Add support for the new Wayland protocol xdg-system-bell

From the release notes:

    system bell - allowing e.g. terminal emulators to hand off system
    bell alerts to the compositor for among other things accessibility
    purposes

The new protocol is used when the new config option
bell.system=yes (and the compositor implements the protocol,
obviously).

The system bell is rung independent of whether the foot window has
keyboard focus or not (thus relying on compositor configuration to
determine whether anything should be done or not in response to the
bell).

The new option is enabled by default.

CHANGELOG.md

@@ -58,7 +58,14 @@
 
 
 ## Unreleased
+
 ### Added
+
+* Support for the new Wayland protocol `xdg-system-bell-v1` protocol
+  (added in wayland-protocols 1.38), via the new config option
+  `bell.system=no|yes` (defaults to `yes`).
+
+
 ### Changed
 
 * The `CSI 21 t` (report window title) and `OSC 176 ?` (report app-id)

config.c

@@ -1139,6 +1139,8 @@ parse_section_bell(struct context *ctx)
         return value_to_bool(ctx, &conf->bell.urgent);
     else if (streq(key, "notify"))
         return value_to_bool(ctx, &conf->bell.notify);
+    else if (streq(key, "system"))
+        return value_to_bool(ctx, &conf->bell.system_bell);
     else if (streq(key, "visual"))
         return value_to_bool(ctx, &conf->bell.flash);
     else if (streq(key, "command"))
@@ -3182,6 +3184,7 @@ config_load(struct config *conf, const char *conf_path,
             .urgent = false,
             .notify = false,
             .flash = false,
+            .system_bell = true,
             .command = {
                 .argv = {.args = NULL},
             },

config.h

@@ -186,6 +186,7 @@ struct config {
         bool urgent;
         bool notify;
         bool flash;
+        bool system_bell;
         struct config_spawn_template command;
         bool command_focused;
     } bell;

doc/foot.ini.5.scd

@@ -445,10 +445,17 @@ Note: do not set *TERM* here; use the *term* option in the main
 
 # SECTION: bell
 
+*system*
+	Boolean, when set to _yes_, ring the system bell. The bell is rung
+	independent of whether the foot window has keyboard focus or
+	not. Exact behavior is compositor dependent.
+	
+	Default: _yes_
+
 *urgent*
-	When set to _yes_, foot will signal urgency to the compositor
-	through the XDG activation protocol whenever *BEL* is received,
-	and the window does NOT have keyboard focus.
+	Boolean, when set to _yes_, foot will signal urgency to the
+	compositor through the XDG activation protocol whenever *BEL* is
+	received, and the window does NOT have keyboard focus.
 	
 	If the compositor does not implement this protocol, the margins
 	will be painted in red instead.
@@ -459,25 +466,25 @@ Note: do not set *TERM* here; use the *term* option in the main
 	Default: _no_
 
 *notify*
-	When set to _yes_, foot will emit a desktop notification using the
-	command specified in the *notify* option whenever *BEL* is
-	received. By default, bell notifications are shown only when the
-	window does *not* have keyboard focus. See
+	Boolean, when set to _yes_, foot will emit a desktop notification
+	using the command specified in the *notify* option whenever *BEL*
+	is received. By default, bell notifications are shown only when
+	the window does *not* have keyboard focus. See
 	_desktop-notifications.inhibit-when-focused_.
 
 	Default: _no_
 
 *visual*
-	When set to _yes_, foot will flash the terminal window. Default:
-	_no_
+	Boolean, when set to _yes_, foot will flash the terminal
+	window. Default: _no_
 
 *command*
 	When set, foot will execute this command when *BEL* is received.
 	Default: none
 
 *command-focused*
-	Whether to run the command on *BEL* even while focused. Default:
-	_no_
+	Boolean, whether to run the command on *BEL* even while
+	focused. Default: _no_
 
 # SECTION: desktop-notifications
 

foot.ini

@@ -45,6 +45,7 @@
 # osc52=enabled  # disabled|copy-enabled|paste-enabled|enabled
 
 [bell]
+# system=yes
 # urgent=no
 # notify=no
 # visual=no

meson.build

@@ -179,6 +179,15 @@ else
   xdg_toplevel_icon = false
 endif
 
+if wayland_protocols.version().version_compare('>=1.38')
+  add_project_arguments('-DHAVE_XDG_SYSTEM_BELL', language: 'c')
+  wl_proto_xml += [wayland_protocols_datadir / 'staging/xdg-system-bell/xdg-system-bell-v1.xml']
+  xdg_system_bell = true
+else
+  xdg_system_bell = false
+endif
+
+
 foreach prot : wl_proto_xml
   wl_proto_headers += custom_target(
     prot.underscorify() + '-client-header',
@@ -414,6 +423,7 @@ summary(
     'IME': get_option('ime'),
     'Grapheme clustering': utf8proc.found(),
     'Wayland: xdg-toplevel-icon-v1': xdg_toplevel_icon,
+    'Wayland: xdg-system-bell-v1': xdg_system_bell,
     'utmp backend': utmp_backend,
     'utmp helper default path': utmp_default_helper_path,
     'Build terminfo': tic.found(),

