fix: preserve user-set uSampler uniform for custom shaders

[BHARATH0153]

Resolves #8200

overview

p5.js overrides the uSampler uniform on user shaders after the user has already set a value via setUniform(). This happens because _setFillUniforms always resets uSampler to the current p5.js texture state.
fixes Track which uniforms have been explicitly set by the user via setUniform(). In _setFillUniforms, skip overriding uSampler if the user has already set it. The tracking is reset each frame in _update() so per-frame setUniform calls are honored.

Changes:

• src/core/p5.Renderer3D.js: skip uSampler override when user set it
• src/webgl/p5.Shader.js: add _userSetUniforms tracking, check _isInternalSetUniform flag
• test/unit/webgl/p5.RendererGL.js: add test verifying user-set uSampler is preserved

PR Checklist

npm run lint passes
Inline reference is included / updated
Unit tests are included / updated

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Thank You!

[perminder-17]

Hi, Thanks for your work on this @BHARATH0153 , I think I'm unable to understand your solution?
The core requirement is that p5.js should not override the uSampler uniform when a user has set it manually on their own shader.

We only need to set uSampler internally in two cases:

1. When the active shader is a built-in shader (not a user-provided one), i.e. it is neither userFillShader nor userImageShader.
2. When a texture is actually active via texture(), i.e. this.states._tex is truthy.

So the condition becomes:

const isUserFillShader =
  fillShader === this.states.userFillShader ||
  fillShader === this.states.userImageShader;

if (this.states._tex || !isUserFillShader) {
  fillShader.setUniform("uSampler", this.states._tex || empty);
}

Does this feels right to you?

[BHARATH0153]

@perminder-17 Great suggestion thanks! I've updated the PR with this approach
Removed _userSetUniforms Set, _isInternalSetUniform flag, and per-frame clearing
Now only overrides uSampler when this.states._tex is active or the shader is built-in
test passes

[perminder-17]

Looks good, do you think we could add one visual test as well as per @davepagurek sketch?

[p5-bot]

Continuous Release

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[BHARATH0153]

@perminder-17 Thanks again for the review I've simplified the approach as you suggested now only overrides uSampler when the shader is built-in or a texture is active. Also added a visual test based on @davepagurek's sketch.

[BHARATH0153]

@davepagurek @perminder-17 please rerun the checks thanks!

[perminder-17]

Hi, thanks for adding the test. I am unable to see the metaData and the screenshot which was generated from that test which were present in this commit : f75f227

I think, you need to run npm test locally to generate those and needs to commit them again in your latest commit.

[BHARATH0153]

@davepagurek @perminder-17 once please rerun the checks

[BHARATH0153]

@perminder-17 @davepagurek all checks have been passed please once review thanks!

[perminder-17]

Looks good to me!