[mutter] Do not cancel Alt+Tab grab due to modifier key events

[Tomas Frydrych <tomasf src gnome org>]

commit a125b0179a0f4949ae18e905ff043e6020950c06
Author: Tomas Frydrych <tf linux intel com>
Date:   Thu Feb 4 07:53:01 2010 +0000

    Do not cancel Alt+Tab grab due to modifier key events
    
    If the user just presses a modifier (e.g., shift) during Alt+Tab grab, we need
    to keep the grab in place to allow the custom Alt+Tab handler to deal with what
    might simply be a change of tabbing direction.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=613126

 src/core/keybindings.c |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/src/core/keybindings.c b/src/core/keybindings.c
index aeccf3c..bff47de 100644
--- a/src/core/keybindings.c
+++ b/src/core/keybindings.c
@@ -2109,6 +2109,16 @@ process_tab_grab (MetaDisplay *display,
               return TRUE;
             }
           break;
+        case META_KEYBINDING_ACTION_NONE:
+          {
+            /*
+             * If this is simply user pressing the Shift key, we do not want
+             * to cancel the grab.
+             */
+            if (is_modifier (display, event->xkey.keycode))
+              return TRUE;
+          }
+
         default:
           break;
         }