Implement getVertexAttrib family for WebGL compatibility (getVertexAttrib, getVertexAttribOffset, etc.)

[EndlessJour9527]

Background

When running sdk/tests/conformance2/attribs/gl-vertex-attrib.html from the EndlessJour9527/WebGL test suite in JSAR Runtime, the following error is encountered:

Uncaught TypeError: gl.getVertexAttrib is not a function

This is a critical WebGL API required by the WebGL specification and by a number of Khronos conformance tests (see WebGL 2.0 spec: getVertexAttrib).

Task

Implement the family of getVertexAttrib APIs so that JSAR correctly passes conformance tests such as:

• gl.getVertexAttrib
• gl.getVertexAttribOffset
• gl.getVertexAttribPointer

Minimal required functionality

• All variants for querying attribute state must be provided and match WebGL 1/2 and Khronos test expectations
  • Accepts all standard parameters: index, pname
  • Handles edge cases required for test coverage

Reference:

• Khronos WebGL2 Test: gl-vertex-attrib.html
• WebGL2 spec section 5.14.9
• Example Chromium implementation: chromium/src/third_party/blink/renderer/modules/webgl/webgl2_rendering_context_base.cc

Acceptance Criteria

• Passing the following conformance test file: sdk/tests/conformance2/attribs/gl-vertex-attrib.html from EndlessJour9527/WebGL
• Returns correct results for all valid function calls
• Throws appropriate exceptions for invalid parameters as per the spec

Implementation Hints (C++)

Implement in C++:

// WebGLRenderingContext getVertexAttrib implementation
void WebGLRenderingContext::getVertexAttrib(GLuint index, GLenum pname, ...) {
  // Reference: https://registry.khronos.org/webgl/specs/latest/2.0/#5.14.9
  // Add switch/case for each valid pname
  switch (pname) {
    case GL_VERTEX_ATTRIB_ARRAY_ENABLED:
      // Return enabled state
      break;
    case GL_VERTEX_ATTRIB_ARRAY_SIZE:
      // Return size
      break;
    // ... handle other cases
    default:
      // Throw exception for invalid pname
      break;
  }
}

Related files to update are in src/client/builtin_scene/webgl_rendering_context.cpp.

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See also JSAR documentation for WebGL 2.0 support and internal architecture documentation.