- if (ctx->Visual.accumRedBits == 0 || ctx->DrawBuffer != ctx->ReadBuffer) {
- gl_error(ctx, GL_INVALID_OPERATION, "glAccum");
+ switch (op) {
+ case GL_ADD:
+ case GL_MULT:
+ case GL_ACCUM:
+ case GL_LOAD:
+ case GL_RETURN:
+ /* OK */
+ break;
+ default:
+ _mesa_error(ctx, GL_INVALID_ENUM, "glAccum(op)");
+ return;
+ }
+
+ if (ctx->DrawBuffer->Visual.haveAccumBuffer == 0) {
+ _mesa_error(ctx, GL_INVALID_OPERATION, "glAccum(no accum buffer)");
+ return;
+ }
+
+ 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)");