Screen scanning: Use an idle source

Instead of refreshing screens at the end of the current main loop
iteration, this now uses a GLib idle source with a very low priority.
This increases the chance of batching multiple refreshes together. Also,
this means that awesome_refresh() does less work.

Signed-off-by: Uli Schlachter <psychon@znc.in>

event.c

@@ -459,7 +459,7 @@ event_handle_configurenotify(xcb_configure_notify_event_t *ev)
     xcb_screen_t *screen = globalconf.screen;
 
     if(ev->window == screen->root)
-        globalconf.screen_need_refresh = true;
+        screen_schedule_refresh();
 
     /* Copy what XRRUpdateConfiguration() would do: Update the configuration */
     if(ev->window == screen->root) {
@@ -881,7 +881,7 @@ event_handle_randr_screen_change_notify(xcb_randr_screen_change_notify_event_t *
         globalconf.screen->height_in_millimeters = ev->mheight;;
     }
 
-    globalconf.screen_need_refresh = true;
+    screen_schedule_refresh();
 }
 
 /** XRandR event handler for RRNotify subtype XRROutputChangeNotifyEvent

event.h

@@ -39,9 +39,6 @@ void client_refresh(void);
 void client_focus_refresh(void);
 void client_destroy_later(void);
 
-/* objects/screen.c */
-void screen_refresh(void);
-
 /* xkb.c */
 void xkb_refresh(void);
 
@@ -49,7 +46,6 @@ static inline int
 awesome_refresh(void)
 {
     xkb_refresh();
-    screen_refresh();
     luaA_emit_refresh();
     drawin_refresh();
     client_refresh();

globalconf.h

@@ -101,7 +101,7 @@ typedef struct
     /** Do we have RandR 1.5 or newer? */
     bool have_randr_15;
     /** Do we have a RandR screen update pending? */
-    bool screen_need_refresh;
+    bool screen_refresh_pending;
     /** Check for XTest extension */
     bool have_xtest;
     /** Check for SHAPE extension */

objects/screen.c

@@ -661,12 +661,10 @@ screen_modified(screen_t *existing_screen, screen_t *other_screen)
     }
 }
 
-void
-screen_refresh(void)
+static gboolean
+screen_refresh(gpointer unused)
 {
-    if(!globalconf.screen_need_refresh || !globalconf.have_randr_13)
-        return;
-    globalconf.screen_need_refresh = false;
+    globalconf.screen_refresh_pending = false;
 
     screen_array_t new_screens;
     screen_array_t removed_screens;
@@ -740,6 +738,18 @@ screen_refresh(void)
 
     if (list_changed)
         luaA_class_emit_signal(L, &screen_class, "list", 0);
+
+    return G_SOURCE_REMOVE;
+}
+
+void
+screen_schedule_refresh(void)
+{
+    if(globalconf.screen_refresh_pending || !globalconf.have_randr_13)
+        return;
+
+    globalconf.screen_refresh_pending = true;
+    g_idle_add_full(G_PRIORITY_LOW, screen_refresh, NULL, NULL);
 }
 
 /** Return the squared distance of the given screen to the coordinates.

objects/screen.h

@@ -56,6 +56,7 @@ void screen_client_moveto(client_t *, screen_t *, bool);
 void screen_update_primary(void);
 void screen_update_workarea(screen_t *);
 screen_t *screen_get_primary(void);
+void screen_schedule_refresh(void);
 
 screen_t *luaA_checkscreen(lua_State *, int);