
+# from the phone are the same layout at the same density, and what
+# differs is only the renderer. Without it the output stays desktop-
+# shaped, which is what every other example wants.
+#
+# `--replay FILE` drives one of the `.touch` recordings the headless
+# tests use (`iris/transcript-fixture/touch/`) into the window through
+# `rig-input`'s `replay-touch` -- one recording, both layers. With
+# `--shot` it also writes `<shot>-before.png` from just before the
+# gesture, since "the list moved" is a claim about two pictures.
 #
 # `--bin` runs a real crate binary instead of an example (E4's
 # `desktop-app`, which is a window a person runs, not a demo) --
@@ -29,19 +48,31 @@ here=$(cd "$(dirname "$0")" && pwd)
 run="${XDG_RUNTIME_DIR:-/tmp}/iris-headless"
 seconds=3
 shot=""
+replay=""
 example=""
 kind=example
+phone=no
+
+# The phone Iris runs the bench on. Not typed from memory: these are
+# `transcript_fixture::PHONE_WIDTH`/`PHONE_HEIGHT`/`PHONE_SCALE`, which
+# in turn come from her own reports -- keep the three in step.
+PHONE_MODE=1080x2424@120Hz
+PHONE_SCALE=2.55
+DESKTOP_MODE=1920x1200@60Hz
 
 while [ $# -gt 0 ]; do
     case "$1" in
         --shot) shot=$2; shift 2 ;;
         --seconds) seconds=$2; shift 2 ;;
         --bin) kind=bin; shift ;;
+        --phone) phone=yes; shift ;;
+        --replay) replay=$2; shift 2 ;;
         --) shift; break ;;
         *) example=$1; shift ;;
     esac
 done
-[ -n "$example" ] || { echo "usage: $0 NAME [--bin] [--shot PNG] [--seconds N] [-- cargo args]" >&2; exit 2; }
+[ -n "$example" ] || { echo "usage: $0 NAME [--bin] [--phone] [--replay TOUCH] [--shot PNG] [--seconds N] [-- cargo args]" >&2; exit 2; }
+[ -z "$replay" ] || [ -f "$replay" ] || { echo "run-headless: no touch script at $replay" >&2; exit 2; }
 
 mkdir -p "$run"
 export SWAYSOCK="$run/sway.sock"
@@ -78,6 +109,27 @@ export WAYLAND_DISPLAY
 
 echo "run-headless: $WAYLAND_DISPLAY (sway $(swaymsg -t get_version --raw | sed -n 's/.*"human_readable":"\([^"]*\)".*/\1/p'))" >&2
 
+# Set every run rather than only when it changes: this compositor is
+# reused across runs (see the socket comment above), so a desktop-shaped
+# run after a phone-shaped one would otherwise inherit the phone's output
+# and silently screenshot the wrong size.
+if [ "$phone" = yes ]; then
+    mode=$PHONE_MODE
+    export IRIS_SCALE="$PHONE_SCALE"
+    echo "run-headless: phone-shaped output $PHONE_MODE at IRIS_SCALE=$PHONE_SCALE" >&2
+else
+    mode=$DESKTOP_MODE
+fi
+swaymsg output HEADLESS-1 mode "$mode" >/dev/null
+# The extent `replay-touch` positions against, so a script's coordinates
+# are the output's own pixels.
+out_w=${mode%x*}
+out_h=${mode#*x}; out_h=${out_h%@*}
+
+# Built before the app starts, so a compile error is not reported as a
+# window that failed to move.
+[ -z "$replay" ] || cargo build --bin replay-touch -p rig-input >&2
+
 cd "$here"
 if [ "$kind" = bin ]; then
     cargo build --bin "$example" "$@" >&2
@@ -111,6 +163,18 @@ while [ $i -lt "$((seconds * 2))" ]; do
     i=$((i + 1)); sleep 0.5
 done
 
