+ /* From the GL 4.0 specification:
+ * If buffer is COLOR, a particular draw buffer DRAW_BUFFERi is
+ * specified by passing i as the parameter drawbuffer, and value
+ * points to a four-element vector specifying the R, G, B, and A
+ * color to clear that draw buffer to. If the draw buffer is one
+ * of FRONT, BACK, LEFT, RIGHT, or FRONT_AND_BACK, identifying
+ * multiple buffers, each selected buffer is cleared to the same
+ * value.
+ *
+ * Note that "drawbuffer" and "draw buffer" have different meaning.
+ * "drawbuffer" specifies DRAW_BUFFERi, while "draw buffer" is what's
+ * assigned to DRAW_BUFFERi. It could be COLOR_ATTACHMENT0, FRONT, BACK,
+ * etc.
+ */
+ if (drawbuffer < 0 || drawbuffer >= (GLint)ctx->Const.MaxDrawBuffers) {
+ return INVALID_MASK;
+ }
+
+ switch (ctx->DrawBuffer->ColorDrawBuffer[drawbuffer]) {