From f9b5cdfeb1a3dbe2c39551d086f2290082f3d789 Mon Sep 17 00:00:00 2001
From: Alexander Larsson <alexl@redhat.com>
Date: Fri, 25 Feb 2011 14:07:48 +0100
Subject: [PATCH] Add api to get the primary monitor of the screen

We don't actually use the full xrandr to get the primary monitor, we
just rely on the xrandr xinerama compat code to return the primary
monitor first. This lets us avoid adding unnecessary xrandr code and
avoids issues with _NET_WM_FULLSCREEN_MONITORS monitor indexes being
defined wrt xinerama monitor index order.

https://bugzilla.gnome.org/show_bug.cgi?id=609258
---
 src/core/screen-private.h |  1 +
 src/core/screen.c         | 28 ++++++++++++++++++++++++++++
 src/meta/screen.h         |  1 +
 3 files changed, 30 insertions(+)

diff --git a/src/core/screen-private.h b/src/core/screen-private.h
index 1d98a1810..acb826a85 100644
--- a/src/core/screen-private.h
+++ b/src/core/screen-private.h
@@ -99,6 +99,7 @@ struct _MetaScreen
   guint32 wm_sn_timestamp;
   
   MetaMonitorInfo *monitor_infos;
+  int primary_monitor_index;
   int n_monitor_infos;
 
   /* Cache the current monitor */
diff --git a/src/core/screen.c b/src/core/screen.c
index b6abbe3b9..252c3e329 100644
--- a/src/core/screen.c
+++ b/src/core/screen.c
@@ -352,6 +352,18 @@ reload_monitor_infos (MetaScreen *screen)
   screen->n_monitor_infos = 0;
   screen->last_monitor_index = 0;
 
+  /* Xinerama doesn't have a concept of primary monitor, however XRandR
+   * does. However, the XRandR xinerama compat code always sorts the
+   * primary output first, so we rely on that here. We could use the
+   * native XRandR calls instead of xinerama, but that would be
+   * slightly problematic for _NET_WM_FULLSCREEN_MONITORS support, as
+   * that is defined in terms of xinerama monitor indexes.
+   * So, since we don't need anything in xrandr except the primary
+   * we can keep using xinerama and use the first monitor as the
+   * primary.
+   */
+  screen->primary_monitor_index = 0;
+
   screen->display->monitor_cache_invalidated = TRUE;
 
   if (g_getenv ("MUTTER_DEBUG_XINERAMA"))
@@ -2140,6 +2152,22 @@ meta_screen_get_n_monitors (MetaScreen *screen)
   return screen->n_monitor_infos;
 }
 
+/**
+ * meta_screen_get_primary_monitor:
+ * @screen: a #MetaScreen
+ *
+ * Gets the index of the primary monitor on this @screen.
+ *
+ * Return value: a monitor index
+ */
+int
+meta_screen_get_primary_monitor (MetaScreen *screen)
+{
+  g_return_val_if_fail (META_IS_SCREEN (screen), 0);
+
+  return screen->primary_monitor_index;
+}
+
 /**
  * meta_screen_get_monitor_geometry:
  * @screen: a #MetaScreen
diff --git a/src/meta/screen.h b/src/meta/screen.h
index ddb29a9e8..06297cc53 100644
--- a/src/meta/screen.h
+++ b/src/meta/screen.h
@@ -76,6 +76,7 @@ int meta_screen_get_active_workspace_index (MetaScreen *screen);
 MetaWorkspace * meta_screen_get_active_workspace (MetaScreen *screen);
 
 int  meta_screen_get_n_monitors       (MetaScreen    *screen);
+int  meta_screen_get_primary_monitor  (MetaScreen    *screen);
 void meta_screen_get_monitor_geometry (MetaScreen    *screen,
                                        int            monitor,
                                        MetaRectangle *geometry);