Offset uniqueness in vector of ColorSteps

[Regina Henschel]

Hi Armin,

Armin Le Grand schrieb am 15.03.2023 um 10:54:
> Hi Regina,
> 
> thought about it deeper, and it's even getting stranger quickly. Let me 
> express my thoughts about possible problems. I will use an example: A 
> ColorStop sequence of four colors, (a..d)o for offset, (a..d)c for the 
> color. So let's look at
> 
>      1) ao = 0%, ac
>      2) bo = 50%, bc
>      3) co = 50%, cc
>      4, do = 100%, dc
> 
> The order these should be used is defined by the offsets.

The order is defined by the order of the <stop> elements in the SVG (and 
ODF) markup. If offsets do not follow this order they have to be 
adjusted on reading the markup. Rules for that are described in
13.2.4 SVG 1.1 (Second Edition) https://www.w3.org/TR/SVG11/
or
14.2.4 SVG 2 (Editors Draft)
https://svgwg.org/svg2-draft/pservers.html#StopNotes

So the order of stops with identical offset is given by the order of 
them in markup and after reading the markup as order in your vector. The 
import filter are responsible to generate the correct vector. And 
painting must use the order inside the vector.

So in your example the vector would always contain 
(0%|ac),(50%|bc),(50%|cc),(100%|dc) and that will generate smooth 
transition from ac to bc, then abrupt change from bc to cc, followed by 
smooth transition from cc to dc.

There is no ambiguity.

Kind regards,
Regina