pgo/pgo.c

@@ -101,6 +101,7 @@ wayl_win_init(struct terminal *term, const char *token)
 void wayl_win_destroy(struct wl_window *win) {}
 void wayl_win_alpha_changed(struct wl_window *win) {}
 bool wayl_win_set_urgent(struct wl_window *win) { return true; }
+bool wayl_win_ring_bell(const struct wl_window *win) { return true; }
 bool wayl_fractional_scaling(const struct wayland *wayl) { return true; }
 
 pid_t

terminal.c

@@ -3683,6 +3683,9 @@ term_bell(struct terminal *term)
         }
     }
 
+    if (term->conf->bell.system_bell)
+        wayl_win_ring_bell(term->window);
+
     if (term->conf->bell.notify) {
         notify_notify(term, &(struct notification){
             .title = xstrdup("Bell"),

tests/test-config.c

@@ -579,6 +579,7 @@ test_section_bell(void)
 
     test_boolean(&ctx, &parse_section_bell, "urgent", &conf.bell.urgent);
     test_boolean(&ctx, &parse_section_bell, "notify", &conf.bell.notify);
+    test_boolean(&ctx, &parse_section_bell, "system", &conf.bell.system_bell);
     test_boolean(&ctx, &parse_section_bell, "command-focused",
                  &conf.bell.command_focused);
     test_spawn_template(&ctx, &parse_section_bell, "command",

wayland.c

@@ -1374,6 +1374,17 @@ handle_global(void *data, struct wl_registry *registry,
     }
 #endif
 
+#if defined(HAVE_XDG_SYSTEM_BELL)
+    else if (streq(interface, xdg_system_bell_v1_interface.name)) {
+        const uint32_t required = 1;
+        if (!verify_iface_version(interface, version, required))
+            return;
+
+        wayl->system_bell = wl_registry_bind(
+            wayl->registry, name, &xdg_system_bell_v1_interface, required);
+    }
+#endif
+
 #if defined(FOOT_IME_ENABLED) && FOOT_IME_ENABLED
     else if (streq(interface, zwp_text_input_manager_v3_interface.name)) {
         const uint32_t required = 1;
@@ -1696,6 +1707,10 @@ wayl_destroy(struct wayland *wayl)
         zwp_text_input_manager_v3_destroy(wayl->text_input_manager);
 #endif
 
+#if defined(HAVE_XDG_SYSTEM_BELL)
+    if (wayl->system_bell != NULL)
+        xdg_system_bell_v1_destroy(wayl->system_bell);
+#endif
 #if defined(HAVE_XDG_TOPLEVEL_ICON)
     if (wayl->toplevel_icon_manager != NULL)
         xdg_toplevel_icon_manager_v1_destroy(wayl->toplevel_icon_manager);
@@ -2247,6 +2262,28 @@ wayl_win_set_urgent(struct wl_window *win)
     return false;
 }
 
+bool
+wayl_win_ring_bell(const struct wl_window *win)
+{
+#if defined(HAVE_XDG_SYSTEM_BELL)
+    if (win->term->wl->system_bell == NULL) {
+        static bool have_warned = false;
+
+        if (!have_warned) {
+            LOG_WARN("compositor does not implement the XDG system bell protocol");
+            have_warned = true;
+        }
+
+        return false;
+    }
+
+    xdg_system_bell_v1_ring(win->term->wl->system_bell, win->surface.surf);
+    return true;
+#else
+    return false;
+#endif
+}
+
 bool
 wayl_win_csd_titlebar_visible(const struct wl_window *win)
 {

wayland.h

@@ -24,6 +24,10 @@
  #include <xdg-toplevel-icon-v1.h>
 #endif
 
+#if defined(HAVE_XDG_SYSTEM_BELL)
+ #include <xdg-system-bell-v1.h>
+#endif
+
 #include <fcft/fcft.h>
 #include <tllist.h>
 
@@ -451,6 +455,10 @@ struct wayland {
     struct xdg_toplevel_icon_manager_v1 *toplevel_icon_manager;
 #endif
 
+#if defined(HAVE_XDG_SYSTEM_BELL)
+    struct xdg_system_bell_v1 *system_bell;
+#endif
+
     bool presentation_timings;
     struct wp_presentation *presentation;
     uint32_t presentation_clock_id;
@@ -492,6 +500,7 @@ void wayl_win_destroy(struct wl_window *win);
 void wayl_win_scale(struct wl_window *win, const struct buffer *buf);
 void wayl_win_alpha_changed(struct wl_window *win);
 bool wayl_win_set_urgent(struct wl_window *win);
+bool wayl_win_ring_bell(const struct wl_window *win);
 
 bool wayl_win_csd_titlebar_visible(const struct wl_window *win);
 bool wayl_win_csd_borders_visible(const struct wl_window *win);