Re: animate incredibly slow compared to 21.3

[Jan D.]

> Stefan Monnier <address@hidden> writes:
>
> > > I was thinking about the situation where the sit-for in line-move
> > > results in a situation where we would adjust the vscroll, and thus
> > > update the display once more.  I haven't noticed this myself, but
> > > I could envision that may cause flickering.
> >
> > I see.  If delaying the Xflush prevents flickering, it might be a 
> > good cheap
> > way to solve this problem.  But I suspect that delaying the Xflush 
> > will only
> > reduce the flickering (the Xserver will still process two screen 
> > updates
> > in quick succession, or does it try to drop operations that are 
> > overridden
> > by subsequent operations already in the queue?).
>
> I don't know the internals of X, but if done properly, the Xserver
> updates an internal bitmap and only transfers that to the screen when
> flushed by Xflush.

Whenever Emacs reads an event from X, an internal XFlush is done by X.  
Also, when the internal outgoing queue in X11 get full, it is sent to 
the server.  It is tricky to depend on this to suspend screen updates.  
There are several places in Emacs where flush and sync is done.

        Jan D.