Add option to change terminal alpha through key-bindings

config.c

@@ -104,6 +104,9 @@ static const char *const binding_action_map[] = {
     [BIND_ACTION_FONT_SIZE_UP] = "font-increase",
     [BIND_ACTION_FONT_SIZE_DOWN] = "font-decrease",
     [BIND_ACTION_FONT_SIZE_RESET] = "font-reset",
+    [BIND_ACTION_ALPHA_UP] = "alpha-increase",
+    [BIND_ACTION_ALPHA_DOWN] = "alpha-decrease",
+    [BIND_ACTION_ALPHA_RESET] = "alpha-reset",
     [BIND_ACTION_SPAWN_TERMINAL] = "spawn-terminal",
     [BIND_ACTION_MINIMIZE] = "minimize",
     [BIND_ACTION_MAXIMIZE] = "maximize",

doc/foot.ini.5.scd

@@ -714,6 +714,15 @@ e.g. *search-start=none*.
 *font-reset*
 	Resets the font size to the default. Default: _Control+0 Control+KP\_0_.
 
+*alpha-increase*
+	Increases alpha by 5%. Default: _not_bound_.
+
+*alpha-decrease*
+	Decreases alpha by 5%. Default: _not_bound_.
+
+*alpha-reset*
+	Resets alpha to the default. Default: _not_bound_.
+
 *spawn-terminal*
 	Spawns a new terminal. If the shell has been configured to emit
 	the OSC 7 escape sequence, the new terminal will start in the

foot.ini

@@ -133,6 +133,9 @@
 # font-increase=Control+plus Control+equal Control+KP_Add
 # font-decrease=Control+minus Control+KP_Subtract
 # font-reset=Control+0 Control+KP_0
+# alpha-increase=none
+# alpha-decrease=none
+# alpha-reset=none
 # spawn-terminal=Control+Shift+n
 # minimize=none
 # maximize=none

input.c

@@ -178,6 +178,18 @@ execute_binding(struct seat *seat, struct terminal *term,
         term_font_size_reset(term);
         return true;
 
+    case BIND_ACTION_ALPHA_UP:
+        term_alpha_increase(term);
+        return true;
+
+    case BIND_ACTION_ALPHA_DOWN:
+        term_alpha_decrease(term);
+        return true;
+
+    case BIND_ACTION_ALPHA_RESET:
+        term_alpha_reset(term);
+        return true;
+
     case BIND_ACTION_SPAWN_TERMINAL:
         term_spawn_new(term);
         return true;

key-binding.h

@@ -25,6 +25,9 @@ enum bind_action_normal {
     BIND_ACTION_FONT_SIZE_UP,
     BIND_ACTION_FONT_SIZE_DOWN,
     BIND_ACTION_FONT_SIZE_RESET,
+    BIND_ACTION_ALPHA_UP,
+    BIND_ACTION_ALPHA_DOWN,
+    BIND_ACTION_ALPHA_RESET,
     BIND_ACTION_SPAWN_TERMINAL,
     BIND_ACTION_MINIMIZE,
     BIND_ACTION_MAXIMIZE,

terminal.c

@@ -2005,6 +2005,27 @@ term_font_size_reset(struct terminal *term)
     return load_fonts_from_conf(term);
 }
 
+bool
+term_alpha_increase(struct terminal *term)
+{
+    term->colors.alpha += 0.05;
+    return true;
+}
+
+bool
+term_alpha_decrease(struct terminal *term)
+{
+    term->colors.alpha -= 0.05;
+    return true;
+}
+
+bool
+term_alpha_reset(struct terminal *term)
+{
+    term->colors.alpha = term->conf->colors.alpha;
+    return true;
+}
+
 bool
 term_font_dpi_changed(struct terminal *term, int old_scale)
 {

terminal.h

@@ -692,6 +692,9 @@ bool term_paste_data_to_slave(
 bool term_font_size_increase(struct terminal *term);
 bool term_font_size_decrease(struct terminal *term);
 bool term_font_size_reset(struct terminal *term);
+bool term_alpha_increase(struct terminal *term);
+bool term_alpha_decrease(struct terminal *term);
+bool term_alpha_reset(struct terminal *term);
 bool term_font_dpi_changed(struct terminal *term, int old_scale);
 void term_font_subpixel_changed(struct terminal *term);