Embedding game process in editor

core/config/engine.cpp

@@ -412,6 +412,14 @@ void Engine::set_freeze_time_scale(bool p_frozen) {
 	freeze_time_scale = p_frozen;
 }
 
+void Engine::set_embedded_in_editor(bool p_enabled) {
+	embedded_in_editor = p_enabled;
+}
+
+bool Engine::is_embedded_in_editor() const {
+	return embedded_in_editor;
+}
+
 Engine::Engine() {
 	singleton = this;
 }

core/config/engine.h

@@ -87,6 +87,7 @@ class Engine {
 	bool editor_hint = false;
 	bool project_manager_hint = false;
 	bool extension_reloading = false;
+	bool embedded_in_editor = false;
 
 	bool _print_header = true;
 
@@ -201,6 +202,8 @@ class Engine {
 	bool notify_frame_server_synced();
 
 	void set_freeze_time_scale(bool p_frozen);
+	void set_embedded_in_editor(bool p_enabled);
+	bool is_embedded_in_editor() const;
 
 	Engine();
 	virtual ~Engine();

core/core_bind.cpp

@@ -1897,6 +1897,10 @@ bool Engine::is_editor_hint() const {
 	return ::Engine::get_singleton()->is_editor_hint();
 }
 
+bool Engine::is_embedded_in_editor() const {
+	return ::Engine::get_singleton()->is_embedded_in_editor();
+}
+
 String Engine::get_write_movie_path() const {
 	return ::Engine::get_singleton()->get_write_movie_path();
 }
@@ -1974,6 +1978,7 @@ void Engine::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("get_script_language", "index"), &Engine::get_script_language);
 
 	ClassDB::bind_method(D_METHOD("is_editor_hint"), &Engine::is_editor_hint);
+	ClassDB::bind_method(D_METHOD("is_embedded_in_editor"), &Engine::is_embedded_in_editor);
 
 	ClassDB::bind_method(D_METHOD("get_write_movie_path"), &Engine::get_write_movie_path);
 

core/core_bind.h

@@ -584,6 +584,8 @@ class Engine : public Object {
 	void set_editor_hint(bool p_enabled);
 	bool is_editor_hint() const;
 
+	bool is_embedded_in_editor() const;
+
 	// `set_write_movie_path()` is not exposed to the scripting API as changing it at run-time has no effect.
 	String get_write_movie_path() const;
 

core/os/os.cpp

@@ -405,6 +405,8 @@ bool OS::has_feature(const String &p_feature) {
 		return _in_editor;
 	} else if (p_feature == "editor_runtime") {
 		return !_in_editor;
+	} else if (p_feature == "embedded_in_editor") {
+		return _embedded_in_editor;
 	}
 #else
 	if (p_feature == "template") {

core/os/os.h

@@ -63,6 +63,7 @@ class OS {
 	bool _stderr_enabled = true;
 	bool _writing_movie = false;
 	bool _in_editor = false;
+	bool _embedded_in_editor = false;
 
 	CompositeLogger *_logger = nullptr;
 

doc/classes/DisplayServer.xml

@@ -1895,6 +1895,9 @@
 		<constant name="FEATURE_NATIVE_DIALOG_FILE_EXTRA" value="26" enum="Feature">
 			The display server supports all features of [constant FEATURE_NATIVE_DIALOG_FILE], with the added functionality of Options and native dialog file access to [code]res://[/code] and [code]user://[/code] paths. See [method file_dialog_show] and [method file_dialog_with_options_show]. [b]Windows, macOS, Linux (X11/Wayland)[/b]
 		</constant>
+		<constant name="FEATURE_WINDOW_EMBEDDING" value="27" enum="Feature">
+			Display server supports embedding a window from another process. [b]Windows, Linux (X11)[/b]
+		</constant>
 		<constant name="MOUSE_MODE_VISIBLE" value="0" enum="MouseMode">
 			Makes the mouse cursor visible if it is hidden.
 		</constant>

