260 lines
7.3 KiB
Diff
260 lines
7.3 KiB
Diff
From 8c9c920325fa10440a96736ba58ec647a0365e22 Mon Sep 17 00:00:00 2001
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From: "Avi Halachmi (:avih)" <avihpit@yahoo.com>
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Date: Sat, 18 Apr 2020 13:56:11 +0300
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Subject: [PATCH] application-sync: support Synchronized-Updates
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See https://gitlab.com/gnachman/iterm2/-/wikis/synchronized-updates-spec
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In a nutshell: allow an application to suspend drawing until it has
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completed some output - so that the terminal will not flicker/tear by
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rendering partial content. If the end-of-suspension sequence doesn't
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arrive, the terminal bails out after a timeout (default: 200 ms).
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The feature is supported and pioneered by iTerm2. There are probably
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very few other terminals or applications which support this feature
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currently.
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One notable application which does support it is tmux (master as of
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2020-04-18) - where cursor flicker is completely avoided when a pane
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has new content. E.g. run in one pane: `while :; do cat x.c; done'
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while the cursor is at another pane.
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The terminfo string `Sync' added to `st.info' is also a tmux extension
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which tmux detects automatically when `st.info` is installed.
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Notes:
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- Draw-suspension begins on BSU sequence (Begin-Synchronized-Update),
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and ends on ESU sequence (End-Synchronized-Update).
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- BSU, ESU are "\033P=1s\033\\", "\033P=2s\033\\" respectively (DCS).
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- SU doesn't support nesting - BSU begins or extends, ESU always ends.
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- ESU without BSU is ignored.
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- BSU after BSU extends (resets the timeout), so an application could
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send BSU in a loop and keep drawing suspended - exactly like it can
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not-draw anything in a loop. But as soon as it exits/aborted then
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drawing is resumed according to the timeout even without ESU.
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- This implementation focuses on ESU and doesn't really care about BSU
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in the sense that it tries hard to draw exactly once ESU arrives (if
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it's not too soon after the last draw - according to minlatency),
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and doesn't try to draw the content just up-to BSU. These two sides
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complement eachother - not-drawing on BSU increases the chance that
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ESU is not too soon after the last draw. This approach was chosen
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because the application's main focus is that ESU indicates to the
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terminal that the content is now ready - and that's when we try to
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draw.
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---
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config.def.h | 6 ++++++
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st.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++--
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st.info | 1 +
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x.c | 22 +++++++++++++++++++---
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4 files changed, 72 insertions(+), 5 deletions(-)
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diff --git a/config.def.h b/config.def.h
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index 6f05dce..80d768e 100644
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--- a/config.def.h
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+++ b/config.def.h
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@@ -56,6 +56,12 @@ int allowwindowops = 0;
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static double minlatency = 8;
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static double maxlatency = 33;
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+/*
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+ * Synchronized-Update timeout in ms
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+ * https://gitlab.com/gnachman/iterm2/-/wikis/synchronized-updates-spec
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+ */
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+static uint su_timeout = 200;
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+
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/*
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* blinking timeout (set to 0 to disable blinking) for the terminal blinking
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* attribute.
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diff --git a/st.c b/st.c
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index 76b7e0d..0582e77 100644
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--- a/st.c
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+++ b/st.c
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@@ -231,6 +231,33 @@ static uchar utfmask[UTF_SIZ + 1] = {0xC0, 0x80, 0xE0, 0xF0, 0xF8};
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static Rune utfmin[UTF_SIZ + 1] = { 0, 0, 0x80, 0x800, 0x10000};
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static Rune utfmax[UTF_SIZ + 1] = {0x10FFFF, 0x7F, 0x7FF, 0xFFFF, 0x10FFFF};
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+#include <time.h>
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+static int su = 0;
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+struct timespec sutv;
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+
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+static void
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+tsync_begin()
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+{
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+ clock_gettime(CLOCK_MONOTONIC, &sutv);
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+ su = 1;
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+}
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+
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+static void
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+tsync_end()
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+{
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+ su = 0;
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+}
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+
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+int
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+tinsync(uint timeout)
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+{
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+ struct timespec now;
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+ if (su && !clock_gettime(CLOCK_MONOTONIC, &now)
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+ && TIMEDIFF(now, sutv) >= timeout)
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+ su = 0;
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+ return su;
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+}
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+
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ssize_t
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xwrite(int fd, const char *s, size_t len)
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{
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@@ -818,6 +845,9 @@ ttynew(char *line, char *cmd, char *out, char **args)
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return cmdfd;
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}
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+static int twrite_aborted = 0;
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+int ttyread_pending() { return twrite_aborted; }
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+
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size_t
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ttyread(void)
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{
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@@ -826,7 +856,7 @@ ttyread(void)
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int ret, written;
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/* append read bytes to unprocessed bytes */
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- ret = read(cmdfd, buf+buflen, LEN(buf)-buflen);
