Re: [RFC] Gradient fill options

[<HBB...@t-...>]

Pierre wrote:
>> > And, more importantly, it's a bit biased, which tends to turn into a
>> > robustness problem.  The bias lies in the arbitrary choice of one 
>> > vertex to be shared by the two first interpolations.

> I'm not sure to understand why it is biased. Each vertex color is
> known. The first vertex is the top left one, after they have been
> sorted.

The bias lies in picking the top left vertex as "the first".  Why should 
this be treated different from the other two?  It doesn't necessarily 
have to cause visible rounding/precision effects, but it can.

This can cause nasty effects like: the same triangle comes out subtly 
different if the scene is rendered upside down or rotated by 90 degress, 
even though the result should be exactly the same.    Other cases of the 
same issue can cause edges to be drawn differently if you switch the 
order of their vertices in the drawline() function call.