Fix nested canvas clipping and clipped clears by bkaradzic-microsoft · Pull Request #1872 · BabylonJS/BabylonNative

bkaradzic-microsoft · 2026-09-11T00:24:13Z

Summary

Intersect rectangular Canvas clips with the active NanoVG scissor so nested, disjoint, translated, signed-rectangle, and restored clips retain parent bounds.
Implement clearRect with opaque destination-out coverage, independent of globalAlpha and filters, while restoring the prior drawing state.
Initialize empty NanoVG filter stacks and add GPU-readback regressions with existing render-test skip handling.
Fix the OpenPBR validation scene's asynchronous mesh-loading race: return the scene only after mesh import and material setup finish, using the existing per-test source replacement support. The reference image, render count, and tolerance are unchanged.
Fix the inherited Vulkan CI gate to require both sampler-boundary tests to run and pass without assuming a fixed total suite size.

Base

Rebased onto master at 4af724a6. Includes signed-rectangle normalization before scissor intersection. This includes the already-merged Canvas work from #1855 and does not depend on the open branding PR #1844.

Validation

Windows x64 / D3D11 / QuickJS, RelWithDebInfo: all 6 selected native cases passed, including all 94 JavaScript cases.
A delayed mesh import reproduced every pixel of the blank CI screenshot on both the PR and its upstream base (41.223% mismatch). With the scene-loading fix, both delayed and ordinary runs pass at 0.733%, below the unchanged 2.5% limit.
The actual snippet's transformed scene creation waits for the import, finishes all 16 material assignments, and propagates import failures.
The Vulkan gate accepts the actual 34-case CI report and rejects missing, skipped, failed, unexecuted, or incomplete required boundary tests.

Signed-rectangle update

Normalize negative width/height before intersecting with the parent clip; preserve the existing transform and antialiasing adjustment.
Cover both signed axes, their combination, and rotated nested clips using byte-identical GPU comparisons with equivalent positive rectangles.
Windows x64 / D3D11 / Chakra / RelWithDebInfo: all 6 selected native cases pass, including 68 JavaScript cases; 27 optional codec cases are pending because those plugins are disabled in this build. The new regression fails against the previous PR head on the first negative-width case and passes with the fix.
No Babylon.js changes, dependency updates, reference changes, or validation-gate adjustments in this update.

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Pull request overview

This PR fixes correctness issues in the Canvas2D NanoVG-backed implementation, specifically around nested clipping behavior and clearRect behavior under clipping/alpha/filters, and adds GPU readback regression tests to prevent regressions.

Changes:

Intersect Canvas rectangle clipping with the active NanoVG scissor to preserve parent clip bounds for nested clips.
Implement clearRect via DESTINATION_OUT coverage while forcing globalAlpha=1 and clearing filters, restoring prior state afterward.
Add GPU readback regression tests for nested clips and clipped clears, with skip handling wired from the native test runner.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
Polyfills/Canvas/Source/nanovg/nanovg_filterstack.h	Initializes filter stack count to avoid undefined state when creating “empty” stacks.
Polyfills/Canvas/Source/Context.cpp	Updates clip handling to use scissor intersection and adjusts `clearRect` compositing to clear only clipped regions independent of alpha/filters.
Apps/UnitTests/Source/Tests.JavaScript.cpp	Exposes a global flag to skip GPU canvas tests when render/external texture tests are disabled.
Apps/UnitTests/JavaScript/src/tests.javaScript.all.ts	Adds GPU readback regression tests for nested clips and clipped `clearRect`.
Apps/UnitTests/JavaScript/dist/tests.javaScript.all.js	Bundled output updated to include the new JS test cases.

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Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

bkaradzic-microsoft · 2026-09-11T01:58:56Z

The Windows/Hermes failure occurred after a successful build: snippet requests returned HTTP 403 on that runner, so all 314 Playground cases failed during scene loading (three failed fetch attempts per case), before rendering.

The same commit passed all 314 cases in the Windows D3D11 and V8 jobs, and the failed snippet URLs now return HTTP 200 from a separate probe. No code or test changes are warranted by this evidence. The failed-only retry (attempt 2, job 103128300425) has now passed both Validation Tests and Unit Tests. All 34 checks are green on the same commit; no code or test changes were needed.

Intersect rectangular clips with the existing NanoVG scissor so nested clips preserve parent bounds and save/restore state. Clear clipped regions with destination-out coverage while ignoring global alpha and filters. Initialize empty filter stacks and add GPU-readback regressions. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 60c2ec68-6de1-445d-9fc9-b699db737eae

Zero-initialize the filter element array because NanoVG copies the full filter stack into state and draw calls. Clarify the existing asymmetric anti-alias clip extension without changing its bounds. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 60c2ec68-6de1-445d-9fc9-b699db737eae

The snippet returns its scene before ImportMeshAsync and onMeshLoad finish, so readiness can capture an empty scene. Preserve the import promise and return the scene only after its completion, using the existing per-test source replacement support. A delayed import reproduced every pixel of the blank CI image on both the PR and its upstream base. The scene now passes with the same delay, without changing the reference image, render count, or tolerance. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 48fa7ec8-0cf6-48a0-b836-10b7ace38c1a