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+ ret = twrite_aborted ? 1 : read(cmdfd, buf+buflen, LEN(buf)-buflen);
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switch (ret) {
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case 0:
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@@ -834,7 +864,7 @@ ttyread(void)
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case -1:
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die("couldn't read from shell: %s\n", strerror(errno));
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default:
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- buflen += ret;
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+ buflen += twrite_aborted ? 0 : ret;
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written = twrite(buf, buflen, 0);
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buflen -= written;
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/* keep any incomplete UTF-8 byte sequence for the next call */
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@@ -994,6 +1024,7 @@ tsetdirtattr(int attr)
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void
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tfulldirt(void)
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{
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+ tsync_end();
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tsetdirt(0, term.row-1);
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}
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@@ -1895,6 +1926,12 @@ strhandle(void)
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xsettitle(strescseq.args[0]);
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return;
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case 'P': /* DCS -- Device Control String */
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+ /* https://gitlab.com/gnachman/iterm2/-/wikis/synchronized-updates-spec */
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+ if (strstr(strescseq.buf, "=1s") == strescseq.buf)
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+ tsync_begin(); /* BSU */
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+ else if (strstr(strescseq.buf, "=2s") == strescseq.buf)
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+ tsync_end(); /* ESU */
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+ return;
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case '_': /* APC -- Application Program Command */
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case '^': /* PM -- Privacy Message */
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return;
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@@ -2436,6 +2473,9 @@ twrite(const char *buf, int buflen, int show_ctrl)
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Rune u;
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int n;
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+ int su0 = su;
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+ twrite_aborted = 0;
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+
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for (n = 0; n < buflen; n += charsize) {
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if (IS_SET(MODE_UTF8)) {
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/* process a complete utf8 char */
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@@ -2446,6 +2486,10 @@ twrite(const char *buf, int buflen, int show_ctrl)
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u = buf[n] & 0xFF;
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charsize = 1;
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}
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+ if (su0 && !su) {
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+ twrite_aborted = 1;
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+ break; // ESU - allow rendering before a new BSU
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+ }
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if (show_ctrl && ISCONTROL(u)) {
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if (u & 0x80) {
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u &= 0x7f;
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diff --git a/st.info b/st.info
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index 8201ad6..b32b446 100644
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--- a/st.info
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+++ b/st.info
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@@ -191,6 +191,7 @@ st-mono| simpleterm monocolor,
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Ms=\E]52;%p1%s;%p2%s\007,
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Se=\E[2 q,
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Ss=\E[%p1%d q,
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+ Sync=\EP=%p1%ds\E\\,
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st| simpleterm,
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use=st-mono,
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diff --git a/x.c b/x.c
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index 210f184..27ff4e2 100644
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--- a/x.c
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+++ b/x.c
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@@ -1861,6 +1861,9 @@ resize(XEvent *e)
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cresize(e->xconfigure.width, e->xconfigure.height);
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}
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+int tinsync(uint);
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+int ttyread_pending();
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+
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void
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run(void)
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{
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@@ -1895,7 +1898,7 @@ run(void)
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FD_SET(ttyfd, &rfd);
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FD_SET(xfd, &rfd);
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- if (XPending(xw.dpy))
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+ if (XPending(xw.dpy) || ttyread_pending())
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timeout = 0; /* existing events might not set xfd */
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seltv.tv_sec = timeout / 1E3;
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@@ -1909,7 +1912,8 @@ run(void)
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}
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clock_gettime(CLOCK_MONOTONIC, &now);
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- if (FD_ISSET(ttyfd, &rfd))
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+ int ttyin = FD_ISSET(ttyfd, &rfd) || ttyread_pending();
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+ if (ttyin)
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ttyread();
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xev = 0;
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@@ -1933,7 +1937,7 @@ run(void)
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* maximum latency intervals during `cat huge.txt`, and perfect
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* sync with periodic updates from animations/key-repeats/etc.
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*/
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- if (FD_ISSET(ttyfd, &rfd) || xev) {
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+ if (ttyin || xev) {
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if (!drawing) {
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trigger = now;
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drawing = 1;
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@@ -1944,6 +1948,18 @@ run(void)
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continue; /* we have time, try to find idle */
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}
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+ if (tinsync(su_timeout)) {
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+ /*
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+ * on synchronized-update draw-suspension: don't reset
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+ * drawing so that we draw ASAP once we can (just after
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+ * ESU). it won't be too soon because we already can
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+ * draw now but we skip. we set timeout > 0 to draw on
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+ * SU-timeout even without new content.
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+ */
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+ timeout = minlatency;
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+ continue;
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+ }
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+
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/* idle detected or maxlatency exhausted -> draw */
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timeout = -1;
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if (blinktimeout && tattrset(ATTR_BLINK)) {
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base-commit: b27a383a3acc7decf00e6e889fca265430b5d329
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--
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2.17.1
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