CommonLua/UI/MainMenu.lua

function OpenPreGameMainMenu(mode, context)
	LoadingScreenOpen("idLoadingScreen", "pregame menu")
	ResetGameSession()
	local dlg = OpenDialog("PreGameMenu")
	if dlg and mode then
		dlg:SetMode(mode, context)
	end
	LoadingScreenClose("idLoadingScreen", "pregame menu")
	if ChangingMap then
		WaitMsg("ChangeMapDone")
	end
	
	TryConnectToServer()
	
	ChangeGameState("setpiece_playing", false) -- in case a setpiece was still playing due to some error
	
	Msg("PreGameMenuOpen")
end

function GetPreGameMainMenu()
	return GetDialog("PreGameMenu")
end

function ResetGameSession()
	Msg("ResetGameSession")
	CloseAllDialogs()
	if GetMap() ~= "" then
		ChangeMap("")
	end
	DoneGame()
end

function OpenIngameMainMenu()
	-- This menu usually opens on pressing "Escape" which is the same key used to skip setpieces.
	-- People spam the key and there is a short time window in which you can pause during the setpiece
	-- and break stuff.
	if IsSetpiecePlaying() then return end

	if not GameState.pregame_menu then
		local menu = GetInGameMainMenu()
		if menu then
			CloseIngameMainMenu()
		else
			Msg("InGameMenuOpen")
			return OpenDialog("InGameMenu")
		end
	end
end

function GetInGameMainMenu()
	return GetDialog("InGameMenu")
end

function CloseIngameMainMenu()
	CloseDialog("InGameMenu")
end

function CloseMenuDialogs()
	local menu = GetPreGameMainMenu() or GetInGameMainMenu()
	if menu and menu.window_state ~= "destroying" then
		CloseDialog(menu)
	end
end