- /* Determine region to operate upon. */
- if (ctx->Scissor.Enabled) {
- xpos = ctx->Scissor.X;
- ypos = ctx->Scissor.Y;
- width = ctx->Scissor.Width;
- height = ctx->Scissor.Height;
+ if (ctx->DrawBuffer != ctx->ReadBuffer) {
+ /* See GLX_SGI_make_current_read or WGL_ARB_make_current_read,
+ * or GL_EXT_framebuffer_blit.
+ */
+ _mesa_error(ctx, GL_INVALID_OPERATION,
+ "glAccum(different read/draw buffers)");
+ return;