Toggle fullscreen mode when pressing Alt + Enter by default

Alt + Enter is a widely followed convention to toggle fullscreen.
This adds support for it both in the editor and projects, as long
as the window is configured to be resizable.

The rationale for providing this feature in all projects is that
many developers don't bother about adding a fullscreen toggle,
especially for smaller/gamejam games. Yet, this convention is
followed by many popular games out there, including AAA games.

The shortcut can be modified or disabled by editing the Input Map
in the Project Settings.

core/config/project_settings.cpp

@@ -1282,6 +1282,7 @@ ProjectSettings::ProjectSettings() {
 	GLOBAL_DEF("display/window/size/transparent", false);
 	GLOBAL_DEF("display/window/size/extend_to_title", false);
 	GLOBAL_DEF("display/window/size/no_focus", false);
+	GLOBAL_DEF("display/window/size/enable_toggle_fullscreen_shortcut", true);
 
 	GLOBAL_DEF(PropertyInfo(Variant::INT, "display/window/size/window_width_override", PROPERTY_HINT_RANGE, "0,7680,1,or_greater"), 0); // 8K resolution
 	GLOBAL_DEF(PropertyInfo(Variant::INT, "display/window/size/window_height_override", PROPERTY_HINT_RANGE, "0,4320,1,or_greater"), 0); // 8K resolution

core/input/input_map.cpp

@@ -351,6 +351,7 @@ static const _BuiltinActionDisplayName _builtin_action_display_names[] = {
     { "ui_filedialog_refresh",                         TTRC("Refresh") },
     { "ui_filedialog_show_hidden",                     TTRC("Show Hidden") },
     { "ui_swap_input_direction ",                      TTRC("Swap Input Direction") },
+    { "ui_toggle_fullscreen",                          TTRC("Toggle Fullscreen") },
     { "",                                              ""}
 	/* clang-format on */
 };
@@ -720,6 +721,11 @@ const HashMap<String, List<Ref<InputEvent>>> &InputMap::get_builtins() {
 	inputs.push_back(InputEventKey::create_reference(Key::QUOTELEFT | KeyModifierMask::CMD_OR_CTRL));
 	default_builtin_cache.insert("ui_swap_input_direction", inputs);
 
+	// ///// Miscellaneous Shortcuts /////
+	inputs = List<Ref<InputEvent>>();
+	inputs.push_back(InputEventKey::create_reference(Key::ENTER | KeyModifierMask::ALT));
+	default_builtin_cache.insert("ui_toggle_fullscreen", inputs);
+
 	return default_builtin_cache;
 }
 

main/main.cpp

@@ -1746,6 +1746,9 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 			}
 		}
 
+		if (!bool(GLOBAL_GET("display/window/size/enable_toggle_fullscreen_shortcut"))) {
+			window_flags |= DisplayServer::WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED_BIT;
+		}
 		if (!bool(GLOBAL_GET("display/window/size/resizable"))) {
 			window_flags |= DisplayServer::WINDOW_FLAG_RESIZE_DISABLED_BIT;
 		}

scene/main/window.cpp

@@ -1383,6 +1383,18 @@ void Window::_window_input(const Ref<InputEvent> &p_ev) {
 		emit_signal(SceneStringNames::get_singleton()->window_input, p_ev);
 	}
 
+	print_line(flags[FLAG_FULLSCREEN_TOGGLE_ENABLED]);
+	if (flags[FLAG_FULLSCREEN_TOGGLE_ENABLED] && p_ev->is_action_pressed("ui_toggle_fullscreen")) {
+		if (mode == MODE_FULLSCREEN || mode == MODE_EXCLUSIVE_FULLSCREEN) {
+			print_line("Going to previous mode: ", itos(toggle_fullscreen_previous_mode));
+			set_mode(toggle_fullscreen_previous_mode);
+		} else {
+			print_line("Going fullscreen");
+			toggle_fullscreen_previous_mode = mode;
+			set_mode(MODE_FULLSCREEN);
+		}
+	}
+
 	if (is_inside_tree()) {
 		push_input(p_ev);
 	}
@@ -2456,6 +2468,7 @@ void Window::_bind_methods() {
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "popup_window"), "set_flag", "get_flag", FLAG_POPUP);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "extend_to_title"), "set_flag", "get_flag", FLAG_EXTEND_TO_TITLE);
 	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "mouse_passthrough"), "set_flag", "get_flag", FLAG_MOUSE_PASSTHROUGH);
+	ADD_PROPERTYI(PropertyInfo(Variant::BOOL, "fullscreen_shortcut_enabled"), "set_flag", "get_flag", FLAG_FULLSCREEN_TOGGLE_ENABLED);
 
