Merge remote-tracking branch 'origin/rustify' into worktree-agent-a16b22e34539b810e

# Conflicts:
#	iris/android-app/src/bench_client.rs
#	iris/android-app/src/bench_jni.rs

iris/android-app/app/src/main/java/dev/iris/android/demo/IrisView.java

@@ -1,8 +1,15 @@
 package dev.iris.android.demo;
 
 import android.app.Activity;
+import android.content.ClipData;
+import android.content.ClipboardManager;
 import android.content.Context;
 import android.view.Gravity;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.Button;
+import android.widget.FrameLayout;
+import android.widget.LinearLayout;
 import android.widget.ScrollView;
 import android.widget.TextView;
 
@@ -68,4 +75,81 @@ public final class IrisView extends RustView {
         scroll.addView(text);
         activity.setContentView(scroll);
     }
+
+    private static final String DIAGNOSTICS_OVERLAY_TAG = "iris-diagnostics-overlay";
+
+    /**
+     * The bench build's keyboard diagnostics capture
+     * (`bench_client.rs`'s `on_insets_changed` /
+     * `capture_keyboard_diagnostics`, via `bench_jni.rs`'s
+     * `PlatformHandle::show_diagnostics_overlay`): unlike
+     * `showRendererError` above, this adds a panel *over* this view
+     * (`MainActivity`'s `FrameLayout` still holds `IrisView` underneath,
+     * running) rather than replacing the activity's content, and gives it
+     * a Copy button and a Close that removes the panel -- so it draws
+     * (and can be read) whether or not iris itself is still putting
+     * anything on screen, without abandoning the session that produced
+     * it. Runs on the UI thread regardless of which thread calls it,
+     * since the call comes from a background task (a delayed capture
+     * after the keyboard opens), and touching the view tree off the UI
+     * thread is undefined.
+     */
+    void showDiagnosticsOverlay(String report) {
+        Context context = getContext();
+        if (!(context instanceof Activity)) {
+            return;
+        }
+        Activity activity = (Activity) context;
+        activity.runOnUiThread(() -> {
+            ViewGroup parent = (ViewGroup) getParent();
+            if (parent == null) {
+                return;
+            }
+            View existing = parent.findViewWithTag(DIAGNOSTICS_OVERLAY_TAG);
+            if (existing != null) {
+                parent.removeView(existing);
+            }
+
+            float density = activity.getResources().getDisplayMetrics().density;
+            int pad = (int) (16 * density);
+
+            LinearLayout overlay = new LinearLayout(activity);
+            overlay.setTag(DIAGNOSTICS_OVERLAY_TAG);
+            overlay.setOrientation(LinearLayout.VERTICAL);
+            overlay.setBackgroundColor(0xEE000000);
+            overlay.setPadding(pad, pad, pad, pad);
+
+            TextView text = new TextView(activity);
+            text.setText(report);
+            text.setTextIsSelectable(true);
+            text.setTextColor(0xFFFFFFFF);
+            ScrollView scroll = new ScrollView(activity);
+            scroll.addView(text);
+            overlay.addView(scroll, new LinearLayout.LayoutParams(
+                    LinearLayout.LayoutParams.MATCH_PARENT, 0, 1f));
+
+            LinearLayout buttonRow = new LinearLayout(activity);
+            buttonRow.setOrientation(LinearLayout.HORIZONTAL);
+            buttonRow.setPadding(0, pad, 0, 0);
+
+            Button copy = new Button(activity);
+            copy.setText("Copy");
+            copy.setOnClickListener(v -> {
+                ClipboardManager clipboard =
+                        (ClipboardManager) activity.getSystemService(Context.CLIPBOARD_SERVICE);
+                if (clipboard != null) {
+                    clipboard.setPrimaryClip(ClipData.newPlainText("iris diagnostics", report));
+                }
+            });
+            Button close = new Button(activity);
+            close.setText("Close");
+            close.setOnClickListener(v -> parent.removeView(overlay));
+            buttonRow.addView(copy);
+            buttonRow.addView(close);
+            overlay.addView(buttonRow);
+
+            parent.addView(overlay, new FrameLayout.LayoutParams(
+                    FrameLayout.LayoutParams.MATCH_PARENT, FrameLayout.LayoutParams.MATCH_PARENT));
+        });
+    }
 }

iris/android-app/src/bench_client.rs

@@ -114,10 +114,17 @@ pub struct BenchClient {
     running: bool,
     /// The keyboard phase's own confirmation channel -- updated from
     /// `on_insets_changed` (the platform's own answer for whether the IME
-    /// is actually visible, per `LogicalInsets::ime_bottom`), read from the
+    /// is actually visible, per `WindowInsets::ime_bottom`), read from the
     /// benchmark's spawned task via the shared `Arc<Mutex<_>>` rather than
     /// `ctx.update`, since neither side needs the widget tree for this.
     ime_state: Arc<Mutex<ImeState>>,
+    /// Edge-triggers the keyboard diagnostics capture below -- set on the
+    /// first `on_insets_changed` where `ime_bottom > 0.0`, cleared on the
+    /// first where it is not, so opening the keyboard fires this once
+    /// rather than on every insets update while it stays open (a rotation
+    /// or a status-bar change with the keyboard already up would otherwise
+    /// re-fire it).
+    keyboard_was_visible: bool,
 }
 
 /// See `BenchClient::ime_state`'s doc. `shown_events`/`hidden_events`
@@ -241,7 +248,7 @@ impl AndroidAppState for BenchClient {
         let tree = (
             top_bar,
             content.height(rest(2)),
-            report_display.height(rest(1)).pad(8),
+            report_display.height(rest(1)).pad(dp(8)),
         )
             .span(Dir::DOWN)
             .add_strong(rsc)
@@ -277,6 +284,7 @@ impl AndroidAppState for BenchClient {
             last_report: None,
             running: false,
             ime_state: Arc::new(Mutex::new(ImeState::default())),
+            keyboard_was_visible: false,
         };
 
         let (backlog, stream_tail) = parse_fixture();
@@ -305,38 +313,93 @@ impl AndroidAppState for BenchClient {
     /// field comment. Rebuilds the row rather than mutating a stored
     /// `Padding` in place, since nothing here holds a handle to one.
     ///
-    /// Also the keyboard phase's own confirmation signal: `ime_bottom`
-    /// crossing 0<->positive is the platform's own answer for whether the
-    /// IME actually opened or closed, fired from the real insets
-    /// callback rather than assumed from having called `show_ime`/
-    /// `hide_ime` -- see `ime_state`'s doc.
+    /// Also two things downstream of the same `ime_bottom` transition:
+    /// **the keyboard phase's own confirmation signal** (`ime_state`'s
+    /// doc -- the platform's own answer for whether the IME actually
+    /// opened or closed, rather than assumed from having called
+    /// `show_ime`/`hide_ime`), and **the trigger for the keyboard
+    /// diagnostics capture** (RUST.md's P0 box): the IME resizing the
+    /// surface is exactly the case a previous commit found wiped text,
+    /// and Iris needs a way to get a report off the phone even if that
+    /// (or some other keyboard-triggered regression) is still happening
+    /// on the build she is holding -- `capture_keyboard_diagnostics`
+    /// below fires ~500ms after the keyboard becomes visible, once per
+    /// keyboard opening, and shows its report in a plain overlay view
+    /// that draws independently of whatever iris itself is doing.
     fn on_insets_changed(
         &mut self,
         rsc: &mut AndroidRsc<Self>,
-        insets: iris::android::LogicalInsets,
+        insets: iris::android::WindowInsets,
     ) {
         let controls = bench_controls(rsc, insets.top);
         (self.top_bar)(rsc).set(controls);
 
