I think this might enable us to use the RGBA buffer directly, but I'm not sure yet.
Well, yes and no.
It looks like the firmware only updates parts of this overlay that actually change. That means, the old (single) guard pixel based detection (which parts of CHDK currently use) would not be usable on the RGBA buffer.
It works on M3 but still conflicting with canon's histogram and electronic level.
That is caused by the firmware continuously updating the overlay. It has no relation to our screen erase method.
There need a synchronization with canon's GUI...
That would not help much as we can't write our OSD fast enough.
Some completely new method might work. Such as
- creating a valid Canon full screen "dialog" that has its own content (say, a bitmap that we provide) and is always visible
- creating a similar layer, but using the Xtensa side API
Sadly, the difficulty to research/accomplish these is pretty high.