diff options
| -rw-r--r-- | config.def.h | 11 | ||||
| -rw-r--r-- | x.c | 120 |
2 files changed, 65 insertions, 66 deletions
diff --git a/config.def.h b/config.def.h index 0895a1f..fdbacfd 100644 --- a/config.def.h +++ b/config.def.h @@ -43,9 +43,14 @@ static unsigned int tripleclicktimeout = 600; /* alt screens */ int allowaltscreen = 1; -/* frames per second st should at maximum draw to the screen */ -static unsigned int xfps = 120; -static unsigned int actionfps = 30; +/* + * draw latency range in ms - from new content/keypress/etc until drawing. + * within this range, st draws when content stops arriving (idle). mostly it's + * near minlatency, but it waits longer for slow updates to avoid partial draw. + * low minlatency will tear/flicker more, as it can "detect" idle too early. + */ +static double minlatency = 8; +static double maxlatency = 33; /* * blinking timeout (set to 0 to disable blinking) for the terminal blinking @@ -1867,10 +1867,9 @@ run(void) XEvent ev; int w = win.w, h = win.h; fd_set rfd; - int xfd = XConnectionNumber(xw.dpy), xev, blinkset = 0, dodraw = 0; - int ttyfd; - struct timespec drawtimeout, *tv = NULL, now, last, lastblink; - long deltatime; + int xfd = XConnectionNumber(xw.dpy), ttyfd, xev, drawing; + struct timespec seltv, *tv, now, lastblink, trigger; + double timeout; /* Waiting for window mapping */ do { @@ -1891,82 +1890,77 @@ run(void) ttyfd = ttynew(opt_line, shell, opt_io, opt_cmd); cresize(w, h); - clock_gettime(CLOCK_MONOTONIC, &last); - lastblink = last; - - for (xev = actionfps;;) { + for (timeout = -1, drawing = 0, lastblink = (struct timespec){0};;) { FD_ZERO(&rfd); FD_SET(ttyfd, &rfd); FD_SET(xfd, &rfd); + if (XPending(xw.dpy)) + timeout = 0; /* existing events might not set xfd */ + + seltv.tv_sec = timeout / 1E3; + seltv.tv_nsec = 1E6 * (timeout - 1E3 * seltv.tv_sec); + tv = timeout >= 0 ? &seltv : NULL; + if (pselect(MAX(xfd, ttyfd)+1, &rfd, NULL, NULL, tv, NULL) < 0) { if (errno == EINTR) continue; die("select failed: %s\n", strerror(errno)); } - if (FD_ISSET(ttyfd, &rfd)) { - ttyread(); - if (blinktimeout) { - blinkset = tattrset(ATTR_BLINK); - if (!blinkset) - MODBIT(win.mode, 0, MODE_BLINK); - } - } + clock_gettime(CLOCK_MONOTONIC, &now); - if (FD_ISSET(xfd, &rfd)) - xev = actionfps; + if (FD_ISSET(ttyfd, &rfd)) + ttyread(); - clock_gettime(CLOCK_MONOTONIC, &now); - drawtimeout.tv_sec = 0; - drawtimeout.tv_nsec = (1000 * 1E6)/ xfps; - tv = &drawtimeout; - - dodraw = 0; - if (blinktimeout && TIMEDIFF(now, lastblink) > blinktimeout) { - tsetdirtattr(ATTR_BLINK); - win.mode ^= MODE_BLINK; - lastblink = now; - dodraw = 1; - } - deltatime = TIMEDIFF(now, last); - if (deltatime > 1000 / (xev ? xfps : actionfps)) { - dodraw = 1; - last = now; + xev = 0; + while (XPending(xw.dpy)) { + xev = 1; + XNextEvent(xw.dpy, &ev); + if (XFilterEvent(&ev, None)) + continue; + if (handler[ev.type]) + (handler[ev.type])(&ev); } - if (dodraw) { - while (XPending(xw.dpy)) { - XNextEvent(xw.dpy, &ev); - if (XFilterEvent(&ev, None)) - continue; - if (handler[ev.type]) - (handler[ev.type])(&ev); + /* + * To reduce flicker and tearing, when new content or event + * triggers drawing, we first wait a bit to ensure we got + * everything, and if nothing new arrives - we draw. + * We start with trying to wait minlatency ms. If more content + * arrives sooner, we retry with shorter and shorter preiods, + * and eventually draw even without idle after maxlatency ms. + * Typically this results in low latency while interacting, + * maximum latency intervals during `cat huge.txt`, and perfect + * sync with periodic updates from animations/key-repeats/etc. + */ + if (FD_ISSET(ttyfd, &rfd) || xev) { + if (!drawing) { + trigger = now; + drawing = 1; } + timeout = (maxlatency - TIMEDIFF(now, trigger)) \ + / maxlatency * minlatency; + if (timeout > 0) + continue; /* we have time, try to find idle */ + } - draw(); - XFlush(xw.dpy); - - if (xev && !FD_ISSET(xfd, &rfd)) - xev--; - if (!FD_ISSET(ttyfd, &rfd) && !FD_ISSET(xfd, &rfd)) { - if (blinkset) { - if (TIMEDIFF(now, lastblink) \ - > blinktimeout) { - drawtimeout.tv_nsec = 1000; - } else { - drawtimeout.tv_nsec = (1E6 * \ - (blinktimeout - \ - TIMEDIFF(now, - lastblink))); - } - drawtimeout.tv_sec = \ - drawtimeout.tv_nsec / 1E9; - drawtimeout.tv_nsec %= (long)1E9; - } else { - tv = NULL; - } + /* idle detected or maxlatency exhausted -> draw */ + timeout = -1; + if (blinktimeout && tattrset(ATTR_BLINK)) { + timeout = blinktimeout - TIMEDIFF(now, lastblink); + if (timeout <= 0) { + if (-timeout > blinktimeout) /* start visible */ + win.mode |= MODE_BLINK; + win.mode ^= MODE_BLINK; + tsetdirtattr(ATTR_BLINK); + lastblink = now; + timeout = blinktimeout; } } + + draw(); + XFlush(xw.dpy); + drawing = 0; } } |