+        let ime_visible = insets.ime_bottom > 0.0;
+
         let mut ime = self.ime_state.lock().unwrap();
-        let now_visible = insets.ime_bottom > 0.0;
-        if now_visible && !ime.visible {
+        if ime_visible && !ime.visible {
             ime.shown_events += 1;
         }
-        if !now_visible && ime.visible {
+        if !ime_visible && ime.visible {
             ime.hidden_events += 1;
         }
-        ime.visible = now_visible;
+        ime.visible = ime_visible;
+        drop(ime);
+
+        if ime_visible && !self.keyboard_was_visible {
+            self.keyboard_was_visible = true;
+            let redraw = rsc.tasks.redraw_handle();
+            rsc.spawn_task(async move |mut ctx| {
+                tokio::time::sleep(Duration::from_millis(KEYBOARD_DIAGNOSTICS_DELAY_MS)).await;
+                ctx.update(|state: &mut BenchClient, rsc| {
+                    state.capture_keyboard_diagnostics(rsc);
+                });
+                redraw.request_redraw();
+            });
+        } else if !ime_visible {
+            self.keyboard_was_visible = false;
+        }
     }
 }
 
+/// How long to wait after the keyboard becomes visible before capturing
+/// diagnostics -- long enough that the resize, the reported wipe (if it is
+/// still happening) and a couple of frames have all had time to land, per
+/// AGENTS.md's "so that operations that finish in milliseconds have states
+/// on the way that nothing can observe" reasoning applied the other way:
+/// this wants to observe the state *after* the transition settles, not
+/// mid-flight.
+const KEYBOARD_DIAGNOSTICS_DELAY_MS: u64 = 500;
+
 type Rsc = AndroidRsc<BenchClient>;
 
-/// `top_pad` is the status-bar inset in logical units (0.0 until
+/// The header row's own backdrop -- see `bench_controls`'s doc comment on
+/// why it needs one at all. A dark neutral rather than pure black
+/// (`android::render::CLEAR_COLOR`) so the row reads as a distinct panel
+/// instead of a hole in the background the buttons happen to float in.
+const HEADER_SURFACE: UiColor = UiColor::new(28, 28, 34, 255);
+
+/// `top_pad` is the status-bar inset in physical pixels (0.0 until
 /// `on_insets_changed` has run once) -- folded in here, rather than
 /// exposing the unadded builder for a caller to `.pad()` itself, because
 /// naming that builder's type at each call site is more machinery than a
 /// top-of-screen padding number is worth.
+///
+/// **Backed by an opaque rect the full size of the row, not just the three
+/// buttons.** Iris's phone report (docs/RUST.md's P0 box, screenshots on
+/// build a9232ac): "the header buttons have nothing behind them and
+/// overlap the transcript text" -- before this, only each button's own
+/// `rect(...)` painted anything, so the gaps between and around them (and
+/// the status-bar strip above them) showed whatever was one layer back
+/// (`CLEAR_COLOR`, black), and the row's true height was three
+/// physical-pixel-sized (`abs`, not `dp`) button boxes rather than the
+/// density-correct size the transcript below was already using post-P0 --
+/// exactly what reads as "overlap" once the two disagree. Fixed two ways
+/// together: a `HEADER_SURFACE` rect stacked behind the whole row (this
+/// function), and every size below moved from a bare number (physical
+/// pixels) to `dp(...)` (IRIS_TODO.md's density-independent length unit),
+/// so the row's reserved height in the outer `Span::DOWN`
+/// (`AndroidAppState::new`) matches what is actually painted.
 fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
     let run_rect = rect(Color::rgb(40, 70, 40))
         .on(
@@ -351,7 +414,7 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Run benchmark").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
     let copy_rect = rect(Color::rgb(50, 50, 60))
@@ -367,7 +430,7 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Copy report").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
     let diag_rect = rect(Color::rgb(60, 45, 70))
@@ -383,12 +446,14 @@ fn bench_controls(rsc: &mut Rsc, top_pad: f32) -> StrongWidget {
         wtext("Diagnostics").size(18).text_align(Align::CENTER),
     )
         .stack()
-        .pad(8)
+        .pad(dp(8))
         .add(rsc);
 
-    (run, copy, diagnostics)
-        .span(Dir::RIGHT)
-        .height(56)
+    let buttons = (run, copy, diagnostics).span(Dir::RIGHT).add(rsc);
+
+    (rect(HEADER_SURFACE), buttons)
+        .stack()
+        .height(dp(56))
         .pad(Padding::top(top_pad))
         .add_strong(rsc)
         .any()
@@ -428,6 +493,36 @@ impl BenchClient {
         self.last_report = Some(report);
     }
 
+    /// The keyboard's own diagnostics capture -- see `on_insets_changed`'s
+    /// doc comment. Reuses `show_diagnostics`'s exact report (so it is the
+    /// same text the on-screen `Diagnostics` button produces, plus the
+    /// per-frame log `FrameReport` already keeps around the resize --
+    /// `frame_report.report()` above covers "the frames around the
+    /// resize" without a second accounting mechanism), then does three
+    /// things the button does not: logs it (so a `logcat` pull gets it
+    /// even if nothing on screen does), copies it to the clipboard
+    /// unprompted, and shows it in the shell's plain overlay view, which
+    /// draws independently of iris's own renderer -- the whole point,
+    /// since the renderer is exactly what might be in the wiped state
+    /// this exists to report on.
+    fn capture_keyboard_diagnostics(&mut self, rsc: &mut Rsc) {
+        self.show_diagnostics(rsc);
+        let Some(report) = self.last_report.clone() else {
+            return;
+        };
+        log::info!("iris keyboard diagnostics:\n{report}");
+        let Some(platform) = &self.platform else {
+            log::info!("iris keyboard diagnostics: no platform handle, can't reach the shell");
+            return;
+        };
+        if platform.copy_to_clipboard("iris keyboard diagnostics", &report) {
+            log::info!("iris keyboard diagnostics: copied to clipboard");
+        } else {
+            log::info!("iris keyboard diagnostics: clipboard copy failed");
+        }
+        platform.show_diagnostics_overlay(&report);
+    }
+
     fn copy_report(&mut self) {
         let Some(report) = &self.last_report else {
             log::info!("iris bench report: nothing to copy -- run the benchmark first");

iris/android-app/src/bench_jni.rs

@@ -222,4 +222,31 @@ impl PlatformHandle {
             .ok()
         }
     }
+
+    /// Shows `report` in the shell's plain-view diagnostics overlay
+    /// (`IrisView.showDiagnosticsOverlay`) -- a real `TextView` plus Copy
+    /// and Close controls, added over whatever iris itself is drawing
+    /// rather than replacing it (unlike `android::view::show_renderer_error`,
+    /// which exists for the case the renderer can never recover from and
+    /// intentionally never returns). Called from a background task after
+    /// the keyboard-open delay (`bench_client.rs`'s `on_insets_changed`),
+    /// so the Java side hops onto the UI thread itself before touching the
+    /// view tree -- see that method's own comment.
+    pub fn show_diagnostics_overlay(&self, report: &str) -> bool {
+        self.try_show_diagnostics_overlay(report).is_some()
+    }
+
+    fn try_show_diagnostics_overlay(&self, report: &str) -> Option<()> {
+        let mut guard = self.vm.attach_current_thread().ok()?;
+        let env: &mut JNIEnv = &mut guard;
+        let jreport = env.new_string(report).ok()?;
+        env.call_method(
+            self.view.as_obj(),
+            "showDiagnosticsOverlay",
+            "(Ljava/lang/String;)V",
+            &[JValue::Object(jreport.as_ref())],
+        )
+        .ok()?;
+        Some(())
+    }
 }

