Re: Redisplay problems?

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: address@hidden,  address@hidden,  address@hidden,  address@hidden,  
> address@hidden
> Date: Thu, 27 Mar 2014 17:13:00 -0400
> 
> > How does all this relate to moving blocks of pixels?
> 
> 0 - frame gets deiconified, we don't redraw anything.
> 1 - we recompute desired matrices.
> 2 - we compare matrices and see that the top part of the frame can be drawn
>     be copying the pixels from the bottom part (assuming here incorrectly
>     that those pixels are in sync with the current matrices).
> 3 - we copy the incorrect pixels and consider ourselves happy to have
>     redisplayed the top-part of the frame :-(
> 
> I think this can't happen, which is why I think it's OK not to redraw
> anything at step 0.

I think it can happen.  See scrolling_window and x_scroll_run that it
calls.