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fix(windows): Cap UI appears as black rectangle in studio recordings (window exclusion is macOS-only) #1737
Description
Bug
On Windows, the Cap recording UI appears as a black rectangle in studio mode recordings, starting from the second recording session. The first recording may be unaffected if the Cap window wasn't visible at capture start.
Root cause
Window exclusion is gated entirely to macOS in apps/desktop/src-tauri/src/recording.rs:
#[cfg(target_os = "macos")]
let excluded_windows = { ... resolve_window_ids(...) };
// later:
#[cfg(target_os = "macos")]
{
builder = builder.with_excluded_windows(excluded_windows.clone());
}resolve_window_ids in window_exclusion.rs is also #[cfg(target_os = "macos")] only. On Windows, with_excluded_windows is never called, so Cap's own UI is always captured.
Expected behaviour
Cap's own windows (recording controls, camera overlay, etc.) should be excluded from the screen capture on Windows, matching the macOS behaviour.
Steps to reproduce
- Open Cap on Windows
- Start a studio mode recording
- Stop and open the editor — first recording may look fine
- Start a second studio mode recording while the Cap UI is visible
- Stop and check the recording — Cap UI appears as a black rectangle
Fix needed
Implement window exclusion for Windows using the appropriate screen capture API (Windows Graphics Capture / DXGI). The exclusion list is already built and available in general_settings::default_excluded_windows() — it just needs to be wired up for the Windows capture pipeline.
Relevant files:
apps/desktop/src-tauri/src/recording.rs:874-893— macOS-only exclusion blockapps/desktop/src-tauri/src/window_exclusion.rs—resolve_window_idsis macOS-only
Activity
linear commentedon Apr 17, 2026
CAP-683
tembo commentedon Apr 17, 2026
This is a well-documented issue. For additional context, #1652 reports the same problem (the "black paddle" in recordings is the Cap recording controls toolbar being captured).
Relevant code locations:
apps/desktop/src-tauri/src/recording.rs:874-893- whereexcluded_windowsis resolved and passed to the builder (macOS-only via#[cfg(target_os = "macos")])apps/desktop/src-tauri/src/window_exclusion.rs:73-98-resolve_window_ids()function that mapsWindowExclusionto actual window IDs (also macOS-only)crates/recording/src/sources/screen_capture/macos.rs:204-228- where the exclusion actually happens using ScreenCaptureKit'sas_content_filter_excluding_windows()PR #1179 context:
The window exclusion system was added in PR #1179 ("feat: Implement new Window excluder system"). The PR description notes: "On macOS, users can exclude any window. However, on Windows, users can only exclude Windows owned by the app due to API limitations."
Technical approach for Windows:
The Windows capture pipeline uses
scap-direct3dwhich wraps Windows.Graphics.Capture. Unlike ScreenCaptureKit on macOS (which has a nativeas_content_filter_excluding_windowsAPI), Windows Graphics Capture doesn't have a built-in window exclusion filter for display captures.The codebase already has
SetWindowDisplayAffinityavailable in the vendored tao (vendor/tao/src/platform_impl/windows/window.rs:1092) viaset_content_protection(). This could be used to exclude Cap's own windows from capture by settingWDA_EXCLUDEFROMCAPTUREon Cap's window handles at creation time. This is actually how many Windows screen recording apps handle self-exclusion - by marking their own windows as excluded rather than filtering during capture.The default exclusion list in
general_settings::default_excluded_windows()(general_settings.rs:62-72) already defines all Cap window titles that should be excluded (Cap, Cap Settings, Cap Recording Controls, Cap Camera, etc.), so the infrastructure is there - it just needs the Windows-specific implementation to callSetWindowDisplayAffinity(hwnd, WDA_EXCLUDEFROMCAPTURE)on these windows.richiemcilroy commentedon Aug 3, 2026
For visibility, we've consolidated #1747 and #1586 into this issue since they're reports of the same underlying problem, Windows recording self-exclusion not yet implemented. This stays open as the tracking issue.