bug#25851: 25.2; GTK warning when starting Emacs when desktop file has more than one frame

[martin rudalics]

> Sorry for the delay. I haven't used master for a while and it doesn't
> like my init file. I've been spending my time on troubleshooting
> that. But now I have things mostly up and running.
>
> 1. I am currently running master from earlier today which includes
> your patch from the 23rd (commit
> fe3af8d4f2a4cd67958f76d1b708e8a78e68cd4f) which I assume is the
> one you want me to test?

Yes.  I attach it so you can (hopefully) apply it to your Emacs 25
instead of ...

> 2. I have not applied your proposed definition of
> `xg_set_geometry' from Message #122
> (https://debbugs.gnu.org/cgi/bugreport.cgi?bug=25851#122). [But I
> still have that in my 25.2 rc2 Emacs, which is currently my
> everyday Emacs.]

... this and test it in your everyday work.

> 3. I have put
>
>    (setq x-gtk-use-window-move t)
>
> in the working part of my init file [the rest of my init file --
> about 10% of it -- is commented out right now].
>
> 4. In my desktop file I have three frames specified each with
> a distinctive size and position.
>
> The result is that:
>
> - Frames are successfully restored to their former size and
> position.
>
> - No GTK warning messages are being emitted.

OK.

> However:
>
> - When I switch between frames using the window manager Alt-tab
> window switching, there is a big flash almost every time when an
> Emacs frame is displayed. I've never seen this problem before.
> (Occasionally I've seen a single line of the display flicker while
> scrolling, but I've never seen Emacs make the whole screen flash
> like this before.)
>
> [The flash is too fast to describe other than to say it is light
> in colour and appears to be horizontal, almost as if there is a
> white or grey highlight being applied randomly to about half the
> lines in the frame and then turned off again.]
>
> [This was after I'd maximized the three frames so that I could use
> them, rather than when they were the smaller size at which they
> were specified in the desktop file I tested with. I tried
> restoring them down to their previous size and didn't see the
> flash, then maximised them again and the flashing was back. I
> suppose that the flashing might also be happening when they're
> small but that my eye isn't fast enough to detect it; not sure.]
>
> Of course this flashing might be unrelated, it might be due to a
> change elsewhere in master.

I'm sure that Eli's suggestion is correct, so please inhibit double
buffering in your init file.

> The display antics at startup are slightly different but still
> there. The sequence seems to be (with three frames in my desktop
> file with distinctive sizes and positions):
>
> a) A largish light-colour-scheme frame is displayed.
>
> b) It shrinks but is still a light colour scheme. (Presumably my
> default font is applied here.)
>
> c) It changes to a dark colour scheme. (Presumably my colour
> scheme is being applied here.)

I don't know what a colour scheme is.  Please send me yours and I'll try
adding it to my .emacs to see which behavior it causes.

BTW I never thought about possible mergings of `initial-frame-alist' or
`default-frame-alist' and the parameter alists applied by desktop.

> d) It sits there for a bit with the various startup messages
> appearing in the echo area.
>
> e) It disappears and the three frames in my init file appear.
> (Alternative explanation: It changes its size and position to that
> of one of the frames in my init file, and the other two frames
> from my init file are displayed.)

I suppose you mean "desktop" instead of "init" file here?

> These antics are different from with Emacs 25 where I never see a
> light-colour-scheme frame unless I start with `-Q'.

To get one aspect right: Do you see the light-colour-scheme frame also
when you don't restore the desktop - with one or three initial frames?
(And what else does master dislike about your init file?)

martin

gtk_window_move.diff
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