[Webkit-unassigned] [Bug 126718] New: [WebGL] Have getProgramParameter return filtered results for ACTIVE_ATTRIBUTES and ACTIVE_UNIFORMS

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=126718

           Summary: [WebGL] Have getProgramParameter return filtered
                    results for ACTIVE_ATTRIBUTES and ACTIVE_UNIFORMS
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebGL
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: bfulgham at webkit.org


The Khronos WebGL test suite assumes that getProgramParameter only returns non-builtin attributes and uniforms.  For example, it assumes that getProgramParameter(ACTIVE_UNIFORMS) returns a count that omits built-in uniforms, such as gl_DepthRange.near, gl_DepthRange.far, etc.

OpenGL itself does return built-in values when you query "glGetActiveUniform" (see https://www.khronos.org/opengles/sdk/docs/man/xhtml/glGetActiveUniform.xml: The spec states that "The list of active uniform variables may include both built-in uniform variables (which begin with the prefix 'gl_') as well as user-defined uniform variable names."). Likewise, glGetActiveAttrib is specified to potentially return built-ins (see http://www.opengl.org/sdk/docs/man/xhtml/glGetActiveAttrib.xml).

OpenGL specifies that when glGetUniformLocation (or glGetAttribLocation) is called for a built-in name (such as gl_DepthRange.near) it should return -1.

The Khronos WebGL test suite treats its inability to retrieve location data for built-ins as an error, resulting in a number of failures.  These failures are consistent between WebKit and Firefox.

Chrome filters these values, and therefore gets a successful test run.

To provide comparable test compliance, we should filter our results the same way, so the web developers see a consistent use case on all platforms.

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