+if [ -n "$replay" ] && kill -0 "$pid" 2>/dev/null; then
+    if [ -n "$shot" ]; then
+        grim "${shot%.png}-before.png"
+        echo "run-headless: wrote ${shot%.png}-before.png (before the gesture)" >&2
+    fi
+    "$here/target/debug/replay-touch" "$out_w" "$out_h" "$replay"
+    # A fling outlives the finger: the gesture's own last sample is not
+    # when the list stops. Long enough for Android's spline to settle
+    # (`FlingCalculator::duration` tops out around a second and a half).
+    sleep 2
+fi
+
 if kill -0 "$pid" 2>/dev/null; then
     [ -n "$shot" ] && grim "$shot" && echo "run-headless: wrote $shot" >&2
     kill "$pid" 2>/dev/null || true

iris/src/default/attr.rs

@@ -1,5 +1,5 @@
 use crate::prelude::*;
-use winit::dpi::{LogicalPosition, LogicalSize};
+use winit::dpi::{PhysicalPosition, PhysicalSize};
 
 impl<T: HasDefaultUiState> FocusHost for T {
     fn recent_click(&mut self) -> bool {
@@ -18,9 +18,11 @@ impl<T: HasDefaultUiState> FocusHost for T {
         let state = self.default_state_mut();
         let Some(region) = region else { return };
         state.window.set_ime_allowed(true);
+        // Physical, like everything else this backend hands winit --
+        // `default::content_scale`.
         state.window.set_ime_cursor_area(
-            LogicalPosition::<f32>::from(region.top_left.tuple()),
+            PhysicalPosition::<f32>::from(region.top_left.tuple()),
-            LogicalSize::<f32>::from(region.size().tuple()),
+            PhysicalSize::<f32>::from(region.size().tuple()),
         );
     }
 }

iris/src/default/input.rs

@@ -17,15 +17,14 @@ pub struct Input {
 }
 
 impl Input {
-    /// `scale_factor` converts winit's physical-pixel event coordinates
+    /// winit's pointer coordinates are physical pixels, which is the
-    /// into the same logical units `UiRenderNode`'s window uniform now uses
+    /// space the whole tree is laid out and hit-tested in -- see
-    /// (`default::render::UiRenderer::new`'s doc comment) -- without it,
+    /// `default::content_scale`. Nothing is converted here; `dp(...)`
-    /// a cursor position and the widget tree it's tested against would be
+    /// resolves against the density at layout time instead.
-    /// in two different units on any monitor whose scale factor isn't 1.0.
+    pub fn event(&mut self, event: &WindowEvent) -> bool {
-    pub fn event(&mut self, event: &WindowEvent, scale_factor: f32) -> bool {
         match event {
             WindowEvent::CursorMoved { position, .. } => {
-                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32) / scale_factor;
+                self.cursor.pos = Vec2::new(position.x as f32, position.y as f32);
                 self.cursor.exists = true;
                 self.cursor.time = Instant::now();
             }
@@ -43,9 +42,7 @@ impl Input {
             WindowEvent::MouseWheel { delta, .. } => {
                 let mut delta = match *delta {
                     MouseScrollDelta::LineDelta(x, y) => Vec2::new(x, y),
-                    MouseScrollDelta::PixelDelta(pos) => {
+                    MouseScrollDelta::PixelDelta(pos) => Vec2::new(pos.x as f32, pos.y as f32),
-                        Vec2::new(pos.x as f32, pos.y as f32) / scale_factor
-                    }
                 };
                 if delta.x == 0.0 && self.modifiers.shift {
                     delta.x = delta.y;
@@ -83,14 +80,12 @@ impl Input {
 }
 
 impl DefaultUiState {
+    /// Physical pixels, matching `WindowEvent::Resized` (what
+    /// `UiRenderState::resize` is given) and the swapchain -- see
+    /// `default::content_scale`.
     pub fn window_size(&self) -> Vec2 {
-        let window = self.renderer.window();
+        let size = self.renderer.window().inner_size();
-        let size = window.inner_size();
+        Vec2::new(size.width as f32, size.height as f32)
-        let scale_factor = window.scale_factor() as f32;
-        Vec2::new(
-            size.width as f32 / scale_factor,
-            size.height as f32 / scale_factor,
-        )
     }
 
     pub fn cursor_state(&self) -> &CursorState {

iris/src/default/mod.rs

@@ -25,6 +25,38 @@ pub use render::*;
 
 pub type Proxy<Event> = EventLoopProxy<Event>;
 
