fix: add DOM renderer fallback for Windows compatibility#722
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djdarcy wants to merge 2 commits intocharmbracelet:mainfrom
Open
fix: add DOM renderer fallback for Windows compatibility#722djdarcy wants to merge 2 commits intocharmbracelet:mainfrom
djdarcy wants to merge 2 commits intocharmbracelet:mainfrom
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The canvas renderer fails in headless Chrome on Windows when WebGL is unavailable (RDP sessions, headless environments, CI). This causes CanvasToImage() calls to return empty frames. Changes: - Switch default renderer from canvas to DOM (tty.go) - Add SwiftShader/ANGLE browser flags for WebGL fallback (vhs.go) - Probe for canvas.xterm-text-layer with timeout; fall back to .xterm-screen element screenshot when canvas is absent (vhs.go) - Use temporary timeout page for probe to avoid context deadline errors on stored elements (vhs.go) - Add diagnostic logging throughout startup, setup, and recording pipeline (evaluator.go, vhs.go) The debug-instrumented version is preserved in this commit for reference. A follow-up commit strips the diagnostic logging. Related: charmbracelet#631 Depends on: tsl0922/ttyd#1501 (ConPTY fix for Windows 11)
Remove verbose debug output from evaluator, browser launch, setup, and recording pipeline. Functional changes preserved: DOM renderer fallback, SwiftShader browser flags, timeout-based canvas probe. The debug-instrumented version is preserved in the previous commit for reference.
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CONTRIBUTING.md.I have created a discussion that was approved by a maintainer (for new features).(not applicable)Fixes #721. Related: #631, tsl0922/ttyd#1501, tsl0922/ttyd#1502.
VHS on Windows produces blank frames because the canvas renderer fails in headless Chrome when WebGL is unavailable. This is compounded by a ConPTY bug in ttyd's MinGW build on Windows 11 25H2 (tracked separately in tsl0922/ttyd#1501).
Changes
tty.go:
canvastodomvhs.go:
use-gl=angle,use-angle=swiftshader,enable-webgl) as WebGL fallbackcanvas.xterm-text-layerwith a 5-second timeout, fall back to.xterm-screenelement screenshotttyd dependency
The bundled
ttyd.win32.exe(MinGW cross-compiled) fails on Windows 11 25H2 withCreateProcessWerror 123. An MSVC-built ttyd resolves this. See:Notes
Happy to adjust the approach. The DOM renderer fallback could be made configurable via environment variable if preferred, and the SwiftShader flags could be opt-in rather than default.
Tested on Windows 11 Pro 25H2 (build 26200.8037) with MSVC-built ttyd, Chrome 134.