Adding a more efficient drawing code.

Thanks Mihail Zenkov <mihail.zenkov@gmail.com> for giving the hint!

2 files changed, 42 insertions, 28 deletions

diff --git a/config.def.h b/config.def.h
index 684adf7..8732ca3 100644
--- a/config.def.h
+++ b/config.def.h
@@ -9,10 +9,13 @@ static char font[] = "Liberation Mono:pixelsize=12:antialias=false:autohint=fals
 static int borderpx = 2;
 static char shell[] = "/bin/sh";
 
-/* double-click timeout (in milliseconds) between clicks for selection */
+/* timeouts (in milliseconds) */
 static unsigned int doubleclicktimeout = 300;
 static unsigned int tripleclicktimeout = 600;
 
+/* frames per second st should at maximum draw to the screen */
+static unsigned int framespersecond = 60;
+
 /* TERM value */
 static char termname[] = "st-256color";
 
diff --git a/st.c b/st.c
index 8206001..f4b419e 100644
--- a/st.c
+++ b/st.c
@@ -3166,10 +3166,12 @@ void
 run(void) {
         XEvent ev;
         fd_set rfd;
-        int xfd = XConnectionNumber(xw.dpy), i;
-        struct timeval drawtimeout, *tv = NULL;
+        int xfd = XConnectionNumber(xw.dpy);
+        struct timeval drawtimeout, *tv = NULL, now, last;
 
-        for(i = 0;; i++) {
+        gettimeofday(&last, NULL);
+
+        for(;;) {
                 FD_ZERO(&rfd);
                 FD_SET(cmdfd, &rfd);
                 FD_SET(xfd, &rfd);
@@ -3179,35 +3181,44 @@ run(void) {
                         die("select failed: %s\n", SERRNO);
                 }
 
-                /*
-                 * Stop after a certain number of reads so the user does not
-                 * feel like the system is stuttering.
-                 */
-                if(i < 1000 && FD_ISSET(cmdfd, &rfd)) {
-                        ttyread();
+                gettimeofday(&now, NULL);
+                /* usecs until (next) frame */
+                drawtimeout.tv_sec = 0;
+                drawtimeout.tv_usec = \
+                        ((1000/framespersecond) - TIMEDIFF(now, last)) * 1000;
 
-                        /*
-                         * Just wait a bit so it isn't disturbing the
-                         * user and the system is able to write something.
-                         */
-                        drawtimeout.tv_sec = 0;
-                        drawtimeout.tv_usec = 5;
-                        tv = &drawtimeout;
-                        continue;
+                /* Let us draw a frame. */
+                if(drawtimeout.tv_usec <= 0) {
+                        draw();
+                        XFlush(xw.dpy);
+
+                        last = now;
+                        tv = NULL;
                 }
-                i = 0;
-                tv = NULL;
 
-                while(XPending(xw.dpy)) {
-                        XNextEvent(xw.dpy, &ev);
-                        if(XFilterEvent(&ev, None))
-                                continue;
-                        if(handler[ev.type])
-                                (handler[ev.type])(&ev);
+                if(FD_ISSET(cmdfd, &rfd))
+                        ttyread();
+
+                if(FD_ISSET(xfd, &rfd)) {
+                        while(XPending(xw.dpy)) {
+                                XNextEvent(xw.dpy, &ev);
+                                if(XFilterEvent(&ev, None))
+                                        continue;
+                                if(handler[ev.type])
+                                        (handler[ev.type])(&ev);
+                        }
+
+                        if(drawtimeout.tv_usec <= 0) {
+                                draw();
+                                XFlush(xw.dpy);
+                        }
                 }
 
-                draw();
-                XFlush(xw.dpy);
+                /* There is still some time to wait until next frame. */
+                if(drawtimeout.tv_usec > 0) {
+                        tv = &drawtimeout;
+                        continue;
+                }
         }
 }