iris: FrameReport, a per-frame wall-time report of iris's own render path

dumpsys gfxinfo cannot see a SurfaceView's own GPU-drawn frames at all
(RUST.md's I5 box), so iris needs its own equivalent of Compose's
render-report button before item 3 of the recommendation can be decided
by a number. FrameReport (iris/core/src/render/frame_report.rs) records
each frame's wall time -- from render()'s redraw start to after
queue.submit + present() -- into a fixed 4096-entry ring, and reports
total frames, janky % (>16.7ms, gfxinfo's own budget), P50/P90/P99 and
the worst. Wired into AndroidUiState and android/view.rs's render(), and
exposed as two named controls ("Frame report", "Reset frame report") on
iris-android-app's transcript screen, logged under the crate's fixed tag
so a script can grep "iris frame report" the way transcript-bench.sh
greps "ai-app render report".

6 new unit tests for the ring/percentile math. cargo fmt/clippy/test
--workspace clean; cargo ndk (iris, transcript-ui, and
iris-android-app --features transcript-screen) all clean.

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

iris/android-app/src/transcript_client.rs

@@ -44,6 +44,12 @@ mod pinned {
 
 pub struct TranscriptClient {
     ui_state: AndroidUiState,
+    /// The screen's own content -- everything under the fixed
+    /// [`frame_report_controls`] bar, which is built once (`new`, below)
+    /// and never touched by `show_message`/`rebuild_transcript`'s own
+    /// `set` calls the way `desktop-app`'s `transcript_ptr` isn't touched
+    /// by rebuilding the session list beside it.
+    content: WeakWidget<WidgetPtr>,
     screen: Option<transcript_ui::TranscriptScreen>,
     /// The folded transcript as of the last rebuild -- kept here (not
     /// re-derived) for the same reason `desktop-app`'s `Client::items`
@@ -94,13 +100,76 @@ fn placeholder<Rsc: HasEvents>(rsc: &mut Rsc, message: &str) -> StrongWidget {
         .any()
 }
 
+/// The two named controls RUST.md's I5 box ("Measurements taken" (b))
+/// drives by name over `ui-trace`, e.g. `ui-trace record --do "tap 'Frame
+/// report'"`. `dumpsys gfxinfo` cannot see this screen's own GPU-drawn
+/// frames at all -- this is the screen's own equivalent of the Compose
+/// app's "Copy render timings" control, logged rather than clipboarded
+/// (no clipboard wiring exists here) under this crate's own fixed
+/// `android_logger` tag (`iris-android-app`, `lib.rs`'s `JNI_OnLoad`),
+/// grep-able on the fixed string `"iris frame report"` the way
+/// `transcript-bench.sh` greps `"ai-app render report"`.
+fn frame_report_controls(rsc: &mut AndroidRsc<TranscriptClient>) -> WeakWidget {
+    type Rsc = AndroidRsc<TranscriptClient>;
+    let report_rect = rect(Color::rgb(50, 50, 60))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, _rsc: &mut Rsc| match ctx
+                .state
+                .android_state()
+                .frame_report
+                .report()
+            {
+                Some(stats) => log::info!("iris frame report: {stats}"),
+                None => log::info!(
+                    "iris frame report: no frames recorded -- scroll first, then press this"
+                ),
+            },
+        )
+        .label("Frame report");
+    let report = (
+        report_rect,
+        wtext("Frame report").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(8)
+        .add(rsc);
+
+    let reset_rect = rect(Color::rgb(70, 40, 40))
+        .on(
+            CursorSense::click(),
+            |ctx: EventIdCtx<'_, Rsc, _, _>, _rsc: &mut Rsc| {
+                ctx.state.android_state_mut().frame_report.reset();
+                log::info!("iris frame report: reset");
+            },
+        )
+        .label("Reset frame report");
+    let reset = (
+        reset_rect,
+        wtext("Reset").size(18).text_align(Align::CENTER),
+    )
+        .stack()
+        .pad(8)
+        .add(rsc);
+
+    (report, reset).span(Dir::RIGHT).height(56).add(rsc)
+}
+
 impl AndroidAppState for TranscriptClient {
     fn new(mut ui_state: AndroidUiState, rsc: &mut AndroidRsc<Self>) -> Self {
+        let content = WidgetPtr::new().add(rsc);
         let loading = placeholder(rsc, "Loading sessions...");
-        ui_state.set_root(loading);
+        content(rsc).set(loading);
+
+        let tree = (frame_report_controls(rsc), content.height(rest(1)))
+            .span(Dir::DOWN)
+            .add_strong(rsc)
+            .any();
+        ui_state.set_root(tree);
 