 	ADD_GROUP("Limits", "");
 	ADD_PROPERTY(PropertyInfo(Variant::VECTOR2I, "min_size", PROPERTY_HINT_NONE, "suffix:px"), "set_min_size", "get_min_size");
@@ -2505,6 +2518,7 @@ void Window::_bind_methods() {
 	BIND_ENUM_CONSTANT(FLAG_POPUP);
 	BIND_ENUM_CONSTANT(FLAG_EXTEND_TO_TITLE);
 	BIND_ENUM_CONSTANT(FLAG_MOUSE_PASSTHROUGH);
+	BIND_ENUM_CONSTANT(FLAG_FULLSCREEN_TOGGLE_ENABLED);
 	BIND_ENUM_CONSTANT(FLAG_MAX);
 
 	BIND_ENUM_CONSTANT(CONTENT_SCALE_MODE_DISABLED);

scene/main/window.h

@@ -60,6 +60,7 @@ class Window : public Viewport {
 		FLAG_POPUP = DisplayServer::WINDOW_FLAG_POPUP,
 		FLAG_EXTEND_TO_TITLE = DisplayServer::WINDOW_FLAG_EXTEND_TO_TITLE,
 		FLAG_MOUSE_PASSTHROUGH = DisplayServer::WINDOW_FLAG_MOUSE_PASSTHROUGH,
+		FLAG_FULLSCREEN_TOGGLE_ENABLED = DisplayServer::WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED,
 		FLAG_MAX = DisplayServer::WINDOW_FLAG_MAX,
 	};
 
@@ -109,12 +110,14 @@ class Window : public Viewport {
 	mutable Size2i max_size;
 	mutable Vector<Vector2> mpath;
 	mutable Mode mode = MODE_WINDOWED;
+	mutable Mode toggle_fullscreen_previous_mode = mode;
 	mutable bool flags[FLAG_MAX] = {};
 	bool visible = true;
 	bool focused = false;
 	WindowInitialPosition initial_position = WINDOW_INITIAL_POSITION_ABSOLUTE;
 
 	bool use_font_oversampling = false;
+	bool fullscreen_shortcut_enabled = false;
 	bool transient = false;
 	bool exclusive = false;
 	bool wrap_controls = false;

servers/display_server.cpp

@@ -853,6 +853,7 @@ void DisplayServer::_bind_methods() {
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_POPUP);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_EXTEND_TO_TITLE);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_MOUSE_PASSTHROUGH);
+	BIND_ENUM_CONSTANT(WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED);
 	BIND_ENUM_CONSTANT(WINDOW_FLAG_MAX);
 
 	BIND_ENUM_CONSTANT(WINDOW_EVENT_MOUSE_ENTER);

servers/display_server.h

@@ -338,6 +338,7 @@ class DisplayServer : public Object {
 		WINDOW_FLAG_POPUP,
 		WINDOW_FLAG_EXTEND_TO_TITLE,
 		WINDOW_FLAG_MOUSE_PASSTHROUGH,
+		WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED,
 		WINDOW_FLAG_MAX,
 	};
 
@@ -351,6 +352,7 @@ class DisplayServer : public Object {
 		WINDOW_FLAG_POPUP_BIT = (1 << WINDOW_FLAG_POPUP),
 		WINDOW_FLAG_EXTEND_TO_TITLE_BIT = (1 << WINDOW_FLAG_EXTEND_TO_TITLE),
 		WINDOW_FLAG_MOUSE_PASSTHROUGH_BIT = (1 << WINDOW_FLAG_MOUSE_PASSTHROUGH),
+		WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED_BIT = (1 << WINDOW_FLAG_FULLSCREEN_TOGGLE_ENABLED),
 	};
 
 	virtual WindowID create_sub_window(WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Rect2i &p_rect = Rect2i());