doc/classes/Engine.xml

@@ -254,6 +254,12 @@
 				[b]Note:[/b] To detect whether the script is running on an editor [i]build[/i] (such as when pressing [kbd]F5[/kbd]), use [method OS.has_feature] with the [code]"editor"[/code] argument instead. [code]OS.has_feature("editor")[/code] evaluate to [code]true[/code] both when the script is running in the editor and when running the project from the editor, but returns [code]false[/code] when run from an exported project.
 			</description>
 		</method>
+		<method name="is_embedded_in_editor" qualifiers="const">
+			<return type="bool" />
+			<description>
+				Returns [code]true[/code] if the game is running embedded in the editor, otherwise returns [code]false[/code]. This is useful to prevent attempting to update window mode or window flags that are not supported when running embedded in the editor.
+			</description>
+		</method>
 		<method name="is_in_physics_frame" qualifiers="const">
 			<return type="bool" />
 			<description>

editor/editor_node.cpp

@@ -755,7 +755,9 @@ void EditorNode::_notification(int p_what) {
 			}
 
 			// Set a low FPS cap to decrease CPU/GPU usage while the editor is unfocused.
-			OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(int(EDITOR_GET("interface/editor/unfocused_low_processor_mode_sleep_usec")));
+			if (unfocused_low_processor_usage_mode_enabled) {
+				OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(int(EDITOR_GET("interface/editor/unfocused_low_processor_mode_sleep_usec")));
+			}
 		} break;
 
 		case NOTIFICATION_WM_ABOUT: {
@@ -6713,6 +6715,10 @@ int EditorNode::execute_and_show_output(const String &p_title, const String &p_p
 	return eta.exitcode;
 }
 
+void EditorNode::set_unfocused_low_processor_usage_mode_enabled(bool p_enabled) {
+	unfocused_low_processor_usage_mode_enabled = p_enabled;
+}
+
 EditorNode::EditorNode() {
 	DEV_ASSERT(!singleton);
 	singleton = this;

editor/editor_node.h

@@ -474,6 +474,8 @@ class EditorNode : public Node {
 
 	bool was_window_windowed_last = false;
 
+	bool unfocused_low_processor_usage_mode_enabled = true;
+
 	static EditorBuildCallback build_callbacks[MAX_BUILD_CALLBACKS];
 	static EditorPluginInitializeCallback plugin_init_callbacks[MAX_INIT_CALLBACKS];
 	static int build_callback_count;
@@ -788,6 +790,8 @@ class EditorNode : public Node {
 	HashMap<StringName, Variant> get_modified_properties_for_node(Node *p_node, bool p_node_references_only);
 	HashMap<StringName, Variant> get_modified_properties_reference_to_nodes(Node *p_node, List<Node *> &p_nodes_referenced_by);
 
+	void set_unfocused_low_processor_usage_mode_enabled(bool p_enabled);
+
 	struct AdditiveNodeEntry {
 		Node *node = nullptr;
 		NodePath parent;

editor/editor_run.cpp

@@ -229,6 +229,9 @@ Error EditorRun::run(const String &p_scene, const String &p_write_movie) {
 		List<String> instance_args(args);
 		RunInstancesDialog::get_singleton()->get_argument_list_for_instance(i, instance_args);
 		RunInstancesDialog::get_singleton()->apply_custom_features(i);
+		if (instance_starting_callback) {
+			instance_starting_callback(i, instance_args);
+		}
 
 		if (OS::get_singleton()->is_stdout_verbose()) {
 			print_line(vformat("Running: %s", exec));
@@ -281,6 +284,13 @@ void EditorRun::stop() {
 	running_scene = "";
 }
 
+OS::ProcessID EditorRun::get_current_process() const {
+	if (pids.is_empty()) {
+		return 0;
+	}
+	return pids.get(0);
+}
+
 EditorRun::EditorRun() {
 	status = STATUS_STOP;
 	running_scene = "";

editor/editor_run.h

@@ -32,6 +32,9 @@
 #define EDITOR_RUN_H
 
 #include "core/os/os.h"
+#include "servers/display_server.h"
+
+typedef void (*EditorRunInstanceStarting)(int p_index, List<String> &r_arguments);
 
 class EditorRun {
 public:
@@ -48,6 +51,8 @@ class EditorRun {
 	String running_scene;
 
 public:
+	inline static EditorRunInstanceStarting instance_starting_callback = nullptr;
+
 	Status get_status() const;
 	String get_running_scene() const;
 
@@ -58,6 +63,7 @@ class EditorRun {
 	void stop_child_process(OS::ProcessID p_pid);
 	bool has_child_process(OS::ProcessID p_pid) const;
 	int get_child_process_count() const { return pids.size(); }
+	OS::ProcessID get_current_process() const;
 
