ai-app/docs/IRIS.md

# iris: notable public API changes

For Iris to read on her own time. Each entry is a change to iris's public
surface that a widget author or app author would notice: a trait method
added, removed or re-shaped; a type that callers construct differently; a
capability that moved. Small and trivial changes do not go here.

An entry gives the date, what changed, why, and a short before/after where
it helps judge the change without the session that made it. Newest first.

## 2026-09-07: a headless harness, replayed touch, and physical-pixel desktop layout

Layer 1 and 2 of docs/RUST.md's "Three test layers".

**New: `iris::harness`** -- a screen driven in-process with no window, no
compositor and no GPU, on a clock the caller advances. `Harness::new(size,
density)` gives you an `Rsc`, a `UiRenderState` and a state that
implements `FocusHost`/`OpenUrl` by *recording* what the platform was
asked for (`keyboard_shown`, `opened_urls`) rather than doing it;
`frame(t_ms)`/`frames_until(..)` run frames, `touch(action, pos, t_ms)`
feeds one pointer sample the way Android's `on_touch_event` does, and
`replay(&TouchScript)` runs a whole recorded gesture. `TouchScript` parses
a plain `t_ms action x y` file (`down`/`move`/`up`/`cancel`), so the
batched 120Hz flick shape your phone actually delivers is a file that
`cargo test` can replay -- something the emulator cannot produce at all.

**New: `List::fling_velocity() -> Option<f32>`**, what the release
measured, readable where it landed rather than by re-timing the gesture.

**Changed: `List` starts a fling's curve at its first `tick_fling`, not
at the release.** The only clock it reads is now the one its driver hands
it; in a running app the difference is at most a frame.

**Changed: the desktop backend lays out in physical pixels with a
density, exactly as Android does.** `iris::default::content_scale(window)`
is the desktop's `content_scale` -- winit's scale factor, overridable with
the `IRIS_SCALE` environment variable -- and it now feeds
`UiRenderState::set_density`/`TextData::density` instead of dividing
coordinates into a separate "logical" space. That division had
`UiRenderState::resize` (physical) and the window uniform (logical)
disagreeing on any display whose scale factor is not 1.0, and rasterised
glyphs at one resolution to display them at another. `Input::event` lost
its `scale_factor` parameter as a result, and `DefaultUiState::
window_size()` now answers physical pixels. On a 1.0 display nothing
changes. The override is what lets `run-headless.sh --phone` open a window
at your phone's own 1080x2424 and 2.55.

## 2026-09-07: widgets can animate, and a fling finally moves

Iris's phone said "fling still doesn't work" twice. The velocity was only
half of it: **nothing in iris advanced an animation between input
events**, so `List::fling` stored a speed that nothing ever applied. Three
public changes come out of fixing that.

**`Widget::tick(&mut self, now: Instant) -> bool`** is a new trait method,
defaulted to `false`, so no existing widget changes. A widget that
overrides it is animating; answering `false` is how it stops.

**`UiData::animate(id)` and `UiData::tick_animations(now) -> bool`** are
the registry and its driver. A gesture that starts an animation registers
the widget; each backend calls `tick_animations` once per frame before the
draw and asks for another frame while it answers `true`. That answer is
the *only* thing in iris that makes a frame happen without an input event,
and an animation's path out is its own `tick` returning false -- nothing
has to remember to unregister it.

    // before: the velocity was stored and never applied
    list(ui).fling(-v);
    // after
    list(ui).fling(-v);
    let id = list.id();
    ui.ui_mut().animate(id);

The two calls are deliberate rather than folded into `fling`: the velocity
is the list's business and whether anything animates at all is the frame
loop's, and a caller driving its own frames (the benchmark, the headless
tests) still calls `tick_fling` directly.

**`FlingCalculator` needs the real display density, and its coefficient
was wrong.** `new(density)` takes physical pixels per `dp` and the
velocity handed to it must be in those same physical pixels -- the
density does *not* cancel out, contrary to what that type's doc used to
claim. Separately, `physical_coefficient` multiplied by the scroll
friction (0.015) where AOSP multiplies by its own tuning constant 0.84, a
factor of 56 inside an exponential. Together they gave an ordinary flick a
**45-second** coast, which nobody could see while flings never animated.
`List` reads its density from the painter now, and
`a_flick_lasts_what_aosps_own_formula_says_it_does` pins the absolute
numbers (0.59s and 621px for 3000px/s at density 2.75) against AOSP's
formula -- the check every previous test could not make, because they all
compared the calculator with itself.

**`MOVE_CHAIN_LIMIT` is 64, not 16**, in `render_state.rs` and
`shader.wgsl` alike. It bounds a walk so a cyclic `parent` cannot hang
either side; it was never meant as a claim about tree depth, and the
transcript screen's composer field sits 17 slots below the root. Past the
bound both walks silently stop summing, so a widget draws and hit-tests
short with nothing to say so; the CPU assert now prints the chain, so a
cycle and a deep tree can be told apart.

## 2026-09-06: tool cards, `ToolState`, and a screen that knows whether its session is working

`transcript_ui::tool` is new: a card per tool call, a group per run
(P1b). Three things in the public surface follow from it.

**`client_core::transcript_fold::ToolState`** is what a card colours
itself by -- `Running`, `Deciding`, `Succeeded`, `Failed`, `NoResult` --
built by `ToolState::of(&item, session_working)`. The pair it exists for
is `Succeeded` against `NoResult`: a call that finished having printed
nothing and a call whose result never arrived both leave an empty
`output`, and drawing them the same way states a verdict nobody reached.
Only the session's own status separates them, which is why `of` takes it.

**`event_model::Event::ToolEnd` gained `is_error`** (`#[serde(default)]`,
so an older transcript still parses), and
`client_core::transcript_fold::TranscriptItem::ToolRun` gained `failed`.
Without them a result was everything a card knew and a broken call drew
exactly as confidently as one that worked -- the missing state, not a
wrong one. Every construction site of both had to gain a field; the value
comes from the CLI's own `tool_result`, read in one place
(`import::tool_result_is_error`) by both the live translator and the
import replay.

**`TranscriptScreen::set_session_working(rsc, bool)`** is new, and is the
only thing that writes it. Before: a card with no result was drawn the
same whether its turn was still going or had been interrupted. After:
only the *newest* row can say "running", because every row behind it
belongs to a turn that has ended, and changing the flag redraws that one
row rather than the screen. `TranscriptScreen::expand_tail_tools(rsc,
bool)` joins it, answering whether there was a tool run to act on -- a
group's expanded appearance is otherwise unreachable from anything that
cannot press the screen.

**`transcript_ui::row::build_row` now returns a `TailRow`** rather than an
`Option<RowBlocks>`: `Blocks` for a message (a delta costs the last
markdown block) or `Tools` for a run (an arriving result costs one card).
One mechanism for "what can this row change cheaply", asked of the row
rather than decided again at each call site. It also takes the row's own
`working` flag.

