rootston: wire up window alpha keybinding

rootston/desktop.c

@@ -278,6 +278,15 @@ void view_rotate(struct roots_view *view, float rotation) {
 	view_damage_whole(view);
 }
 
+void view_cycle_alpha(struct roots_view *view) {
+	view->alpha -= 0.05;
+	/* Don't go completely transparent */
+	if (view->alpha < 0.1) {
+		view->alpha = 1.0;
+	}
+	view_damage_whole(view);
+}
+
 void view_close(struct roots_view *view) {
 	if (view->close) {
 		view->close(view);

rootston/keyboard.c

@@ -106,6 +106,11 @@ static void keyboard_binding_execute(struct roots_keyboard *keyboard,
 		}
 	} else if (strcmp(command, "next_window") == 0) {
 		roots_seat_cycle_focus(seat);
+	} else if (strcmp(command, "alpha") == 0) {
+		struct roots_view *focus = roots_seat_get_focus(seat);
+		if (focus != NULL) {
+			view_cycle_alpha(focus);
+		}
 	} else if (strncmp(exec_prefix, command, strlen(exec_prefix)) == 0) {
 		const char *shell_cmd = command + strlen(exec_prefix);
 		pid_t pid = fork();

rootston/rootston.ini.example

@@ -42,8 +42,10 @@ meta-key = Logo
 # - "exec" to execute a shell command
 # - "close" to close the current view
 # - "next_window" to cycle through windows
+# - "alpha" to cycle a window's alpha channel
 [bindings]
 Logo+Shift+e = exit
 Logo+q = close
 Logo+m = maximize
 Alt+Tab = next_window
+Ctrl+Shift+a = alpha