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mobile: Render frames on demand so an idle screen costs no CPU - #55

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huacnlee wants to merge 6 commits into
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longbridge:upstream/08-demand-driven-frames-so-an-idle-screen-c
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huacnlee wants to merge 6 commits into
itsbalamurali:mainfrom
longbridge:upstream/08-demand-driven-frames-so-an-idle-screen-c

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@huacnlee

@huacnlee huacnlee commented Sep 27, 2026 •

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Description

The iOS window implemented neither PlatformWindow::frame_waker nor schedule_frame, so a host had to tick GPUI on every vsync and let it discover there was nothing to draw — ~2% of a core at 60 Hz (4% at 120 Hz) on an idle screen.

IosWindow now carries a FrameDemand (new platform-neutral module, unit-tested) shared with the FFI layer:

  • frame_waker / schedule_frame raise demand and call a host-registered waker on the first demand since the last tick.
  • gpui_ios_request_frame clears demand before the frame and returns whether GPUI wants another (demand re-raised mid-frame, or text input waiting).
  • New gpui_ios_set_frame_waker(window, waker, context) registers the host callback.
  • Software-keyboard text and keyboard-height changes go through mark_text_input_dirty(), which also wakes every window.

A host pauses its CADisplayLink when gpui_ios_request_frame returns false and resumes it from the waker (example/ios/main.m). Hosts that tick unconditionally keep working.

Measured on the Longbridge AI chat (iPhone 17 Pro simulator, Release): idle CPU 2% → 0.0%; scrolling, fling, focus and caret unchanged.

Breaking Changes

  • gpui_ios_request_frame now returns bool instead of void. Update the header your host compiles against; Swift callers must consume the result.
- void gpui_ios_request_frame(void *window_ptr);
+ bool gpui_ios_request_frame(void *window_ptr);
- gpui_ios_request_frame(window)
+ _ = gpui_ios_request_frame(window)

🤖 Generated with Claude Code

🤖 Generated with Claude Code

huacnlee and others added 6 commits September 27, 2026 20:05
Switch the mobile platform and the example from Zed git dependencies to the
matching `gpui-pre` / `gpui-pre-wgpu` 0.3.4 crates.io packages (imported as
`gpui` / `gpui_wgpu`, so no `use` changes are needed). This removes the
`[patch.crates-io]` async-task fork and every git dependency, which makes the
crate publishable to crates.io and lets consumers depend on it without
reproducing Zed's patches.

Adapt to the platform and styling API differences, fix the "wpgu" typo in the
crate description, and update the publish workflow to check the iOS backends
before publishing and to treat the `dry-run` input as the boolean it is.

Test plan:
- cargo check --all-targets
- cargo check --target aarch64-apple-ios / aarch64-apple-ios-sim
- cargo test --lib
Embed GPUI Kit's Markdown TextView in a Swift-owned UIKit window instead
of letting GPUI create the iOS example's window. A child controller
renders into `GPUITextView: UIView`; native Compact / Expanded controls
exercise layout changes. The light English sample puts emphasis, quotes,
nested lists, code, tables, and tasks on the first screen.

Fix two startup failures exposed by the simulator: supply the UIKit
display handle to wgpu 29, and retain the `run_embedded` application
handle so native callbacks cannot outlive the GPUI app. Synchronize
layout and redraw without implicit animations during size changes.
Correct the Xcode static-library paths and build directory.

Pins GPUI Kit to commit `7d9efcd2069f9eaa6eb3ba6345aac4aa7d87c9f7` from
longbridge/gpui-kit#3045, so a sibling local
checkout is not required. No crates are published.

The embedding example supports one GPUI view for the application
lifetime; independent destruction and multiple instances are not
implemented.

- Passed `cargo check --manifest-path example/Cargo.toml --target
aarch64-apple-ios-sim` with the pinned Git dependency.
- Built the Swift app with Xcode for the iOS simulator and ran it on
iPhone 17 Pro / iOS 26.5 using the same GPUI Kit source revision
locally.
- Verified light Markdown rendering, native controls, and Compact /
Expanded resizing.
- Passed `git diff --check` and `bash -n example/build.sh`.
- Embedded scrolling needs manual verification: the automation tool
emitted touch begin/end without move events. Transient resize jitter
also needs visual confirmation.
- No Android, physical-device, or performance testing performed.

