[Editor] Disable embedded mode, if --headless is in the main instance argument list.

Author: bruvzg

editor/run/game_view_plugin.cpp

@@ -44,6 +44,7 @@
 #include "editor/gui/window_wrapper.h"
 #include "editor/run/editor_run_bar.h"
 #include "editor/run/embedded_process.h"
+#include "editor/run/run_instances_dialog.h"
 #include "editor/settings/editor_feature_profile.h"
 #include "editor/settings/editor_settings.h"
 #include "editor/themes/editor_scale.h"
@@ -672,6 +673,14 @@ GameView::EmbedAvailability GameView::_get_embed_available() {
 		return EMBED_NOT_AVAILABLE_PROJECT_DISPLAY_DRIVER;
 	}
 
+	if (RunInstancesDialog::get_singleton()) {
+		List<String> instance_args;
+		RunInstancesDialog::get_singleton()->get_argument_list_for_instance(0, instance_args);
+		if (instance_args.find("--headless")) {
+			return EMBED_NOT_AVAILABLE_HEADLESS;
+		}
+	}
+
 	EditorRun::WindowPlacement placement = EditorRun::get_window_placement();
 	if (placement.force_fullscreen) {
 		return EMBED_NOT_AVAILABLE_FULLSCREEN;
@@ -731,6 +740,9 @@ void GameView::_update_ui() {
 		case EMBED_NOT_AVAILABLE_SINGLE_WINDOW_MODE:
 			state_label->set_text(TTRC("Game embedding not available in single window mode."));
 			break;
+		case EMBED_NOT_AVAILABLE_HEADLESS:
+			state_label->set_text(TTRC("Game embedding not available when the game starts in headless mode."));
+			break;
 	}
 
 	if (available == EMBED_AVAILABLE) {

editor/run/game_view_plugin.h

@@ -129,6 +129,7 @@ class GameView : public VBoxContainer {
 		EMBED_NOT_AVAILABLE_FULLSCREEN,
 		EMBED_NOT_AVAILABLE_SINGLE_WINDOW_MODE,
 		EMBED_NOT_AVAILABLE_PROJECT_DISPLAY_DRIVER,
+		EMBED_NOT_AVAILABLE_HEADLESS,
 	};
 
 	inline static GameView *singleton = nullptr;