Two smaller ones. `client_core::tool_summary::parse_tool_input` is
`ToolInput.kt`'s subject/description/timeout/rest split, and
`client_core::durations::format_millis` is `Durations.kt`'s -- both pure,
both with the Kotlin's own tests ported.

## 2026-09-06: a tap is its own gesture outcome, and opening a URL is a backend capability

Three related additions, all for following a markdown link.

**`iris::platform::OpenUrl`** is a new trait beside `attr::FocusHost`, and
has the same shape: declared in `iris`, implemented once per backend (a
detached `xdg-open`/`open`/`start` on the desktop, an `ACTION_VIEW` intent
on Android, deferred to the next view callback exactly the way
`pending_show_keyboard` is). A widget asks for the capability by bound --
`Rsc::State: FocusHost + OpenUrl` -- instead of a caller threading a
callback down through every builder. One method, not a general "run an
intent": a narrower capability is a narrower thing to get wrong. Nothing
is returned; the platform either shows a browser or does not, and both
are outside the process.

**`GestureOutcome::Tapped`** is new. `Released(None)` used to mean both
"the press ended having selected something" and "the press ended having
done nothing at all", and only the second is a tap. Any caller that acts
on a tap -- following a link -- must not also act when the finger was
panning the list past that link, so the distinction is made once, in the
gesture machine every widget already shares, rather than timed again per
widget. `DragArbiter::is_undecided()` is what answers it.
`Selection::drag` returns the outcome now instead of `()`.

**`DragArbiter`/`DragGesture` take an axis** (`::on(Axis)`; `::new()` is
still vertical). A code fence pans across its own long lines exactly the
way a transcript pans down its rows, and the two were the same state
machine with `dx` and `dy` swapped. `WidgetLike::scrollable_on(axis)`
joins `scrollable()` for the same reason. Before this, a horizontal
`Scroll` existed but could not be dragged by a finger at all -- its
arbiter only ever committed on the vertical axis.

Two smaller ones in the same pass. **`TextEditCtx::byte_at(pos, size)`**
answers which byte of the text a tap landed on, doing the same
region-relative transform `select` does, without handing out the parley
layout a caller could shape against stale text. And **`Rect::radius` now
takes a `Len`**, so a corner can be written in `dp` and come out the same
physical size on every display; a bare number still means physical pixels.

**One behaviour change worth knowing about**: `Rect::is_size_independent()`
answers `false` now. It answered `true`, and a `Rect` fills whatever
region it is given -- so `draw_inner`'s fast path, which rewrites a
widget's primitives in place instead of redrawing it, could not reproduce
what `draw` would have done. A `.background(rect(..))` behind
variable-height content kept the size of the provisional pass its parent
`Span` had drawn it at, which on the transcript screen meant one code
block's panel covering every block below it. Costs one primitive's redraw
when a rect is resized.

## 2026-09-06: a transcript row is a column of blocks, and a block is the selection unit

`transcript-ui`'s row builder used to make **one** `TextEdit` per message.
It makes one per top-level markdown block now -- heading, paragraph,
fenced code, list, table -- in a `Span::down`, because a streamed delta
into a single buffer re-shaped the whole message through parley on every
event. `client_core::markdown_blocks::split_blocks` does the splitting;
`row::RowBlocks::apply_delta` updates the block a delta lands in and
leaves the rest of the message's layout alone.

**The change to judge, since it is what a reader feels**:
`Selection` is keyed by `SelKey = (RowKey, u32)` -- a row and a block --
so **a block, not a row, is the unit a selection steps in**. A drag still
runs from a reply into the tool output beneath it and copies as one
thing; what changed is that the row under the finger is filled in block by
block rather than all at once, which is if anything closer to what the
old shortcut in `Selection`'s module doc was apologising for. `register`
takes a `SelKey`; `unregister` still takes a `RowKey` and now drops every
block of it (dropping only the first is how a freed widget gets left in
the map -- the shape docs/REVIEW-2026-09-06.md's finding 1 called out).

`Selection::locate(ui, render, pos_window)` is new: which block is under a
window position, with that block's own local position and size. The
list-level handler uses it for the pointer-captured half of a drag,
instead of computing a row-local position from `List::extent`.

`row::build_row` returns `(RowKey, StrongWidget, Option<RowBlocks>)` --
the third is the per-block state a caller keeps only for the row a reply
is streaming into, and is `None` for a tool run, which never streams.

## 2026-09-06: a reported `Size` may not carry `dp`; `Len::fold_dp`

**New: `Len::fold_dp(density) -> Len`** -- the same fold `apply_rest` does
(`dp` becomes physical pixels), but staying a `Len` so `rest` survives.

**New rule, and it is a rule about every widget, not about the two that
broke it**: a `Len` a widget *reports* from `draw` must not carry an
unresolved `dp`. `dp` is an input unit -- a number the widget author wrote
-- and the containers that consume a reported length read `abs`, `rel` and
`rest` straight off it (`Span`'s placement arithmetic, `Pad`'s addition),
so a reported `dp` is silently worth **zero**. `MaxSize` and `Sized` both
returned the caller's declared `Len` as written; a `.max_height(dp(168))`
therefore gave its child a slot of nothing the moment the cap actually
applied, which is what made the composer's bar collapse. Both put their
declared lengths through `fold_dp` now, and
`UiRenderState::draw_inner` `debug_assert!`s the invariant after every
`Widget::draw`, so a widget that gets this wrong says so at the mistake
rather than laying out at zero somewhere else.

Nothing changes for a caller: `.max_height(dp(48))` is written the same
way. It is only widget *authors* who now have a rule to follow, and a
debug build that enforces it.

## 2026-09-06: `Painter::set_mask` reuses one slot; `ActiveData` gains two fields

**`Painter::set_mask(region)` allocates its widget's mask slot once and
rewrites it in place** on every later draw, instead of pushing a new one
each time. It has to: `draw_inner`'s unchanged-region fast path does not
revisit a descendant whose own region did not change, so those descendants
go on referencing whichever slot they were first drawn under. Pushing a
fresh slot per draw left the composer's field clipped to a box the bar had
long since moved away from -- four live mask entries, none of them the
`Masked`'s current region -- and it drew nothing at all. Same call, same
signature; only the lifetime changed.

**`ActiveData` gains `own_mask` and `move_applied`** (both public, since
`ActiveData` is). `own_mask` is the slot above, `MaskIdx::NONE` for a
widget that sets no mask. `move_applied` is how much of a widget's own
move-slot delta its `region` already accounts for: `mov` shifts both,
`Painter::reposition` shifts only the slot, and `resolved_region` -- and so
every hit test -- has to subtract it. Without that a widget that had been
panned had its *own* hit box at twice the pan while its descendants were
correct, which made the composer's field untappable after a finger drag.

## 2026-09-06: `Scroll` pans on a finger drag, and a vertical drag in a focused text field no longer selects

Three related public changes, all in aid of IRIS_TODO.md's "the composer
has no touch-drag scroll".

