UserControl ScaleMode issue

[LaVolpe]

But following code did not work...

Oops, my bad. It will work for forms, classes but for usercontrols, it is actually ObjPtr(UserControl.Extender) if I recall correctly. By using the IS operator is easier anyway.

... I guess, it is not so easy. Let's say, I have determined, that the coder did resize the uc via the visual editor. - How do I get the original position? I could introduce a static variable, where I can save the current uc position for the next resize event. But what, if the coder moves the uc fist and does resize it afterwards? - If a control is moved in the visual editor, no event will be fired, right? The only way I can go would be, to use a timer I guess - but this would be a very bad solution for my understanding. Do you have another idea?

Moving the uc is out of your control and not really a player here. The offset you can cache is the X,Y distance of the top/left-most control inside your uc to the 0,0 position of the uc's container hwnd. So if the control is resized using left-side grab handles, your uc will get a resize event. At that point, you can test the top/left most control to see where its relation is to the uc's container's 0,0 position. If it is different, offset all of your controls the difference between the top/left most control's current position and its last position. Where this logic fails is if a user moves a control within your uc during design time; do you get any event to let you know it was moved, so you can re-cache the offset?

...I guess this is only possible with API. Somebody who uses API that way should know what he is doing.

Not really. Set myControl.Container = Picture1. No APIs.

I'll take a look at why MoveWindow api is not refreshing the uc. Maybe a simple UserControl.Refresh would do the trick? Maybe SetWindowPos vs MoveWindow?