Normalize negative rectangle extents before NanoVG scissor intersection, preserving parent bounds, transforms, and the existing AA adjustment. Add GPU readback coverage for both signed axes and rotated nested clips, comparing all pixels with equivalent positive rectangles. The regression fails against the previous PR head and passes with the normalization. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 60c2ec68-6de1-445d-9fc9-b699db737eae

`validation_native.js` has workarounds for bugs in the examples (not in Babylon Native), and today they run for every test. This gives each one an ID and runs it only for tests that list it in `config.json`: ```json "workarounds": ["wait-for-readiness"] ``` The `workarounds` lists double as the list of examples to fix. | ID | Example bug | Origin | Enabled tests | |---|---|---|---| | `wait-for-readiness` | Renders before utility scenes, GUI images, or material effects are ready | #1890 | 15 | | `undeclared-name` | Reads the browser-only global `name` | #1823 | 0 | | `prime-effect-layers` | Captures effect-layer output on the first frame | #1913 | 9 | | `leak-cleanup` | Leaves scenes, textures, or Draco state behind | #1830 / #1838 | 2 | | `wait-for-import` | Starts a model load in `createScene` without awaiting it (was a `replace` patch) | #1872 | 1 | | `opaque-clear-alpha` | Clears opaque but leaves alpha < 1 in the image (was an unconditional gate) | #1913 | 9 | - Without `wait-for-readiness`, the runner matches the browser harness: main-scene `executeWhenReady`, then `renderCount` frames. - Harness resets the browser also does stay unconditional (stencil, scissor, reverse depth, `releaseEffects`, hardware scaling, `OnPluginActivatedObservable.clear()`). - Without `opaque-clear-alpha`, translucent pixels are always composited over the canvas background, as in the browser. - Unknown IDs fail config load (exit 1). - `--list` prints the IDs as a fifth TSV column. - The runner logs `Workaround '<id>' applied for '<title>'` whenever a workaround changes what it does. - Docs: `AddingNewValidationTests.md` and the debugging instructions. ### How tests were assigned I ran the 371 enabled tests three times (V8/D3D11) with every workaround on for every test, and assigned each test the workarounds that triggered for it. Every assignment triggered in 3/3 runs except "GUI Images in Grid" (1/3). Notes: - With every workaround off, all 371 still passed locally, so on this machine the assignments are precautionary. Other engines or graphics APIs may genuinely need them. - `undeclared-name` has no current users. Excluded tests were also checked with `--include-excluded`, and none raised `name is not defined`. The ID is kept for future use. `wait-for-import` and `opaque-clear-alpha` were assigned the same way: the `replace` patch's test, and the 9 tests that failed with the alpha gate removed. ### Validation - V8/D3D11 RelWithDebInfo, final config: `ran=371 passed=371 failed=0`. - A bogus ID makes config load fail as expected. --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: c46f0590-2707-466b-93c7-bb74316f385a

Copilot AI lite review requested due to automatic review settings September 11, 2026 00:24

Copilot AI reviewed Sep 11, 2026

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Comment thread Polyfills/Canvas/Source/Context.cpp

Comment thread Polyfills/Canvas/Source/Context.cpp Outdated

Comment thread Apps/UnitTests/JavaScript/src/tests.javaScript.all.ts

bkaradzic-microsoft requested a lite review from Copilot September 11, 2026 00:46

Copilot started reviewing on behalf of bkaradzic-microsoft September 11, 2026 00:49 View session

Copilot AI reviewed Sep 11, 2026

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Comment thread Apps/UnitTests/JavaScript/src/tests.javaScript.all.ts

Copilot started reviewing on behalf of bkaradzic-microsoft September 11, 2026 02:17 View session

bkaradzic-microsoft requested review from CedricGuillemet, bghgary and ryantrem September 11, 2026 23:04

This was referenced Sep 13, 2026

Add arbitrary-path clipping (clip-path / clip-rule) on a reserved stencil bit femtovg/femtovg#324

Merged

Roadmap: Canvas 2D / SVG conformance slices (dependencies, risk, test cross-references) rebeckerspecialties/femtovg#5

Open

bkaradzic-microsoft force-pushed the pr/canvas-clip-clear branch 4 times, most recently from 8589386 to f1a87e5 Compare September 16, 2026 23:26

bkaradzic-microsoft and others added 4 commits September 18, 2026 07:27

bkaradzic-microsoft force-pushed the pr/canvas-clip-clear branch from 055b39a to 763b288 Compare September 18, 2026 14:30

CedricGuillemet approved these changes Sep 18, 2026

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bkaradzic-microsoft enabled auto-merge (squash) September 18, 2026 15:48

bkaradzic-microsoft merged commit 2a9dc94 into BabylonJS:master Sep 18, 2026
35 checks passed

bkaradzic-microsoft mentioned this pull request Oct 8, 2026

Key validation example workarounds per test in config.json #1920

Merged

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Fix nested canvas clipping and clipped clears - #1872

Fix nested canvas clipping and clipped clears#1872
bkaradzic-microsoft merged 4 commits into
BabylonJS:masterfrom
bkaradzic-microsoft:pr/canvas-clip-clear

bkaradzic-microsoft commented Sep 11, 2026 •

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bkaradzic-microsoft commented Sep 11, 2026 •

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bkaradzic-microsoft commented Sep 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

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Signed-rectangle update

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bkaradzic-microsoft commented Sep 11, 2026 •

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