**`Scroll::drag(render, id, sense, pos_window, now)` is new**, and
`WidgetLike::scrollable()` now registers it alongside the wheel handler it
already registered -- so anything built with `.scrollable()` pans on a
finger drag with no extra wiring at the call site. It goes through the same
`sense::DragGesture` that `transcript-ui::Selection::drag` drives `List`
with (arbitration, `DRAG_SLOP`, velocity, pointer capture), rather than a
second copy of that widget's wiring: `DragGesture` owns the mechanics and
each caller decides only what a committed pan *means*. `Scroll::amt()` is
new too, the read-only pan position a test or a scroll indicator needs.

There is deliberately **no fling** on `Scroll`. Unlike `List` it has no
per-frame tick to animate one with (`List::set_redraw_handle`/`tick_fling`),
and the areas it wraps today are at most a screenful, where Android does not
fling either. The released velocity is dropped rather than approximated.

**A vertical drag inside an already-focused `TextEdit` no longer extends a
selection.** `iris::attr`'s `on_press` used to treat a focused field as the
plain `click_or_drag` case -- every `Pressing` frame updated the selection.
It now applies the same `DRAG_SLOP` rule the *unfocused* branch already
applied: a press that moves past the slop vertically abandons its pending
selection for the rest of the gesture, so the scroll area around the field
gets the drag instead. Horizontal drag-to-select is unchanged, and a long
press still starts a selection. This is Android's own `EditText` behaviour
(a vertical drag scrolls; only a long press selects), and it is what makes
"swipe up over the composer to scroll the transcript" work without dragging
a highlight through the message you were typing.

**`UiRenderState::orphaned_primitives()` is new**, and `update` now
`debug_assert!`s (debug builds only) that nothing is orphaned. An orphan is
a primitive still bound for the GPU that no live `ActiveData` names -- a
copy nothing can move, clip or free. That was the doubled `Compacted:` row
on the phone; see the same date's commit `76b1f99` and docs/RUST.md. The
per-frame guard is a count comparison (O(active widgets)); the walk that
names the offenders only runs when the counts disagree, because the walk is
O(primitives) and made a debug build on a phone too slow to finish a
benchmark run.

## 2026-09-06: a tap on a text field always leaves a caret

`TextEditCtx::select` used to compare the tap position against the
*laid-out text's* own box and set `selection = None` for anything outside
it. A press only reaches `select` after being hit-tested to the widget, so
that "outside" meant the field's own padding -- or, for an **empty** field,
everything, since an empty layout is a zero-width box. So tapping an empty
composer focused it and opened the keyboard while leaving no caret, and
`TextEditCtx::insert`/`insert_str` return early with no caret: every
keystroke was dropped in silence, and no glyph ever appeared. Parley's
`from_point`/`extend_to_point` already clamp a point outside the layout to
the nearest cursor position, which is also what a tap in a field's padding
should do.

Behaviour change a caller would notice, in one line: **`select` with a
non-drag position now always produces a selection; it no longer clears
one.** Clearing is `TextEditCtx::deselect`, which is what the backends'
focus handling already calls. A drag is unchanged -- with no previous
selection there is still nothing to extend, so it produces none.

`insert_str` also gained a `debug_assert!` for the no-caret case, so an
insert routed to an unfocused field fails at the mistake in a debug build
instead of silently swallowing input.

## 2026-09-06: `List::anchor_position_display`## 2026-09-06: `List::anchor_position_display`, `FrameReport::mark_phase`/`phase_stats`/`late_at_hz` (RUST.md's "Benchmark v2")

`List` gained `anchor_position_display(&self) -> String`, reporting the
anchor's own row index and pixel offset (`idx=N/off=Mpx`, or
`idx=more-before`/`idx=more-after`/`idx=none`) -- what a scripted
benchmark reads to report fling travel. Note the anchor does not
necessarily change *slot* over a long scroll (this widget's own documented
design: the anchor is a stable identity, not re-derived from what's on
screen each frame), so this is not the same measurement as a Compose
`LazyListState.firstVisibleItemIndex`, which does track the true topmost
visible row -- the `off` half is what actually reflects how far a fling
travelled.

`iris_core::render::frame_report::FrameReport` gained three methods for
per-phase benchmark reporting: `mark_phase(name)` records a named phase
boundary at the current frame/instant; `phase_stats(now, refresh_hz)`
returns one `PhaseStats` (frames, wall duration, late count/percent,
p50/p90/p99, worst) per marked phase, sliced from the existing ring by a
new parallel `index_ring`; `late_at_hz(refresh_hz)` gives the whole run's
late count/percent judged against an arbitrary refresh rate rather than
the fixed 60Hz `JANK_THRESHOLD` every existing caller still uses (a
separate method, not a parameter on `report()`, so nothing else changes
behaviour). `RING_CAPACITY` grew 4096->16384 to hold a full multi-phase
run without evicting earlier phases' samples.

## 2026-09-06: `List::fling`, `VelocityTracker`, `FlingCalculator` (IRIS_TODO.md's "swiping has no momentum")

`iris::widget::List` gained a real fling: `fling(velocity_px_per_s)` starts
one (cancelled by the next touch-down via `cancel_fling`, or automatically
once it settles or reaches loaded content's start/end), `is_scrolling()`
reports whether one is running, and `tick_fling(now: Instant) -> bool`
advances it and returns whether it is still going -- a caller that owns a
`RequestRedraw` handle can hand it to the list once via the new
`set_redraw_handle`, after which `List` re-arms its own next frame while
flinging with no further polling needed; a caller driving a scripted
benchmark instead calls `tick_fling` itself in a loop, same as it already
drives `scroll`.

The physics is `iris::sense::FlingCalculator` + `VelocityTracker`
(`sense.rs`, beside `DragArbiter`): a port of AOSP `SplineOverScroller`'s
deceleration curve (the same one Compose's own `ScrollableDefaults.
flingBehavior()` uses), cited at the definition, so a fling here travels
the same distance a Compose `LazyColumn` would for the same initial
velocity. `VelocityTracker` estimates that velocity from the drag's last
~100ms of samples rather than one frame's last delta. Unit-tested:
velocity from known samples, fling distance/duration against the closed-
form spline result (within 1%), cancel-on-touch, and the start/end clamp
(a fling stops rather than scrolling into content that was never loaded).

Before: a touch-drag panned exactly as far as the finger moved and stopped
dead on release. After: releasing mid-drag continues scrolling and
decelerates, matching the muscle memory every other Android scroll view
already trained. `transcript_ui::selection::Selection::drag` wires this in
-- a release only flings if the gesture had committed to panning
(`DragArbiter::is_panning`, new), never a selection or an undecided tap.

## 2026-09-06: `UiRenderNode::new` returns `Result`, not `Self` (RUST.md's P0 box, phone-crash fix)

`iris_core::UiRenderNode::new(device, queue, config)` now returns
`Result<Self, String>` instead of `Self`. Why: it used to let a bind-group-
layout validation failure reach wgpu's default error handler, which panics
with no way for a caller to intervene -- exactly what aborted the P0 bench
APK on Iris's phone with the crash report truncated to "wgpu error:
Validation Error" and nothing else recoverable. It now runs its creation
calls inside wgpu error scopes and returns the full error text (wgpu's own
"Caused by" chain) as `Err` instead.

