Author: Christopher Brandsma

How to find out if your ActiveX control is running in Design mode or Run mode

Answer:

Every now and then an ActiveForm developer will want to add a feature to an ActiveX 
control that only shows up in either Design-Time or Run-Time (splash screens and 
nag screens are an example). (Background: Design-Time is when a control is applied 
to a form in the Visual Basic environment; Run-Time is when the control is running 
inside of an executable).  If you are using TActiveXControl as you’re base object, 
you get this for free.  If you are using TActiveForm you have to work for the 
information. 

The property we need is UserMode.  If this property is True we are in Run-Time 
mode; if False we are in Design-Time mode. UserMode is one of the AmbientProperties 
that a control’s container is supposed to provide.  Delphi even supplies an 
interface call IAmbientDispatch in AxCtrls for retrieving the ambient properties.   

To get it: Your ActiveForm has a property called ActiveFormControl.ClientSite.  
This property is set sometime before your control's OnShow event (ClientSite will 
not be set in the constructor or the initialize procedures).  Cast ClientSite to an 
IAmbientDispatch (found in AxCtrls), then get the UserMode property. (see code 
below) 

1   procedure TDesignCtrl.HandleOnShow(Sender: TObject);
2   var
3     b: Boolean;
4     pIAmbient: IAmbientDispatch;
5   begin
6     pIAmbient := Self.ActiveFormControl.ClientSite as IAmbientDispatch;
7     b := pIAmbient.UserMode;
8   
9     if b then
10      ShowMessage('is in runtime mode')
11    else
12      ShowMessage('is in design mode');
13  end;


There are other properties in the IAmbientDispatch interface that could also be useful to a control writer so feel free to experiment.