iris/core/src/orientation/len.rs

@@ -9,7 +9,31 @@ pub struct Size {
 
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Len {
+    /// Physical pixels -- a raw device pixel, unaffected by the display's
+    /// density. Rare to want directly (a hairline border is the usual
+    /// case); most sizes should be `dp` instead. See `dp`'s own doc for why
+    /// the two are kept separate rather than one field a caller has to
+    /// remember to pre-multiply.
     pub abs: f32,
+    /// Density-independent pixels -- Android's `dp` / CSS's reference pixel
+    /// (1 unit = 1/160in), resolved against the display's density at
+    /// layout time (`apply_rest`'s `density` parameter) rather than at the
+    /// point a widget is built, since density is a property of the device
+    /// this ends up running on, not of the widget tree. This is the unit
+    /// IRIS_TODO.md's "a density-independent length unit" item asked for,
+    /// 2026-09-06: before it existed, every size in the tree was `abs`
+    /// (physical pixels), and the only way to make a 16px design draw at
+    /// the right *size* on a denser display was a single global multiply
+    /// applied to the whole rendered scene after layout -- which is also
+    /// what made text blurry (RUST.md's P0 box, "blurry ... glyphs drawn
+    /// at logical size and stretched by the scale"): a glyph rasterised at
+    /// 16 physical px and then stretched 3x by that global multiply is a
+    /// 48px area sampled from a 16px bitmap. Resolving `dp` per-length at
+    /// layout time instead means the font size handed to the text shaper
+    /// is already the physical size (`16.0.dp() * 3.0`), so the glyph
+    /// atlas rasterises at the display's real resolution and nothing
+    /// downstream needs to stretch anything.
+    pub dp: f32,
     pub rel: f32,
     pub rest: f32,
 }
@@ -67,10 +91,10 @@ impl Size {
         }
     }
 
-    pub fn to_uivec2(self) -> UiVec2 {
+    pub fn to_uivec2(self, density: f32) -> UiVec2 {
         UiVec2 {
-            x: self.x.apply_rest(),
-            y: self.y.apply_rest(),
+            x: self.x.apply_rest(density),
+            y: self.y.apply_rest(density),
         }
     }
 
@@ -98,26 +122,43 @@ impl Size {
 impl Len {
     pub const ZERO: Self = Self {
         abs: 0.0,
+        dp: 0.0,
         rel: 0.0,
         rest: 0.0,
     };
 
     pub const REST: Self = Self {
         abs: 0.0,
+        dp: 0.0,
         rel: 0.0,
         rest: 1.0,
     };
 
-    pub fn apply_rest(&self) -> UiScalar {
+    /// Resolves to a `UiScalar`, folding `dp` into `abs` pixels against
+    /// `density` (physical pixels per dp -- 1.0 on a desktop or an
+    /// unscaled display, `content_scale` on Android; see `dp`'s field
+    /// doc). Every other component of `Len` is already resolution-
+    /// independent (`rel` is a fraction of the parent; `rest` becomes a
+    /// fraction too, below), so `density` only ever touches this one term.
+    pub fn apply_rest(&self, density: f32) -> UiScalar {
         UiScalar {
             rel: self.rel + if self.rest > 0.0 { 1.0 } else { 0.0 },
-            abs: self.abs,
+            abs: self.abs + self.dp * density,
         }
     }
 
     pub fn abs(abs: impl UiNum) -> Self {
         Self {
             abs: abs.to_f32(),
+            dp: 0.0,
+            rel: 0.0,
+            rest: 0.0,
+        }
+    }
+    pub fn dp(dp: impl UiNum) -> Self {
+        Self {
+            abs: 0.0,
+            dp: dp.to_f32(),
             rel: 0.0,
             rest: 0.0,
         }
@@ -125,6 +166,7 @@ impl Len {
     pub fn rel(rel: impl UiNum) -> Self {
         Self {
             abs: 0.0,
+            dp: 0.0,
             rel: rel.to_f32(),
             rest: 0.0,
         }
@@ -132,6 +174,7 @@ impl Len {
     pub fn rest(ratio: impl UiNum) -> Self {
         Self {
             abs: 0.0,
+            dp: 0.0,
             rel: 0.0,
             rest: ratio.to_f32(),
         }
@@ -144,6 +187,15 @@ pub mod len_fns {
     pub fn abs(abs: impl UiNum) -> Len {
         Len {
             abs: abs.to_f32(),
+            dp: 0.0,
+            rel: 0.0,
+            rest: 0.0,
+        }
+    }
+    pub fn dp(dp: impl UiNum) -> Len {
+        Len {
+            abs: 0.0,
+            dp: dp.to_f32(),
             rel: 0.0,
             rest: 0.0,
         }
@@ -151,6 +203,7 @@ pub mod len_fns {
     pub fn rel(rel: impl UiNum) -> Len {
         Len {
             abs: 0.0,
+            dp: 0.0,
             rel: rel.to_f32(),
             rest: 0.0,
         }
@@ -158,14 +211,15 @@ pub mod len_fns {
     pub fn rest(ratio: impl UiNum) -> Len {
         Len {
             abs: 0.0,
+            dp: 0.0,
             rel: 0.0,
             rest: ratio.to_f32(),
         }
     }
 }
 
-impl_op!(Len Add add; abs rel rest);
-impl_op!(Len Sub sub; abs rel rest);
+impl_op!(Len Add add; abs dp rel rest);
+impl_op!(Len Sub sub; abs dp rel rest);
 
 impl_op!(Size Add add; x y);
 impl_op!(Size Sub sub; x y);
@@ -187,6 +241,9 @@ impl std::fmt::Display for Len {
         if self.abs != 0.0 {
             write!(f, "{} abs;", self.abs)?;
         }
+        if self.dp != 0.0 {
+            write!(f, "{} dp;", self.dp)?;
+        }
         if self.rel != 0.0 {
             write!(f, "{} rel;", self.rel)?;
         }

iris/core/src/primitive/text.rs

@@ -66,6 +66,17 @@ pub struct TextData {
     pub layout_cx: LayoutContext<UiColor>,
     scale_cx: ScaleContext,
     pub atlas: GlyphAtlas,
+    /// Physical pixels per dp -- a second copy of
+    /// `UiRenderState::density`, kept here too because `TextEditCtx::layout`
+    /// (cursor movement and hit-testing, `widget/text/edit.rs`) shapes text
+    /// from an event callback that has a `TextData` but no `Painter`, so it
+    /// has nowhere else to read the display's density from. Both copies are
+    /// set together, from the one place either backend learns the real
+    /// value (`android::view::new_peer`); this is the same accepted
+    /// duplication as `AndroidRenderer::content_scale`; a single source of
+    /// truth would mean carrying a `Painter` (or output size) into every
+    /// input handler for the sake of one field.
+    pub density: f32,
 }
 
 impl Default for TextData {
@@ -75,6 +86,7 @@ impl Default for TextData {
             layout_cx: LayoutContext::new(),
             scale_cx: ScaleContext::new(),
             atlas: GlyphAtlas::default(),
+            density: 1.0,
         };
         data.register_bundled_fonts();
         data
@@ -363,7 +375,7 @@ pub struct TextBuffer {
     /// `set_spans` forces `shaped` to `None` directly, the same way `edit`
     /// does, since spans change far less often than a naive equality check
     /// on the whole `Vec` would cost to compute every frame.
-    shaped: Option<(TextAttrs, Option<f32>)>,
+    shaped: Option<(TextAttrs, Option<f32>, f32)>,
 }
 
 impl TextBuffer {
@@ -419,19 +431,42 @@ impl TextBuffer {
         Vec2::new(self.layout.width(), self.layout.height())
     }
 
