bug#38497: 27.0.50; Frame is not rendered when frame-resize-pixelwise it 't

[Ihor Radchenko]

> One possible reason for not clearing the frame is that you have
> double-buffering enabled.  Can you disable it and try again?  (If you
> don't know how, search for "double buffering" in etc/NEWS.26.)

I tried to disable double buffering.
Running emacs -Q --eval "(add-to-list 'default-frame-alist
'(inhibit-double-buffering . t))", the redrawing works without any
issues.

Now, I am wondering if the issue I reported is just specific to my
system or others can also reproduce it with emacs compiled with xft,
cairo, and lucid enabled. If so, would it make sense to disable double
buffering by default for this combination of build options?

Best,
Ihor

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Ihor Radchenko <yantar92@gmail.com>
>> Cc: rudalics@gmx.at, 38497@debbugs.gnu.org
>> Date: Sun, 15 Dec 2019 21:43:34 +0800
>> 
>> > That's unheard of.  Does redraw-display at least blank the entire
>> > frame?
>> 
>> Nope. I don't see anything changing. 
>
> That's impossible.  When you invoke redraw-display, Emacs on X calls
> the function x_clear_frame, which calls x_clear_window, which calls
> XClearWindow.  Do you see this sequence of calls if you step through
> the code with a derbugger?
>
> One possible reason for not clearing the frame is that you have
> double-buffering enabled.  Can you disable it and try again?  (If you
> don't know how, search for "double buffering" in etc/NEWS.26.)
>
> Failing that, the only way I can explain this is that you have some
> "optimization" feature in your video hardware and/or driver, and that
> is the cause of all the problems you report in this thread.  Please
> review the settings of your video driver software, and turn off any
> "optimization" or "advanced" feature you find there.  If that doesn't
> help, maybe upgrading to a newer version of the video driver will
> help.