render: don’t create/destroy the title update timer each time

Create it once when instantiating the terminal. Add a boolean to track
whether the timer is running or not.

render.c

@@ -3501,26 +3501,10 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
     }
 }
 
-static bool
-fdm_title_update(struct fdm *fdm, int fd, int events, void *data)
-{
-    struct terminal *term = data;
-    fdm_del(fdm, fd);
-
-    term->render.title.timer_fd = -1;
-    render_update_title(term);
-
-    struct timeval now;
-    if (gettimeofday(&now, NULL) == 0)
-        term->render.title.last_update = now;
-
-    return true;
-}
-
 void
 render_refresh_title(struct terminal *term)
 {
-    if (term->render.title.timer_fd >= 0)
+    if (term->render.title.is_armed)
         return;
 
     struct timeval now;
@@ -3531,23 +3515,11 @@ render_refresh_title(struct terminal *term)
     timersub(&now, &term->render.title.last_update, &diff);
 
     if (diff.tv_sec == 0 && diff.tv_usec < 8333) {
-        int fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK);
-        if (fd < 0)
-            return;
-
         const struct itimerspec timeout = {
             .it_value = {.tv_nsec = 8333 * 1000 - diff.tv_usec * 1000},
         };
 
-        if (timerfd_settime(fd, 0, &timeout, NULL) < 0) {
+        timerfd_settime(term->render.title.timer_fd, 0, &timeout, NULL);
-            close(fd);
-            return;
-        }
-
-        if (!fdm_add(term->fdm, fd, EPOLLIN, &fdm_title_update, term))
-            close(fd);
-        else
-            term->render.title.timer_fd = fd;
     } else {
         term->render.title.last_update = now;
         render_update_title(term);

terminal.c

@@ -552,6 +552,31 @@ fdm_app_sync_updates_timeout(
     return true;
 }
 
+static bool
+fdm_title_update_timeout(struct fdm *fdm, int fd, int events, void *data)
+{
+    if (events & EPOLLHUP)
+        return false;
+
+    struct terminal *term = data;
+    uint64_t unused;
+    ssize_t ret = read(term->render.title.timer_fd, &unused, sizeof(unused));
+
+    if (ret < 0) {
+        if (errno == EAGAIN)
+            return true;
+        LOG_ERRNO("failed to read title update throttle timer");
+        return false;
+    }
+
+    struct itimerspec reset = {{0}};
+    timerfd_settime(term->render.title.timer_fd, 0, &reset, NULL);
+    term->render.title.is_armed = false;
+
+    render_refresh_title(term);
+    return true;
+}
+
 static bool
 initialize_render_workers(struct terminal *term)
 {
@@ -980,6 +1005,7 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
     int delay_lower_fd = -1;
     int delay_upper_fd = -1;
     int app_sync_updates_fd = -1;
+    int title_update_fd = -1;
 
     struct terminal *term = malloc(sizeof(*term));
     if (unlikely(term == NULL)) {
@@ -987,27 +1013,33 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
         return NULL;
     }
 
-    if ((ptmx = posix_openpt(O_RDWR | O_NOCTTY)) == -1) {
+    if ((ptmx = posix_openpt(O_RDWR | O_NOCTTY)) < 0) {
         LOG_ERRNO("failed to open PTY");
         goto close_fds;
     }
-    if ((flash_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) == -1) {
+    if ((flash_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) < 0) {
         LOG_ERRNO("failed to create flash timer FD");
         goto close_fds;
     }
-    if ((delay_lower_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) == -1 ||
+    if ((delay_lower_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) < 0 ||
-        (delay_upper_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) == -1)
+        (delay_upper_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) < 0)
     {
         LOG_ERRNO("failed to create delayed rendering timer FDs");
         goto close_fds;
     }
 
-    if ((app_sync_updates_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) == -1)
+    if ((app_sync_updates_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) < 0)
     {
         LOG_ERRNO("failed to create application synchronized updates timer FD");
         goto close_fds;
     }
 
+    if ((title_update_fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC | TFD_NONBLOCK)) < 0)
+    {
+        LOG_ERRNO("failed to create title update throttle timer FD");
+        goto close_fds;
+    }
+
     if (ioctl(ptmx, (unsigned int)TIOCSWINSZ,
               &(struct winsize){.ws_row = 24, .ws_col = 80}) < 0)
     {
@@ -1032,7 +1064,8 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
     if (!fdm_add(fdm, flash_fd, EPOLLIN, &fdm_flash, term) ||
         !fdm_add(fdm, delay_lower_fd, EPOLLIN, &fdm_delayed_render, term) ||
         !fdm_add(fdm, delay_upper_fd, EPOLLIN, &fdm_delayed_render, term) ||
-        !fdm_add(fdm, app_sync_updates_fd, EPOLLIN, &fdm_app_sync_updates_timeout, term))
+        !fdm_add(fdm, app_sync_updates_fd, EPOLLIN, &fdm_app_sync_updates_timeout, term) ||
+        !fdm_add(fdm, title_update_fd, EPOLLIN, &fdm_title_update_timeout, term))
     {
         goto err;
     }
@@ -1114,7 +1147,8 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
             .scrollback_lines = conf->scrollback.lines,
             .app_sync_updates.timer_fd = app_sync_updates_fd,
             .title = {
-                .timer_fd = -1,
+                .is_armed = false,
+                .timer_fd = title_update_fd,
             },
             .workers = {
                 .count = conf->render_worker_count,
@@ -1220,6 +1254,7 @@ close_fds:
     fdm_del(fdm, delay_lower_fd);
     fdm_del(fdm, delay_upper_fd);
     fdm_del(fdm, app_sync_updates_fd);
+    fdm_del(fdm, title_update_fd);
 
     free(term);
     return NULL;

terminal.h

@@ -490,6 +490,7 @@ struct terminal {
 
         struct {
             struct timeval last_update;
+            bool is_armed;
             int timer_fd;
         } title;