Anybody can give me a hint how xojo implement Control.DrawInto? Is it a hard code control style into a graphics object or using some API?

You should get a normal paint event call, shouldn’t you?

Yes. I create a simple rectangle on that event to be displayed on IDE. But, the event is also called when invoke Control.DrawInto. So, I’m thinking to implement simple rectangle on IDE and draw the control style/UI when user invoke DrawInto like Xojo control.

DrawInto is implemented through the OffScreenPaint event if I remember correctly.

Yes, drawOffscreenFunction event