[Spice-devel] [PATCH spice] spicec-x11: Fix modifier keys getting stuck (rhbz#655048)

[Hans de Goede]

Currently modifier keys (ctrl, alt) can get stuck when using the x11 client.
To reproduce under gnome:
-focus the client window without causing it to grab the keyborad (click on
 the title bar not the window)
-press crlt + alt + right arrow to switch virtual desktop
-press crlt + alt + left arrow to switch back
-notice ctrl + alt are stuck pressed

What is happening here is:
-We get a focus out event, caused by the hotkey combi key grab, focus event
 notify mode == NotifyGrab, and release all keys -> good
-We get another focus out event, as we really loose the focus.
 notify mode == NotifyWhileGrabbed, which we ignore as we already lost
 focus before
-We get a focus in event, as the focus is returning to us, but we don't
 really have the focus yet, as the hotkey combi key grab is still active
 (ie ctrl + alt are still pressed).
 We now sync the vm's modifier key state with the current X-server state,
 telling the vm ctrl + alt are pressed. Note we do this by directly reading
 the X-server keyboard status, we are not getting any key press events from the
 X-server -> bad
-We get another focus in event, as we really get the focus back,
 notify mode == NotifyUngrab. We ignore this one as already have gained the
 focus before. If we were to sync the vm modifier state here, all would be
 well we would no longer see the modifier keys pressed, or if we would we
 would get a release event when they get released (testing has shown both).

The solution here is to ignore the first focus in event, and do the modifier
sync on the second focus in event, or more in general to ignore focus events
where notify mode == NotifyWhileGrabbed.
---
 client/x11/red_window.cpp |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/client/x11/red_window.cpp b/client/x11/red_window.cpp
index c50e307..6e8cd58 100644
--- a/client/x11/red_window.cpp
+++ b/client/x11/red_window.cpp
@@ -866,6 +866,11 @@ void RedWindow_p::win_proc(XEvent& event)
         break;
     }
     case FocusIn:
+        /* Ignore focus events caused by grabbed (hotkeys) */
+        if (event.xfocus.mode == NotifyWhileGrabbed) {
+            break;
+        }
+
         if (event.xany.serial < focus_serial) {
             DBG(0, "Ignored FocusIn win=%p (serial=%d, Last foucs serial=%d)",
                    red_window,  event.xany.serial, focus_serial);
@@ -886,6 +891,11 @@ void RedWindow_p::win_proc(XEvent& event)
         }
         break;
     case FocusOut:
+        /* Ignore focus events caused by grabbed (hotkeys) */
+        if (event.xfocus.mode == NotifyWhileGrabbed) {
+            break;
+        }
+
         if (event.xany.serial <= focus_serial) {
             DBG(0, "Ignored FocusOut win=%p (serial=%d, Last foucs serial=%d)",
                    red_window, event.xany.serial, focus_serial);
-- 
1.7.3.2