[gtk+/gtk-3-22] win32 event: check for NULL display or dev mgr

[Руслан Ижбулатов <ruslanizhb src gnome org>]

commit 0b129f3534381e8ef659c57d470aeb17fe87b252
Author: Andrew Chadwick <a t chadwick gmail com>
Date:   Fri Nov 18 15:12:57 2016 +0000

    win32 event: check for NULL display or dev mgr
    
    The recent Wintab testing revealed an interesting edge case: we cannot
    for certain say that windowing system messages will not be received
    while the default display and its device manager are still being set up.
    We've ruled out the Wintab case now, but cannot rule out some future bit
    of runtime DLL code doing stuff at this critical time.
    
    This commit detects and avoids a potential null pointer dereference in
    the message handling code while detecting grabs. Grabs don't really
    exist yet, if the default display and/or its device manager are not yet
    globally known.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=774379

 gdk/win32/gdkevents-win32.c |   39 ++++++++++++++++++++++++++++++---------
 1 files changed, 30 insertions(+), 9 deletions(-)
---
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index cc103a1..7c77f0a 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -2097,10 +2097,10 @@ gdk_event_translate (MSG  *msg,
   GdkWindow *window = NULL;
   GdkWindowImplWin32 *impl;
 
-  GdkWindow *new_window;
+  GdkWindow *new_window = NULL;
 
-  GdkDeviceManager *device_manager;
-  GdkDeviceManagerWin32 *device_manager_win32;
+  GdkDeviceManager *device_manager = NULL;
+  GdkDeviceManagerWin32 *device_manager_win32 = NULL;
 
   GdkDeviceGrabInfo *keyboard_grab = NULL;
   GdkDeviceGrabInfo *pointer_grab = NULL;
@@ -2153,13 +2153,34 @@ gdk_event_translate (MSG  *msg,
       return FALSE;
     }
 
-  device_manager = gdk_display_get_device_manager (display);
-  device_manager_win32 = GDK_DEVICE_MANAGER_WIN32 (device_manager);
+  /* gdk_event_translate() can be called during initialization, if something
+   * sends MSGs. In this case, the default display or its device manager will
+   * be NULL, so avoid trying to read the active grabs.
+   * https://bugzilla.gnome.org/show_bug.cgi?id=774379
+   */
+  if (display != NULL)
+    {
+      device_manager = gdk_display_get_device_manager (display);
+    }
+  else
+    {
+      GDK_NOTE (EVENTS, g_print (" (no GdkDisplay)"));
+    }
+
+  if (device_manager != NULL)
+    {
+      device_manager_win32 = GDK_DEVICE_MANAGER_WIN32 (device_manager);
+    }
+  else
+    {
+      GDK_NOTE (EVENTS, g_print (" (no GdkDeviceManager)"));
+    }
 
-  keyboard_grab = _gdk_display_get_last_device_grab (display,
-                                                     device_manager_win32->core_keyboard);
-  pointer_grab = _gdk_display_get_last_device_grab (display,
-                                                    device_manager_win32->core_pointer);
+  if (device_manager_win32 != NULL)
+    {
+      keyboard_grab = _gdk_display_get_last_device_grab (display, device_manager_win32->core_keyboard);
+      pointer_grab = _gdk_display_get_last_device_grab (display, device_manager_win32->core_pointer);
+    }
 
   g_object_ref (window);