Creating a round or triangular component?

Mission:        To create a CLX component which is paints itself, but is not neccessarily rectangular.
Functionality:  Only areas of the Canvas which have been painted should define the object bounds.

Established:    I have created a component descended from TGraphicControl (CLX), which in its OnPaint handler, draws an ellipse. 
Problem:        When the user clicks on one of the rectangular Corners of the canvas (where there is _no_ paint), event handlers such as OnMouseDown, OnMouseMove still get fired. Components which are behind this component (eg. TForm) should rather receive these events when the clicked canvas area is unpainted (transparent).

I know this is a big mission, especially as I cannot use WinSDK or the VCL, but perhaps somebody has some suggestions, or has done this before?

Thanks,
Richard


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