Very appreciate the detailed and comprehensive info, things are far more complex than I thought!
Noticed there are some “geometry->GetVertexData()” calls, not sure but it looks like this could be used for something like “CoronaCanvasInitialSize” which only fetch initial width and height of rendering geometry and won’t response to updated one. initial size would be helpful for calculating aspect.
Another inspiration is “CoronaScreenSampler” which fetch the render data from memory. this could be done by using snapshot as root group for gameplay objects and simply apply shader effect on it. just not sure is that a efficient way to do rather than fetching render data.
After all, these are “make life easier” ideas not imperative ones, so they shall be flagged “Low Priority”, many thanks for your reply! 