🚀 go-pugleaf

I am currently developing a modelling application using InterViews and 
Unidraw. I have succesfully constructed an idraw type interface using ibuild.
I now need to combine this interface  with my modelling application. A number
of basic questions have arisen:

	How do I access the co-ordinate information from the polygons,
	rectangles, ellipses which I have draw using the interface?
	(I need this information for processing by the application)
	
	I need to associate a material type (steel, graphite etc..)
	to each component. To do this must I derive new components 
	from the existing Unidraw polygons, rectangles etc.. ?

	The following is a more general graphics problem:

	The modelling application requires polygons and ellipses 
	which do not intersect. Thus once I obtain the coordinates 
	from the interface they must have a clipping operation to
	produce non intersecting components. Does such a clipping 
	algorithm exist? (I do not need to actually display the 
	result of the operation as it would look the same, but I
	need the result for the application). So for example a
	bolt can be created simply by drawing a polygon and the
	a circle concentrically. Unidraw sees this as two components
	a filled polygon and an ellipse. My application needs to
	see a polygon with a hole and an ellipse. This is a simple 
	example but the possibilities are complex. I would appreciate
	any pointers to a good graphics book which may deal with this
	topic.


Thanks in advance for any help.



Trinity College
Dublin
Ireland

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