[EtienneLescot]

Summary

On KDE Plasma (Wayland), recording a window failed after the countdown with "the screen share delivered no frame within 10 s" whenever the window was still. Screens were fine.

Cause. The helper threw away up to 8 crop-less frames of a window stream while it waited for a SPA_META_VideoCrop rectangle. mutter negotiates that block and fills it a few frames late, so waiting made sense there. KWin never negotiates it. It sizes the stream to the window, sends one frame when the stream starts, then sends more only when the window repaints. A still window's only frame was discarded, and the start timed out.

Fix. Only wait for a crop when the negotiated buffers actually carry the VideoCrop block. That is read from the first buffer-info report, which the shim sends before the same buffer's frame. GNOME keeps its current behaviour.

Related issue

Reported on Discord (#ask-community) by a Debian 13 / KDE Plasma 6 / AMD Renoir user on v2.1.1.

Type of change

• Bug fix

Release impact

• Patch

Desktop impact

• Linux

Testing

• Reporter's logs (v2.1.1): a still terminal window times out. Typing in it during the countdown produces window-crop-missing … 8 frames, then capture started, which confirms the diagnosis.
• KWin 6.3.6 source: WindowScreenCastSource sends one frame on resume(), then one per Window::damaged. ScreenCastStream offers no VideoCrop meta.
• Helper tests: cargo test --bin openscreen-pipewire-helper in WSL (rustc 1.98.1): 101 passed, including the new only_a_negotiated_video_crop_block_is_worth_waiting_for. rustc 1.94.1 hits an ICE on an existing capture.rs test, on main as well.
• Not yet verified: no run on a real KDE session with the new build. I'll ask the reporter to try the CI build.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved window capture handling when crop metadata is available, reducing the chance of using a frame before its crop information is ready. When crop metadata isn’t available, capture can proceed without waiting for it.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 03e9a866-fb8c-4d99-83af-7efd5dffd976

📥 Commits

Reviewing files that changed from the base of the PR and between 00f332b and 03a2b12.

📒 Files selected for processing: 1

• electron/native/pipewire-capture/src/main.rs

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📝 Walkthrough

Window capture now waits for a crop rectangle only when the stream negotiated VideoCrop metadata. The BufferInfo handler records this metadata state, and tests cover metadata detection.

Changes: Crop metadata handling

Layer / File(s)	Summary
Negotiated crop detection and frame handling electron/native/pipewire-capture/src/main.rs	The helper detects VideoCrop in metadata, and the BufferInfo handler updates the negotiated state. Window frames without a crop wait only when that metadata was negotiated. Tests cover metadata presence and absence.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~8 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 03a2b

Capture no longer waits for crop metadata when a stream did not negotiate it, while retaining the wait for streams that did. No concrete merge-blocking risk is established.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly identifies the Linux KDE window-recording fix and matches the main change.
Description check		The description provides a clear summary, root cause, fix, change classification, release and platform impact, and detailed testing results. The Related issue field remains as “Fixes #” without an iss…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Description check

Explanation

The description provides a clear summary, root cause, fix, change classification, release and platform impact, and detailed testing results. The Related issue field remains as “Fixes #” without an issue number, but the rest of the description is substantially complete.

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✨ Finishing Touches: 💡 1

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