gecko/content/canvas/src/WebGLContextValidate.cpp

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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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 * for the specific language governing rights and limitations under the
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 * The Original Code is mozilla.org code.
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 * The Initial Developer of the Original Code is
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 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
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 * Contributor(s):
 *   Vladimir Vukicevic <vladimir@pobox.com> (original author)
 *   Mark Steele <mwsteele@gmail.com>
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#include "WebGLContext.h"

using namespace mozilla;

/*
 * Verify that we can read count consecutive elements from each bound VBO.
 */

PRBool
WebGLContext::ValidateBuffers(PRUint32 count)
{
    GLint currentProgram = -1;
    GLint numAttributes = -1;

    MakeContextCurrent();

    // XXX cache this per program
    gl->fGetIntegerv(LOCAL_GL_CURRENT_PROGRAM, &currentProgram);
    if (currentProgram == -1) {
        // what?
        LogMessage("glGetIntegerv GL_CURRENT_PROGRAM failed: 0x%08x", (uint) gl->fGetError());
        return PR_FALSE;
    }

    gl->fGetProgramiv(currentProgram, LOCAL_GL_ACTIVE_ATTRIBUTES, &numAttributes);
    if (numAttributes == -1) {
        // what?
        LogMessage("glGetProgramiv GL_ACTIVE_ATTRIBUTES failed: 0x%08x", (uint) gl->fGetError());
        return PR_FALSE;
    }

    // is this valid?
    if (numAttributes > (GLint) mAttribBuffers.Length()) {
        // what?
        LogMessage("GL_ACTIVE_ATTRIBUTES > GL_MAX_VERTEX_ATTRIBS");
        return PR_FALSE;
    }
    PRUint32 maxAttribs = numAttributes;

    for (PRUint32 i = 0; i < maxAttribs; ++i) {
      WebGLVertexAttribData& vd = mAttribBuffers[i];

      // is this a problem?
      if (!vd.enabled)
          continue;

      if (vd.buf == nsnull) {
          LogMessage("No VBO bound to index %d (or it's been deleted)!", i);
          return PR_FALSE;
      }

      GLuint needed = vd.offset + (vd.stride ? vd.stride : vd.size) * count;
      if (vd.buf->ByteLength() < needed) {
          LogMessage("VBO too small for bound attrib index %d: need at least %d bytes, but have only %d", i, needed, vd.buf->ByteLength());
          return PR_FALSE;
      }
    }

    return PR_TRUE;
}