modeless dialog modal. However ShowModal() can't be called twice
without intervening EndModal() calls.
+ Note that this function creates a temporary event loop which takes
+ precedence over the application's main event loop (see wxEventLoopBase)
+ and which is destroyed when the dialog is dismissed.
+ This also results in a call to wxApp::ProcessPendingEvents().
+
@return The value set with SetReturnCode().
@see EndModal(), GetReturnCode(), SetReturnCode()