Both callers changed to match: `android::render::AndroidRenderer::new`
itself now returns `Result<Self, String>` too, building a fuller report
(adapter identity, the limits/downlevel flags a layout validates against,
then wgpu's text) on failure -- its caller,
`android::view::IrisViewPeer::surface_changed`, logs that report as one
logcat line and shows it on screen (a new `IrisView.showRendererError`,
called via an ordinary JNI method call rather than a new `native fn`)
instead of letting the process abort. `default::render::UiRenderer::new`
(the winit/desktop backend) still panics on failure -- there is no
on-screen fallback there -- but the panic message is now the same full
text rather than whatever wgpu's own handler would have printed.

No change for an app that never constructs a `UiRenderNode` directly (every
current one goes through `AndroidRenderer`/`UiRenderer`), but anyone who
does needs an `?`/`.expect()`/`match` at the call site now. Full audit and
the named hypothesis for what actually failed on the phone are in
RUST.md's P0 box, "iris bench crash on the phone, 2026-09-06."

## 2026-09-05: `AndroidAppState::platform_ready` (RUST.md's P0 box, iris half)

Added a second, optional lifecycle method to `iris::android::AndroidAppState`
(`iris/src/android/view.rs`), called once from `new_peer` right after `new`:

```rust
fn platform_ready(&mut self, rsc: &mut AndroidRsc<Self>, vm: JavaVM, view: GlobalRef) {}
```

Default does nothing, so every existing implementor (`Client`,
`TranscriptClient`) is unaffected. It exists for a caller that needs to call
into Java itself beyond what a `RequestRedraw` handle already covers --
P0's bench build (`iris-android-app`'s new `bench` feature,
`bench_client.rs`/`bench_jni.rs`) uses it to hold a `JavaVM` + `GlobalRef`
to the view so its "Copy report" control and once-a-second battery sampler
can call `BatteryManager`/`ClipboardManager` through the view's own
`Context`, from a background tokio task as well as the UI thread. `new`
itself was not extended with these two parameters: most implementors need
nothing here, and `new`'s job is building the widget tree, not holding a
platform handle. `vm`/`view` are independent handles from the ones
`new_peer` keeps for its own `RequestRedraw` (a fresh `get_java_vm`/
`new_global_ref` each), so storing them has no effect on that mechanism.

## 2026-09-05 (later still): `iris_core::device_limits()`, and iris no longer requests compute-shader limits

New public function, `iris_core::device_limits() -> wgpu::Limits`. Why:
`adapter.request_device`'s `required_limits` was `Limits::default()` plus
a `max_buffer_size` override in both platform backends, and
`Limits::default()` requests desktop-tier compute-shader limits
unconditionally (`max_compute_workgroups_per_dimension: 65535`) even
though nothing in `iris`/`iris-core` uses a `ComputePipeline` — that
crashed device creation outright on a downlevel GL adapter reporting
OpenGL ES 3.0 (no compute shaders at all: the Android emulator's
`EMU_GPU=software` path, and any real GLES-3.0-only Android device).
`device_limits()` is what both `android::render::AndroidRenderer::new`
and `default::render::UiRenderer::new` now build their `required_limits`
from, so the request cannot drift between the two backends.

Before: `Limits { max_buffer_size: 1 << 30, ..Default::default() }`
inlined in each backend. After: `iris_core::device_limits()`, which is
the same thing with the six `max_compute_*` fields additionally zeroed.
A caller building its own `DeviceDescriptor` outside these two backends
(there are none today, but a third platform backend would want this)
should call `device_limits()` rather than reaching for
`Limits::default()` directly, unless it genuinely adds a compute pass —
in which case it wants the specific compute limits that pass needs, not
the desktop-tier default for everything.

## 2026-09-05 (later the same day): `iris_core::FrameReport` (RUST.md's I5 box)

New public type, `iris_core::FrameReport` (re-exported from `iris_core`'s
`render` module alongside `FrameStats` and `JANK_THRESHOLD`). Why: `dumpsys
gfxinfo` cannot see a `SurfaceView`'s own GPU-drawn frames at all, so a
`wgpu`-rendered iris screen had no way to ask "was this smooth" the way
Compose's own in-app render report already can -- item 3 of RUST.md's
recommendation was stuck on a one-sided number for exactly this reason.

`FrameReport::record(elapsed: Duration)` is called once per frame (wired
into `android/view.rs`'s `render()`, wrapping the same span from redraw
start to after `queue.submit`+`present()` that Compose's report and
`gfxinfo` both count) and writes into a fixed 4096-entry ring -- no
allocation on the hot path. `FrameReport::report() -> Option<FrameStats>`
gives total frames, janky % (over `JANK_THRESHOLD`, the same 16.7ms 60Hz
budget `gfxinfo` uses), P50/P90/P99 and the worst; `None` if nothing has
been recorded since the last `reset()`, not a zeroed report that would
read as a real measurement. `FrameStats`'s `Display` line says plainly
that it measures up to `present()` being called, not GPU/compositor
completion, since wgpu's `present()` isn't fenced against either.

`AndroidUiState` gained a `pub frame_report: FrameReport` field --
anything with `HasAndroidUiState` can now read or reset it. Before this,
there was no way to ask iris's own render path how long a frame took at
all, on any backend.

Before/after, for a caller that already has `ui_state: &AndroidUiState`:

```rust
// before: no such question could be asked
// after:
match ui_state.frame_report.report() {
    Some(stats) => log::info!("iris frame report: {stats}"),
    None => log::info!("iris frame report: no frames recorded yet"),
}
ui_state.frame_report.reset(); // via android_state_mut()
```

`iris-android-app`'s transcript screen exposes this as two named,
tappable controls ("Frame report", "Reset frame report") rather than
requiring a caller to wire its own UI -- see `transcript_client.rs`'s
`frame_report_controls`.

## 2026-09-05: `Tasks::redraw_handle` (RUST.md's I5 Android integration)

New public method on `iris::task::Tasks`, `redraw_handle(&self) ->
Arc<dyn RequestRedraw>`. Why: a caller running its own long-lived loop
*inside* one spawned task (a live SSE follow, the Android transcript
client's `select_session`) has no other way to ask for a frame after each
`TaskCtx::update` -- `Tasks::spawn`'s own wrapper only requests one, after
the whole async closure finishes, which fits a single request-then-update
but not a stream that needs to be seen redrawing after *each* event. This
is the same gap `iris/desktop-app`'s module doc names for why it uses
winit's `Proxy<AppEvent>` instead of `Tasks` -- android-view has no
`Proxy`, so this is what closes it there.