-    /// Lay the text out, unless it is already laid out for these attributes and
-    /// this width.
-    pub fn shape(&mut self, data: &mut TextData, attrs: &TextAttrs, width: Option<f32>) {
-        if self.shaped.as_ref() == Some(&(attrs.clone(), width)) {
+    /// Lay the text out, unless it is already laid out for these
+    /// attributes, this width and this density.
+    ///
+    /// **`attrs.font_size`/`line_height` and every span's own `font_size`
+    /// are density-independent (dp) units, multiplied by `density` here --
+    /// the one place text crosses from the widget tree's dp sizes into the
+    /// physical pixels the shaper and rasteriser (`TextData::place`) both
+    /// then work in.** This is what makes glyphs sharp on a dense display:
+    /// before this existed, `font_size` was already a physical-pixel value
+    /// (RUST.md's P0 box's global-scale stopgap resolved density by
+    /// stretching the whole rendered frame afterward instead), so a glyph
+    /// was rasterised small and then upscaled by whatever the display's
+    /// scale factor was -- exactly the blur Iris's report described.
+    /// Multiplying here instead means the font size hitting `ScaleContext`
+    /// in `place` below is already the display's real physical size, so
+    /// the atlas holds a bitmap at the resolution it is actually shown at.
+    /// `GlyphKey.size` already keys on that resolved `font_size`
+    /// (`(font_size * 16.0).round()`), so a cache entry is naturally per
+    /// physical size with no change needed there.
+    pub fn shape(
+        &mut self,
+        data: &mut TextData,
+        attrs: &TextAttrs,
+        width: Option<f32>,
+        density: f32,
+    ) {
+        if self.shaped.as_ref() == Some(&(attrs.clone(), width, density)) {
             return;
         }
         let mut builder = data
             .layout_cx
             .ranged_builder(&mut data.font_cx, &self.text, 1.0, true);
         builder.push_default(StyleProperty::FontFamily(attrs.family.family()));
-        builder.push_default(StyleProperty::FontSize(attrs.font_size));
+        builder.push_default(StyleProperty::FontSize(attrs.font_size * density));
         builder.push_default(StyleProperty::LineHeight(LineHeight::Absolute(
-            attrs.line_height,
+            attrs.line_height * density,
         )));
         builder.push_default(StyleProperty::Brush(attrs.color));
         for span in &self.spans {
@@ -443,7 +478,7 @@ impl TextBuffer {
                 builder.push(StyleProperty::FontFamily(family.family()), range.clone());
             }
             if let Some(size) = span.font_size {
-                builder.push(StyleProperty::FontSize(size), range.clone());
+                builder.push(StyleProperty::FontSize(size * density), range.clone());
             }
             if span.bold {
                 builder.push(StyleProperty::FontWeight(FontWeight::BOLD), range.clone());
@@ -459,7 +494,7 @@ impl TextBuffer {
         self.layout.break_all_lines(width);
         self.layout
             .align(Alignment::Start, AlignmentOptions::default());
-        self.shaped = Some((attrs.clone(), width));
+        self.shaped = Some((attrs.clone(), width, density));
     }
 }
 
@@ -576,8 +611,9 @@ impl TextData {
         attrs: &TextAttrs,
         width: Option<f32>,
         textures: &mut Textures,
+        density: f32,
     ) -> RenderedText {
-        buffer.shape(self, attrs, width);
+        buffer.shape(self, attrs, width, density);
         let glyphs = self.place(buffer, textures);
         RenderedText {
             glyphs: std::sync::Arc::new(glyphs),

iris/core/src/ui/painter.rs

@@ -165,8 +165,10 @@ impl<'a> Painter<'a> {
         attrs: &TextAttrs,
         width: Option<f32>,
     ) -> RenderedText {
+        let density = self.state.density;
         let ui = self.rsc.ui_mut();
-        ui.text.render(buffer, attrs, width, &mut ui.textures)
+        ui.text
+            .render(buffer, attrs, width, &mut ui.textures, density)
     }
 
     /// Draw a laid-out string: one quad per glyph, all sampling the atlas.
@@ -210,6 +212,12 @@ impl<'a> Painter<'a> {
         self.state.output_size
     }
 
+    /// Physical pixels per `dp` -- see `UiRenderState::density`'s field
+    /// doc. What `Len::dp`'s `apply_rest` call resolves against.
+    pub fn density(&self) -> f32 {
+        self.state.density
+    }
+
     pub fn px_size(&mut self) -> Vec2 {
         self.region.size().to_abs(self.state.output_size)
     }

iris/core/src/ui/render_state.rs

@@ -9,6 +9,12 @@ pub struct UiRenderState {
     pub active: HashMap<WidgetId, ActiveData>,
     pub layers: PrimitiveLayers,
     pub(super) output_size: Vec2,
+    /// Physical pixels per `dp` -- see `Len::dp`'s field doc. `1.0` (an
+    /// unscaled display) until a backend that knows its own density calls
+    /// `set_density` (Android's `content_scale`, read at `surface_changed`
+    /// time); the winit backend has no analogous per-monitor value wired up
+    /// yet and stays at the default.
+    pub(super) density: f32,
 
     old_root: Option<WidgetId>,
     resized: bool,
@@ -35,6 +41,7 @@ impl UiRenderState {
             active: Default::default(),
             layers: Default::default(),
             output_size: Vec2::ZERO,
+            density: 1.0,
             old_root: None,
             resized: false,
             draw_started: Default::default(),
@@ -60,6 +67,20 @@ impl UiRenderState {
         self.resized = true;
     }
 
+    /// Sets the physical-pixels-per-dp ratio every `Len::dp` in the tree
+    /// resolves against from the next layout pass on -- see `density`'s
+    /// field doc. Not folded into `resize` because the two change on
+    /// different triggers (a surface resize on every rotation or keyboard
+    /// open; a density change only if the app follows the display to a
+    /// different screen, which Android surfaces separately).
+    pub fn set_density(&mut self, density: f32) {
+        self.density = density;
+    }
+
+    pub fn density(&self) -> f32 {
+        self.density
+    }
+
     pub fn update<'a>(&mut self, root: impl Into<Option<&'a StrongWidget>>, rsc: &mut dyn UiRsc) {
         // safety mechanism for memory leaks; might wanna return a result instead so user can
         // decide whether to panic or not
@@ -311,7 +332,7 @@ impl UiRenderState {
         };
         let from = active
             .size
-            .to_uivec2()
+            .to_uivec2(self.density)
             .align(RegionAlign::TOP_LEFT)
             .within(&active.region);
         let slot = active.move_slot;

iris/examples/message_list.rs

@@ -68,12 +68,15 @@ fn build_row<Rsc: UiRsc + 'static>(rsc: &mut Rsc, i: usize) -> StrongWidget {
         let mut span = Span::empty(Dir::DOWN);
         span.push(text);
         span.push(img);
-        span.pad(8.0).background(rect(tint)).add_strong(rsc).any()
+        span.pad(dp(8.0))
+            .background(rect(tint))
+            .add_strong(rsc)
+            .any()
     } else {
         wtext(row_text(i))
             .wrap(true)
             .color(text_color)
-            .pad(8.0)
+            .pad(dp(8.0))
             .background(rect(tint))
             .add_strong(rsc)
             .any()

iris/src/android/mod.rs

@@ -23,7 +23,7 @@ mod view;
 pub use insets::Insets;
 pub use render::AndroidRenderer;
 pub use view::{
-    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, LogicalInsets,
+    AndroidAppState, AndroidRsc, AndroidUiState, HasAndroidUiState, IrisViewPeer, WindowInsets,
     new_peer,
 };
 

iris/src/android/render.rs

@@ -208,14 +208,14 @@ impl AndroidRenderer {
         surface.configure(&device, &config);
 
         let encoder = Self::create_encoder(&device);
-        // Logical size (physical / `content_scale`) -- see
-        // `android::view::AndroidUiState::content_scale`'s field comment
-        // for why this crate now divides at all (RUST.md's P0 box, "text
-        // is far too small"). The swapchain above stays at the real
-        // physical `width`/`height` for a sharp framebuffer.
-        let logical_size =
-            iris_core::util::Vec2::new(width as f32 / content_scale, height as f32 / content_scale);
-        let ui = match UiRenderNode::new(&device, &queue, &config, logical_size) {
+        // Physical pixels, matching the swapchain's own `width`/`height`
+        // exactly -- see `android::view::AndroidUiState::content_scale`'s
+        // field comment for why this is no longer divided into a separate
+        // logical space (that stopgap is what made text blurry, RUST.md's
+        // P0 box). `Len::dp` folds the density in at layout time instead,
+        // so nothing here needs to know it at all.
+        let window_size = iris_core::util::Vec2::new(width as f32, height as f32);
+        let ui = match UiRenderNode::new(&device, &queue, &config, window_size) {
             Ok(ui) => ui,
             Err(wgpu_error) => return Err(Self::diagnostic(&adapter, &wgpu_error)),
         };
@@ -398,25 +398,27 @@ impl AndroidRenderer {
         submit_start.elapsed()
     }
 
