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From Herbert Duerr <...@apache.org>
Subject Re: Build fails in main/drawinglayer/source/texture/texture3d.cxx
Date Wed, 17 Oct 2012 11:48:32 GMT
On 17.10.2012 10:29, Armin Le Grand wrote:
> I made some changes, got no errors on win (what means nothing as we
> know). It's strange since ColorData is just a typedef (to sal_Int32) and
> I see no way to auto-convert BitmapColor to it, so 'operator Color()' in
> class Color should be used.

BitmapColor has implicit conversion operators for both
	BitmapColor::operator Color()
and
	BitmapColor::operator sal_uInt8()
Since Color has a constructor for an unsigned integer
	Color( sal_uInt32 nColor)
the conversion is ambiguous, even if the second alternative needs an 
extra type conversion from sal_uInt8 to sal_uInt32.

This shows again that implicit conversions are very tricky even for 
experienced developers. So I suggest to prefer explicit constructors 
over implicit ones. Unfortunately explicit conversion operators are only 
available since C++11.

Things like e.g. the implicit conversion from BitmapColor to sal_uInt8 
are too slick for my taste anyway and they should IMHO be made explicit 
by replacing their uses by something like GetIndex(), so the C++11 
feature of explicit conversion operators can be dispensed with.

Herbert

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