Quit Engine by closing the root page

When the root page gets closed the engine quits instead or crashing.
The root pages are changed to use that mechanism to quit the engine.
This removes the need of `Engine.Exit` for the GUI.

binaries/data/mods/mod/gui/modmod/modmod.js

@@ -85,6 +85,10 @@ function init(data, hotloadData)
 	initGUIButtons(data);
 	if (g_HasIncompatibleMods)
 		Engine.OpenChildPage("page_incompatible_mods.xml", {});
+
+	return new Promise(closePageCallback => {
+		Engine.GetGUIObjectByName("quitButton").onPress = closePageCallback;
+	});
 }
 
 function initMods()

binaries/data/mods/mod/gui/modmod/modmod.xml

@@ -190,7 +190,6 @@
 		<!-- BUTTONS -->
 		<object name="quitButton" type="button" style="ModernButtonRed" size="100%-932 100%-44 100%-752 100%-16">
 			<translatableAttribute id="caption">Quit</translatableAttribute>
-			<action on="Press">Engine.Exit();</action>
 		</object>
 
 		<object name="cancelButton" type="button" style="ModernButtonRed" size="100%-932 100%-44 100%-752 100%-16" hotkey="cancel">

binaries/data/mods/public/gui/pregame/MainMenuItemHandler.js

@@ -4,8 +4,9 @@
  */
 class MainMenuItemHandler
 {
-	constructor(menuItems)
+	constructor(closePageCallback, menuItems)
 	{
+		this.closePageCallback = closePageCallback;
 		this.menuItems = menuItems;
 		this.lastTickTime = Date.now();
 
@@ -74,7 +75,7 @@ class MainMenuItemHandler
 		this.lastOpenItem = item;
 
 		if (item.onPress)
-			item.onPress();
+			item.onPress(this.closePageCallback);
 		else
 			this.openSubmenu(i);
 	}

binaries/data/mods/public/gui/pregame/MainMenuItems.js

@@ -287,7 +287,7 @@ var g_MainMenuItems = [
 	{
 		"caption": translate("Exit"),
 		"tooltip": translate("Exit the game."),
-		"onPress": async() => {
+		"onPress": async(closePageCallback) => {
 			const buttonIndex = await messageBox(
 				400, 200,
 				translate("Are you sure you want to quit 0 A.D.?"),
@@ -295,7 +295,7 @@ var g_MainMenuItems = [
 				[translate("No"), translate("Yes")]);
 
 			if (buttonIndex === 1)
-				Engine.Exit();
+				closePageCallback();
 		}
 	}
 ];

binaries/data/mods/public/gui/pregame/MainMenuPage.js

@@ -3,10 +3,11 @@
  */
 class MainMenuPage
 {
-	constructor(data, hotloadData, mainMenuItems, backgroundLayerData, projectInformation, communityButtons)
+	constructor(closePageCallback, data, hotloadData, mainMenuItems, backgroundLayerData,
+		projectInformation, communityButtons)
 	{
 		this.backgroundHandler = new BackgroundHandler(pickRandom(backgroundLayerData));
-		this.menuHandler = new MainMenuItemHandler(mainMenuItems);
+		this.menuHandler = new MainMenuItemHandler(closePageCallback, mainMenuItems);
 		this.splashScreenHandler = new SplashScreenHandler(data, hotloadData && hotloadData.splashScreenHandler);
 
 		new MusicHandler();

binaries/data/mods/public/gui/pregame/mainmenu.js

@@ -10,14 +10,16 @@ var g_MainMenuPage;
 
 function init(data, hotloadData)
 {
-	g_MainMenuPage =
-		new MainMenuPage(
+	return new Promise(closePageCallback => {
+		g_MainMenuPage = new MainMenuPage(
+			closePageCallback,
 			data,
 			hotloadData,
 			g_MainMenuItems,
 			g_BackgroundLayerData,
 			g_ProjectInformation,
 			g_CommunityButtons);
+	});
 }
 
 function getHotloadData()

source/main.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -431,6 +431,8 @@ static void Frame(RL::Interface* rlInterface)
 		g_NetClient->Poll();
 
 	g_GUI->TickObjects();
+	if (g_GUI->GetPageCount() == 0)
+		QuitEngine();
 
 	if (rlInterface)
 		rlInterface->TryApplyMessage();

source/ps/scripting/JSInterface_Main.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -34,16 +34,10 @@
 #include "scriptinterface/FunctionWrapper.h"
 #include "tools/atlas/GameInterface/GameLoop.h"
 
-extern void QuitEngine();
 extern void StartAtlas();
 
 namespace JSI_Main
 {
-void QuitEngine()
-{
-	::QuitEngine();
-}
-
 void StartAtlas()
 {
 	::StartAtlas();
@@ -126,7 +120,6 @@ std::string CalculateMD5(const std::string& input)
 
 void RegisterScriptFunctions(const ScriptRequest& rq)
 {
-	ScriptFunction::Register<&QuitEngine>(rq, "Exit");
 	ScriptFunction::Register<&StartAtlas>(rq, "RestartInAtlas");
 	ScriptFunction::Register<&AtlasIsAvailable>(rq, "AtlasIsAvailable");
 	ScriptFunction::Register<&IsAtlasRunning>(rq, "IsAtlasRunning");