+ }
+
+ /* From the OpenGL 4.0 specification, page 256:
+ * "For both the default framebuffer and framebuffer objects, the
+ * constants FRONT, BACK, LEFT, RIGHT, and FRONT_AND_BACK are not
+ * valid in the bufs array passed to DrawBuffers, and will result in
+ * the error INVALID_ENUM. This restriction is because these
+ * constants may themselves refer to multiple buffers, as shown in
+ * table 4.4."
+ * Previous versions of the OpenGL specification say INVALID_OPERATION,
+ * but the Khronos conformance tests expect INVALID_ENUM.
+ */
+ if (_mesa_bitcount(destMask[output]) > 1) {
+ _mesa_error(ctx, GL_INVALID_ENUM, "%s(invalid buffer %s)",
+ caller, _mesa_enum_to_string(buffers[output]));
+ return;
+ }
+
+ /* From the OpenGL 3.0 specification, page 259:
+ * "If the GL is bound to the default framebuffer and DrawBuffers is
+ * supplied with a constant (other than NONE) that does not indicate
+ * any of the color buffers allocated to the GL context by the window
+ * system, the error INVALID_OPERATION will be generated.
+ *
+ * If the GL is bound to a framebuffer object and DrawBuffers is
+ * supplied with a constant from table 4.6 [...] then the error
+ * INVALID_OPERATION results."
+ */