[meld] meldwindow: Add F10 as a main menu accelerator (#539)

[Kai Willadsen <kaiw src gnome org>]

commit fc430ed8d5273042aca32f88bbd134f360d041c1
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Thu Dec 31 06:48:55 2020 +1000

    meldwindow: Add F10 as a main menu accelerator (#539)

 meld/accelerators.py           | 1 +
 meld/meldwindow.py             | 8 ++++++--
 meld/resources/ui/appwindow.ui | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/meld/accelerators.py b/meld/accelerators.py
index ad116e06..ccf2ea7e 100644
--- a/meld/accelerators.py
+++ b/meld/accelerators.py
@@ -23,6 +23,7 @@ VIEW_ACCELERATORS: Dict[str, Union[str, Sequence[str]]] = {
     'view.save-as': '<Primary><Shift>S',
     'view.undo': '<Primary>Z',
     'win.close': '<Primary>W',
+    'win.gear-menu': 'F10',
     'win.new-tab': '<Primary>N',
     'win.stop': 'Escape',
     # File comparison actions
diff --git a/meld/meldwindow.py b/meld/meldwindow.py
index 73535233..0235a1e6 100644
--- a/meld/meldwindow.py
+++ b/meld/meldwindow.py
@@ -74,12 +74,16 @@ class MeldWindow(Gtk.ApplicationWindow):
         state_actions = (
             (
                 "fullscreen", self.action_fullscreen_change,
-                GLib.Variant.new_boolean(False)
+                GLib.Variant.new_boolean(False),
+            ),
+            (
+                "gear-menu", None, GLib.Variant.new_boolean(False),
             ),
         )
         for (name, callback, state) in state_actions:
             action = Gio.SimpleAction.new_stateful(name, None, state)
-            action.connect('change-state', callback)
+            if callback:
+                action.connect('change-state', callback)
             self.add_action(action)
 
         # Initialise sensitivity for important actions
diff --git a/meld/resources/ui/appwindow.ui b/meld/resources/ui/appwindow.ui
index bd18b640..f0122083 100644
--- a/meld/resources/ui/appwindow.ui
+++ b/meld/resources/ui/appwindow.ui
@@ -168,6 +168,7 @@
         </child>
         <child>
           <object class="GtkMenuButton" id="gear_menu_button">
+            <property name="action-name">win.gear-menu</property>
             <property name="visible">true</property>
             <property name="can_focus">False</property>
             <child>