         let mut client = Self {
             ui_state,
+            content,
             screen: None,
             items: Vec::new(),
             session_id: None,
@@ -120,7 +189,7 @@ impl AndroidAppState for TranscriptClient {
 impl TranscriptClient {
     fn show_message(&mut self, rsc: &mut AndroidRsc<Self>, message: &str) {
         let widget = placeholder(rsc, message);
-        self.android_state_mut().set_root(widget);
+        (self.content)(rsc).set(widget);
         self.screen = None;
     }
 
@@ -286,7 +355,7 @@ impl TranscriptClient {
             });
         }
 
-        self.android_state_mut().set_root(tree);
+        (self.content)(rsc).set(tree);
         self.screen = Some(screen);
     }
 

iris/core/src/render/frame_report.rs

@@ -0,0 +1,213 @@
+use std::time::Duration;
+
+/// The frame budget `dumpsys gfxinfo` also uses to call a frame "janky": the
+/// 60Hz vsync period. Kept as the same threshold so a percentage from this
+/// report and a percentage from `gfxinfo` mean the same thing.
+pub const JANK_THRESHOLD: Duration = Duration::from_nanos(16_666_667);
+
+/// Enough frames for several minutes of scrolling before the oldest ones
+/// start being overwritten -- the same "diagnostic, not a log" sizing
+/// `FrameStats.kt`'s `CAP` uses on the Compose side, chosen independently
+/// here since a `Duration` is smaller than the six `Long` arrays it keeps.
+const RING_CAPACITY: usize = 4096;
+
+/// A per-frame wall-time report iris keeps of itself, because `dumpsys
+/// gfxinfo` cannot see a `SurfaceView`'s own GPU-drawn frames at all
+/// (RUST.md's I5 box, "Measurements taken" (b)): it instruments Android's
+/// ordinary Skia/HWUI View-drawing pipeline, which a `wgpu`-rendered
+/// `SurfaceView` bypasses entirely. `record` is meant to be called once per
+/// frame, wrapping the same span Compose's own render report and `gfxinfo`
+/// count -- from the frame's redraw/update start to after the frame is
+/// handed to the platform to present.
+///
+/// **What this does not measure**: wgpu's `present()` call queues the frame
+/// with the compositor and returns; it is not fenced against the GPU
+/// actually finishing the frame or the compositor actually showing it, the
+/// way `gfxinfo`'s own `GPU_DURATION`/vsync accounting is. So a sample here
+/// is "how long the CPU took to build and submit this frame", not
+/// "how long the frame took to reach the screen" -- named in
+/// [`FrameStats`]'s own `Display` line rather than presented as the latter,
+/// per the standing rule against showing an inferred number as a measured
+/// one where the two differ.
+///
+/// Fixed-size ring, no allocation on the hot path -- `report()` is the only
+/// place that allocates (a sort over the current ring), and it is only
+/// ever called from a button tap, not once per frame.
+pub struct FrameReport {
+    ring: Box<[Duration; RING_CAPACITY]>,
+    /// How many of `ring`'s slots hold a real sample -- saturates at
+    /// `RING_CAPACITY`, unlike `total_frames` below which keeps counting.
+    len: usize,
+    pos: usize,
+    /// All frames recorded since the last `reset`, even past `RING_CAPACITY`
+    /// -- what `janky_percent` divides by, so a long run's percentage stays
+    /// correct even once the ring itself only holds the most recent frames.
+    total_frames: u64,
+    janky_frames: u64,
+}
+
+/// One resolved reading. `Display` is the log line both the "Frame report"
+/// button and `transcript-bench.sh`-style scripts read, grep-able on
+/// `"iris frame report"`.
+pub struct FrameStats {
+    pub total_frames: u64,
+    pub janky_percent: f64,
+    pub p50: Duration,
+    pub p90: Duration,
+    pub p99: Duration,
+    pub worst: Duration,
+}
+
+impl std::fmt::Display for FrameStats {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "frames={} janky%={:.2} p50={:.1}ms p90={:.1}ms p99={:.1}ms worst={:.1}ms \
+             (measures redraw-start to after present() is called, not GPU/compositor \
+             completion)",
+            self.total_frames,
+            self.janky_percent,
+            self.p50.as_secs_f64() * 1000.0,
+            self.p90.as_secs_f64() * 1000.0,
+            self.p99.as_secs_f64() * 1000.0,
+            self.worst.as_secs_f64() * 1000.0,
+        )
+    }
+}
+
+impl FrameReport {
+    pub fn new() -> Self {
+        Self {
+            ring: Box::new([Duration::ZERO; RING_CAPACITY]),
+            len: 0,
+            pos: 0,
+            total_frames: 0,
+            janky_frames: 0,
+        }
+    }
+
+    /// Record one frame's elapsed wall time. O(1), no allocation.
