Improve support for multihead setups

Fix panel, app switcher, and looking glass to limit themselves to the
primary monitor, and run dialog to limit itself to the monitor
containing the currently-focused window.

The overview is also limited to the primary monitor now (with the
other monitors being blacked out), although the workspaces within the
overview are shaped like the full "screen" (the bounding box of all
monitors). To be fixed later.

https://bugzilla.gnome.org/show_bug.cgi?id=593060

src/shell-global.c

@@ -869,3 +869,99 @@ shell_global_create_root_pixmap_actor (ShellGlobal *global)
 
   return clutter_clone_new (global->root_pixmap);
 }
+
+/**
+ * shell_global_get_monitors:
+ * @global: the #ShellGlobal
+ *
+ * Gets a list of the bounding boxes of the active screen's monitors.
+ *
+ * Return value: (transfer full) (element-type GdkRectangle): a list
+ * of monitor bounding boxes.
+ */
+GSList *
+shell_global_get_monitors (ShellGlobal *global)
+{
+  MetaScreen *screen = shell_global_get_screen (global);
+  GSList *monitors = NULL;
+  MetaRectangle rect;
+  int i;
+
+  g_assert (sizeof (MetaRectangle) == sizeof (GdkRectangle) &&
+            G_STRUCT_OFFSET (MetaRectangle, x) == G_STRUCT_OFFSET (GdkRectangle, x) &&
+            G_STRUCT_OFFSET (MetaRectangle, y) == G_STRUCT_OFFSET (GdkRectangle, y) &&
+            G_STRUCT_OFFSET (MetaRectangle, width) == G_STRUCT_OFFSET (GdkRectangle, width) &&
+            G_STRUCT_OFFSET (MetaRectangle, height) == G_STRUCT_OFFSET (GdkRectangle, height));
+
+  for (i = meta_screen_get_n_monitors (screen) - 1; i >= 0; i--)
+    {
+      meta_screen_get_monitor_geometry (screen, i, &rect);
+      monitors = g_slist_prepend (monitors,
+                                  g_boxed_copy (GDK_TYPE_RECTANGLE, &rect));
+    }
+  return monitors;
+}
+
+/**
+ * shell_global_get_primary_monitor:
+ * @global: the #ShellGlobal
+ *
+ * Gets the bounding box of the primary monitor (the one that the
+ * panel is on).
+ *
+ * Return value: the bounding box of the primary monitor
+ */
+GdkRectangle *
+shell_global_get_primary_monitor (ShellGlobal  *global)
+{
+  MetaScreen *screen = shell_global_get_screen (global);
+  MetaRectangle rect;
+
+  g_assert (sizeof (MetaRectangle) == sizeof (GdkRectangle) &&
+            G_STRUCT_OFFSET (MetaRectangle, x) == G_STRUCT_OFFSET (GdkRectangle, x) &&
+            G_STRUCT_OFFSET (MetaRectangle, y) == G_STRUCT_OFFSET (GdkRectangle, y) &&
+            G_STRUCT_OFFSET (MetaRectangle, width) == G_STRUCT_OFFSET (GdkRectangle, width) &&
+            G_STRUCT_OFFSET (MetaRectangle, height) == G_STRUCT_OFFSET (GdkRectangle, height));
+
+  meta_screen_get_monitor_geometry (screen, 0, &rect);
+  return g_boxed_copy (GDK_TYPE_RECTANGLE, &rect);
+}
+
+/**
+ * shell_global_get_focus_monitor:
+ * @global: the #ShellGlobal
+ *
+ * Gets the bounding box of the monitor containing the window that
+ * currently contains the keyboard focus.
+ *
+ * Return value: the bounding box of the focus monitor
+ */
+GdkRectangle *
+shell_global_get_focus_monitor (ShellGlobal  *global)
+{
+  MetaScreen *screen = shell_global_get_screen (global);
+  MetaDisplay *display = meta_screen_get_display (screen);
+  MetaWindow *focus = meta_display_get_focus_window (display);
+  MetaRectangle rect, wrect;
+  int nmonitors, i;
+
+  if (focus)
+    {
+      meta_window_get_outer_rect (focus, &wrect);
+      nmonitors = meta_screen_get_n_monitors (screen);
+
+      /* Find the monitor that the top-left corner of @focus is on. */
+      for (i = 0; i < nmonitors; i++)
+        {
+          meta_screen_get_monitor_geometry (screen, i, &rect);
+
+          if (rect.x < wrect.x && rect.y < wrect.y &&
+              rect.x + rect.width > wrect.x &&
+              rect.y + rect.height > wrect.y)
+            return g_boxed_copy (GDK_TYPE_RECTANGLE, &rect);
+        }
+    }
+
+  meta_screen_get_monitor_geometry (screen, 0, &rect);
+  return g_boxed_copy (GDK_TYPE_RECTANGLE, &rect);
+}

src/shell-global.h

@@ -73,6 +73,10 @@ void shell_global_format_time_relative_pretty (ShellGlobal *global, guint delta,
 
 ClutterActor *shell_global_create_root_pixmap_actor (ShellGlobal *global);
 
+GSList       *shell_global_get_monitors        (ShellGlobal  *global);
+GdkRectangle *shell_global_get_primary_monitor (ShellGlobal  *global);
+GdkRectangle *shell_global_get_focus_monitor   (ShellGlobal  *global);
+
 G_END_DECLS
 
 #endif /* __SHELL_GLOBAL_H__ */