From ce67a9ea6b3bbce18ea80a238fa2104afaa3971c Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Fri, 11 Dec 2015 18:09:12 +0200
Subject: [PATCH] Refresh the screen only when there's no events to process

---
 source/main.c | 49 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/source/main.c b/source/main.c
index 3532854..3f78884 100644
--- a/source/main.c
+++ b/source/main.c
@@ -42,6 +42,7 @@ typedef struct CompositedScreen
 	CompositedWindow *windows;
 	unsigned nwindows;
 	unsigned windows_capacity;
+	int dirty;
 } CompositedScreen;
 
 typedef struct Compositor
@@ -53,6 +54,7 @@ typedef struct Compositor
 	PFNGLXCREATECONTEXTATTRIBSARBPROC glXCreateContextAttribsARB;
 	PFNGLXBINDTEXIMAGEEXTPROC glXBindTexImageEXT;
 	PFNGLXRELEASETEXIMAGEEXTPROC glXReleaseTexImageEXT;
+	int dirty;
 } Compositor;
 
 static const char *vshader =
@@ -303,6 +305,18 @@ CompositedScreen *find_screen_by_root(Compositor *compositor, Window root)
 	return NULL;
 }
 
+CompositedScreen *find_screen_by_window(Compositor *compositor, Window w)
+{
+	unsigned i, j;
+
+	for(i=0; i<compositor->nscreens; ++i)
+		for(j=0; j<compositor->screens[i].nwindows; ++j)
+			if(compositor->screens[i].windows[j].window==w)
+				return &compositor->screens[i];
+
+	return NULL;
+}
+
 int initialize_screen(Compositor *compositor, unsigned number)
 {
 	CompositedScreen *screen;
@@ -456,10 +470,27 @@ void process_unmap_event(Compositor *compositor, XUnmapEvent *event)
 		window->map_state = IsUnviewable;
 }
 
-void process_event(Compositor *compositor)
+void process_damage_event(Compositor *compositor, XDamageNotifyEvent *event)
+{
+	CompositedScreen *screen = find_screen_by_window(compositor, event->drawable);
+	if(!screen)
+		return;
+
+	screen->dirty = 1;
+	compositor->dirty = 1;
+}
+
+int process_event(Compositor *compositor)
 {
 	XEvent event;
-	XNextEvent(compositor->display, &event);
+	if(compositor->dirty)
+	{
+		if(!XCheckMaskEvent(compositor->display, -1, &event))
+			return 0;
+	}
+	else
+		XNextEvent(compositor->display, &event);
+
 	switch(event.type)
 	{
 	case CreateNotify:
@@ -472,9 +503,13 @@ void process_event(Compositor *compositor)
 		process_unmap_event(compositor, &event.xunmap);
 		break;
 	default:
-		if(event.type!=compositor->damage_event+XDamageNotify)
+		if(event.type==compositor->damage_event+XDamageNotify)
+			process_damage_event(compositor, (XDamageNotifyEvent *)&event);
+		else
 			printf("Event %d\n", event.type);
 	}
+
+	return 1;
 }
 
 void refresh_screens(Compositor *compositor)
@@ -508,7 +543,11 @@ void refresh_screens(Compositor *compositor)
 		}
 		XUngrabServer(compositor->display);
 		glXSwapBuffers(compositor->display, screen->glx_window);
+
+		screen->dirty = 0;
 	}
+
+	compositor->dirty = 0;
 }
 
 int main()
@@ -520,8 +559,8 @@ int main()
 
 	while(1)
 	{
-		process_event(&compositor);
-		refresh_screens(&compositor);
+		if(!process_event(&compositor))
+			refresh_screens(&compositor);
 	}
 
 	shutdown_compositor(&compositor);
-- 
2.43.0