Re: Merging the pgtk branch

[Yuuki Harano]

On Mon, 02 Aug 2021 14:49:37 +0300,
        Eli Zaretskii <eliz@gnu.org> wrote:
>> >> -install: all install-arch-indep install-etcdoc install-arch-dep 
>> >> install-$(NTDIR) blessmail install-eln
>> >> +install: all install-arch-indep install-etcdoc install-arch-dep 
>> >> install-$(NTDIR) blessmail install-eln install-gsettings-schemas
>> >>   @true
>> > 
>> > Does this mean gsettings-schemas will be installed by non-PGTK builds
>> > as well?  If not, where are the conditions to prevent that?
>> 
>> Yes, it is installed if gsettings is enabled, even if non-PGTK builds.
> 
> Is that useful without the PGTK build?  What is that used for?

No, it is not useful for non-PGTK build.

X build supports X defaults.  But GTK doesn't support it.
Instead, I implemented this hook with gsettings:
  terminal->get_string_resource_hook = pgtk_get_string_resource;

gsettings supports type. Type of each key is written in the schema file
etc/org.gnu.emacs.defaults.gschema.xml.
(I implemented this feature instead of X defaults, so types of all the key
are string.)

However, I'm not sure whether people want Xdefaults-like feature.
Emacs' frame parameters are enough...


>> >> --- a/lisp/server.el
>> >> +++ b/lisp/server.el
>> >> @@ -900,12 +900,17 @@ server-create-window-system-frame
>> >>        )
>> >  
>> >>      (cond (w
>> >> -           (server--create-frame
>> >> -            nowait proc
>> >> -            `((display . ,display)
>> >> -              ,@(if parent-id
>> >> -                    `((parent-id . ,(string-to-number parent-id))))
>> >> -              ,@parameters)))
>> >> +           (condition-case nil
>> >> +               (server--create-frame
>> >> +                nowait proc
>> >> +                `((display . ,display)
>> >> +                  ,@(if parent-id
>> >> +                        `((parent-id . ,(string-to-number parent-id))))
>> >> +                  ,@parameters))
>> >> +             (error
>> >> +              (server-log "Window system unsupported" proc)
>> >> +              (server-send-string proc "-window-system-unsupported \n")
>> >> +              nil)))
>> > 
>> > Why is this change needed?
>> 
>> emacsclient tries WAYLAND_DISPLAY, and DISPLAY if the first try is failed.
>> The code catches the display connection failure, and returns the failure
>> to emacsclient.
> 
> Hmm... what about window-systems that have neither WAYLAND_DISPLAY nor
> DISPLAY? will this always fail?  I feel that I'm missing something
> here: why wasn't this needed before?

Sorry, I mistook.

GTK supports GDK_BACKEND environment variable.

If GDK_BACKEND=wayland, GTK tries only wayland connection.
If GDK_BACKEND=x11, GTK tries only X connection.
If GDK_BACKEND=wayland,x11, GTK tries wayland connection, and X
connection if the first try failed.

If GDK_BACKEND=x11 and DISPLAY is not set, then emacs fails to start.
----
luna:objs % unset DISPLAY
luna:objs % GDK_BACKEND=x11 ./src/emacs      

(emacs:322982): Gtk-WARNING **: 00:31:26.986: cannot open display: 
luna:objs % 
----

If GDK_BACKEND=x11 and DISPLAY=:0, then emacs starts.
However, `emacsclient -c` first tries with WAYLAND_DISPLAY and
it fails, because GDK_BACKEND=x11 and emacs itself does not open
wayland connection.

The error is:
----
-error Cannot&_connect&_to&_display&_server&_wayland&-1
----
(In case of WAYLAND_DISPLAY=wayland-1.)

And emacsclient does not retry.

I wanted to work around this error.
I send -window-system-unsupported by that change.
In this case, emacsclient retry with alt_display, which is
DISPLAY by another change.

> what about window-systems that have neither WAYLAND_DISPLAY nor
> DISPLAY? will this always fail?

emacsclient.c:
----
#if defined (NS_IMPL_COCOA)
      alt_display = "ns";
#elif defined (HAVE_NTGUI)
      alt_display = "w32";
#endif
----
  if (!display)
    {
      display = alt_display;
      alt_display = NULL;
    }
----

On ns and w32, display is set.

To make sure whether that change works on ns and w32,
it is needed to test on such machines.
I didn't test on such machines.

-- 
Yuuki Harano