[mutter] Handle meta_screen_get_monitor_for_point() returning NULL

[Rui Matos <rtcm src gnome org>]

commit 8b801aac772f92b2c6d8341931b03bbe8d5f8cd6
Author: Rui Matos <tiagomatos gmail com>
Date:   Mon Mar 7 17:24:13 2016 +0100

    Handle meta_screen_get_monitor_for_point() returning NULL
    
    On the X11 backend we don't track the pointer position in
    priv->current_x/y which remain set to zero. That means we never set
    the clutter stage cursor if point 0,0 isn't covered by any monitor
    since we return early.
    
    Commit 4bebc5e5fa8aade8a96c769bf2365abe0948f6ce introduced this to
    avoid crashing on the prepare-at handlers when the cursor position
    doesn't fall inside any monitor area but we can handle that higher up
    in the stack. In that case, the sprite's scale doesn't matter since
    the cursor won't be shown anyway so we can skip setting it.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=763159

 src/backends/meta-cursor-renderer.c |   15 ---------------
 src/core/screen.c                   |    3 ++-
 src/wayland/meta-wayland-pointer.c  |    5 +++--
 3 files changed, 5 insertions(+), 18 deletions(-)
---
diff --git a/src/backends/meta-cursor-renderer.c b/src/backends/meta-cursor-renderer.c
index a76241b..48cd239 100644
--- a/src/backends/meta-cursor-renderer.c
+++ b/src/backends/meta-cursor-renderer.c
@@ -27,8 +27,6 @@
 #include "meta-cursor-renderer.h"
 
 #include <meta/meta-backend.h>
-#include <backends/meta-backend-private.h>
-#include <backends/meta-monitor-manager-private.h>
 #include <meta/util.h>
 
 #include <cogl/cogl.h>
@@ -118,14 +116,6 @@ meta_cursor_renderer_calculate_rect (MetaCursorRenderer *renderer,
   };
 }
 
-static gboolean
-is_cursor_in_monitors_area (int x, int y)
-{
-  MetaMonitorManager *monitor_manager = meta_backend_get_monitor_manager (meta_get_backend ());
-  return meta_monitor_manager_get_monitor_at_point (monitor_manager,
-                                                    (gfloat) x, (gfloat) y) >= 0;
-}
-
 static void
 update_cursor (MetaCursorRenderer *renderer,
                MetaCursorSprite   *cursor_sprite)
@@ -134,11 +124,6 @@ update_cursor (MetaCursorRenderer *renderer,
   gboolean handled_by_backend;
   gboolean should_redraw = FALSE;
 
-  /* do not render cursor if it is not on any monitor. Such situation
-   * can occur e. g. after monitor hot-plug */
-  if (!is_cursor_in_monitors_area (priv->current_x, priv->current_y))
-    return;
-
   if (cursor_sprite)
     meta_cursor_sprite_prepare_at (cursor_sprite,
                                    priv->current_x,
diff --git a/src/core/screen.c b/src/core/screen.c
index 934b3af..0e056b3 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1233,7 +1233,8 @@ root_cursor_prepare_at (MetaCursorSprite *cursor_sprite,
   monitor = meta_screen_get_monitor_for_point (screen, x, y);
 
   /* Reload the cursor texture if the scale has changed. */
-  meta_cursor_sprite_set_theme_scale (cursor_sprite, monitor->scale);
+  if (monitor)
+    meta_cursor_sprite_set_theme_scale (cursor_sprite, monitor->scale);
 }
 
 static void
diff --git a/src/wayland/meta-wayland-pointer.c b/src/wayland/meta-wayland-pointer.c
index 2936afc..b8a1385 100644
--- a/src/wayland/meta-wayland-pointer.c
+++ b/src/wayland/meta-wayland-pointer.c
@@ -1011,8 +1011,9 @@ cursor_sprite_prepare_at (MetaCursorSprite *cursor_sprite,
   if (!meta_xwayland_is_xwayland_surface (surface))
     {
       monitor = meta_screen_get_monitor_for_point (screen, x, y);
-      meta_cursor_sprite_set_texture_scale (cursor_sprite,
-                                            (float)monitor->scale / surface->scale);
+      if (monitor)
+        meta_cursor_sprite_set_texture_scale (cursor_sprite,
+                                              (float)monitor->scale / surface->scale);
     }
   meta_wayland_surface_update_outputs (surface);
 }