From 535c82d628909b4f54774885e7de366c07fa9779 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Tue, 15 Jun 2021 17:27:50 +0200
Subject: [PATCH] render: use a timer instead of relying on the frame callback
 for title update throttling
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Using the frame callback works most of the time, but e.g. Sway doesn’t
call it while the window is hidden, and thus prevents us from updating
the title in e.g. stacked views.

This patch uses a timer FD instead. We store a timestamp from when the
title was last updated. When the application wants to update the
title, we first check if we already have a timer running, and if so,
does nothing.

If no timer is running, check the timestamp. If enough time has
passed, update the title immediately.

If not, instantiate a timer and wait for it to trigger.

Set the minimum time between two updates to ~8ms (twice per frame, for
a 60Hz output, and ~once per frame on a 120Hz output).

Closes #591
---
 CHANGELOG.md |  2 ++
 render.c     | 63 +++++++++++++++++++++++++++++++++++++++++-----------
 terminal.c   | 10 ++++++---
 terminal.h   |  7 ++++--
 4 files changed, 64 insertions(+), 18 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b7e2f51a..6ea8eec3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -184,6 +184,8 @@
   (https://codeberg.org/dnkl/foot/issues/586).
 * Crash in scrollback search when current XKB layout is missing
   _compose_ definitions.
+* Window title not being updated while window is hidden
+  (https://codeberg.org/dnkl/foot/issues/591).
 
 
 ### Security
diff --git a/render.c b/render.c
index bebb479a..20af86aa 100644
--- a/render.c
+++ b/render.c
@@ -2992,13 +2992,11 @@ frame_callback(void *data, struct wl_callback *wl_callback, uint32_t callback_da
     bool grid = term->render.pending.grid;
     bool csd = term->render.pending.csd;
     bool search = term->is_searching && term->render.pending.search;
-    bool title = term->render.pending.title;
     bool urls = urls_mode_is_active(term) > 0 && term->render.pending.urls;
 
     term->render.pending.grid = false;
     term->render.pending.csd = false;
     term->render.pending.search = false;
-    term->render.pending.title = false;
     term->render.pending.urls = false;
 
     struct grid *original_grid = term->grid;
@@ -3013,9 +3011,6 @@ frame_callback(void *data, struct wl_callback *wl_callback, uint32_t callback_da
         quirk_weston_csd_off(term);
     }
 
-    if (title)
-        render_update_title(term);
-
     if (search)
         render_search_box(term);
 
@@ -3447,19 +3442,17 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
         bool grid = term->render.refresh.grid;
         bool csd = term->render.refresh.csd;
         bool search = term->is_searching && term->render.refresh.search;
-        bool title = term->render.refresh.title;
         bool urls = urls_mode_is_active(term) && term->render.refresh.urls;
 
-        if (!(grid | csd | search | title | urls))
+        if (!(grid | csd | search | urls))
             continue;
 
-        if (term->render.app_sync_updates.enabled && !(csd | search | title | urls))
+        if (term->render.app_sync_updates.enabled && !(csd | search | urls))
             continue;
 
         term->render.refresh.grid = false;
         term->render.refresh.csd = false;
         term->render.refresh.search = false;
-        term->render.refresh.title = false;
         term->render.refresh.urls = false;
 
         if (term->window->frame_callback == NULL) {
@@ -3474,8 +3467,6 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
                 render_csd(term);
                 quirk_weston_csd_off(term);
             }
-            if (title)
-                render_update_title(term);
             if (search)
                 render_search_box(term);
             if (urls)
@@ -3494,7 +3485,6 @@ fdm_hook_refresh_pending_terminals(struct fdm *fdm, void *data)
             term->render.pending.grid |= grid;
             term->render.pending.csd |= csd;
             term->render.pending.search |= search;
-            term->render.pending.title |= title;
             term->render.pending.urls |= urls;
         }
     }
@@ -3511,10 +3501,57 @@ 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)
 {
-    term->render.refresh.title = true;
+    if (term->render.title.timer_fd >= 0)
+        return;
+
+    struct timeval now;
+    if (gettimeofday(&now, NULL) < 0)
+        return;
+
+    struct timeval diff;
+    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) {
+            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);
+    }
 }
 
 void
diff --git a/terminal.c b/terminal.c
index e689f4f6..aef21d72 100644
--- a/terminal.c
+++ b/terminal.c
@@ -1113,6 +1113,9 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
         .render = {
             .scrollback_lines = conf->scrollback.lines,
             .app_sync_updates.timer_fd = app_sync_updates_fd,
+            .title = {
+                .timer_fd = -1,
+            },
             .workers = {
                 .count = conf->render_worker_count,
                 .queue = tll_init(),
@@ -1289,6 +1292,7 @@ term_shutdown(struct terminal *term)
 
     fdm_del(term->fdm, term->selection.auto_scroll.fd);
     fdm_del(term->fdm, term->render.app_sync_updates.timer_fd);
+    fdm_del(term->fdm, term->render.title.timer_fd);
     fdm_del(term->fdm, term->delayed_render_timer.lower_fd);
     fdm_del(term->fdm, term->delayed_render_timer.upper_fd);
     fdm_del(term->fdm, term->blink.fd);
@@ -1304,6 +1308,7 @@ term_shutdown(struct terminal *term)
 
     term->selection.auto_scroll.fd = -1;
     term->render.app_sync_updates.timer_fd = -1;
+    term->render.title.timer_fd = -1;
     term->delayed_render_timer.lower_fd = -1;
     term->delayed_render_timer.upper_fd = -1;
     term->blink.fd = -1;
@@ -1354,6 +1359,7 @@ term_destroy(struct terminal *term)
 
     fdm_del(term->fdm, term->selection.auto_scroll.fd);
     fdm_del(term->fdm, term->render.app_sync_updates.timer_fd);
+    fdm_del(term->fdm, term->render.title.timer_fd);
     fdm_del(term->fdm, term->delayed_render_timer.lower_fd);
     fdm_del(term->fdm, term->delayed_render_timer.upper_fd);
     fdm_del(term->fdm, term->cursor_blink.fd);
@@ -2670,9 +2676,7 @@ term_enable_app_sync_updates(struct terminal *term)
     /* Disable pending refresh *iff* the grid is the *only* thing
      * scheduled to be re-rendered */
     if (!term->render.refresh.csd && !term->render.refresh.search &&
-        !term->render.refresh.title &&
-        !term->render.pending.csd && !term->render.pending.search &&
-        !term->render.pending.title)
+        !term->render.pending.csd && !term->render.pending.search)
     {
         term->render.refresh.grid = false;
         term->render.pending.grid = false;
diff --git a/terminal.h b/terminal.h
index b96621fd..c810c0f0 100644
--- a/terminal.h
+++ b/terminal.h
@@ -474,7 +474,6 @@ struct terminal {
             bool grid;
             bool csd;
             bool search;
-            bool title;
             bool urls;
         } refresh;
 
@@ -483,13 +482,17 @@ struct terminal {
             bool grid;
             bool csd;
             bool search;
-            bool title;
             bool urls;
         } pending;
 
         bool margins;  /* Someone explicitly requested a refresh of the margins */
         bool urgency;  /* Signal 'urgency' (paint borders red) */
 
+        struct {
+            struct timeval last_update;
+            int timer_fd;
+        } title;
+
         int scrollback_lines; /* Number of scrollback lines, from conf (TODO: move out from render struct?) */
 
         struct {