+/// The desktop's `content_scale`: physical pixels per dp, the same
+/// quantity Android reads from `DisplayMetrics.density` and feeds to
+/// `UiRenderState::set_density` (`android::view::AndroidUiState::
+/// content_scale`'s field comment). Everything in this backend is
+/// physical pixels -- the window size, the pointer, the widget tree --
+/// and `dp(...)` is what resolves against this at layout time, exactly
+/// as on the phone. That is a correction from an earlier version that
+/// divided winit's coordinates into a separate "logical" space instead:
+/// it left `UiRenderState::resize` (physical, from `WindowEvent::
+/// Resized`) and the window uniform (logical) disagreeing on any
+/// display whose scale factor is not 1.0, and it rasterised glyphs at
+/// one resolution to display them at another -- the blur the phone's own
+/// stopgap produced before `dp` existed.
+///
+/// **`IRIS_SCALE` overrides it**, which is how a phone-shaped desktop
+/// window runs the phone's density (`run-headless.sh --phone`,
+/// docs/RUST.md's layer 2). An unparsable value is a typo in a command
+/// somebody just typed, so it says so and uses the window's own answer
+/// rather than silently laying out at the wrong density.
+pub fn content_scale(window: &Window) -> f32 {
+    match std::env::var("IRIS_SCALE") {
+        Err(_) => window.scale_factor() as f32,
+        Ok(text) => match text.trim().parse::<f32>() {
+            Ok(scale) if scale > 0.0 => scale,
+            _ => {
+                log::warn!("IRIS_SCALE={text:?} is not a positive number; using the window's own");
+                window.scale_factor() as f32
+            }
+        },
+    }
+}
+
 pub struct DefaultUiState {
     pub root: Option<StrongWidget>,
     pub renderer: UiRenderer,
@@ -214,8 +246,16 @@ impl<State: DefaultAppState> AppState for DefaultApp<State> {
         window.set_visible(true);
         let default_state = DefaultUiState::new(window, access_adapter);
         let (mut rsc, task_recv) = DefaultRsc::init(default_state.window.clone());
+        // Both copies of the density, set before the first widget is
+        // built so text shapes at the right size on the opening frame --
+        // the same pair `android::view::new_peer` sets from
+        // `content_scale`. See `iris_core::TextData::density` for why the
+        // shaper keeps its own.
+        let scale = content_scale(default_state.window.as_ref());
+        rsc.ui.text.density = scale;
         let state = State::new(default_state, &mut rsc, proxy);
-        let render = UiRenderState::new();
+        let mut render = UiRenderState::new();
+        render.set_density(scale);
         Self {
             rsc,
             state,
@@ -247,8 +287,7 @@ impl<State: DefaultAppState> AppState for DefaultApp<State> {
         ui_state
             .access_adapter
             .process_event(&ui_state.window, &event);
-        let scale_factor = ui_state.renderer.window().scale_factor() as f32;
+        let input_changed = ui_state.input.event(&event);
-        let input_changed = ui_state.input.event(&event, scale_factor);
         let cursor_state = ui_state.cursor_state().clone();
         let old = ui_state.focus;
         if cursor_state.buttons.left.is_start() {

iris/src/default/render.rs

@@ -66,13 +66,11 @@ impl UiRenderer {
         self.config.width = size.width;
         self.config.height = size.height;
         self.surface.configure(&self.device, &self.config);
-        // Logical, matching `new`'s own seed -- see the comment there.
+        // Physical, matching `new`'s own seed -- see the comment there.
-        let scale_factor = self.window.scale_factor() as f32;
+        self.ui.resize(
-        let logical = Vec2::new(
+            Vec2::new(size.width as f32, size.height as f32),
-            size.width as f32 / scale_factor,
+            &self.queue,
-            size.height as f32 / scale_factor,
         );
-        self.ui.resize(logical, &self.queue);
     }
 
