Improvement #7: Add double buffering

Add double buffering with X DBE extension in hope to get rid of the
tearing issue. Thanks to cairo-compmgr for providing hints. Could be
enabled with --dbe. Only very limited tests have been done, I don't know
if it actually solves the tearing issue. My estimation is it is harmful
for performance, but I found no clear evidence. Experimental, so no
configuration file option is available for it.

MONITOR_REPAINT is broken if --dbe is turned on, this is intended for
testing whether DBE is actually working.

1 files changed, 3 insertions, 0 deletions

diff --git a/compton.h b/compton.h
index 6aac338e9..ee505985a 100644
--- a/compton.h
+++ b/compton.h
@@ -75,6 +75,7 @@
 #include <X11/extensions/Xrender.h>
 #include <X11/extensions/shape.h>
 #include <X11/extensions/Xrandr.h>
+#include <X11/extensions/Xdbe.h>
 
 #ifdef CONFIG_VSYNC_DRM
 #include <fcntl.h>
@@ -314,6 +315,8 @@ typedef struct _options {
   int refresh_rate;
   /// VSync method to use;
   vsync_t vsync;
+  /// Whether to enable double buffer.
+  Bool dbe;
 
   // Shadow
   Bool wintype_shadow[NUM_WINTYPES];