bug#36250: Allow Emacs to be resized arbitrarily

[martin rudalics]

> Unconstrained resize of Emacs is widely tested, e.g. I've been using
> for years Emacs on i3wm, which just ignores the property, thus
> resizes Emacs arbitrarily. Also: I don't touch in this patch
> `frame_resize_pixelwise` variable, because it's used for something
> else; in particular, setting this variable had no influence on the
> problem.

Why do you think that 'frame_resize_pixelwise' is used for something
else?  gtkutil.c uses it to assign the increments as

  size_hints.width_inc = frame_resize_pixelwise ? 1 : FRAME_COLUMN_WIDTH (f);
  size_hints.height_inc = frame_resize_pixelwise ? 1 : FRAME_LINE_HEIGHT (f);

> 1: https://bugs.kde.org/show_bug.cgi?id=408746#c8
> 2: https://github.com/kwin-scripts/kwin-tiling/issues/161

There Martin Flöser says on 2019-06-16

> Given the resize increment provided by emacs (8x17) it is impossible
> to fullscreens the window with the used resolution. 1326 doesn't
> divide by 8 and 681 doesn't divide by 17.

so it appears that you did _not_ set 'frame-resize-pixelwise' since
otherwise the 8 x 17 wouldn't be there.  Can you please clarify.

If setting 'frame-resize-pixelwise' does not work as intended, we
apparently fail to set the increments in due time.  But then this is
to my knowledge the first time this happens since we introduced that
variable and we certainly have to fix that.  So if it does not work
for some reason, please use GDB with a checkpoint at these assignments
and tell us whether frame_resize_pixelwise really wasn't set properly.

Thanks, martin