     fn create_encoder(device: &Device) -> CommandEncoder {
@@ -162,21 +160,12 @@ impl UiRenderer {
         // by:" chain as the message, since `UiRenderNode::new` returns it
         // rather than letting wgpu's own default handler panic first (see
         // that function's doc comment).
-        // Logical size (physical / `scale_factor`), matching what the
+        // Physical size, the same units the swapchain, `WindowEvent::
-        // Android backend now reports too (`android::render::
+        // Resized`, the pointer and the widget tree all use -- see
-        // AndroidRenderer::new`, `content_scale`) -- the swapchain still
+        // `default::content_scale` for why this backend stopped dividing
-        // configures at the real physical resolution above; only the
+        // into a separate logical space, and what disagreed while it did.
-        // window uniform layout/hit-testing agree on is scaled. Without
+        let physical_size = Vec2::new(size.width as f32, size.height as f32);
-        // this a window on any monitor whose scale factor isn't 1.0 would
+        let ui = UiRenderNode::new(&device, &queue, &config, physical_size)
-        // have the identical "everything too small" bug RUST.md's P0 box
-        // found on Iris's phone, just never noticed here because this
-        // crate's own dev monitors happen to run at 1.0.
-        let scale_factor = window.scale_factor() as f32;
-        let logical_size = Vec2::new(
-            size.width as f32 / scale_factor,
-            size.height as f32 / scale_factor,
-        );
-        let ui = UiRenderNode::new(&device, &queue, &config, logical_size)
             .expect("Could not create iris render node!");
 
         Self {

iris/transcript-fixture/examples/phone.rs

@@ -0,0 +1,73 @@
+//! Layer 2 of docs/RUST.md's "Three test layers": the fixture-backed
+//! transcript screen in a phone-shaped window, for looking at.
+//!
+//!     iris/run-headless.sh phone --phone --shot /tmp/phone.png -- -p transcript-fixture
+//!
+//! `--phone` sets the headless sway output to the phone's own 1080x2424
+//! and exports `IRIS_SCALE=2.55`, so this draws at the density Iris's
+//! phone reports (`transcript_fixture::PHONE_SCALE`) rather than the
+//! desktop's 1.0 -- same screen, same fixture and the same folding as
+//! the Android bench and the headless tests, so what differs between a
+//! screenshot here and one from the phone is the renderer, never the
+//! data.
+//!
+//! No server: `transcript-fixture` embeds the transcript. Colour,
+//! spacing, type and anything a person has to *see* is answered here;
+//! anything with an assertion behind it belongs in `tests/
+//! phone_screen.rs` one layer down.
+
+use iris::prelude::*;
+use winit::{dpi::PhysicalSize, window::WindowAttributes};
+
+fn main() {
+    DefaultApp::<Client>::run();
+}
+
+#[derive(DefaultUiState)]
+pub struct Client {
+    ui_state: DefaultUiState,
+    #[allow(dead_code)]
+    screen: Option<transcript_ui::TranscriptScreen>,
+}
+
+impl DefaultAppState for Client {
+    fn window_attributes() -> WindowAttributes {
+        WindowAttributes::default()
+            .with_title("iris transcript (bench fixture)")
+            .with_inner_size(PhysicalSize::new(
+                transcript_fixture::PHONE_WIDTH,
+                transcript_fixture::PHONE_HEIGHT,
+            ))
+    }
+
+    fn new(
+        mut ui_state: DefaultUiState,
+        rsc: &mut DefaultRsc<Self>,
+        _: Proxy<Self::Event>,
+    ) -> Self {
+        let screen = match transcript_fixture::open(rsc, &mut ui_state) {
+            Ok(opened) => {
+                // A fling coasts only while something asks for the next
+                // frame; on the desktop that is the window's own redraw
+                // request (`List::fling`'s doc).
+                let handle = rsc.tasks.redraw_handle();
+                (opened.screen.list)(rsc).set_redraw_handle(handle);
+                Some(opened.screen)
+            }
+            // On screen rather than a panic: this window exists to be
+            // looked at, and "the fixture stopped folding" is something
+            // to read, not a process that vanished (UI_RULES.md).
+            Err(message) => {
+                let text = wtext(format!("Couldn't fold the bench fixture: {message}"))
+                    .color(Color::WHITE)
+                    .wrap(true)
+                    .pad(dp(16))
+                    .add_strong(rsc)
+                    .any();
+                ui_state.set_root(text);
+                None
+            }
+        };
+        Self { ui_state, screen }
+    }
+}