+    pub fn record(&mut self, elapsed: Duration) {
+        self.ring[self.pos] = elapsed;
+        self.pos = (self.pos + 1) % RING_CAPACITY;
+        self.len = (self.len + 1).min(RING_CAPACITY);
+        self.total_frames += 1;
+        if elapsed > JANK_THRESHOLD {
+            self.janky_frames += 1;
+        }
+    }
+
+    /// Clears every counter and every sample -- what the "Reset frame
+    /// report" control calls, so a report covers only what was scrolled
+    /// after the button was pressed (the same reason `FrameStats.kt`'s
+    /// `reset()` exists on the Compose side).
+    pub fn reset(&mut self) {
+        self.len = 0;
+        self.pos = 0;
+        self.total_frames = 0;
+        self.janky_frames = 0;
+    }
+
+    /// `None` if nothing has been recorded since the last reset -- the
+    /// "no frames recorded, scroll first" case, not a zeroed report that
+    /// would read as a real (perfect) measurement.
+    pub fn report(&self) -> Option<FrameStats> {
+        if self.len == 0 {
+            return None;
+        }
+        let mut samples: Vec<Duration> = self.ring[..self.len].to_vec();
+        samples.sort_unstable();
+        let pct = |p: usize| samples[(samples.len() * p / 100).min(samples.len() - 1)];
+        Some(FrameStats {
+            total_frames: self.total_frames,
+            janky_percent: 100.0 * self.janky_frames as f64 / self.total_frames as f64,
+            p50: pct(50),
+            p90: pct(90),
+            p99: pct(99),
+            worst: *samples.last().expect("len > 0 checked above"),
+        })
+    }
+}
+
+impl Default for FrameReport {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn no_frames_reports_none() {
+        assert!(FrameReport::new().report().is_none());
+    }
+
+    #[test]
+    fn one_frame_is_every_percentile_and_the_worst() {
+        let mut r = FrameReport::new();
+        r.record(Duration::from_millis(10));
+        let stats = r.report().unwrap();
+        assert_eq!(stats.total_frames, 1);
+        assert_eq!(stats.p50, Duration::from_millis(10));
+        assert_eq!(stats.p99, Duration::from_millis(10));
+        assert_eq!(stats.worst, Duration::from_millis(10));
+        assert_eq!(stats.janky_percent, 0.0);
+    }
+
+    #[test]
+    fn percentiles_and_worst_over_a_known_set() {
+        let mut r = FrameReport::new();
+        // 100 samples, 1ms..=100ms, fed out of order so the ring's own
+        // order is not what gives the right answer -- the sort has to.
+        for ms in (1..=100).rev() {
+            r.record(Duration::from_millis(ms));
+        }
+        let stats = r.report().unwrap();
+        assert_eq!(stats.total_frames, 100);
+        assert_eq!(stats.p50, Duration::from_millis(51));
+        assert_eq!(stats.p90, Duration::from_millis(91));
+        assert_eq!(stats.p99, Duration::from_millis(100));
+        assert_eq!(stats.worst, Duration::from_millis(100));
+    }
+
+    #[test]
+    fn jank_threshold_matches_gfxinfos_60hz_budget() {
+        let mut r = FrameReport::new();
+        r.record(Duration::from_nanos(16_666_667)); // exactly on budget: not janky
+        r.record(Duration::from_nanos(16_666_668)); // one ns over: janky
+        let stats = r.report().unwrap();
+        assert_eq!(stats.janky_percent, 50.0);
+    }
+
+    #[test]
+    fn janky_percent_is_over_all_time_frames_not_just_the_ring() {
+        // Fewer than RING_CAPACITY frames, all janky, then a fresh reset --
+        // the percentage must reset to 0, not divide by a stale count.
+        let mut r = FrameReport::new();
+        for _ in 0..10 {
+            r.record(Duration::from_millis(50));
+        }
+        assert_eq!(r.report().unwrap().janky_percent, 100.0);
+        r.reset();
+        assert!(r.report().is_none());
+        r.record(Duration::from_millis(1));
+        assert_eq!(r.report().unwrap().janky_percent, 0.0);
+    }
+
+    #[test]
+    fn ring_wraps_without_growing_past_capacity() {
+        let mut r = FrameReport::new();
+        for i in 0..(RING_CAPACITY * 2) {
+            r.record(Duration::from_millis(1 + (i % 5) as u64));
+        }
+        let stats = r.report().unwrap();
+        // total_frames keeps the full count even once the ring has wrapped.
+        assert_eq!(stats.total_frames, (RING_CAPACITY * 2) as u64);
+        // but every sample the ring can report on is still one of the five
+        // values fed in, since a wrap can only overwrite with more of the
+        // same pattern here.
+        assert!(stats.worst <= Duration::from_millis(5));
+    }
+}

