Fix Embed Game not available when multi window is disabled

doc/classes/EditorSettings.xml

@@ -887,6 +887,7 @@
 			If [code]true[/code], embed modal windows such as docks inside the main editor window. When single-window mode is enabled, tooltips will also be embedded inside the main editor window, which means they can't be displayed outside of the editor window. Single-window mode can be faster as it does not need to create a separate window for every popup and tooltip, which can be a slow operation depending on the operating system and rendering method in use.
 			This is equivalent to [member ProjectSettings.display/window/subwindows/embed_subwindows] in the running project, except the setting's value is inverted.
 			[b]Note:[/b] To query whether the editor can use multiple windows in an editor plugin, use [method EditorInterface.is_multi_window_enabled] instead of querying the value of this editor setting.
+			[b]Note:[/b] If [code]true[/code], game embedding is disabled.
 		</member>
 		<member name="interface/editor/ui_layout_direction" type="int" setter="" getter="">
 			Editor UI default layout direction.
@@ -971,7 +972,7 @@
 			If [code]true[/code], display OpenType features marked as [code]hidden[/code] by the font file in the [Font] editor.
 		</member>
 		<member name="interface/multi_window/enable" type="bool" setter="" getter="">
-			If [code]true[/code], multiple window support in editor is enabled. The following panels can become dedicated windows (i.e. made floating): Docks, Script editor, and Shader editor.
+			If [code]true[/code], multiple window support in editor is enabled. The following panels can become dedicated windows (i.e. made floating): Docks, Script editor, Shader editor, and Game Workspace.
 			[b]Note:[/b] When [member interface/editor/single_window_mode] is [code]true[/code], the multi window support is always disabled.
 			[b]Note:[/b] To query whether the editor can use multiple windows in an editor plugin, use [method EditorInterface.is_multi_window_enabled] instead of querying the value of this editor setting.
 		</member>
@@ -1148,6 +1149,7 @@
 		</member>
 		<member name="run/window_placement/rect" type="int" setter="" getter="">
 			The window mode to use to display the project when starting the project from the editor.
+			[b]Note:[/b] Game embedding is not available for "Force Maximized" or "Force Fullscreen."
 		</member>
 		<member name="run/window_placement/rect_custom_position" type="Vector2" setter="" getter="">
 			The custom position to use when starting the project from the editor (in pixels from the top-left corner). Only effective if [member run/window_placement/rect] is set to [b]Custom Position[/b].

doc/classes/ProjectSettings.xml

@@ -879,6 +879,7 @@
 		</member>
 		<member name="display/window/size/mode" type="int" setter="" getter="" default="0">
 			Main window mode. See [enum DisplayServer.WindowMode] for possible values and how each mode behaves.
+			[b]Note:[/b] Game embedding is available only in the "Windowed" mode.
 		</member>
 		<member name="display/window/size/no_focus" type="bool" setter="" getter="" default="false">
 			Main window can't be focused. No-focus window will ignore all input, except mouse clicks.

editor/plugins/game_view_plugin.cpp

@@ -223,7 +223,7 @@ void GameView::_instance_starting(int p_idx, List<String> &r_arguments) {
 	if (!is_feature_enabled) {
 		return;
 	}
-	if (p_idx == 0 && embed_on_play && make_floating_on_play && !window_wrapper->get_window_enabled() && _get_embed_available() == EMBED_AVAILABLE) {
+	if (p_idx == 0 && embed_on_play && make_floating_on_play && window_wrapper->is_window_available() && !window_wrapper->get_window_enabled() && _get_embed_available() == EMBED_AVAILABLE) {
 		// Set the Floating Window default title. Always considered in DEBUG mode, same as in Window::set_title.
 		String appname = GLOBAL_GET("application/config/name");
 		appname = vformat("%s (DEBUG)", TranslationServer::get_singleton()->translate(appname));
@@ -431,7 +431,7 @@ GameView::EmbedAvailability GameView::_get_embed_available() {
 	if (!DisplayServer::get_singleton()->has_feature(DisplayServer::FEATURE_WINDOW_EMBEDDING)) {
 		return EMBED_NOT_AVAILABLE_FEATURE_NOT_SUPPORTED;
 	}
-	if (!EditorNode::get_singleton()->is_multi_window_enabled()) {
+	if (get_tree()->get_root()->is_embedding_subwindows()) {
 		return EMBED_NOT_AVAILABLE_SINGLE_WINDOW_MODE;
 	}
 
@@ -505,11 +505,12 @@ void GameView::_update_ui() {
 }
 
 void GameView::_update_embed_menu_options() {
+	bool is_multi_window = window_wrapper->is_window_available();
 	PopupMenu *menu = embed_options_menu->get_popup();
 	menu->set_item_checked(menu->get_item_index(EMBED_RUN_GAME_EMBEDDED), embed_on_play);
-	menu->set_item_checked(menu->get_item_index(EMBED_MAKE_FLOATING_ON_PLAY), make_floating_on_play);
+	menu->set_item_checked(menu->get_item_index(EMBED_MAKE_FLOATING_ON_PLAY), make_floating_on_play && is_multi_window);
 
-	menu->set_item_disabled(menu->get_item_index(EMBED_MAKE_FLOATING_ON_PLAY), !embed_on_play);
+	menu->set_item_disabled(menu->get_item_index(EMBED_MAKE_FLOATING_ON_PLAY), !embed_on_play || !is_multi_window);
 
 	fixed_size_button->set_pressed(embed_size_mode == SIZE_MODE_FIXED);
 	keep_aspect_button->set_pressed(embed_size_mode == SIZE_MODE_KEEP_ASPECT);