-    /// Logical size (physical / `content_scale`) -- the unit layout and
-    /// hit-testing use, matching the window uniform's own units. See
+    /// Physical pixels -- the unit layout and hit-testing use, matching
+    /// the window uniform's own units. See
     /// `android::view::AndroidUiState::content_scale`'s field comment.
     pub fn size(&self) -> iris_core::util::Vec2 {
-        iris_core::util::Vec2::new(
-            self.config.width as f32 / self.content_scale,
-            self.config.height as f32 / self.content_scale,
-        )
+        iris_core::util::Vec2::new(self.config.width as f32, self.config.height as f32)
     }
 
+    /// Reconfigures the surface and rewrites the window uniform for a new
+    /// physical size -- deliberately the *only* two things this does.
+    /// `device`, `ui`'s atlas, buffers and bind groups are untouched, so a
+    /// call here (as opposed to a fresh `AndroidRenderer::new`) never
+    /// invalidates a glyph the CPU-side cache already placed in the atlas.
+    /// See `android::view::IrisViewPeer::surface_changed`'s doc comment for
+    /// why that distinction matters -- it is what keeps text on screen
+    /// across an IME resize.
     pub fn resize(&mut self, width: u32, height: u32) {
         self.config.width = width;
         self.config.height = height;
         self.surface.configure(&self.device, &self.config);
-        let logical = iris_core::util::Vec2::new(
-            width as f32 / self.content_scale,
-            height as f32 / self.content_scale,
-        );
-        self.ui.resize(logical, &self.queue);
+        let size = iris_core::util::Vec2::new(width as f32, height as f32);
+        self.ui.resize(size, &self.queue);
     }
 }
 

iris/src/android/view.rs

@@ -70,19 +70,31 @@ pub struct AndroidUiState {
     /// because `dumpsys gfxinfo` cannot see a `SurfaceView`'s own
     /// GPU-drawn frames at all. See `iris_core::FrameReport`'s own doc.
     pub frame_report: FrameReport,
-    /// `DisplayMetrics.density` (`new_peer`'s doc comment), read once at
-    /// view construction: physical pixels per dp on this device. Neither
-    /// this crate nor `default::` had ever divided by it before RUST.md's
-    /// P0 box's phone report ("text is far too small") -- `window_size`
-    /// below and `surface_changed`'s call into `UiRenderState::resize` both
-    /// report *logical* (physical / `content_scale`) dimensions now, which
-    /// is what makes a `font_size: 16.0` 16 dp rather than 16 raw device
-    /// pixels on a ~3x-density phone. The actual wgpu surface/swapchain
-    /// stays at the real physical resolution (`AndroidRenderer`'s own
-    /// `config.width/height`) for a sharp framebuffer; only the *logical*
-    /// coordinate system layout, hit-testing and the window uniform agree
-    /// on is scaled. Touch coordinates (`on_touch_event`) are divided by
-    /// this too, so they land in the same space layout is using.
+    /// `DisplayMetrics.density` (`new_peer`'s doc comment): physical pixels
+    /// per dp on this device, read once at view construction and carried
+    /// on `UiRenderState::density` (`render.set_density`, `new_peer`) from
+    /// then on -- every `Len::dp` in the widget tree resolves against it at
+    /// layout time (`Len::dp`'s field doc, IRIS_TODO.md's
+    /// "density-independent length unit" item, 2026-09-06).
+    ///
+    /// **Everything else in this module is physical pixels, matching the
+    /// real wgpu surface/swapchain resolution** -- window size, touch
+    /// coordinates, insets. That is a correction from an earlier version
+    /// of this comment, which had `window_size`/`surface_changed`'s
+    /// `UiRenderState::resize` call divide by `content_scale` into a
+    /// *logical* coordinate space instead, as a global stopgap for
+    /// RUST.md's P0 box's phone report ("text is far too small"). That
+    /// stopgap fixed the size but not the *sharpness*: dividing to logical
+    /// units meant a `16.0`-sized glyph rasterised at 16 physical px and
+    /// then implicitly upscaled ~3x by the NDC mapping onto the real
+    /// physical framebuffer -- the exact "blurry ... glyphs drawn at
+    /// logical size and stretched by the scale" Iris reported next.
+    /// Resolving `dp` at layout time replaces it: a widget author writes
+    /// `dp(16)` for a size that should look the same physical size on any
+    /// density, and everything downstream (layout, hit-testing, the window
+    /// uniform, and the font size handed to the text shaper) works in the
+    /// display's own physical pixels throughout, so nothing is
+    /// rasterised at one resolution and displayed at another.
     pub content_scale: f32,
     /// The last insets `render()` saw -- compared each frame so
     /// `AndroidAppState::on_insets_changed` fires only when they actually
@@ -154,21 +166,26 @@ pub trait AndroidAppState: HasAndroidUiState {
     /// (RUST.md's P0 box: "the status-bar inset is not applied" reported
     /// the two top buttons sitting under it, because nothing read `.top`
     /// at all), and again on a rotation or the keyboard opening/closing.
-    /// `insets` is in the same *logical* units `content_scale` converts
-    /// everything else to (physical / `content_scale`), so a widget can add
-    /// it to a layout size directly. The default does nothing -- most
-    /// screens have no chrome that sits under a system bar.
+    /// `insets` is in the same physical-pixel units everything else in the
+    /// tree now uses (`AndroidUiState::content_scale`'s field comment), so
+    /// a widget can add it to a layout size directly -- `dp(...) +
+    /// abs(insets.top)` if the widget wants a density-independent size
+    /// plus the system bar's own (already-physical) height. The default
+    /// does nothing -- most screens have no chrome that sits under a
+    /// system bar.
     #[allow(unused_variables)]
-    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: LogicalInsets) {}
+    fn on_insets_changed(&mut self, rsc: &mut AndroidRsc<Self>, insets: WindowInsets) {}
 }
 
-/// `insets::Insets`, converted from physical to logical units -- see
-/// `AndroidUiState::content_scale`'s field comment. A distinct type from
-/// `insets::Insets` (rather than dividing in place) so a reader at the call
-/// site can tell which unit a value is already in without checking where it
-/// came from.
+/// `insets::Insets` as `f32`, for the widget-facing callback above -- a
+/// distinct type from `insets::Insets` so a caller of `on_insets_changed`
+/// is not coupled to that module's own (`i32`, JNI-shaped) representation.
+/// Both are physical pixels; this used to divide by `content_scale` into a
+/// separate *logical* unit (hence the old name, `LogicalInsets`), back when
+/// the rest of layout was logical too -- see `AndroidUiState::content_scale`'s
+/// field comment for why that stopgap is gone.
 #[derive(Clone, Copy, Default, Debug, PartialEq)]
-pub struct LogicalInsets {
+pub struct WindowInsets {
     pub left: f32,
     pub top: f32,
     pub right: f32,
@@ -176,14 +193,14 @@ pub struct LogicalInsets {
     pub ime_bottom: f32,
 }
 
