ok, the sketching is the fastest part of the system.
Of any area it is the one place where minimal work is done to the canvas.
Simply extend the current drawing by 1 line and refresh.
liqbase always waits for xv to inform it that the frame is completely sent and I do not touch the memory again until I receive this event (overdrawing before this event is a different and leads to tearing).

Since I am not updating the whole display and sending a bitmap which is very similar to current display it appears as though the LCD controller itself is eating the lower portion of the page.

Perhaps it is caused by another process attempting to update its portion of the framebuffer when XV is meant to have it locked?

Has this been noticed anywhere else?



Also, if it occurs, try switching to a different drawing tool, the others work "live" and refresh the whole screen from top to bottom including buttons and stuff.