**A real bug this uncovered, not a hypothetical**: calling the returned
handle's `request_redraw()` from the background thread crashed the process
(`SIGABRT`, `Result::unwrap() on an Err value: JavaException`) the first
time an Android transcript fetch called it a second time. `android/render.rs`'s
`AndroidRedrawHandle` was already attaching the calling thread to the JVM
correctly, but its `request_redraw` called `View::post_frame_callback`,
whose Java side calls `Choreographer.getInstance()` -- which throws unless
the *calling* thread already has a `Looper`, and a tokio worker thread,
even freshly JNI-attached, has none. Fixed by routing through
`View::post_delayed(0)` instead (Android's own thread-safe "queue work onto
this View's UI thread" primitive, needing no caller-side `Looper`), landing
on a new `IrisViewPeer::delayed_callback` override that drains tasks and
renders -- same body as `do_frame`, on the UI thread where
`post_frame_callback` is safe again. Any future caller of `redraw_handle()`
from a background thread gets this for free; nothing about the fix is
specific to the transcript screen.

## 2026-09-05: `transcript_ui::build_tree` (RUST.md's E4)

`transcript_ui::build` claimed the whole window (`ui_state.set_root(tree)`)
as its last step, which is right for a window that *is* the transcript
screen (the winit example, an eventual Android cdylib) and wrong for the
desktop app, which puts a session list beside it. `build_tree` is `build`
minus that last step: it returns `(TranscriptScreen, StrongWidget)` instead
of just `TranscriptScreen`, and the caller decides where the tree goes —
into `ui_state.set_root`, or into a `WidgetPtr` alongside something else
(`iris/desktop-app`'s `rebuild_transcript`). `build` is now one line calling
`build_tree` and doing the `set_root` itself, so existing callers are
unaffected.

```rust
// before, and still available, for a caller that wants to *be* the window:
let screen = transcript_ui::build(rsc, &mut ui_state, rows);

// new, for a caller embedding the screen beside something else:
let (screen, tree) = transcript_ui::build_tree(rsc, rows);
some_widget_ptr(rsc).set(tree);
```


## 2026-09-05: `DragArbiter`, pan-vs-select for one shared touch gesture (RUST.md's I5)

New public type, `iris::sense::DragArbiter`. Why: a widget author who
registers both a list-level pan and a row-level drag-to-select on the same
touch gesture has no way to arbitrate between them — `core/src/sense.rs`'s
`run_sensors` always gives the innermost layer first refusal, so the inner
one wins every frame it is pressed, not just the frame the press started
(this is exactly what left transcript-ui's touch-drag panning unreachable
until now). `DragArbiter` is one small state machine, one instance per
gesture surface (a whole list, not per row), that a caller drives with its
own `press_start`/`update`/`release` calls and a caller-supplied `Instant`
(so it is unit-testable without a real clock or a render harness). It
decides the way Android itself does: an ordinary vertical drag pans
immediately; a stationary press held `LONG_PRESS` (500ms) starts a
selection, which any further drag then extends; a horizontal drag while
something is already selected extends it immediately, skipping the wait.

```rust
// One per list, held alongside whatever state coordinates the rows:
let mut arbiter = DragArbiter::new();

// On press-down:
arbiter.press_start(pos, Instant::now(), already_selected);
// Every frame the button/finger stays down:
match arbiter.update(pos, Instant::now()) {
    DragOutcome::Pan(dy) => list.scroll(-dy),
    DragOutcome::SelectStart => selection.begin(...),
    DragOutcome::SelectExtend => selection.extend(...),
    DragOutcome::Undecided => {}
}
// On release:
arbiter.release();
```

`transcript-ui`'s `Selection::drag` (`transcript-ui/src/selection.rs`) is
the reference caller: every row's `CursorSense::click_or_drag() |
CursorSense::unclick()` handler routes through one `Selection`-owned
arbiter instead of calling `begin`/`extend` directly, so a drag that starts
on a row's own rendered text now pans the list correctly instead of
always starting a selection. 8 new unit tests in `iris/src/sense.rs`'s
`drag_arbiter_tests` module.

### 2026-09-05, later: `DragArbiter::is_idle()`, recovering a missed `press_start`

Follow-up to the above, from a real touch-scroll dropout: a gesture's
`ACTION_DOWN` can land on a caller's own dead space (a row's padding, a
gap, a header with no handler) that never calls `press_start`, so the
first frame the arbiter actually sees is a `Pressing`-shaped `update`
with no matching start. Before this, `update`'s `Idle` arm had no way to
tell that apart from "nothing is happening" and answered `Undecided`
forever for the rest of that gesture. `is_idle(&self) -> bool` lets a
caller notice the gap and recover: if `is_idle()` is true on a frame the
caller knows a press is genuinely down (its own `Pressing`/equivalent
sense fired), call `press_start` right there instead of assuming one
already happened. `transcript-ui`'s `Selection::drag` is the reference
caller — one new match arm, checked before the ordinary `update`-only
case. Any other `DragArbiter` caller with the same "one sensor per
sub-region, no fallback for dead space" shape has the same gap and wants
the same recovery.

## 2026-09-05: `SpanStyle`, per-range text styling (RUST.md's I5)

A `TextBuffer` used to have exactly one style (`TextAttrs`: colour, size,
family, ...) for its whole string, applied via `push_default` into parley's
ranged builder. `SpanStyle` is a second, optional layer: a byte range plus
whichever of colour/family/font size/bold/italic/underline it overrides,
pushed with parley's own `push(property, range)` instead. Why: a transcript
row's markdown (a heading, **bold**, `inline code`, a link) all inside one
wrapped paragraph needs each to carry its own look while the paragraph
still wraps and selects as a single buffer — the thing `masonry`'s
`TextArea` cannot do (`StyleSet` is one style for the whole editor,
`text_area.rs:43-44`'s `// TODO: RichTextInput`), and the reason this
existed at all.

```rust
let (text, spans) = transcript_ui::markdown::render_markdown(src, 16.0);
wtext(text)
    .spans(spans)   // new: TextBuilder::spans, on both Text and TextEdit
    .editable(EditMode::MultiLine)
    .add(rsc);
```

Two things a widget author should know before reaching for it:

- **Call `.spans()` before or after `.editable()`, both work** — the field
  lives on `TextBuilder` itself, not either output type, and both
  `TextOutput::run` and `TextEditOutput::run` apply it to the buffer via
  `TextBuffer::set_spans`. **These two call sites are a pair**: adding a
  third `TextBuilderOutput` impl without also calling `set_spans` there
  reproduces the exact bug this box shipped once already (spans silently
  dropped for `TextEdit`, found only by screenshotting, not by any test —
  `markdown.rs`'s own unit tests check string/range logic, which is
  correct in isolation and proves nothing about whether the render path
  ever sees it).
- **Colour is now per-glyph, not per-buffer.** `PlacedGlyph` gained a
  `color: UiColor` field (from parley's own per-run `Style::brush`), and
  `Painter::glyphs` draws each glyph in its own colour instead of
  `RenderedText::color` uniformly. `RenderedText::color` still exists (the
  buffer's *base* colour, for a caller that wants it as a whole, e.g. to
  tint a cursor) but no longer drives what a glyph actually renders as.

