+
+ /* Create a front/left color buffer which wraps the user-provided buffer.
+ * There is no back color buffer.
+ * If the user tries to use a 8, 16 or 32-bit/channel buffer that
+ * doesn't match what Mesa was compiled for (CHAN_BITS) the
+ * _mesa_add_renderbuffer() function will create a "wrapper" renderbuffer
+ * that converts rendering from CHAN_BITS to the user-requested channel
+ * size.
+ */
+ if (!osmesa->rb) {
+ osmesa->rb = new_osmesa_renderbuffer(&osmesa->mesa, osmesa->format, type);
+ _mesa_remove_renderbuffer(osmesa->gl_buffer, BUFFER_FRONT_LEFT);
+ _mesa_add_renderbuffer(osmesa->gl_buffer, BUFFER_FRONT_LEFT, osmesa->rb);
+ assert(osmesa->rb->RefCount == 2);
+ }
+