}
+/**
+ * A convenience function for direct state access that throws
+ * GL_INVALID_OPERATION if the renderbuffer doesn't exist.
+ */
+struct gl_renderbuffer *
+_mesa_lookup_renderbuffer_err(struct gl_context *ctx, GLuint id,
+ const char *func)
+{
+ struct gl_renderbuffer *rb;
+
+ rb = _mesa_lookup_renderbuffer(ctx, id);
+ if (!rb || rb == &DummyRenderbuffer) {
+ _mesa_error(ctx, GL_INVALID_OPERATION,
+ "%s(non-existent renderbuffer %u)", func, id);
+ return NULL;
+ }
+
+ return rb;
+}
+
+
/**
* Helper routine for getting a gl_framebuffer.
*/
extern struct gl_renderbuffer *
_mesa_lookup_renderbuffer(struct gl_context *ctx, GLuint id);
+extern struct gl_renderbuffer *
+_mesa_lookup_renderbuffer_err(struct gl_context *ctx, GLuint id,
+ const char *func);
+
extern struct gl_framebuffer *
_mesa_lookup_framebuffer(struct gl_context *ctx, GLuint id);