 	EditorRun();
 };

editor/gui/editor_run_bar.cpp

@@ -344,6 +344,10 @@ void EditorRunBar::stop_child_process(OS::ProcessID p_pid) {
 	}
 }
 
+OS::ProcessID EditorRunBar::get_current_process() const {
+	return editor_run.get_current_process();
+}
+
 void EditorRunBar::set_movie_maker_enabled(bool p_enabled) {
 	write_movie_button->set_pressed(p_enabled);
 }
@@ -356,14 +360,39 @@ HBoxContainer *EditorRunBar::get_buttons_container() {
 	return main_hbox;
 }
 
+void EditorRunBar::_instance_starting(int p_idx, List<String> &r_arguments) {
+	singleton->_instance_starting_internal(p_idx, r_arguments);
+}
+
+void EditorRunBar::_instance_starting_internal(int p_index, List<String> &r_arguments) {
+	Array arguments;
+
+	// We need to convert the an Array so it can be passed as parameter in a signal.
+	for (const String &arg : r_arguments) {
+		arguments.push_back(arg);
+	}
+
+	emit_signal(SNAME("instance_starting"), p_index, arguments);
+
+	// Copy back to a List.
+	r_arguments.clear();
+	for (const Variant &arg : arguments) {
+		r_arguments.push_back(arg);
+	}
+}
+
 void EditorRunBar::_bind_methods() {
 	ADD_SIGNAL(MethodInfo("play_pressed"));
+	ADD_SIGNAL(MethodInfo("instance_starting", PropertyInfo(Variant::INT, "index"), PropertyInfo(Variant::ARRAY, "arguments")));
 	ADD_SIGNAL(MethodInfo("stop_pressed"));
 }
 
 EditorRunBar::EditorRunBar() {
 	singleton = this;
 
+	// Callback from EditorRun to propagate the instance_starting signal.
+	editor_run.instance_starting_callback = _instance_starting;
+
 	main_panel = memnew(PanelContainer);
 	add_child(main_panel);
 

editor/gui/editor_run_bar.h

@@ -83,6 +83,9 @@ class EditorRunBar : public MarginContainer {
 	void _run_scene(const String &p_scene_path = "");
 	void _run_native(const Ref<EditorExportPreset> &p_preset);
 
+	static void _instance_starting(int p_idx, List<String> &r_arguments);
+	void _instance_starting_internal(int p_index, List<String> &r_arguments);
+
 protected:
 	void _notification(int p_what);
 	static void _bind_methods();
@@ -102,6 +105,7 @@ class EditorRunBar : public MarginContainer {
 
 	OS::ProcessID has_child_process(OS::ProcessID p_pid) const;
 	void stop_child_process(OS::ProcessID p_pid);
+	OS::ProcessID get_current_process() const;
 
 	void set_movie_maker_enabled(bool p_enabled);
 	bool is_movie_maker_enabled() const;

editor/gui/editor_scene_tabs.cpp

@@ -30,11 +30,13 @@
 
 #include "editor_scene_tabs.h"
 
+#include "editor/editor_main_screen.h"
 #include "editor/editor_node.h"
 #include "editor/editor_resource_preview.h"
 #include "editor/editor_settings.h"
 #include "editor/editor_string_names.h"
 #include "editor/editor_undo_redo_manager.h"
+#include "editor/gui/editor_run_bar.h"
 #include "editor/inspector_dock.h"
 #include "editor/themes/editor_scale.h"
 #include "scene/gui/box_container.h"
@@ -90,6 +92,14 @@ void EditorSceneTabs::_scene_tab_hovered(int p_tab) {
 	if (!bool(EDITOR_GET("interface/scene_tabs/show_thumbnail_on_hover"))) {
 		return;
 	}
+
+	// Currently the tab previews are displayed under the running game process when embed.
+	// Right now, the easiest technique to fix that is to prevent displaying the tab preview
+	// when the user is in the Game View.
+	if (EditorNode::get_singleton()->get_editor_main_screen()->get_selected_index() == EditorMainScreen::EDITOR_GAME && EditorRunBar::get_singleton()->is_playing()) {
+		return;
+	}
+
 	int current_tab = scene_tabs->get_current_tab();
 
 	if (p_tab == current_tab || p_tab < 0) {