Enable the use of flash as visual bell

With this patch we can configure flash in the bell section. The colors
section allow now to configure the color and translucency of the
flash.

CHANGELOG.md

@@ -74,10 +74,13 @@
   - `scrollback-down-page` (shift+page-down)
   - `scrollback-down-half-page` (none)
   - `scrollback-down-line` (none)
+* Support for visual bell which flashes the terminal window.
+  ([#1508][1508]).
 
 [1077]: https://codeberg.org/dnkl/foot/issues/1077
 [1364]: https://codeberg.org/dnkl/foot/issues/1364
 [419]: https://codeberg.org/dnkl/foot/issues/419
+[1508]: https://codeberg.org/dnkl/foot/issues/1508
 
 
 ### Changed

config.c

@@ -1054,6 +1054,8 @@ parse_section_bell(struct context *ctx)
         return value_to_bool(ctx, &conf->bell.urgent);
     else if (strcmp(key, "notify") == 0)
         return value_to_bool(ctx, &conf->bell.notify);
+    else if (strcmp(key, "visual") == 0)
+        return value_to_bool(ctx, &conf->bell.flash);
     else if (strcmp(key, "command") == 0)
         return value_to_spawn_template(ctx, &conf->bell.command);
     else if (strcmp(key, "command-focused") == 0)
@@ -1237,6 +1239,7 @@ parse_section_colors(struct context *ctx)
         return true;
     }
 
+    else if (strcmp(key, "flash") == 0) color = &conf->colors.flash;
     else if (strcmp(key, "foreground") == 0) color = &conf->colors.fg;
     else if (strcmp(key, "background") == 0) color = &conf->colors.bg;
     else if (strcmp(key, "selection-foreground") == 0) color = &conf->colors.selection_fg;
@@ -1320,6 +1323,21 @@ parse_section_colors(struct context *ctx)
         return true;
     }
 
+    else if (strcmp(key, "flash-alpha") == 0) {
+        float alpha;
+        if (!value_to_float(ctx, &alpha))
+            return false;
+
+        if (alpha < 0. || alpha > 1.) {
+            LOG_CONTEXTUAL_ERR("not in range 0.0-1.0");
+            return false;
+        }
+
+        conf->colors.flash_alpha = alpha * 65535.;
+        return true;
+    }
+
+
     else {
         LOG_CONTEXTUAL_ERR("not valid option");
         return false;
@@ -2980,6 +2998,7 @@ config_load(struct config *conf, const char *conf_path,
         .bell = {
             .urgent = false,
             .notify = false,
+            .flash = false,
             .command = {
                 .argv = {.args = NULL},
             },
@@ -3003,6 +3022,8 @@ config_load(struct config *conf, const char *conf_path,
         .colors = {
             .fg = default_foreground,
             .bg = default_background,
+            .flash = 0x7f7f00,
+            .flash_alpha = 0x7fff,
             .alpha = 0xffff,
             .selection_fg = 0x80000000,  /* Use default bg */
             .selection_bg = 0x80000000,  /* Use default fg */

config.h

@@ -160,6 +160,7 @@ struct config {
     struct {
         bool urgent;
         bool notify;
+        bool flash;
         struct config_spawn_template command;
         bool command_focused;
     } bell;
@@ -202,6 +203,8 @@ struct config {
     struct {
         uint32_t fg;
         uint32_t bg;
+        uint32_t flash;
+        uint32_t flash_alpha;
         uint32_t table[256];
         uint16_t alpha;
         uint32_t selection_fg;

doc/foot.ini.5.scd

@@ -394,6 +394,11 @@ Note: do not set *TERM* here; use the *term* option in the main
 
 	Default: _no_
 
+*visual*
+	When set to _yes_, foot will flash terminal window.
+
+	Default: _no_
+
 *command*
 	When set, foot will execute this command when *BEL* is received.
 	Default: none
@@ -609,6 +614,17 @@ can configure the background transparency with the _alpha_ option.
 	https://en.wikipedia.org/wiki/ANSI_escape_code#8-bit for an
 	explanation of the remainder.
 
