Re: [boost] Library Proposal: Boost.Geom 2D and 3D Geometric Primitives

From: Joel de Guzman (joel_at_[hidden])
Date: 2005-06-29 06:49:24

Anis Benyelloul wrote:
> Joel de Guzman <joel <at> boost-consulting.com> writes:
> 
> 
>>Example: I need to XOR a YRegion
>>with a MacRegion.
> 
> 
> Although actual library implmentation permits mixed implmentation
> computations, I really doubt you'll ever need to do that. Do you think that 
> you may be using Xlib's XRegion and Mac's MacRegion (and Windows' RGN) in the 
> same program ? Usually you'll just choose one implmentation and stick with it 
> throughout your project... This still remanis a consistency concern, however.

Right. Ok Fair enough.

>>The thing is, a classic mac region is an
>>opaque data type (actually, it's not implemented as a collection
>>of boxes). The mere fact that it is opaque makes it impossible
>>to even copy a mac region to a YRegion.
> 
> 
> Right ! Let me add that Window's RGN is also an opaque type. Well maybe a 
> geom::region is useful but I don't think that MacRegion XRegion and RGN are 
> suitable implmentation of what we define as a ``region''.

The problem with opaque data types is that they are limited to only
what they offer. The reason why I wanted interoperability is that
at the very least, I'd want to assign, say, a Mac Region to a
cross-platform region. That way, I can, say, transform the more
versatile cross-platform region, scale it, rotate it, etc. These
functions are not available in the platform specific region.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net