[mutter/cherry-pick-67aab7c1] clutter: Do not latch modifiers on modifier keys

[Marco Trevisan <marcotrevi src gnome org>]

commit d9cc8530ec2a55d6d67649fc68f23da86a5ccc7e
Author: Carlos Garnacho <carlosg gnome org>
Date:   Wed Oct 3 20:43:21 2018 +0000

    clutter: Do not latch modifiers on modifier keys
    
    If the user maps eg. Alt+F2 to a pad button, the MetaInputSettings will
    send the full Alt press, F2 press, F2 release, Alt release sequence.
    However the keycode corresponding to Alt is found in level 1, so the
    Shift modifier gets unintendedly latched in addition to the Alt key
    press/release pair.
    
    We could probably improve keycode lookup heuristics so level=0 (and
    no modifier latching) is preferred, but we can do without it altogether
    for modifier keys.
    
    
    (cherry picked from commit 67aab7c13812befde061f0d2068b431b04dcbc98)

 clutter/clutter/x11/clutter-virtual-input-device-x11.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/clutter/clutter/x11/clutter-virtual-input-device-x11.c 
b/clutter/clutter/x11/clutter-virtual-input-device-x11.c
index b86ded0d0..e16ba3fd0 100644
--- a/clutter/clutter/x11/clutter-virtual-input-device-x11.c
+++ b/clutter/clutter/x11/clutter-virtual-input-device-x11.c
@@ -147,14 +147,16 @@ clutter_virtual_input_device_x11_notify_keyval (ClutterVirtualInputDevice *virtu
       return;
     }
 
-  if (key_state == CLUTTER_KEY_STATE_PRESSED)
+  if (!_clutter_keymap_x11_get_is_modifier (keymap, keycode) &&
+      key_state == CLUTTER_KEY_STATE_PRESSED)
     clutter_keymap_x11_latch_modifiers (keymap, level, TRUE);
 
   XTestFakeKeyEvent (clutter_x11_get_default_display (),
                      (KeyCode) keycode,
                      key_state == CLUTTER_KEY_STATE_PRESSED, 0);
 
-  if (key_state == CLUTTER_KEY_STATE_RELEASED)
+  if (!_clutter_keymap_x11_get_is_modifier (keymap, keycode) &&
+      key_state == CLUTTER_KEY_STATE_RELEASED)
     clutter_keymap_x11_latch_modifiers (keymap, level, FALSE);
 }