Font size (was: Merging the pgtk branch)

[Kévin Le Gouguec]

Hello,

AFAICT the branch builds and runs fine --with-pgtk --with-xwidgets
--with-cairo on Debian 10 (XFCE).

One hiccup: unless I'm mistaken, this build does not consult
~/.Xresources anymore.  That led me to discover --with-gconf and
font-use-system-font (I did not use these options previously); I am now
a bit confused about how font sizes work.

On master, with font-use-system-font set to nil, here is what C-u C-x =
says for various values of emacs.font in ~/.Xresources:

.Xresources¹    C-u C-x =²
9               12
10              13
10.5            14
11              15

¹ "XX" in "emacs.font: DejaVu Sans Mono-XX"
² "XX" in "ftcrhb:-PfEd-DejaVu Sans 
Mono-normal-normal-normal-*-XX-*-*-*-m-0-iso10646-1"

On master --with-gconf and feature/pgtk, with font-use-system-font set
to t, here is what C-u C-x = says for various GSettings:

GSettings³      C-u C-x =
9               12
10              13
10.5            ERROR (see below)
11              15

³ "XX" in "gsettings org.gnome.desktop.interface monospace-font-name 'DejaVu 
Sans Mono XX'"

As it happens, "10.5" (reported as "14" inside Emacs) is the size I find
the most comfortable on my screen; unfortunately if I run:

$ gsettings set org.gnome.desktop.interface monospace-font-name 'DejaVu Sans 
Mono 10.5'

Emacs emits a warning:

> set-face-attribute: Font not available: #<font-spec nil nil DejaVu\
> Sans\ Mono\ 10\.5 nil nil nil nil nil nil nil nil nil ((:name
> . "DejaVu Sans Mono 10.5") (:user-spec . "DejaVu Sans Mono 10.5"))>

Is this expected?  Otherwise, should I report an issue?  (AFAICT it is
not specific to the pgtk branch)