[gnome-tetravex/arnaudb/new-theme-2] Use an enum for saving theme.

[Arnaud B. <arnaudb src gnome org>]

commit 61a067d39cb191bb8ff9b6e7350ca4202defad56
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Wed Oct 9 23:28:34 2019 +0200

    Use an enum for saving theme.
    
    That will feel better,
    if using dconf-editor.

 data/org.gnome.Tetravex.gschema.xml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
---
diff --git a/data/org.gnome.Tetravex.gschema.xml b/data/org.gnome.Tetravex.gschema.xml
index 34b08cb..254c1cd 100644
--- a/data/org.gnome.Tetravex.gschema.xml
+++ b/data/org.gnome.Tetravex.gschema.xml
@@ -1,4 +1,9 @@
 <schemalist>
+  <enum id="org.gnome.Tetravex.Theme">
+    <value value="0" nick="extrusion"/>
+    <value value="1" nick="neoretro"/>
+    <value value="2" nick="nostalgia"/>
+  </enum>
   <schema id="org.gnome.Tetravex" path="/org/gnome/Tetravex/" gettext-domain="gnome-tetravex">
     <key name="grid-size" type="i">
       <default>3</default>
@@ -31,7 +36,7 @@
       <!-- Translators: description of a settings key, see 'dconf-editor 
/org/gnome/Tetravex/mouse-forward-buttons' -->
       <description>For users which have a mouse with “Forward” and “Back” buttons, this key will set which 
button activates the “Redo” command. Possible values range between 6 and 14.</description>
     </key>
-    <key name="theme" type="s">
+    <key name="theme" enum="org.gnome.Tetravex.Theme">
       <default>'extrusion'</default>
       <!-- Translators: summary of a settings key, see 'dconf-editor /org/gnome/Tetravex/theme' -->
       <summary>Theme</summary>