Call XSync in redraw

It is necessary call to XSync if you want a good tput flash, because in
other way you can not be sure that white screen will be shown.
---
 st.c |    1 +
 1 file changed, 1 insertion(+)

1 files changed, 1 insertions, 0 deletions

diff --git a/st.c b/st.c
index b013bca..f4ad23d 100644
--- a/st.c
+++ b/st.c
@@ -2150,6 +2150,7 @@ redraw(void) {
 	struct timespec tv = {0, REDRAW_TIMEOUT * 1000};
 	tfulldirt();
 	draw();
+	XSync(xw.dpy, False); /* necessary for a good tput flash */
 	nanosleep(&tv, NULL);
 }