emacs: Switch to lucid as the default toolkit

Because of long standing bugs and stability issues & an
uncollaborative upstream there has been talk on the emacs-devel
mailing list to switch the default toolkit to
Lucid (https://lists.gnu.org/archive/html/emacs-devel/2022-08/msg00752.html).
The GTK build also has issues with Xinput2, something that both we and
upstream want to enable by default in Emacs 29.

This situation has prompted me to use both Lucid an no-toolkit (pure X11) Emacs
as a daily driver in recent weeks to evaluate what the
advantages/drawbacks are and I have concluded that, at least for me,
switching the toolkit to Lucid is strictly an upgrade.
It has resulted in better stability (there are far fewer tiny UX
issues that are hard to understand/identify) & a snappier UI.
On top of that the closure size is reduced by ~10%.

In the pure X11 build I noticed some unsharpness around fonts so this
is not a good default choice.

As with everything there is a cost, and that is uglier (I think most
would agree but of course this is subjective) menu bars for
those that use them and no GTK scroll bars.

For anyone who still wants to use GTK they could of course still
choose to do so via the new `emacs-gtk` attribute but I think this
is a bad default.

A note to Wayland users:
This does not affect Wayland compatibility in any way since that will
already need a PGTK build variant in the future.

nixos/doc/manual/from_md/release-notes/rl-2211.section.xml

@@ -384,6 +384,14 @@
           <literal>cosigned</literal> binary anymore.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          Emacs now uses the Lucid toolkit by default instead of GTK
+          because of stability and compatibility issues. Users who still
+          wish to remain using GTK can do so by using
+          <literal>emacs-gtk</literal>.
+        </para>
+      </listitem>
       <listitem>
         <para>
           riak package removed along with

nixos/doc/manual/release-notes/rl-2211.section.md

@@ -134,6 +134,9 @@ Available as [services.patroni](options.html#opt-services.patroni.enable).
 
 - `pkgs.cosign` does not provide the `cosigned` binary anymore.
 
+- Emacs now uses the Lucid toolkit by default instead of GTK because of stability and compatibility issues.
+  Users who still wish to remain using GTK can do so by using `emacs-gtk`.
+
 - riak package removed along with `services.riak` module, due to lack of maintainer to update the package.
 
 - xow package removed along with the `hardware.xow` module, due to the project being deprecated in favor of `xone`,  which is available via the `hardware.xone` module.

pkgs/applications/editors/emacs/generic.nix

@@ -18,7 +18,7 @@
 , withX ? !stdenv.isDarwin
 , withNS ? stdenv.isDarwin
 , withGTK2 ? false, gtk2-x11 ? null
-, withGTK3 ? true, gtk3-x11 ? null, gsettings-desktop-schemas ? null
+, withGTK3 ? false, gtk3-x11 ? null, gsettings-desktop-schemas ? null
 , withXwidgets ? false, webkitgtk ? null, wrapGAppsHook ? null, glib-networking ? null
 , withMotif ? false, motif ? null
 , withSQLite3 ? false

pkgs/top-level/all-packages.nix

@@ -27084,6 +27084,7 @@ with pkgs;
   em = callPackage ../applications/editors/em { };
 
   emacs = emacs28;
+  emacs-gtk = emacs28-gtk;
   emacs-nox = emacs28-nox;
 
   emacs28 = callPackage ../applications/editors/emacs/28.nix {
@@ -27098,6 +27099,10 @@ with pkgs;
     inherit (darwin) sigtool;
   };
 
+  emacs28-gtk = emacs28.override {
+    withGTK3 = true;
+  };
+
   emacs28-nox = lowPrio (emacs28.override {
     withX = false;
     withNS = false;