Re: define_color vs. xw-color-values, or pixel vs. red, green and blue

[Jason Rumney]

Juanma Barranquero wrote:
> So I suppose the question is: why does xw-color-values do
>
>  return list3 (make_number ((GetRValue (foo.pixel) << 8)
>                             | GetRValue (foo.pixel)),
>                make_number ((GetGValue (foo.pixel) << 8)
>                             | GetGValue (foo.pixel)),
>                make_number ((GetBValue (foo.pixel) << 8)
>                             | GetBValue (foo.pixel)));
>
> instead of
>
>  return list3 (make_number (foo.red),
>                make_number (foo.green),
>                make_number (foo.blue));

I think the bug is actually in w32_defined_color. White should map to 
(ffff,ffff,ffff), which it does using the code in xw-color-values, but 
w32_defined_color maps it to (ff00,ff00,ff00). This is due to windows 
only supporting 8 bits per color channel, while Emacs expects 16.

Correcting this bug would allow us to use the latter code in 
xw-color-values, which is more clear.