Allow setting vector uniforms by name. #179927

walley892 · 2025-12-16T07:26:01Z

Create a few thin wrappers around UniformFloatSlot that allow users to get Vector uniforms by name and set all elements in one go.

Before:

shader.getUniformFloat('uColor', 0).set(color.r);
shader.getUniformFloat('uColor', 1).set(color.g);
shader.getUniformFloat('uColor', 2).set(color.b);

After:

shader.getUniformVec3('uColor').set(color.r, color.g, color.b);

This enforces that the requested vector is actually of the requested size. For example:

shader.getUniformVec2('someVec3Uniform');

will fail instead of allowing partial uniform access.

Follow up

This doesn't add list or matrix datatypes, those will come later.
Also doesn't have anything super fancy like accessors/setters for individual elements.

Pre-launch Checklist

[ x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
[ x] I read the [Tree Hygiene] wiki page, which explains my responsibilities.
[ x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
[ x] I signed the [CLA].
[ x] I listed at least one issue that this PR fixes in the description above.
[ x] I updated/added relevant documentation (doc comments with ///).
[ x] I added new tests to check the change I am making, or this PR is [test-exempt].
[ x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
[ x] All existing and new tests are passing.

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Code Review

This pull request introduces convenient wrappers for setting vector uniforms by name, which is a great improvement for shader development ergonomics. The implementation adds getUniformVec{2,3,4} methods and corresponding UniformVec*Slot classes, along with size validation to prevent partial uniform access.

My review focuses on improving code maintainability by reducing duplication and fixing an issue in one of the new tests. Specifically, I've pointed out repeated logic in the getUniformVec* methods across different files and suggested refactoring. I also found a test case that seems to be using incorrect data and assertions, which I've flagged as critical to ensure test reliability. The other tests look good and cover the new error-handling logic well.

engine/src/flutter/lib/web_ui/test/canvaskit/fragment_program_test.dart

engine/src/flutter/lib/ui/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/shaders.dart

engine/src/flutter/testing/dart/fragment_shader_test.dart

engine/src/flutter/lib/ui/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/shaders.dart

gaaclarke

Looking good, just some minor cleanup

engine/src/flutter/testing/dart/fragment_shader_test.dart

engine/src/flutter/lib/ui/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/painting.dart

engine/src/flutter/lib/web_ui/lib/src/engine/skwasm/skwasm_impl/shaders.dart

engine/src/flutter/lib/web_ui/test/canvaskit/fragment_program_test.dart

eyebrowsoffire

Web changes look good!

gaaclarke

lgtm!

engine/src/flutter/lib/ui/painting.dart

flar

Some comments about the efficiency of the implementation.

Also, I see a lot of negative tests (fails if ...), but I don't see some positive tests that it actually returns the object if you make the right request. Did I miss something?

engine/src/flutter/lib/ui/painting.dart

flar · 2025-12-19T21:40:27Z

engine/src/flutter/lib/ui/painting.dart

  }

+  List<UniformFloatSlot> _getSlotsForUniform(String name, int size) {
+    final int dataSize = _program._getUniformVectorSize(name);


This implementation is causing 2 lookups by name, can they be combined? It's an internal function so what about having the getIndex function take the size and it gets verified before returning the index (~~size of 0 or -1~~ null to indicate "I don't care about the size")?

Actually, the way to do an optional parameter in Dart is int? and pass null for the access that doesn't require a size constraint.

How's that looking?

flar · 2025-12-19T21:41:28Z

engine/src/flutter/lib/ui/painting.dart

+  /// }
+  /// ```
+  UniformVec2Slot getUniformVec2(String name) {
+    final List<UniformFloatSlot> slots = _getSlotsForUniform(name, 2);


What's the cost of creating a list in the _getSlots function vs. just returning the index (after verifying the size) and then constructing the slots inline here?

I'm not sure if there's a differing cost for that kind of thing in Dart. I have it this way for code reuse

Actually, I'm not sure if this comment is dovetailing with your comment above or if it's a comment about the efficiency of returning lists in Dart

It's about unnecessary creation of lists. Maybe Dart is smart enough to optimize that out, I don't know.

walley892 · 2025-12-19T22:30:12Z

Some comments about the efficiency of the implementation.

Also, I see a lot of negative tests (fails if ...), but I don't see some positive tests that it actually returns the object if you make the right request. Did I miss something?

Thanks for the review. Added some happy path tests

flar

LGTM

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Add UniformVecX classes

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fix web test

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Merge remote-tracking branch 'upstream/master' into dart-get-uniforms

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flar comments and docstring update

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use nullable default for optional argument

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remove _getUniformVectorSize from the web code

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Merge remote-tracking branch 'upstream/master' into dart-get-uniforms

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Allow setting vector uniforms by name. #179927

Allow setting vector uniforms by name. #179927

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walley892 commented Dec 16, 2025

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