bug#27357: 26.0.50; Emacs starts fullscreen in Ubuntu 17.04

[martin rudalics]

> In 16.10, things worked as normal, but in Ubuntu 17.04 Emacs starts in
> fullscreen mode.  That is, emacs -Q says:
>
> (frame-parameter nil 'fullscreen)
> maximized

Does this match the state of the window manager maximized button?  What
happens when you click it?

> If I say "emacs -geometry 20x20 -Q", then Emacs isn't fullscreen, but
> instead starts with a frame that is approximately 84 characters by 46
> characters.
>
> This is on a HiDPI screen:
>
> larsi@mouse:~$ dconf read /com/ubuntu/user-interface/scale-factor
> {'eDP1': 11, 'eDP-1': 12}

Can you try without scaling?

> Emacs 25 appears to behave the same as git Emacs, so whatever's going on
> isn't a new bug, I think.
>
> I tried grepping through the Emacs source code to find out what sets the
> `maximized' value, and it's perhaps the get_current_wm_state thing?  I'm
> not sure.

It should be.  Can you get a backtrace from there?

> I also note that Emacs has a gaggle of options to switch fullscreen mode
> on, but apparently none to switch it off?

(set-frame-parameter nil 'fullscreen nil)

or ‘toggle-frame-maximized’.

martin