Mattias Gaertner wrote

For win32 the normal paint messages should be enough. Please test, if the designer is getting the paint messages and if they are handled at the right time (after letting the control draw itself). Maybe we need to adapt the BeginPaint, EndPaint to the designer.

I now understand better. TWinControl.WMPaint needs to send the lm_paint through the perform method, not only call WMPaint.

However, now I have another problem: the designerdevicecontext.FDCSize is (0,0) and stays so. The line GetDeviceSize (designerprocs.pas:286) never gets executed. Can you help me?

Micha.