Index: binaries/data/mods/mod/gui/common/functions_msgbox.js
===================================================================
--- binaries/data/mods/mod/gui/common/functions_msgbox.js   (revision 22653)
+++ binaries/data/mods/mod/gui/common/functions_msgbox.js   (working copy)
@@ -1,52 +1,20 @@
-// We want to pass callback functions for the different buttons in a convenient way.
-// Because passing functions accross compartment boundaries is a pain, we just store them here together with some optional arguments.
-// The messageBox page will return the code of the pressed button and the according function will be called.
-var g_MessageBoxBtnFunctions = [];
-var g_MessageBoxCallbackArgs = [];
-
-function messageBoxCallbackFunction(btnCode)
-{
-   if (btnCode !== undefined && g_MessageBoxBtnFunctions[btnCode])
-   {
-       // Cache the variables to make it possible to call a messageBox from a callback function.
-       let callbackFunction = g_MessageBoxBtnFunctions[btnCode];
-       let callbackArgs = g_MessageBoxCallbackArgs[btnCode];
-
-       g_MessageBoxBtnFunctions = [];
-       g_MessageBoxCallbackArgs = [];
-
-       if (callbackArgs !== undefined)
-           callbackFunction(callbackArgs);
-       else
-           callbackFunction();
-       return;
-   }
-
-   g_MessageBoxBtnFunctions = [];
-   g_MessageBoxCallbackArgs = [];
-}
-
 function messageBox(mbWidth, mbHeight, mbMessage, mbTitle, mbButtonCaptions, mbBtnCode, mbCallbackArgs)
 {
-   if (g_MessageBoxBtnFunctions && g_MessageBoxBtnFunctions.length)
-   {
-       warn("A messagebox was called when a previous callback function is still set, aborting!");
-       return;
-   }
-
-   g_MessageBoxBtnFunctions = mbBtnCode;
-   g_MessageBoxCallbackArgs = mbCallbackArgs || g_MessageBoxCallbackArgs;
-
-   Engine.PushGuiPage("page_msgbox.xml", {
-       "width": mbWidth,
-       "height": mbHeight,
-       "message": mbMessage,
-       "title": mbTitle,
-       "buttonCaptions": mbButtonCaptions,
-       "callback": mbBtnCode && "messageBoxCallbackFunction"
-   });
+   Engine.PushGuiPage(
+       "page_msgbox.xml",
+       {
+           "width": mbWidth,
+           "height": mbHeight,
+           "message": mbMessage,
+           "title": mbTitle,
+           "buttonCaptions": mbButtonCaptions
+       },
+       btnCode => {
+           if (mbBtnCode !== undefined && mbBtnCode[btnCode])
+               mbBtnCode[btnCode](mbCallbackArgs ? mbCallbackArgs[btnCode] : undefined);
+       });
 }

 function openURL(url)
 {
    Engine.OpenURL(url);