---------

Co-authored-by: Codex <codex@openai.com>
A released iOS touch currently leaves GPUI's synthetic mouse over the
last control, keeping hover feedback active. Clear the pointer hit test
and emit MouseExited after touch end/cancellation and momentum frames,
while preserving the original position for click and scroll dispatch.

Handle UIKit cancellation separately so it never commits a deferred tap
or starts a momentum fling. Cancel an active scroll with
TouchPhase::Cancelled.

Update the example's GPUI Kit revision to include mobile tooltip
suppression, tap-triggered HoverCard behavior, and the inline is_mobile
helper from longbridge/gpui-kit#3045.

- Built the Swift-hosted iOS example for aarch64-apple-ios-sim.
- Used a temporary simulator smoke view to check HoverCard opens on tap,
remains open when its content is tapped, and closes on outside tap.
- Checked a normal ghost button with a configured tooltip: no lingering
hover background or tooltip after release.
- Restored the original chat example and rebuilt it with the final Kit
revision.
- GPUI Kit regression tests cover desktop hover and mobile tap
interaction.
- UIKit cancellation was reviewed in code; no system-cancellation
gesture was injected. Android was not changed or tested. No crates
published.

Co-authored-by: Codex <codex@openai.com>
## Summary

Apply the iOS touch cleanup from #3 to Android. After touch
release/cancellation and every momentum frame, move the synthetic
pointer outside the window and emit MouseExited so hover does not remain
on the last control. Preserve original coordinates for click and scroll
dispatch.

Handle ACTION_CANCEL independently: discard queued coalesced scroll,
reset velocity, stop inertia, and emit ScrollWheel(Cancelled) for an
active scroll. Never turn cancellation into a tap or fling, and ignore
stray moves with no active touch.

Add regression tests and update an existing test to use the renamed
gpu_specs API.

## Test Plan

- Android arm64/API 31 cargo-ndk library check passed.
- Built the Android unit-test executable and ran touch tests on an
Android API 34 arm64 emulator: 5 passed.
- Tests cover tap coordinates, pending-tap cancellation,
coalesced-scroll cancellation, and post-momentum hover cleanup.
- This verification covers platform event dispatch; Android app UI
testing is ongoing separately.

Co-authored-by: Codex <codex@openai.com>
iOS and Android Chinese keyboards could not reliably compose text, Add
files returned an error or no result, and converting every drag to
scroll prevented controls from claiming touch gestures.

- Use a native UITextView composition buffer to provide UITextInput
support and forward plain and attributed marked text, UTF-16 selection,
commits, and deletion to GPUI.
- Present an asynchronous UIDocumentPicker, returning sandbox copies of
selected files (including images in Files), with multi-selection and
cancellation support.
- Forward UIKit contacts as GPUI TouchEvents with stable IDs. GPUI's
existing recognizer handles taps, long presses, control drags,
scrolling, and inertia, replacing the duplicate iOS mouse/scroll
synthesis.
- Add an Android InputConnection bridge with native-thread composition
delivery, UTF-16 selection, Unicode-safe deletion, and session checks
for stale callbacks. Keep legacy TextInput commit/backspace callbacks
working. Custom hosts use GpuiInputActivity; the example inherits it.
- Connect Android file prompts to SAF and copy content URIs into app
cache on a worker before returning readable paths. Register the picker
Activity in the example.
- Forward Android contacts as TouchEvents, preserve multiple pointer
identities, and distinguish cancellation from release. Remove duplicate
mouse/momentum synthesis, desktop Fontconfig loading on Android, and
unconditional frame presentation (matching the existing ai-chat host
workarounds).
- Fix two simulator Debug crashes: UIKit dynamically forwards public
keyboard trait setters, and NSString byte initializers require `const
void *` rather than byte-pointer encoding. Correct the matching URL/maps
initializer calls too.

This uses existing GPUI 0.3.4 APIs; no GPUI core changes. TextView
selection and scrollbar thumb dragging also require the companion
gpui-kit handlers. The file pickers accept images accessible through
Files/Documents; they do not add a separate Photos library entry point.

