Re: Redisplay problems?

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Date: Thu, 20 Mar 2014 17:00:49 -0400
> Cc: Christian Lynbech <address@hidden>, James Cloos <address@hidden>,
>       Kan-Ru Chen (陳侃如) <address@hidden>,
>       address@hidden
> 
> > But it's a redraw when we expose a hitherto invisible/obscured frame
> > whose contents have changed while it was invisible/obscured.
> 
> Yes, of course, but you can look at it as "deiconify with the old
> display content" (without recomputing matrices nor redrawing) followed
> by a normal redisplay (which may recompute matrices and/or redraw
> depending on whether something actually did change while the frame was
> invisible).

That would cause an unpleasant momentary display of wrong contents.

Anyway, I very much doubt that an iconified frame might have its
current matrices outdated.  What is the use case for this to happen?

> >> Part of the reason it's still fuzzy is that xdisp.c seems to recompute
> >> the matrices when it finds a "garbaged" frame,
> > But we do have to compute the new matrices to know whether they have
> > changed.  I'm fully confused now.
> 
> No, if the "redisplay" bits are "false" we know that nothing has changed.

Are these bits reset for windows on iconified frames?  If so, you have
no other way but marking such frames "garbaged" when they are deiconified.