bug#1867: Resizing window causes text flickering when using antialiased font on X

[Jan D.]

Chong Yidong skrev 2011-10-05 23:57:
> Eli Zaretskii<eliz@gnu.org>  writes:
>
> > The way redisplay is written, _any_ change to dimensions of _any_
> > window sets a flag that will cause a thorough redisplay of all the
> > windows on all the visible frames.  However, I'd expect that redisplay
> > of any window not affected by the resizing be limited to redrawing the
> > cursor.
>
> Resizing a window redraws all windows on the same frame, even those
> unaffected by the resizing.

But according to Eli, the redraw optimizations in Emacs display engine 
should not actually redraw anything in unchanged windows.
According to the desciption window 3 is totally unchanged, but flickers 
anyway.
But this was on 23.0.60.  Many bugs has been fixed since.

> The right way to fix flickering in Emacs is to implement double
> buffering, which is not a trivial project.

If we are aiming for a general solution across all ports this is true.
A pure X solution might be easier if we use the double buffer extension.

        Jan D.