315274 2026-05-21 05:00:25 -0700 WebGPU+WebXR on visionOS: setScissorRect unusable on XR projection layer 2026-05-27 15:19:14 -0700 1 1 1 Unclassified WebKit WebXR Safari 26 Vision Pro visionOS 26 RESOLVED FIXED InRadar P2 Normal --- 1 mvaligursky mwyrzykowski djg kkinnunen mwyrzykowski webkit-bug-importer oldest_to_newest 2212885 0 mvaligursky 2026-05-21 05:00:25 -0700 ### Environment - WebXR (immersive-vr) + WebGPU via XRGPUBinding ### Bug Creating a projection layer yields: - colorTexture (attachment) extent: e.g. 1888×1792 - subImage.viewport: e.g. 4338×3478 (larger than the attachment) setViewport works fine with either size — including the oversized view extent. setScissorRect cannot be used at all: - setScissorRect(0, 0, 1888, 1792) // attachment size → renders only into top-left ~1/3 of the eye ❌ - setScissorRect(0, 0, 4338, 3478) // view size → WebGPU validation error (scissor must fit attachment) ❌ - no setScissorRect call // default → renders full eye ✅ Per WebGPU spec, scissor starts at the full attachment, so the attachment-sized call should be a no-op equivalent to omitting it. On visionOS the explicit call appears to be interpreted as a positional hint for the compositor's mapping of the layer texture to the eye display. ### Impact WebGPU engines that call setScissorRect as part of standard pass setup (PlayCanvas in this case) render into a sub-rectangle of the eye on AVP. Engines/samples that happen not to call it (Toji's vr-barebones, webgpu-metaballs) render correctly. Current workaround: suppress setScissorRect entirely on the XR path. ### Repro WebXR-Samples vr-barebones.html with one added setScissorRect call before the draw reproduces it. https://github.com/immersive-web/webxr-samples 2213103 1 webkit-bug-importer 2026-05-21 16:39:06 -0700 <rdar://problem/177664498> 2213695 2 mwyrzykowski 2026-05-24 13:47:57 -0700 setScissorRect(0, 0, 1888, 1792) // attachment size is correct based on the WebGPU specification as x, y, width, height are in pixels - I will fix this up 2213906 3 mwyrzykowski 2026-05-25 12:17:24 -0700 Pull request: https://github.com/WebKit/WebKit/pull/65631 2215155 4 ews-feeder 2026-05-27 15:19:11 -0700 Committed 314005@main (eda478cddb5d): <https://commits.webkit.org/314005@main> Reviewed commits have been landed. Closing PR #65631 and removing active labels.