## 2026-09-05: accessibility names via AccessKit (RUST.md's I4)

`.label()` (already in `trait_fns.rs`, previously unused anywhere in-tree)
is now load-bearing: it's the one thing that puts a widget in the AccessKit
tree `iris_core::ui::access::AccessTree` builds and both backends push
out. A widget author who wants a control to be findable by name (and
tappable by name, through `ui-trace`/a real screen reader) calls `.label()`
on it; nothing else is required, and a widget nobody labels is invisible
to this system at zero cost, not just zero UI.

```rust
let button = rect(Color::LIME)
    .on(CursorSense::click(), move |_, rsc| { ... })
    .label("Add task");   // now findable by uiautomator/AccessKit as "Add task"
```

Two new things a widget author might touch directly:

- **`Widget::access_role(&self) -> accesskit::Role`**, default `Unknown`.
  Override it if your widget has a real platform equivalent —
  `TextEdit` now returns `TextInput`/`MultilineTextInput` by `EditMode`.
  Only consulted for a widget that also has a `.label()`; an unlabelled
  widget's `access_role` is never called.
- **`Widgets::named() -> impl Iterator<Item = WidgetId>`** — every widget
  with an explicit label, for anything else that wants to walk the same
  set `AccessTree` does.

Nothing about `Painter`, `draw`, or the layout/move machinery changed —
this sits entirely beside them, reading `resolved_region`'s output rather
than participating in producing it.

## 2026-09-05: `List`, a virtualised bottom-anchored list (RUST.md's I3)

A new widget, `iris::widget::List` (`iris/src/widget/list.rs` -- read its
module doc first), for the transcript's kind of screen: variable-height
rows, keyed by a `u64`, composed only while visible, moved rather than
re-laid-out on scroll, a scroll anchor that survives a row inserted above
it, "more" sentinels at each end, and "hold the edge nearest the tap" when
a row's height changes (`note_tap`, resolved in the layout pass).

```rust
let mut list = List::new(Axis::Y);
list.push_back(ListRow::new(key, row_widget));   // O(1)
list.push_front(ListRow::new(older_key, row));   // O(1), anchor unaffected
list.set_more_before(Some(spinner_widget));      // sentinel, drawn at the edge
list.note_tap(viewport_y);                       // before mutating a row's height
let (top, bottom) = list.extent(key).unwrap();   // last frame's on-screen box, if visible
```

Built entirely out of existing primitives (`Painter::widget`/`widget_within`/
`reposition`/`draw_twice`, and `draw_inner`'s own old-children diffing) --
no new mechanism was added to the render core for it. One correctness
lesson worth reading even for other widgets: a row that fills whatever
region it is offered (`Rect`, `is_size_independent`) cannot be measured at
a throwaway oversized region and then merely `reposition`ed into place --
`reposition` only ever writes an offset, never a size, so the oversized
primitive stays oversized. `List` fixes this by caching each row's real
height once measured and placing an already-known row directly at its
exact box; see `list.rs`'s `place` for the full reasoning and
`a_fill_shaped_background_is_not_left_oversized` for the regression test.

## 2026-09-05: a second backend (android-view), and what moved to make room for it

RUST.md's I2. Three changes a widget or app author would notice, all in
service of the same thing: `default` (winit) and the new `android`
(android-view) backends sharing what does not depend on windowing.

- **`Selector`/`Selectable`'s bound changed from `Rsc::State:
  HasDefaultUiState` to `Rsc::State: FocusHost`** (new trait, `attr.rs`).
  `HasDefaultUiState` still exists and still works — `default/attr.rs` now
  implements `FocusHost` for anything that has it — so a winit app's
  existing code is unaffected. An Android app implements `FocusHost` via
  `HasAndroidUiState` instead. Affects only an app that referenced
  `HasDefaultUiState` directly at a `Selectable`/`Selector` call site
  rather than through `.attr::<Selectable>(())`, which nothing in-tree
  does.
- **`Tasks::init` takes `Arc<dyn RequestRedraw>` instead of
  `Arc<winit::window::Window>`.** `RequestRedraw` (`task.rs`) is one method,
  `fn request_redraw(&self)`; `winit::window::Window` implements it
  (`default/render.rs`), so `Tasks::init(window)` at a call site is
  unchanged by inference. Only matters if something constructed a `Tasks`
  directly rather than through `DefaultRsc`/`AndroidRsc`.
- **`TextEdit::apply_event`/`TextInputResult` are `#[cfg(not(target_os =
  "android"))]`** — they take a `winit::event::KeyEvent`, which does not
  exist on Android; `android/input.rs` drives the same primitives
  (`backspace`/`delete`/`motion`/`insert`, all still unconditional) from
  `ndk::event::Keycode` directly instead. New unconditional getters on the
  way: `TextEdit::text()`/`selection_range()`/`caret()`, and
  `TextEditCtx::delete_byte_range`/`set_cursor_byte` — the primitives
  `android/ime.rs`'s `InputConnection` bridge needed and that were not
  previously exposed publicly.

## 2026-09-04: `Widget::draw` reports the size it used; `desired_width`/`desired_height` are gone

A widget used to implement three methods (`draw`, `desired_width`,
`desired_height`); it now implements one, `fn draw(&mut self, painter: &mut
Painter) -> Size`, which draws into `painter.region()` and returns how much
of it was used. Why: the two extra methods routinely re-simulated what
`draw` was about to do anyway (`Span::desired_ortho` copied its own draw
loop to get cross-axis sizing right) — one visit per widget per frame
instead of up to three. A container that needs a child's size before
placing it (alignment, centering) draws the child once at a provisional
region, reads the returned `Size`, and calls the new `Painter::reposition`
to move it into its final spot — an O(1) offset write, not a second draw. A
widget whose drawn output never depends on the size it's given (a
fixed-size `Rect`, a decoded `Image`) overrides the new `fn
is_size_independent(&self) -> bool { false }` to `true`, which skips
redrawing it when only its offered region changes shape.

```rust
// before
fn draw(&mut self, painter: &mut Painter) { /* ... */ }
fn desired_width(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }
fn desired_height(&mut self, ctx: &mut SizeCtx) -> Len { /* ... */ }

// after
fn draw(&mut self, painter: &mut Painter) -> Size { /* ... */ }
```

`SizeCtx` and `Cache` are gone with it — see `LAYOUT.md` for the full
design, the move-offset mechanism this shipped alongside, and the file
list.

## 2026-09-04: texture pipeline rebuilt off the binding array

`Textures`/`TextureHandle`, `GlyphPrimitive`, and `UiRenderNode::new` all
changed shape. Why: the old pipeline bound every texture ever drawn in one
`binding_array<texture_2d<f32>>` and asked every device, unconditionally,
for `VK_EXT_descriptor_indexing` — a real share of Android GPUs lack it,
and it failed outright on the Android emulator's software Vulkan. See
TEXTURES.md's "Recommended shape" and "Implemented, 2026-09-04".

