Re: Redisplay issue

[joakim@verona.se]

Eli Zaretskii <eliz@gnu.org> writes:

>> Date: Fri, 27 Nov 2015 14:31:55 -0800
>> From: Yuan MEI <yuan.mei.list@gmail.com>
>> 
>>     Sometimes when I switch to another virtual desktop then come back
>> to emacs
>
> What is a "virtual desktop" in this case?
>
>> the entire frame shows only the background color, no letter
>> or only part of the frame is visible.  This does not happen all the
>> time though.  I just happened to capture a screenshot (attached, I
>> hope the mailing server accepts it.)
>
> The screenshot shows a text-mode Emacs frame, AFAICT.  Does this
> happen only with text-mode frames, or do you see that in GUI frames as
> well?
>
> If this happens with text-mode frames only, then that's not an Emacs
> problem.  It's a problem with the terminal emulator (xterm etc.) you
> are using: it should sense the switch and redraw the display on the
> low level.
>
> When Emacs runs on a TTY, it doesn't listen to any expose or conceal
> messages sent by the windowing system, so it has no idea that its
> display was concealed or exposed, and cannot initiate a redisplay in
> these situations.  From the Emacs POV, a TTY frame is the only thing
> displayed by the console device, and the only way such a frame can be
> concealed and exposed is by stopping Emacs (with the likes of "C-z")
> and then resuming it.  And these are the only cases a TTY frame will
> be completely redrawn.
>
> GUI frames are different: Emacs gets expose events for them, and
> should react by redrawing the exposed portion(s) of the frame.
>

FWIW I have also been experiencing redrawing issues lately.
I have believed this was some problem with my desktop remoting software,
x2go, but I'm beginning to suspect Emacs has some issue.

I have used x2go and emacs for years with no problems whatsoever, but I
can't rule out recent upgrades of my operating system as the source of
my problem.

I think I run the same window manager as Yuan as well.

-- 
Joakim Verona