Touch-driven focus changes finish the current composition before
dispatch. On iOS, programmatic focus switches without a touch or
keyboard hide still need a platform focus identity signal; clearing the
previous GPUI field's marked state on programmatic blur remains a
follow-up.

- Passed: `cargo check --target aarch64-apple-ios --lib --offline
--no-default-features --features camera,video_player`.
- Passed: `cargo check --target aarch64-apple-ios-sim --lib --offline
--no-default-features --features camera,video_player`.
- Passed: Android backend library/test cross-compilation with NDK 27,
and the complete ai-chat Android host's `cargo ndk -t arm64-v8a
--platform 26 check --locked --offline` using these local changes.
- Passed: Android API 34 Java compilation, including the host's
`:app:compileDebugJavaWithJavac` task.
- Passed: 2 host-run regression tests for the actual Unicode deletion
and legacy callback helpers; Android touch regression tests compile but
were not run on a device.
- Passed: Rust formatting and `git diff --check`.
- Passed on iOS 26.5 simulator Debug: input focus and English input;
software Pinyin `ni` followed by selecting `你` inserts Chinese into the
GPUI input; explicit keyboard dismissal; Files picker opens and cancels
twice without crashing or reopening the keyboard.
- Passed: native objc2 Debug probe reproduces the old NSString signature
rejection and verifies corrected English, Chinese/emoji, Chinese URL and
empty-string roundtrips. Keyboard-trait forwarding was also checked
against this UIKit runtime.

- Passed: attributed-marked-text runtime probe reaches the override
once, preserves ni composition and UTF-16 selection, then commits
Chinese. Requester confirmed Chinese input and subsequent iOS/Android
device testing complete.
- Passed: full ai-chat Android Debug and optimized Release builds,
installation and startup on Samsung Android 12 ARM64; Release package
verified non-debuggable.
- Not addressed by a dedicated fix: the reported held-key repeat case
(discrete 256 insert/delete callbacks pass), or the separately
identified insertText:alternatives:style: entry point. No system
autorepeat validation is claimed by those discrete-callback tests.

---------

Co-authored-by: Codex <codex@openai.com>
## Description

The iOS window implemented neither `PlatformWindow::frame_waker` nor
`schedule_frame`, so a host had to tick GPUI on every vsync and let it
discover there was nothing to draw — ~2% of a core at 60 Hz (4% at 120
Hz) on an idle screen.

`IosWindow` now carries a `FrameDemand` (new platform-neutral module,
unit-tested) shared with the FFI layer:

- `frame_waker` / `schedule_frame` raise demand and call a
host-registered waker on the first demand since the last tick.
- `gpui_ios_request_frame` clears demand before the frame and returns
whether GPUI wants another (demand re-raised mid-frame, or text input
waiting).
- New `gpui_ios_set_frame_waker(window, waker, context)` registers the
host callback.
- Software-keyboard text and keyboard-height changes go through
`mark_text_input_dirty()`, which also wakes every window.

A host pauses its `CADisplayLink` when `gpui_ios_request_frame` returns
`false` and resumes it from the waker (`example/ios/main.m`). Hosts that
tick unconditionally keep working.

Measured on the Longbridge AI chat (iPhone 17 Pro simulator, Release):
idle CPU 2% → 0.0%; scrolling, fling, focus and caret unchanged.

## Breaking Changes

- `gpui_ios_request_frame` now returns `bool` instead of `void`. Update
the header your host compiles against; Swift callers must consume the
result.

```diff
- void gpui_ios_request_frame(void *window_ptr);
+ bool gpui_ios_request_frame(void *window_ptr);
```

```diff
- gpui_ios_request_frame(window)
+ _ = gpui_ios_request_frame(window)
```

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Codex <codex@openai.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
@huacnlee
huacnlee force-pushed the upstream/08-demand-driven-frames-so-an-idle-screen-c branch from 7daacbb to 3de4bbe Compare September 27, 2026 12:06
@huacnlee huacnlee changed the title Demand-driven frames so an idle screen costs no CPU mobile: Render frames on demand so an idle screen costs no CPU Sep 27, 2026
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