Opaque pointer passed through unchanged, not owned or
copied. Keep its target alive for every invocation, including clone replay.
Returns
void
Remarks
The callback runs when the renderer processes the draw list, such as during
SFML.Render; do not call ImGui widgets from it. Frame callbacks remain
alive until the owning context's next frame or shutdown. Clones retain
copied callbacks independently, including callbacks appended to the clone.
Append a JavaScript draw callback to a DrawList.