+*flash*
+	Color to use for the terminal window flash.
+
+	Default: _7f7f00_.
+
+*flash_alpha*
+	Flash translucency. A value in the range 0.0-1.0, where 0.0
+	means completely transparent, and 1.0 is opaque.
+
+	Default: _0.5_.
+
 *alpha*
 	Background translucency. A value in the range 0.0-1.0, where 0.0
 	means completely transparent, and 1.0 is opaque. Default: _1.0_.

foot.ini

@@ -43,6 +43,7 @@
 [bell]
 # urgent=no
 # notify=no
+# visual=no
 # command=
 # command-focused=no
 
@@ -77,6 +78,8 @@
 # alpha=1.0
 # background=242424
 # foreground=ffffff
+# flash=7f7f00
+# flash_alpha=0.5
 
 ## Normal/regular colors (color palette 0-7)
 # regular0=242424  # black

render.c

@@ -1588,7 +1588,9 @@ render_overlay(struct terminal *term)
         break;
 
     case OVERLAY_FLASH:
-        color = (pixman_color_t){.red=0x7fff, .green=0x7fff, .blue=0, .alpha=0x7fff};
+        color = color_hex_to_pixman_with_alpha(
+                term->conf->colors.flash,
+                term->conf->colors.flash_alpha);
         break;
     }
 
@@ -2193,7 +2195,7 @@ render_csd_button_maximize_maximized(
             { x_margin + shrink, y_margin + thick, thick, width - 2 * thick - shrink },
             { x_margin + width - thick - shrink, y_margin + thick, thick, width - 2 * thick - shrink },
             { x_margin + shrink, y_margin + width - thick - shrink, width - 2 * shrink, thick }});
-    
+
     pixman_image_unref(src);
 
 }

terminal.c

@@ -1170,6 +1170,8 @@ term_init(const struct config *conf, struct fdm *fdm, struct reaper *reaper,
         .colors = {
             .fg = conf->colors.fg,
             .bg = conf->colors.bg,
+            .flash = conf->colors.flash,
+            .flash_alpha = conf->colors.flash_alpha,
             .alpha = conf->colors.alpha,
             .selection_fg = conf->colors.selection_fg,
             .selection_bg = conf->colors.selection_bg,
@@ -1922,7 +1924,9 @@ term_reset(struct terminal *term, bool hard)
     fdm_del(term->fdm, term->blink.fd); term->blink.fd = -1;
     term->colors.fg = term->conf->colors.fg;
     term->colors.bg = term->conf->colors.bg;
+    term->colors.flash = term->conf->colors.flash;
     term->colors.alpha = term->conf->colors.alpha;
+    term->colors.flash_alpha = term->conf->colors.flash_alpha;
     term->colors.selection_fg = term->conf->colors.selection_fg;
     term->colors.selection_bg = term->conf->colors.selection_bg;
     term->colors.use_custom_selection = term->conf->colors.use_custom.selection;
@@ -3270,6 +3274,7 @@ term_flash(struct terminal *term, unsigned duration_ms)
 void
 term_bell(struct terminal *term)
 {
+
     if (!term->bell_action_enabled)
         return;
 
@@ -3288,6 +3293,9 @@ term_bell(struct terminal *term)
     if (term->conf->bell.notify)
         notify_notify(term, "Bell", "Bell in terminal");
 
+    if (term->conf->bell.flash)
+        term_flash(term, 100);
+
     if ((term->conf->bell.command.argv.args != NULL) &&
         (!term->kbd_focus || term->conf->bell.command_focused))
     {

terminal.h

@@ -508,6 +508,8 @@ struct terminal {
     struct {
         uint32_t fg;
         uint32_t bg;
+        uint32_t flash;
+        uint32_t flash_alpha;
         uint32_t table[256];
         uint16_t alpha;
         uint32_t selection_fg;