bell: optionally render margins in red when receiving BEL

Add anew config option, ‘bell=none|set-urgency’. When set to
‘set-urgency’, the margins will be painted in red (if the window did
not have keyboard focus).

This is intended as a cheap replacement for the ‘urgency’ hint, that
doesn’t (yet) exist on Wayland.

Closes #157

CHANGELOG.md

@@ -21,6 +21,14 @@
   terminfo). This mode can be enabled/disabled with `CSI ? 45 h` and
   `CSI ? 45 l`. It is **enabled** by default
   (https://codeberg.org/dnkl/foot/issues/150).
+* **bell** option to `foot.ini`. Can be set to `set-urgency` to make
+  foot render the margins in red when receiving `BEL` while **not**
+  having keyboard focus. Note that Wayland does **not** implement an
+  _urgency_ hint like X11, but that there is a
+  [proposal](https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/9)
+  to add support for this. The value `set-urgency` was chosen for
+  forward-compatibility, in the hopes that this proposal eventualizes
+  (https://codeberg.org/dnkl/foot/issues/157).
 
 
 ### Changed

config.c

@@ -517,6 +517,20 @@ parse_section_main(const char *key, const char *value, struct config *conf,
         conf->pad_y = y;
     }
 
+    else if (strcmp(key, "bell") == 0) {
+        if (strcmp(value, "set-urgency") == 0)
+            conf->bell_set_urgency = true;
+        else if (strcmp(value, "none") == 0)
+            conf->bell_set_urgency = false;
+        else {
+            LOG_AND_NOTIFY_ERR(
+                "%s:%d: [default]: bell: "
+                "expected either 'set-urgency' or 'none'", path, lineno);
+            conf->bell_set_urgency = false;
+            return false;
+        }
+    }
+
     else if (strcmp(key, "initial-window-mode") == 0) {
         if (strcmp(value, "windowed") == 0)
             conf->startup_mode = STARTUP_WINDOWED;
@@ -1867,6 +1881,7 @@ config_load(struct config *conf, const char *conf_path,
         },
         .pad_x = 2,
         .pad_y = 2,
+        .bell_set_urgency = false,
         .startup_mode = STARTUP_WINDOWED,
         .fonts = tll_init(),
         .scrollback = {

config.h

@@ -72,6 +72,8 @@ struct config {
     unsigned pad_x;
     unsigned pad_y;
 
+    bool bell_set_urgency;
+
     enum { STARTUP_WINDOWED, STARTUP_MAXIMIZED, STARTUP_FULLSCREEN } startup_mode;
 
     tll(struct config_font) fonts;

csi.c

@@ -363,6 +363,7 @@ decset_decrst(struct terminal *term, unsigned param, bool enable)
         /* DECSCNM */
         term->reverse = enable;
         term_damage_all(term);
+        term_damage_margins(term);
         break;
 
     case 6: {

doc/foot.ini.5.scd

@@ -91,6 +91,22 @@ in this order:
 	(including SMT). Note that this is not always the best value. In
 	some cases, the number of physical _cores_ is better.
 
+*bell*
+	Action to perform when receiving a *BEL* character. Can be set to
+	either *set-urgency* or *none*.
+	
+	When set to *set-urgency*, the margins will be painted in red
+	whenever *BEL* is received while the window does *not* have
+	keyboard focus. Note that Wayland currently does not have an
+	_urgency_ hint like X11. The value *set-urgency* was chosen for
+	forward-compatibility in the hopes that a corresponding Wayland
+	protocol is added in the future (in which case foot will use that
+	instead of painting its margins red).
+
+	When set to *none*, no special action is taken when receiving *BEL*.
+	
+	Default: _none_.
+
 
 # SECTION: scrollback
 

foot.ini

@@ -9,6 +9,7 @@
 # term=foot
 # login-shell=no
 # workers=<number of logical CPUs>
+# bell=none
 
 [scrollback]
 # lines=1000

render.c

@@ -541,6 +541,35 @@ draw_cursor:
     return cell_cols;
 }
 
+static void
+render_urgency(struct terminal *term, struct buffer *buf)
+{
+    uint32_t red = term->colors.table[1];
+    pixman_color_t bg = color_hex_to_pixman(red);
+
+    if (term->is_searching)
+        color_dim(&bg);
+
+    int width = min(min(term->margins.left, term->margins.right),
+                    min(term->margins.top, term->margins.bottom));
+
+    pixman_image_fill_rectangles(
+        PIXMAN_OP_SRC, buf->pix[0], &bg, 4,
+        (pixman_rectangle16_t[]){
+            /* Top */
+            {0, 0, term->width, width},
+
+            /* Bottom */
+            {0, term->height - width, term->width, width},
+
+            /* Left */
+            {0, width, width, term->height - 2 * width},
+
+            /* Right */
+            {term->width - width, width, width, term->height - 2 * width},
+        });
+}
+
 static void
 render_margin(struct terminal *term, struct buffer *buf,
               int start_line, int end_line, bool apply_damage)
@@ -578,6 +607,9 @@ render_margin(struct terminal *term, struct buffer *buf,
              term->margins.right, line_count * term->cell_height},
     });
 
+    if (term->render.urgency)
+        render_urgency(term, buf);
+
     if (apply_damage) {
         /* Top */
         wl_surface_damage_buffer(

terminal.c

@@ -2073,6 +2073,12 @@ term_kbd_focus_in(struct terminal *term)
         return;
 
     term->kbd_focus = true;
+
+    if (term->render.urgency) {
+        term->render.urgency = false;
+        term_damage_margins(term);
+    }
+
     cursor_refresh(term);
 
     if (term->focus_events)
@@ -2363,6 +2369,17 @@ term_flash(struct terminal *term, unsigned duration_ms)
     }
 }
 
+void
+term_bell(struct terminal *term)
+{
+    if (term->kbd_focus || !term->conf->bell_set_urgency)
+        return;
+
+    /* There's no 'urgency' hint in Wayland - we just paint the margins red */
+    term->render.urgency = true;
+    term_damage_margins(term);
+}
+
 bool
 term_spawn_new(const struct terminal *term)
 {

terminal.h

@@ -389,6 +389,7 @@ struct terminal {
         } pending;
 
         bool margins;  /* Someone explicitly requested a refresh of the margins */
+        bool urgency;  /* Signal 'urgency' (paint borders red) */
 
         int scrollback_lines; /* Number of scrollback lines, from conf (TODO: move out from render struct?) */
 
@@ -574,6 +575,7 @@ void term_xcursor_update_for_seat(struct terminal *term, struct seat *seat);
 
 void term_set_window_title(struct terminal *term, const char *title);
 void term_flash(struct terminal *term, unsigned duration_ms);
+void term_bell(struct terminal *term);
 bool term_spawn_new(const struct terminal *term);
 
 void term_enable_app_sync_updates(struct terminal *term);

vt.c

@@ -124,8 +124,7 @@ action_execute(struct terminal *term, uint8_t c)
 
     case '\a':
         /* BEL - bell */
-        // LOG_INFO("BELL");
-        // term_flash(term, 50);
+        term_bell(term);
         break;
 
     case '\b':