- **`UiRenderNode::new` drops its `limits: UiLimits` parameter, and
  `UiLimits` is gone.** Before: `UiRenderNode::new(&device, &queue,
  &config, UiLimits::default())`. After: `UiRenderNode::new(&device,
  &queue, &config)`. Nothing replaces it — there are no more
  binding-array limits to size.
- **`src/default/render.rs`'s device request asks for no features and no
  binding-array limits.** Before: `required_features:
  Features::TEXTURE_BINDING_ARRAY | Features::PARTIALLY_BOUND_BINDING_ARRAY
  | Features::SAMPLED_TEXTURE_AND_STORAGE_BUFFER_ARRAY_NON_UNIFORM_INDEXING`
  plus two `max_binding_array_*` limits. After: `Features::empty()` (the
  `DeviceDescriptor` default) and only `max_buffer_size` set, which was
  never about the binding array.
- **`TextureHandle` has no `primitive()` method any more**; a caller
  outside `iris` shouldn't have been calling it (it fed the old renderer's
  internals), but if something did: use `image_index()` for a standalone
  image's bind-group index. There is no equivalent for a page — a page has
  no bind group of its own now, see below.
- **`GlyphPrimitive` has no public constructor from a struct literal.**
  Before: `GlyphPrimitive { uv_min, uv_max, view_idx, sampler_idx, color,
  flags }`. After: `GlyphPrimitive::new(uv_min, uv_max, layer, color,
  flags)` — one `layer` (the shared atlas array's layer) instead of a
  `view_idx`/`sampler_idx` pair, since a page is now a layer of one array
  texture rather than its own bound texture.
- **A widget author drawing images is unaffected**: `Painter::texture`/
  `texture_at`/`texture_within` and `Textures::add` keep their signatures.
  What changed underneath is that each standalone image now gets its own
  `wgpu::BindGroup` and draw call instead of a slot in the shared array —
  invisible from the widget API, visible only in `UiRenderNode`'s internals
  and in `iris`'s device requirements.

## 2026-09-05: `FrameReport` splits each frame at `queue.submit`

`FrameStats` gains two fields, and `FrameReport` gains a second recording
method, to answer "is a slow frame iris's own CPU work or the driver/GPU"
with a number instead of a guess (RUST.md's I5 box).

- **`FrameReport::record_split(total, submit_to_present)`** is a second way
  to record a frame, alongside the existing `record(total)` (unchanged,
  and still what a caller with no split should use — it now reads as
  `cpu_p50 == total`, `gpu_wait_p50 == 0`, rather than fabricating a
  number for a half it never measured).
- **`FrameStats` gains `cpu_p50` and `gpu_wait_p50`**: medians of
  redraw-start-to-submit and submit-to-after-`present()` respectively,
  independent of each other and of the existing `p50`/`p90`/`p99`/`worst`
  (which are unchanged, and still over the whole frame). The Android
  renderer's `draw()` now returns the `submit_to_present` `Duration` it
  measured, which `android::view::render()` passes to `record_split`.
- **Caveat carried in both doc comments**: `submit_to_present` is not
  fenced against the GPU actually finishing — it is "how long the CPU was
  blocked handing the frame to the driver," not a confirmed GPU-completion
  time. Enough to separate "iris is slow building the frame" from "iris is
  slow handing it off," not enough to claim an exact GPU budget.

## 2026-09-05: `List::replace_back`/`List::clear`, and `TranscriptScreen::apply`

Fixes the "every client refolds and rebuilds the whole widget tree per
streamed event" cost RUST.md's P0 box measured (20 events/second against a
~3,200-row transcript). Two small additions to `iris::widget::List`
(`iris/src/widget/list.rs`), plus one new method on `transcript-ui`'s
`TranscriptScreen`.

- **`List::replace_back(row: ListRow) -> Option<ListRow>`**: swaps the
  *last* row's widget for a new one without moving it — same slot index,
  so an anchor already pinned there (in particular a list flush with its
  own end) stays pinned, and a `List` scrolled elsewhere is untouched.
  `None` if the list is empty. `RowKey` may differ between the old and new
  row; only `heights`/`extents` care, and both are invalidated for the
  evicted key the same way `pop_back` already does.
- **`List::clear()`**: drops every loaded row and resets to `List::new`'s
  state (`more_before`/`more_after` untouched — a caller that wants those
  cleared too calls `set_more_before(None)`/`set_more_after(None)` itself).
  The fallback path for a change that touches more than the tail.
- **`transcript_ui::TranscriptScreen::apply(&self, rsc, old: &[TranscriptItem], new: &[TranscriptItem])`**:
  the incremental alternative to rebuilding the whole screen from
  `transcript_ui::build_tree` on every folded event. Diffs the two
  `group_tool_runs` outputs and picks the cheapest update: nothing changed
  (no-op), a pure append (`push_row`, unchanged cost), or — the common
  streaming case, a delta into a still-open assistant message — a rebuild
  of just the one changed row via `List::replace_back`, with any further
  new rows appended after it. A row changing *before* the tail (only
  `group_tool_runs` retroactively grouping tool calls into a run does
  this) falls back to `List::clear` plus a full rebuild, counted in
  `TranscriptScreen::take_rebuilds()`. **A caller that keeps its own
  row-keyed side table alongside `List` (`Selection`'s `rows:
  BTreeMap<RowKey, WeakWidget<TextEdit>>` is the one this crate has) must
  clear it in step with `List::clear()`** — the fallback drops every row
  `List` was holding, so any side table not cleared the same way is left
  pointing at widgets the clear just freed (docs/REVIEW-2026-09-06.md
  finding 1, fixed 2026-09-06 by `Selection::clear()`, called from
  `apply`'s `Rebuild` arm right before `List::clear()`). `bench_client.rs`, `transcript_client.rs`
  and `desktop-app/app.rs` all call this now instead of rebuilding on every
  event; only the opening page (and `apply`'s own fallback) still calls
  `build_tree`.
- **`TextEditCtx::set_with_spans(text, spans)`**: `set()` plus a fresh
  `Vec<SpanStyle>` in one call, needed because a streamed row's markdown
  re-renders to both a new string and a new span list on every delta and
  the two have to land together — a stale span list drawn against new
  text can point past its end. `set()` itself is unchanged (still clears
  spans to none, as before).

Measured on this checkout's emulator (`iris/android-app/run-bench.sh`,
release, x86_64, `force-gles`): worst-frame and p99 during the streaming
phase dropped from 369.3ms/284.5ms (full rebuild per event, prior pass) to
~101–130ms/~76–103ms across three runs (this fix) — see RUST.md's P0 box
for the full numbers and the comparison's caveats (different AVD
instances, not a controlled A/B on identical hardware state).

## 2026-09-06: bundled fonts, `content_scale`, `AndroidAppState::on_insets_changed`

From RUST.md's P0 box, working Iris's first real-phone report (font/scale/
inset bugs the emulator never showed).

