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Infrastructure: Implement native Windows Composition screenshot capture #4260
Description
Goal
Implement native window-scoped screenshot capture for Windows Fabric and Win32 Paper Composition content. Parent: #4275.
Status - 2026-10-01
Completed capture-implementation milestone. PR #4306 delivered the backend. Interactive fidelity/DPI qualification, explicit per-artifact provenance, and locked-session diagnostics remain open in #4348.
This split preserves the original unfinished reliability criteria; implementation delivery is not a claim that screenshots are qualified production evidence.
Delivered
- Window-scoped Windows Graphics Capture with D3D11 readback and WIC PNG encoding, shared by Fabric and Paper endpoints.
- Native element crops and scale-factor information.
- Occlusion-independent capture, explicit minimized/unavailable errors, and no implicit restore/move operation to manufacture a capture.
- Supported native WebDriver/agent screenshot APIs and documented provider behavior.
- Capture remains optional evidence, not a pixel-difference deterministic gate.
The old conditional WinAppDriver screenshot/fallback design is superseded by the Appium-independent native provider. No second capture backend or whole-desktop screenshot harness is needed.
Follow-up
#4348 preserves real Windows/Win32 Composition validation, live 100/150/200% DPI and crop fidelity, hosted/interactive reliability, capture source/identity/dimensions metadata, locked/noninteractive preflight, confinement/privacy, and observed-capture documentation.
#4328 separately owns baseline/candidate/diff comparisons and reviewer reports. #4349/#4345 own CI and release qualification.
Activity
[-]Deliver a reliable Windows Composition screenshot capture path[/-][+]Infrastructure: Deliver a reliable Windows Composition screenshot capture path[/+]JasonVMo commentedon Sep 3, 2026
Status update - 2026-09-03
PR #4306 completed the capture implementation. The shared native
Windows/Win32 provider now uses window-scoped Windows Graphics Capture with
D3D11 readback and WIC PNG encoding, supports element crops, records scale
factor, remains occlusion-independent, and reports minimized or unavailable
capture explicitly. The new driver no longer depends on WinAppDriver, so the
issue's conditional WinAppDriver fallback design is obsolete.
Remaining: qualify window and element capture against real Windows Fabric
and Win32 applications on unlocked interactive desktops at 100%, 150%, and
200% DPI; measure hosted-runner reliability; add explicit per-artifact capture
provenance; verify locked/non-interactive diagnostics before capture; and
confirm artifact confinement, privacy, and documentation against the observed
captures. Screenshots remain optional evidence and never a deterministic gate.
[-]Infrastructure: Deliver a reliable Windows Composition screenshot capture path[/-][+]Infrastructure: Implement native Windows Composition screenshot capture[/+]JasonVMo commentedon Oct 1, 2026
Native Windows/Win32 capture is implemented by #4306. Closing the backend-delivery milestone; interactive fidelity, live DPI/crops, provenance, locked-session diagnostics, reliability, and privacy qualification remain preserved in #4348. Visual comparison/reporting remains #4328.