iris/core/src/render/mod.rs

@@ -11,12 +11,14 @@ use wgpu::{
 
 mod atlas;
 mod data;
+mod frame_report;
 mod primitive;
 mod texture;
 mod util;
 
 pub use atlas::*;
 pub use data::{Mask, MaskIdx, MoveIdx, MoveOffset};
+pub use frame_report::{FrameReport, FrameStats, JANK_THRESHOLD};
 pub use primitive::*;
 
 const SHAPE_SHADER: &str = include_str!("./shader.wgsl");

iris/src/android/view.rs

@@ -57,6 +57,11 @@ pub struct AndroidUiState {
     /// The AccessKit tree itself -- see `iris_core::AccessTree`'s doc
     /// comment.
     pub access: AccessTree,
+    /// iris's own frame-time report (RUST.md's I5 box, "Measurements
+    /// taken" (b)) -- `render()` below records into it once per frame,
+    /// 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,
 }
 
 impl AndroidUiState {
@@ -72,6 +77,7 @@ impl AndroidUiState {
             shared,
             access_adapter: Default::default(),
             access: AccessTree::new(),
+            frame_report: FrameReport::new(),
         }
     }
 
@@ -262,6 +268,13 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
                 .and_then(|r| self.render.window_region(r, &self.rsc)),
             self.window_size(),
         );
+        // iris's own frame-time report (RUST.md's I5 box, "Measurements
+        // taken" (b)): started here, at the same point a redraw request
+        // fires, and stopped after `renderer.draw()`'s `queue.submit` +
+        // `present()` -- the span Compose's render report and `gfxinfo`
+        // both count. See `iris_core::FrameReport`'s own doc for exactly
+        // what this does and does not measure.
+        let frame_start = Instant::now();
         let ui_state = self.state.android_state_mut();
         self.render.update(&ui_state.root, &mut self.rsc);
         let ui_state = self.state.android_state_mut();
@@ -270,6 +283,10 @@ impl<State: AndroidAppState> IrisViewPeer<State> {
         };
         renderer.update(&mut self.rsc.ui, &mut self.render);
         renderer.draw();
+        self.state
+            .android_state_mut()
+            .frame_report
+            .record(frame_start.elapsed());
         let ui_state = self.state.android_state();
         log::debug!(
             "render(): after update active={} root_px={:?}",