-impl LogicalInsets {
-    fn from_physical(insets: Insets, content_scale: f32) -> Self {
+impl WindowInsets {
+    fn from_physical(insets: Insets) -> Self {
         Self {
-            left: insets.left as f32 / content_scale,
-            top: insets.top as f32 / content_scale,
-            right: insets.right as f32 / content_scale,
-            bottom: insets.bottom as f32 / content_scale,
-            ime_bottom: insets.ime_bottom as f32 / content_scale,
+            left: insets.left as f32,
+            top: insets.top as f32,
+            right: insets.right as f32,
+            bottom: insets.bottom as f32,
+            ime_bottom: insets.ime_bottom as f32,
         }
     }
 }
@@ -343,10 +360,9 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
         let ui_state = self.state.android_state();
         let current_insets = ui_state.insets();
         if current_insets != ui_state.last_insets {
-            let content_scale = ui_state.content_scale;
-            let logical = LogicalInsets::from_physical(current_insets, content_scale);
+            let physical = WindowInsets::from_physical(current_insets);
             self.state.android_state_mut().last_insets = current_insets;
-            self.state.on_insets_changed(&mut self.rsc, logical);
+            self.state.on_insets_changed(&mut self.rsc, physical);
         }
 
         let ui_state = self.state.android_state();
@@ -504,16 +520,10 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
     ) -> bool {
         self.drain_tasks();
         let action = event.action_masked(&mut ctx.env);
-        // Device (physical) pixels, same as every other Android coordinate
-        // -- divided so a touch lands in the same *logical* space layout
-        // now uses (`AndroidUiState::content_scale`'s field comment).
-        // Without this, `window_size()` reporting logical dims while touch
-        // stayed physical would land every tap off by exactly the density
-        // factor on any phone denser than 1x.
-        let ui_state = self.state.android_state();
-        let content_scale = ui_state.content_scale;
-        let x = event.x(&mut ctx.env) / content_scale;
-        let y = event.y(&mut ctx.env) / content_scale;
+        // Device (physical) pixels, same space layout now uses throughout
+        // -- see `AndroidUiState::content_scale`'s field comment.
+        let x = event.x(&mut ctx.env);
+        let y = event.y(&mut ctx.env);
         let ui_state = self.state.android_state_mut();
         match action {
             MotionAction::Down => {
@@ -564,7 +574,6 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         height: i32,
     ) {
         self.drain_tasks();
-        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
         // The layout engine's own notion of the canvas size is separate
         // from the wgpu surface's -- winit's backend sets it from
         // `WindowEvent::Resized`, and there is no equivalent automatic
@@ -574,29 +583,55 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         // whatever size `UiRenderState::new` starts at instead of the
         // surface's real one.
         //
-        // **Logical, not physical** -- `content_scale`'s field comment on
-        // `AndroidUiState`. This call sets `UiRenderState::output_size`,
-        // which is what every widget's absolute `PixelRegion` (a fixed
-        // `.height(56)`, in particular) is computed against; `AndroidRenderer`'s
-        // own `size()`/`resize()`/`new()` already report logical dimensions
-        // to the *shader*'s window uniform, so leaving this call on raw
-        // physical `width`/`height` split the two into different units --
-        // layout placed a "56"-unit-tall row in an ~2219-tall physical
-        // canvas (an absolute, correctly-56-unit box), the shader then
-        // divided that same 56 by a ~845-unit *logical* window dimension,
-        // and the row rendered far too short rather than too tall or
-        // right, because a fixed-size item's absolute unit value never
-        // adapts to the mismatch the way a `rest(n)`-proportional one
-        // does. Found by measuring a fresh install's top button row at
-        // ~40 physical px instead of the ~147px `56 * content_scale`
-        // predicts, immediately after the density fix below was added.
-        let content_scale = self.state.android_state().content_scale;
-        self.render
-            .resize((width as f32 / content_scale, height as f32 / content_scale));
-        // Drop the old renderer (and the surface it owns) before building
-        // one from the new window -- see `AndroidRenderer`'s doc comment.
-        let ui_state = self.state.android_state_mut();
-        ui_state.renderer = None;
+        // **Physical pixels, matching `AndroidRenderer`'s own
+        // `size()`/`resize()`/`new()`** -- `AndroidUiState::content_scale`'s
+        // field comment. This call sets `UiRenderState::output_size`, which
+        // every `rel`/`rest` length resolves against and every `abs`
+        // pixel-region compares to directly; a `dp(56)` height now folds
+        // in the density at `Len::apply_rest` time instead of this call
+        // dividing the whole window into a separate logical space, which
+        // is what used to make every `abs`-unit size (a fixed `.height(56)`
+        // in particular) mean something different from a `rest`-based one.
+        self.render.resize((width as f32, height as f32));
+
+        // **Reuse the existing renderer (device, atlas, buffers, bind
+        // groups) when one is already live -- only reconfigure the
+        // surface.** `surfaceChanged` fires on *every* size or format
+        // change, not only on a genuinely new `Surface`/window: showing
+        // the IME under `adjustResize` resizes the same `SurfaceView` and
+        // is reported through this exact callback. Rebuilding the whole
+        // `AndroidRenderer` here used to mean a fresh `UiRenderNode::new`
+        // -- a brand-new, empty glyph atlas and fresh GPU buffers -- while
+        // `iris_core`'s CPU-side glyph cache (`primitive/text.rs`) kept the
+        // atlas coordinates it had already handed out against the *old*
+        // atlas. Every glyph then drew from a UV rectangle that pointed
+        // into a texture that had just been recreated empty, so text
+        // vanished on the first keyboard open while rects (which never go
+        // through the atlas) kept drawing -- exactly the "rectangles stay,
+        // glyphs disappear" Iris reported. Confirmed by reading this path
+        // end to end (no fresh-atlas rebuild anywhere in `resize()` below,
+        // only in `AndroidRenderer::new`) before changing anything, per
+        // AGENTS.md's "verify before finishing".
+        //
+        // `AndroidRenderer::resize` only reconfigures the wgpu surface and
+        // rewrites the window uniform -- device, atlas, buffers and bind
+        // groups are untouched, so the glyph cache's coordinates stay
+        // valid. A genuinely new surface (after `surface_destroyed`, e.g.
+        // backgrounding) still goes through `AndroidRenderer::new` below,
+        // since `renderer` is `None` in that case.
+        let already_live = self.state.android_state().renderer.is_some();
+        if already_live {
+            let ui_state = self.state.android_state_mut();
+            ui_state
+                .renderer
+                .as_mut()
+                .expect("checked Some above")
+                .resize(width as u32, height as u32);
+            self.render(ctx);
+            return;
+        }
+
+        let window = holder.surface(&mut ctx.env).to_native_window(&mut ctx.env);
         // `AndroidRenderer::new` used to panic here through wgpu's own
         // default uncaptured-error handler on a bind-group-layout
         // validation failure -- exactly what aborted the P0 bench APK on
@@ -607,6 +642,11 @@ impl<State: AndroidAppState> ViewPeer for IrisViewPeer<State> {
         // the one place in the app that can turn it into something a
         // person can read, since `ctx.view`/`ctx.env` (needed to reach the
         // Java side) are only in scope inside a `ViewPeer` callback.
+        //
+        // `content_scale` reaches `AndroidRenderer` only for the
+        // Diagnostics page's report text now -- window size and the
+        // shader's window uniform are physical pixels throughout (see the
+        // `resize` call above), not divided by it.
         let content_scale = self.state.android_state().content_scale;
         match AndroidRenderer::new(window, width as u32, height as u32, content_scale) {
             Ok(renderer) => {
@@ -771,15 +811,22 @@ pub fn new_peer<'local, State: AndroidAppState>(
         state: Default::default(),
         _state: PhantomData,
     };
+    // See `TextData::density`'s field doc for why this is set alongside
+    // `render.set_density` below rather than read from there.
+    rsc.ui.text.density = content_scale;
     let shared = Rc::new(RefCell::new(Shared::default()));
     let ui_state = AndroidUiState::new(shared.clone(), content_scale);
     let mut state = State::new(ui_state, &mut rsc);
     let platform_vm = env.get_java_vm().unwrap();
     let platform_view = env.new_global_ref(&view.0).unwrap();
     state.platform_ready(&mut rsc, platform_vm, platform_view);
+    let mut render = UiRenderState::new();
+    // Every `Len::dp` in the tree resolves against this from now on -- see
+    // `UiRenderState::density`'s field doc and `Len::dp`'s.
+    render.set_density(content_scale);
     let peer = IrisViewPeer {
         rsc,
-        render: UiRenderState::new(),
+        render,
         state,
         task_recv,
     };

