Add editor setting for AcceptDialog OK/Cancel buttons positioning

The position (left/right) of the Cancel and OK buttons in AcceptDialog
are DisplayServer specific, as Windows uses OK/Cancel and macOS uses Cancel/OK.

Linux/X11 currently uses the macOS convention which is also the GTK+/GNOME one,
though it's not consistent with Qt/KDE applications which follow the Windows
convention.

Since that can't satisfy everyone, it's best if it's configurable also for the
editor (it's already configurable for the project).

Fixes #59379.

editor/editor_node.cpp

@@ -6181,10 +6181,17 @@ EditorNode::EditorNode() {
 	// Define a minimum window size to prevent UI elements from overlapping or being cut off.
 	DisplayServer::get_singleton()->window_set_min_size(Size2(1024, 600) * EDSCALE);
 
-	ResourceLoader::set_abort_on_missing_resources(false);
 	FileDialog::set_default_show_hidden_files(EditorSettings::get_singleton()->get("filesystem/file_dialog/show_hidden_files"));
 	EditorFileDialog::set_default_show_hidden_files(EditorSettings::get_singleton()->get("filesystem/file_dialog/show_hidden_files"));
 	EditorFileDialog::set_default_display_mode((EditorFileDialog::DisplayMode)EditorSettings::get_singleton()->get("filesystem/file_dialog/display_mode").operator int());
+
+	int swap_cancel_ok = EDITOR_GET("interface/editor/accept_dialog_cancel_ok_buttons");
+	if (swap_cancel_ok != 0) { // 0 is auto, set in register_scene based on DisplayServer.
+		// Swap on means OK first.
+		AcceptDialog::set_swap_cancel_ok(swap_cancel_ok == 2);
+	}
+
+	ResourceLoader::set_abort_on_missing_resources(false);
 	ResourceLoader::set_error_notify_func(this, _load_error_notify);
 	ResourceLoader::set_dependency_error_notify_func(this, _dependency_error_report);
 

editor/editor_settings.cpp

@@ -438,6 +438,9 @@ void EditorSettings::_load_defaults(Ref<ConfigFile> p_extra_config) {
 	EDITOR_SETTING_USAGE(Variant::BOOL, PROPERTY_HINT_NONE, "interface/editor/single_window_mode", false, "", PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED)
 	_initial_set("interface/editor/mouse_extra_buttons_navigate_history", true);
 	_initial_set("interface/editor/save_each_scene_on_quit", true); // Regression
+	EDITOR_SETTING_USAGE(Variant::INT, PROPERTY_HINT_ENUM, "interface/editor/accept_dialog_cancel_ok_buttons", 0,
+			vformat("Auto (%s),Cancel First,OK First", DisplayServer::get_singleton()->get_swap_cancel_ok() ? "OK First" : "Cancel First"),
+			PROPERTY_USAGE_DEFAULT | PROPERTY_USAGE_RESTART_IF_CHANGED);
 #ifdef DEV_ENABLED
 	EDITOR_SETTING(Variant::INT, PROPERTY_HINT_ENUM, "interface/editor/show_internal_errors_in_toast_notifications", 0, "Auto (Enabled),Enabled,Disabled")
 #else

editor/project_manager.cpp

@@ -2594,6 +2594,12 @@ ProjectManager::ProjectManager() {
 
 	EditorFileDialog::set_default_show_hidden_files(EditorSettings::get_singleton()->get("filesystem/file_dialog/show_hidden_files"));
 
+	int swap_cancel_ok = EDITOR_GET("interface/editor/accept_dialog_cancel_ok_buttons");
+	if (swap_cancel_ok != 0) { // 0 is auto, set in register_scene based on DisplayServer.
+		// Swap on means OK first.
+		AcceptDialog::set_swap_cancel_ok(swap_cancel_ok == 2);
+	}
+
 	set_anchors_and_offsets_preset(Control::PRESET_FULL_RECT);
 	set_theme(create_custom_theme());