Both do more or less the same but with different methods - one puts
pixels into a buffer using the CPU, the other puts pixels into a buffer
using the GPU.
However, they are behaving slightly different, which they shouldn't.
Lets first address the misleading disconnect in naming, and later we'll
make them behave more similarly.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1361
We'd check if there was any queued redraw on the stage, but this is
inappropriate for two reasons:
1) A monitor and area screen cast source only cares about damage on a
subset of the stage.
2) The global pending-redraw is going away when paint scheduling will be
more view centric.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1285
It takes coordinates in stage coordinate space, and will result in
a screen cast stream consisting of that area, but scaled up by the scale
factor of the view that overlaps with the area and has the highest scale
factor.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1207