iris/src/widget/list.rs

@@ -752,9 +752,10 @@ impl List {
         let axis = self.axis;
         let output_len = painter.output_size().axis(axis);
         let container_len = painter.region().axis(axis).len();
+        let density = painter.density();
         let resolve = move |used: Size| -> f32 {
             used.axis(axis)
-                .apply_rest()
+                .apply_rest(density)
                 .within_len(container_len)
                 .to_abs(output_len)
         };

iris/src/widget/position/align.rs

@@ -17,14 +17,15 @@ impl Widget for Aligned {
         // already-resolved region double-applies that composition and is
         // wrong for any widget nested below the root.
         let used = painter.widget(&self.inner);
+        let density = painter.density();
         let region = match self.align.tuple() {
-            (Some(x), Some(y)) => used.to_uivec2().align(RegionAlign { x, y }),
+            (Some(x), Some(y)) => used.to_uivec2(density).align(RegionAlign { x, y }),
             (Some(x), None) => {
-                let x = used.x.apply_rest().align(x);
+                let x = used.x.apply_rest(density).align(x);
                 UiRegion::new(x, UiSpan::FULL)
             }
             (None, Some(y)) => {
-                let y = used.y.apply_rest().align(y);
+                let y = used.y.apply_rest(density).align(y);
                 UiRegion::new(UiSpan::FULL, y)
             }
             (None, None) => UiRegion::FULL,

iris/src/widget/position/max_size.rs

@@ -9,12 +9,12 @@ pub struct MaxSize {
 impl MaxSize {
     /// Caps a reported length at `max`, comparing in pixels since `Len`'s
     /// rel/abs/rest components are not otherwise comparable.
-    fn clamp(len: Len, max: Option<Len>, output: f32) -> Len {
+    fn clamp(len: Len, max: Option<Len>, output: f32, density: f32) -> Len {
         let Some(max) = max else {
             return len;
         };
-        let len_px = len.apply_rest().to_abs(output);
-        let max_px = max.apply_rest().to_abs(output);
+        let len_px = len.apply_rest(density).to_abs(output);
+        let max_px = max.apply_rest(density).to_abs(output);
         if len_px > max_px { max } else { len }
     }
 
@@ -24,11 +24,11 @@ impl MaxSize {
     /// start, if it does not. Needed so the child is never painted bigger
     /// than the size this widget reports for it -- see the identical
     /// requirement noted on `Sized::draw`.
-    fn clamp_region(offered_px: f32, max: Option<Len>, output: f32) -> UiSpan {
+    fn clamp_region(offered_px: f32, max: Option<Len>, output: f32, density: f32) -> UiSpan {
         let Some(max) = max else {
             return UiSpan::FULL;
         };
-        let max_scalar = max.apply_rest();
+        let max_scalar = max.apply_rest(density);
         let max_px = max_scalar.to_abs(output);
         if offered_px > max_px {
             max_scalar.align(AxisAlign::Neg)
@@ -41,15 +41,16 @@ impl MaxSize {
 impl Widget for MaxSize {
     fn draw(&mut self, painter: &mut Painter) -> Size {
         let output = painter.output_size();
+        let density = painter.density();
         let offered = painter.px_size();
         let region = UiRegion {
-            x: Self::clamp_region(offered.x, self.x, output.x),
-            y: Self::clamp_region(offered.y, self.y, output.y),
+            x: Self::clamp_region(offered.x, self.x, output.x, density),
+            y: Self::clamp_region(offered.y, self.y, output.y, density),
         };
         let used = painter.widget_within(&self.inner, region);
         Size {
-            x: Self::clamp(used.x, self.x, output.x),
-            y: Self::clamp(used.y, self.y, output.y),
+            x: Self::clamp(used.x, self.x, output.x, density),
+            y: Self::clamp(used.y, self.y, output.y, density),
         }
     }
 }

iris/src/widget/position/pad.rs

@@ -7,9 +7,12 @@ pub struct Pad {
 
 impl Widget for Pad {
     fn draw(&mut self, painter: &mut Painter) -> Size {
-        let used = painter.widget_within(&self.inner, self.padding.region());
-        let width = self.padding.left + self.padding.right;
-        let height = self.padding.top + self.padding.bottom;
+        let density = painter.density();
+        let used = painter.widget_within(&self.inner, self.padding.region(density));
+        let width =
+            self.padding.left.apply_rest(density).abs + self.padding.right.apply_rest(density).abs;
+        let height =
+            self.padding.top.apply_rest(density).abs + self.padding.bottom.apply_rest(density).abs;
         Size {
             x: used.x + Len::abs(width),
             y: used.y + Len::abs(height),
@@ -17,23 +20,29 @@ impl Widget for Pad {
     }
 }
 
+/// Each side is a `Len`, not a bare `f32`, so `.pad(dp(10))` resolves
+/// against the display's density the same way any other size does -- see
+/// `Len::dp`'s field doc. `.pad(10)` (a bare number) still works via
+/// `From<T: UiNum>` below, unchanged: it becomes an `abs` (physical-pixel)
+/// `Len`, exactly as a bare number always has meant elsewhere in this
+/// crate.
 pub struct Padding {
-    pub left: f32,
-    pub right: f32,
-    pub top: f32,
-    pub bottom: f32,
+    pub left: Len,
+    pub right: Len,
+    pub top: Len,
+    pub bottom: Len,
 }
 
 impl Padding {
     pub const ZERO: Self = Self {
-        left: 0.0,
-        right: 0.0,
-        top: 0.0,
-        bottom: 0.0,
+        left: Len::ZERO,
+        right: Len::ZERO,
+        top: Len::ZERO,
+        bottom: Len::ZERO,
     };
 
-    pub fn uniform(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn uniform(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
             left: amt,
             right: amt,
@@ -41,80 +50,84 @@ impl Padding {
             bottom: amt,
         }
     }
-    pub fn region(&self) -> UiRegion {
+    pub fn region(&self, density: f32) -> UiRegion {
         let mut region = UiRegion::FULL;
-        region.x.start.abs += self.left;
-        region.y.start.abs += self.top;
-        region.x.end.abs -= self.right;
-        region.y.end.abs -= self.bottom;
+        region.x.start.abs += self.left.apply_rest(density).abs;
+        region.y.start.abs += self.top.apply_rest(density).abs;
+        region.x.end.abs -= self.right.apply_rest(density).abs;
+        region.y.end.abs -= self.bottom.apply_rest(density).abs;
         region
     }
-    pub fn x(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn x(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
             left: amt,
             right: amt,
-            top: 0.0,
-            bottom: 0.0,
+            top: Len::ZERO,
+            bottom: Len::ZERO,
         }
     }
-    pub fn y(amt: impl UiNum) -> Self {
-        let amt = amt.to_f32();
+    pub fn y(amt: impl Into<Len>) -> Self {
+        let amt = amt.into();
         Self {
-            left: 0.0,
-            right: 0.0,
+            left: Len::ZERO,
+            right: Len::ZERO,
             top: amt,
             bottom: amt,
         }
     }
 
