The (old) C-firmware featured a transition animation where the entire screen was moved or wiped out of the frame very quickly (4 directions could be chosen).
This was achieved by a second framebuffer (_transition_framebuffer) of the entire LCD.
At the start of such a transition - it basically captured a screenshot copy into said framebuffer and then with following frames shifted or cropped the content of this second framebuffer towards the move direction.
The animations start was triggered like this:
The animation itself was handled here:
How could we best bring this back in the C++ Firmware?
The effect can be seen in this video: