This PR implements the WebGL validateProgram method as requested in the issue, following the MDN specification with complete end-to-end implementation and comprehensive test coverage.

Overview

The validateProgram method validates a WebGL program against the current WebGL state and stores the validation result in the program's VALIDATE_STATUS parameter, which can be queried using getProgramParameter.

Usage

// Create and link a program
const program = gl.createProgram();
gl.attachShader(program, vertexShader);
gl.attachShader(program, fragmentShader);
gl.linkProgram(program);

// Validate the program
gl.validateProgram(program);

// Check validation status
const isValid = gl.getProgramParameter(program, gl.VALIDATE_STATUS);
if (isValid) {
    gl.useProgram(program);
} else {
    console.error('Program validation failed:', gl.getProgramInfoLog(program));
}

Implementation Details

Command Buffer Layer:

• Added COMMAND_BUFFER_VALIDATE_PROGRAM_REQ enum constant
• Added ValidateProgramCommandBufferRequest class following existing patterns

Client Graphics Layer:

• Implemented WebGLContext::validateProgram() method with proper error handling
• Added validation status tracking to WebGLProgram class (validateStatus_, setValidateStatus(), getValidateStatus())
• Updated getProgramParameter() to handle WEBGL_VALIDATE_STATUS queries

JavaScript Bindings:

• Added ValidateProgram method to WebGLBaseRenderingContext with proper argument validation
• Registered the method in N-API binding macros

Renderer Processing:

• Added OnValidateProgram function that calls glValidateProgram() on the OpenGL program
• Registered the VALIDATE_PROGRAM command buffer handler to route requests to the renderer
• Follows the same pattern as other simple program operations like useProgram

Test Coverage

Added comprehensive test page at fixtures/html/webgl-conformance/validateprogram-test.html that covers:

• API Availability: Verifies method and constant existence
• Valid Program Tests: Tests validation of properly linked programs
• Invalid Program Tests: Tests validation of programs with shader incompatibilities
• Error Handling: Tests null/invalid program scenarios
• Integration Tests: Tests validateProgram with useProgram workflow
• Visual Results: Color-coded pass/fail indicators with detailed test descriptions

WebGL Specification Compliance

✅ Method signature: void validateProgram(WebGLProgram program)
✅ Validates program against current WebGL state
✅ Stores result in VALIDATE_STATUS parameter (0x8B83)
✅ Queryable via getProgramParameter(program, gl.VALIDATE_STATUS)
✅ Proper error handling for null/invalid programs
✅ Complete end-to-end processing from JavaScript to OpenGL renderer

The implementation provides a complete data flow from the JavaScript API through the command buffer system to the OpenGL renderer, ensuring the validation is properly executed and results are accessible to applications.

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