-    pub fn top(amt: impl UiNum) -> Self {
+    pub fn top(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.top = amt.to_f32();
+        s.top = amt.into();
         s
     }
 
-    pub fn bottom(amt: impl UiNum) -> Self {
+    pub fn bottom(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.bottom = amt.to_f32();
+        s.bottom = amt.into();
         s
     }
 
-    pub fn left(amt: impl UiNum) -> Self {
+    pub fn left(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.left = amt.to_f32();
+        s.left = amt.into();
         s
     }
 
-    pub fn right(amt: impl UiNum) -> Self {
+    pub fn right(amt: impl Into<Len>) -> Self {
         let mut s = Self::ZERO;
-        s.right = amt.to_f32();
+        s.right = amt.into();
         s
     }
 
-    pub fn with_top(mut self, amt: impl UiNum) -> Self {
-        self.top = amt.to_f32();
+    pub fn with_top(mut self, amt: impl Into<Len>) -> Self {
+        self.top = amt.into();
         self
     }
 
-    pub fn with_bottom(mut self, amt: impl UiNum) -> Self {
-        self.bottom = amt.to_f32();
+    pub fn with_bottom(mut self, amt: impl Into<Len>) -> Self {
+        self.bottom = amt.into();
         self
     }
 
-    pub fn with_left(mut self, amt: impl UiNum) -> Self {
-        self.left = amt.to_f32();
+    pub fn with_left(mut self, amt: impl Into<Len>) -> Self {
+        self.left = amt.into();
         self
     }
 
-    pub fn with_right(mut self, amt: impl UiNum) -> Self {
-        self.right = amt.to_f32();
+    pub fn with_right(mut self, amt: impl Into<Len>) -> Self {
+        self.right = amt.into();
         self
     }
 }
 
-impl<T: UiNum> From<T> for Padding {
+/// Covers both a bare number (`.pad(8)`, via `Len`'s own `From<N: UiNum>`
+/// blanket -- an `abs`/physical-pixel `Len`) and a `Len` directly
+/// (`.pad(dp(10))`) with the one impl, since `Len: Into<Len>` is the
+/// reflexive case of the same bound.
+impl<T: Into<Len>> From<T> for Padding {
     fn from(amt: T) -> Self {
-        Self::uniform(amt.to_f32())
+        Self::uniform(amt.into())
     }
 }

iris/src/widget/position/scroll.rs

@@ -43,7 +43,7 @@ impl Widget for Scroll {
 
         self.content_len = used
             .axis(axis)
-            .apply_rest()
+            .apply_rest(painter.density())
             .within_len(container_len)
             .to_abs(output_len);
 

iris/src/widget/position/sized.rs

@@ -17,12 +17,13 @@ impl Widget for Sized {
         // learn its size, then moves it into place with a pure
         // translation; that translation is only valid if what got painted
         // is already the reported size, anchored the same way both times.
+        let density = painter.density();
         let mut region = UiRegion::FULL;
         if let Some(x) = self.x {
-            region.x = x.apply_rest().align(AxisAlign::Neg);
+            region.x = x.apply_rest(density).align(AxisAlign::Neg);
         }
         if let Some(y) = self.y {
-            region.y = y.apply_rest().align(AxisAlign::Neg);
+            region.y = y.apply_rest(density).align(AxisAlign::Neg);
         }
         let used = painter.widget_within(&self.inner, region);
         Size {

iris/src/widget/position/span.rs

@@ -4,12 +4,18 @@ use std::marker::PhantomData;
 pub struct Span {
     pub children: Vec<StrongWidget>,
     pub dir: Dir,
-    pub gap: f32,
+    /// A `Len` (not a bare `f32`) so `dp(4)` resolves against the display's
+    /// density the same way any other size in the tree does -- see
+    /// `Len::dp`'s field doc. Only the `abs` component (folded from `dp` at
+    /// draw time, `Widget::draw` below) is meaningful here; `rel`/`rest`
+    /// were never supported for a gap and still are not.
+    pub gap: Len,
 }
 
 impl Widget for Span {
     fn draw(&mut self, painter: &mut Painter) -> Size {
         let axis = self.dir.axis;
+        let gap = self.gap.apply_rest(painter.density()).abs;
 
         // Phase 1: draw each child once, at the ambient (unmodified, full)
         // region a size-only query used to see before this migration, to
@@ -25,7 +31,7 @@ impl Widget for Span {
             .map(|child| painter.widget(child).axis(axis))
             .collect();
 
-        let gap_total = self.gap * self.children.len().saturating_sub(1) as f32;
+        let gap_total = gap * self.children.len().saturating_sub(1) as f32;
         let total = lens.iter().fold(Len::abs(gap_total), |s, &l| s + l);
 
         // Phase 2: place each child for real, using the lengths just
@@ -54,7 +60,7 @@ impl Widget for Span {
                 child_region.flip(axis);
             }
             let used = painter.widget_within(child, child_region);
-            start.abs += self.gap;
+            start.abs += gap;
 
             let ortho = used.axis(!axis);
             if ortho.rel > 0.0 || ortho.rest > 0.0 {
@@ -82,12 +88,12 @@ impl Span {
         Self {
             children: Vec::new(),
             dir,
-            gap: 0.0,
+            gap: Len::ZERO,
         }
     }
 
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
+    pub fn gap(mut self, gap: impl Into<Len>) -> Self {
+        self.gap = gap.into();
         self
     }
 
@@ -103,7 +109,7 @@ impl Span {
 pub struct SpanBuilder<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag> {
     pub children: Wa,
     pub dir: Dir,
-    pub gap: f32,
+    pub gap: Len,
     _pd: PhantomData<(State, Tag)>,
 }
 
@@ -129,13 +135,13 @@ impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
         Self {
             children,
             dir,
-            gap: 0.0,
+            gap: Len::ZERO,
             _pd: PhantomData,
         }
     }
 
-    pub fn gap(mut self, gap: impl UiNum) -> Self {
-        self.gap = gap.to_f32();
+    pub fn gap(mut self, gap: impl Into<Len>) -> Self {
+        self.gap = gap.into();
         self
     }
 }

iris/src/widget/text/edit.rs

@@ -141,7 +141,8 @@ impl<'a> TextEditCtx<'a> {
     fn layout(&mut self) -> &Layout<UiColor> {
         let attrs = self.text.view.attrs.clone();
         let width = self.text.view.wrap_width();
-        self.text.view.buf.shape(self.data, &attrs, width);
+        let density = self.data.density;
+        self.text.view.buf.shape(self.data, &attrs, width, density);
         self.text.view.buf.layout()
     }
 

iris/transcript-ui/src/composer.rs

@@ -39,7 +39,7 @@ where
         .label("Message")
         .add(rsc);
 
-    let bar: WeakWidget = (field.pad(12).width(rest(1)),)
+    let bar: WeakWidget = (field.pad(dp(12)).width(rest(1)),)
         .span(Dir::RIGHT)
         .background(rect(UiColor::new(40, 40, 46, 255)))
         .add(rsc);

iris/transcript-ui/src/row.rs

@@ -174,8 +174,8 @@ where
 
     (header, field.width(rest(1)))
         .span(Dir::DOWN)
-        .gap(4)
-        .pad(10)
+        .gap(dp(4))
+        .pad(dp(10))
         .add_strong(rsc)
         .any()
 }