[mutter] MetaMonitorManager: Track primary monitor by pointer instead of index

[Jonas Ådahl <jadahl src gnome org>]

commit c9360566638ce22ec584a4468fa1ea93587c815d
Author: Jonas Ådahl <jadahl gmail com>
Date:   Mon Nov 28 20:43:27 2016 +0800

    MetaMonitorManager: Track primary monitor by pointer instead of index
    
    Instead of keeping an index in an array to keep track of the current
    primary logical monitor, just keep a pointer instead.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=777732

 src/backends/meta-backend.c                 |   15 +++++----------
 src/backends/meta-monitor-manager-private.h |    6 +++---
 src/backends/meta-monitor-manager.c         |   23 ++++++++++++++++-------
 src/core/screen.c                           |    8 +++++++-
 src/core/window.c                           |   11 +----------
 5 files changed, 32 insertions(+), 31 deletions(-)
---
diff --git a/src/backends/meta-backend.c b/src/backends/meta-backend.c
index c17c123..ac6bd30 100644
--- a/src/backends/meta-backend.c
+++ b/src/backends/meta-backend.c
@@ -115,16 +115,11 @@ center_pointer (MetaBackend *backend)
 {
   MetaBackendPrivate *priv = meta_backend_get_instance_private (backend);
   MetaMonitorManager *monitor_manager = priv->monitor_manager;
-  MetaLogicalMonitor *logical_monitors, *primary;
-  unsigned int n_logical_monitors;
-  int primary_monitor_index;
-
-  logical_monitors =
-    meta_monitor_manager_get_logical_monitors (monitor_manager,
-                                               &n_logical_monitors);
-  primary_monitor_index =
-    meta_monitor_manager_get_primary_index (monitor_manager);
-  primary = &logical_monitors[primary_monitor_index];
+  MetaLogicalMonitor *primary;
+
+  primary =
+    meta_monitor_manager_get_primary_logical_monitor (monitor_manager);
+
   meta_backend_warp_pointer (backend,
                              primary->rect.x + primary->rect.width / 2,
                              primary->rect.y + primary->rect.height / 2);
diff --git a/src/backends/meta-monitor-manager-private.h b/src/backends/meta-monitor-manager-private.h
index 7a35fa5..f36a7a5 100644
--- a/src/backends/meta-monitor-manager-private.h
+++ b/src/backends/meta-monitor-manager-private.h
@@ -306,7 +306,7 @@ struct _MetaMonitorManager
 
   MetaLogicalMonitor *logical_monitors;
   unsigned int n_logical_monitors;
-  int primary_monitor_index;
+  MetaLogicalMonitor *primary_logical_monitor;
 
   int dbus_name_id;
 
@@ -368,6 +368,8 @@ int                 meta_monitor_manager_get_num_logical_monitors (MetaMonitorMa
 MetaLogicalMonitor *meta_monitor_manager_get_logical_monitors (MetaMonitorManager *manager,
                                                                unsigned int       *n_logical_monitors);
 
+MetaLogicalMonitor *meta_monitor_manager_get_primary_logical_monitor (MetaMonitorManager *manager);
+
 MetaOutput         *meta_monitor_manager_get_outputs       (MetaMonitorManager *manager,
                                                            unsigned int       *n_outputs);
 
@@ -379,8 +381,6 @@ void                meta_monitor_manager_get_resources     (MetaMonitorManager
                                                             MetaOutput         **outputs,
                                                             unsigned int        *n_outputs);
 
-int                 meta_monitor_manager_get_primary_index (MetaMonitorManager *manager);
-
 void                meta_monitor_manager_get_screen_size   (MetaMonitorManager *manager,
                                                             int                *width,
                                                             int                *height);
diff --git a/src/backends/meta-monitor-manager.c b/src/backends/meta-monitor-manager.c
index d1d8f00..e81eb7e 100644
--- a/src/backends/meta-monitor-manager.c
+++ b/src/backends/meta-monitor-manager.c
@@ -247,6 +247,7 @@ make_logical_config (MetaMonitorManager *manager)
   /* Now walk the list of outputs applying extended properties (primary
      and presentation)
   */
+  manager->primary_logical_monitor = NULL;
   for (i = 0; i < manager->n_outputs; i++)
     {
       MetaOutput *output;
@@ -283,12 +284,20 @@ make_logical_config (MetaMonitorManager *manager)
         logical_monitor->winsys_id = output->winsys_id;
 