- **`TextData` now bundles Noto Sans + Noto Sans Mono** (regular/bold/
  italic/bold-italic static faces, OFL) and registers them ahead of the
  platform's own fonts in the `SansSerif`/`Monospace` generic-family
  lists, rather than relying on the platform's font enumeration alone.
  `TextData::font_diagnostics() -> FontDiagnostics` reports what was found
  and what each style axis resolved to — logged once at startup and shown
  on a screen's Diagnostics page if it has one. Adds ~3.6 MB uncompressed
  to any binary linking `iris-core`; `build-apk.sh`'s own output says the
  delivered (compressed) number.
- **`UiRenderNode::new`/`resize` now take the window size explicitly**
  (`window_size: impl Into<Vec2>`) instead of deriving it from the
  surface's physical `SurfaceConfiguration`. Existing callers pass a
  *logical* size (physical ÷ density/scale-factor) now; this is what makes
  a `font_size: 16.0` 16 dp instead of 16 raw device pixels on a
  high-density phone. Before this, `scale_factor` did not exist anywhere
  in the crate, on either platform.
- **`AndroidUiState::content_scale: f32`** (`DisplayMetrics.density`, read
  once in `new_peer`) and the desktop equivalent (`window.scale_factor()`)
  now divide every physical-pixel number before it reaches layout or
  touch handling — see `content_scale`'s own field doc for the full list
  of what depends on it.
- **New: `AndroidAppState::on_insets_changed(&mut self, rsc, LogicalInsets)`**,
  a default-no-op hook called from `render()` exactly when
  `AndroidUiState::insets()` changes. Nothing previously consumed
  `insets().top` at all; a screen with chrome under the status bar
  implements this to pad it, in the same logical units `content_scale`
  converts everything else to.
- **New: `iris_core::WgpuErrorLog`**, installed via `Device::
  on_uncaptured_error` on the Android device (wgpu's default handler is an
  unconditional panic outside `UiRenderNode::new`'s own error scopes).
  Explicit `Arc`-backed value passed to the callback and kept on
  `AndroidRenderer`, not a global — a caller wanting one on desktop builds
  its own the same way.

## 2026-09-06: `Len::dp`, physical pixels throughout, the keyboard glyph wipe

Iris's phone report on build a9232ac (screenshots): text now the right
size but blurry; the keyboard still wipes every glyph; the header buttons
have nothing behind them. All three are fixed; this entry is the public
API side. docs/LAYOUT.md has the layout-side writeup, docs/RUST.md's P0
box has the full investigation and the phone verification still to do.

- **The keyboard wipe was `surface_changed` rebuilding the whole renderer
  on every resize**, including an IME-driven one — a fresh, empty glyph
  atlas while the CPU-side glyph cache kept UV coordinates from the old
  one. `surface_changed` now calls `AndroidRenderer::resize` (reconfigures
  the surface and window uniform only) when a renderer is already live,
  and only builds a new one when there genuinely isn't one yet.
- **`Len` has a third field, `dp`** (Android's dp / CSS's reference pixel,
  1/160in), beside the existing `abs` (now explicitly *physical* pixels)
  and `rel`/`rest`. `len_fns::dp`/`Len::dp` construct one, used exactly
  like `abs`/`rel`/`rest` — `dp(16)` instead of a bare `16` wherever a
  size should look the same physical size on any density. This is the
  unit IRIS_TODO.md's "density-independent length unit" item asked for;
  it replaces the previous stopgap (the whole rendered scene divided by
  `content_scale` then implicitly stretched back up), which is also what
  made text blurry — a glyph rasterised at the small, pre-stretch size and
  then upscaled onto the real framebuffer.
- **`UiRenderState`/`Painter` gained `density()`/`set_density()`** (physical
  pixels per dp). Every place a length resolves (`Len::apply_rest`,
  `Size::to_uivec2`) now takes it; `Span::gap` and `Padding`'s four sides
  moved from a bare `f32` to `Len` so they take `dp(...)` too. A bare
  number anywhere is unaffected — still `abs`, physical pixels.
- **Text is rasterised at physical resolution now.** `TextBuffer::shape`
  takes `density` and multiplies `font_size`/`line_height` (and any span
  override) by it before handing them to parley, so the atlas holds a
  bitmap at the size it is actually shown at rather than a low-resolution
  one stretched afterward.
- **Everything at the Android boundary is physical pixels now** — window
  size, touch coordinates, insets (`LogicalInsets` renamed
  `WindowInsets`). The previous "logical" division by `content_scale` is
  gone; `content_scale` now feeds `set_density` instead.
- Not yet verified on Iris's actual phone (this pass had no device) —
  built and checked on this checkout's emulator only. RUST.md's P0 box
  says what she should check for: crisp text at two densities, the
  keyboard no longer wiping, and the header's background.

## 2026-09-06: composing text, focus-on-tap, and atlas invalidation on a new renderer

Three small but public API changes, from the same phone-report pass as the
entry above (RUST.md's P0 box has the full account, including a real bug
still not root-caused).

- **`FocusHost` gained `is_focused(&self, id) -> bool`** (both platform
  impls). `attr.rs`'s `Selector`/`Selectable` used to grant focus (and so
  request the IME) on the very first frame of *any* press, before it was
  known whether the gesture was a tap or a drag — a swipe over a text
  field wrongly summoned the keyboard. They now wait for a completed tap
  (press and release with no frame crossing `sense::DRAG_SLOP`) unless the
  field is already focused, in which case dragging inside it to select
  text is unchanged. `TextEdit` gained one new `pub(crate)` field
  (`press_origin`) to track this; no public surface change there.
- **`android::ime`'s `InputConnection` now calls `InputMethodManager::
  updateSelection` after every edit** (`IrisViewPeer::update_ime_selection`,
  called from `after_input`). Gboard was holding keystrokes back because
  nothing ever told it where the app's own selection/composing region had
  moved to — this is what android-view's own demo does in its `render()`
  and this bridge never did.
- **`GlyphAtlas::clear()` and `Textures::reset()`** (`iris_core`). Called
  together, once, from `android::view`'s `surface_changed` exactly when a
  *genuinely new* `AndroidRenderer` is built (backgrounding and returning,
  not a keyboard-triggered resize, which already reuses the renderer) —
  both CPU-side caches otherwise kept pointing at the old, now-destroyed
  device's textures, which is why text used to vanish again after leaving
  and returning to the app.

## 2026-09-06: `take_counters` counts text layouts too

One public API change, from the verification pass over the composer-scroll
and per-block-row work (RUST.md's "Verification pass over Tasks A and B").

- **`UiRenderState::take_counters` returns four numbers, not three**:
  `(draws, region rewrites, move writes, **text shapes**)`. The new one is
  bumped in `Painter::render_text`, which `TextView::render` only reaches
  on a cache miss, so it counts layouts actually computed rather than
  layouts asked for. Callers destructuring the tuple need one more `_`.

  It exists because a draw counter cannot answer the question the
  per-block transcript row was built for. A widget can be redrawn without
  re-shaping (the layout is memoized by width) and re-shaped without any
  extra draw, and re-shaping is the expensive half — so "a streamed delta
  costs one block" was, until now, argued from the code rather than
  measured. With the counter it is a test: one delta into a 100-paragraph
  reply shapes exactly **1** text layout, the same as into a
  one-paragraph one.