main: Add utility function _mesa_lookup_renderbuffer_err.

[Fredrik: Generate an error for non-existent renderbuffers]

Reviewed-by: Fredrik Höglund <fredrik@kde.org>
Signed-off-by: Fredrik Höglund <fredrik@kde.org>

src/mesa/main/fbobject.c

@@ -120,6 +120,27 @@ _mesa_lookup_renderbuffer(struct gl_context *ctx, GLuint id)
 }
 
 
+/**
+ * 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.
  */

src/mesa/main/fbobject.h

@@ -64,6 +64,10 @@ _mesa_get_incomplete_framebuffer(void);
 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);