       if (logical_monitor->is_primary)
-        manager->primary_monitor_index = logical_monitor->number;
+        manager->primary_logical_monitor = logical_monitor;
     }
 
   manager->n_logical_monitors = logical_monitors->len;
   manager->logical_monitors = (void*)g_array_free (logical_monitors, FALSE);
 
+  /*
+   * If no monitor was marked as primary, fall back on marking the first
+   * logical monitor the primary one.
+   */
+  if (!manager->primary_logical_monitor &&
+      manager->n_logical_monitors > 0)
+    manager->primary_logical_monitor = &manager->logical_monitors[0];
+
   if (manager_class->add_monitor)
     for (i = 0; i < manager->n_logical_monitors; i++)
       manager_class->add_monitor (manager, &manager->logical_monitors[i]);
@@ -1305,6 +1314,12 @@ meta_monitor_manager_get_logical_monitors (MetaMonitorManager *manager,
   return manager->logical_monitors;
 }
 
+MetaLogicalMonitor *
+meta_monitor_manager_get_primary_logical_monitor (MetaMonitorManager *manager)
+{
+  return manager->primary_logical_monitor;
+}
+
 MetaOutput *
 meta_monitor_manager_get_outputs (MetaMonitorManager *manager,
                                   unsigned int       *n_outputs)
@@ -1339,12 +1354,6 @@ meta_monitor_manager_get_resources (MetaMonitorManager  *manager,
     }
 }
 
-int
-meta_monitor_manager_get_primary_index (MetaMonitorManager *manager)
-{
-  return manager->primary_monitor_index;
-}
-
 void
 meta_monitor_manager_get_screen_size (MetaMonitorManager *manager,
                                       int                *width,
diff --git a/src/core/screen.c b/src/core/screen.c
index 6ba1f10..1023fd7 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -1732,10 +1732,16 @@ meta_screen_get_primary_monitor (MetaScreen *screen)
   MetaBackend *backend = meta_get_backend ();
   MetaMonitorManager *monitor_manager =
     meta_backend_get_monitor_manager (backend);
+  MetaLogicalMonitor *logical_monitor;
 
   g_return_val_if_fail (META_IS_SCREEN (screen), 0);
 
-  return meta_monitor_manager_get_primary_index (monitor_manager);
+  logical_monitor =
+    meta_monitor_manager_get_primary_logical_monitor (monitor_manager);
+  if (logical_monitor)
+    return logical_monitor->number;
+  else
+    return 0;
 }
 
 /**
diff --git a/src/core/window.c b/src/core/window.c
index 03a6453..5013609 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -3565,9 +3565,6 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
   MetaBackend *backend = meta_get_backend ();
   MetaMonitorManager *monitor_manager =
     meta_backend_get_monitor_manager (backend);
-  MetaLogicalMonitor *logical_monitors;
-  unsigned int n_logical_monitors;
-  int primary_monitor_index;
   const MetaLogicalMonitor *old, *new;
 
   if (window->fullscreen_monitors[0] != -1)
@@ -3588,15 +3585,9 @@ meta_window_update_for_monitors_changed (MetaWindow *window)
   if (!new)
     new = find_monitor_by_winsys_id (window, old->winsys_id);
 
-  logical_monitors =
-    meta_monitor_manager_get_logical_monitors (monitor_manager,
-                                               &n_logical_monitors);
-  primary_monitor_index =
-    meta_monitor_manager_get_primary_index (monitor_manager);
-
   /* Fall back to primary if everything else failed */
   if (!new)
-    new = &logical_monitors[primary_monitor_index];
+    new = meta_monitor_manager_get_primary_logical_monitor (monitor_manager);
 
   if (window->tile_mode != META_TILE_NONE)
     window->tile_monitor_number = new->number;