[mutter] window: Force update monitor on hot plugs

[Jonas Ådahl <jadahl src gnome org>]

commit 8d3e053059cd202e740076caedfc8e3ac149066a
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Aug 24 12:56:31 2018 +0200

    window: Force update monitor on hot plugs
    
    Commit a3da4b8d5bd217c0262fd9361036877d155a300f changed updating of
    window monitors to always use take affect when it was done from a
    non-user operation. This could cause feed back loops when a non-user
    driven operation would trigger the changing of a monitor, which itself
    would trigger changing of the monitor again due to a window scale
    change.
    
    The reason for the change, was that when the window monitor changed due
    to a hot plug, if it didn't actually change, eventually the window
    monitor pointer would be pointing to freed memory.
    
    Instead of force updating the monitor on all non-user operations, just
    do it on hot plugs. This allows for the feedback loop preventing logic
    to still do what its supposed to do, without risking dangling pointers
    on hot plugs.
    
    Related: https://gitlab.gnome.org/GNOME/mutter/issues/189
    Closes: https://gitlab.gnome.org/GNOME/mutter/issues/192

 src/core/window-private.h         | 1 +
 src/core/window.c                 | 4 ++--
 src/wayland/meta-window-wayland.c | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/core/window-private.h b/src/core/window-private.h
index b11511f44..76c454417 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -125,6 +125,7 @@ typedef enum _MetaWindowUpdateMonitorFlags
 {
   META_WINDOW_UPDATE_MONITOR_FLAGS_NONE = 0,
   META_WINDOW_UPDATE_MONITOR_FLAGS_USER_OP = 1 << 0,
+  META_WINDOW_UPDATE_MONITOR_FLAGS_FORCE = 1 << 1,
 } MetaWindowUpdateMonitorFlags;
 
 typedef struct _MetaPlacementRule
diff --git a/src/core/window.c b/src/core/window.c
index bd752d95b..f8b0e0128 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -3826,7 +3826,7 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
   if (window->override_redirect || window->type == META_WINDOW_DESKTOP)
     {
       meta_window_update_monitor (window,
-                                  META_WINDOW_UPDATE_MONITOR_FLAGS_NONE);
+                                  META_WINDOW_UPDATE_MONITOR_FLAGS_FORCE);
       return;
     }
 
@@ -3862,7 +3862,7 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
   else
     {
       meta_window_update_monitor (window,
-                                  META_WINDOW_UPDATE_MONITOR_FLAGS_NONE);
+                                  META_WINDOW_UPDATE_MONITOR_FLAGS_FORCE);
     }
 }
 
diff --git a/src/wayland/meta-window-wayland.c b/src/wayland/meta-window-wayland.c
index 574593231..f73f3e104 100644
--- a/src/wayland/meta-window-wayland.c
+++ b/src/wayland/meta-window-wayland.c
@@ -413,7 +413,7 @@ meta_window_wayland_update_main_monitor (MetaWindow                   *window,
       return;
     }
 
-  if (flags & META_WINDOW_UPDATE_MONITOR_FLAGS_USER_OP)
+  if (flags & META_WINDOW_UPDATE_MONITOR_FLAGS_FORCE)
     {
       window->monitor = to;
       return;