[css-transforms-1] Fix mistakes in Example 5 (closes #4767)

[afdw]

No description provided.

[afdw]

Marked as non substantive for IPR from ash-nazg.

[astearns]

@smfr this seems fine to me, but I’d like to get your eyes on it.

[mclegrand]

Ah, I missed this MR when I finally decided to act on my report #5520 this morning (in #5702), sorry. I think the illustration also needs an update

[afdw]

@mclegrand my PR was designed so that it corresponds to the illustration. See http://web.cse.ohio-state.edu/~wang.3602/courses/cse5542-2013-spring/6-Transformation_II.pdf, there are 2 different ways to think about transformations. So I think my version is actually fully coherent if we think about it as post-multiplication / transform with respect to the local origin and basis. Also, this corresponds to the order of matrices in the resulting product. But the canvas specification implies the other variant (pre-multiplication / transform with respect to the global origin and basis). So what do you think? Which approach will be better?

[mclegrand]

Well, the important thing is that it's the same example as in Example 1 and Example 2 :)

IMO, the whole spec (mostly section 3) revolves around the CTM (current transformation matrix) concept which (still IMO) works best when thought in terms of pre-multiplication ( f(x) = F×x multiplied by the left ). But even with post-mul, I don't think the illustration makes sense as it shows an object being modified and not a coordinate system ?

[afdw]

But even with post-mul, I don't think the illustration makes sense as it shows an object being modified and not a coordinate system ?

Yes, the axis are kind of implicit currently, and should probable be added.

IMO, the whole spec (mostly section 3) revolves around the CTM (current transformation matrix) concept which (still IMO) works best when thought in terms of pre-multiplication ( f(x) = F×x multiplied by the left ).

My opinion is that ideally both approaches to thinking about it should be described. I think it would eliminate the confusion one might have here. As this is a specification about transformations, this should should not be too unrelated I think?