[whatwg] Canvas "coordinate space units"

Aryeh Gregor Simetrical+w3c at gmail.com
Thu Jul 15 14:27:59 PDT 2010

On Thu, Jul 15, 2010 at 6:11 AM, Philip Taylor <excors+whatwg at gmail.com> wrote:
> In "Drawing model": "For shapes, the current fill, stroke, and line
> styles must be honored, and the stroke must itself also be subjected
> to the current transformation matrix". Also it says "(Transformations
> affect the path when the path is created, not when it is painted,
> though the stroke style is still affected by the transformation during
> painting.)". So I think it's clear enough that the width of the stroke
> will be scaled by the CTM.

Maybe it would be clearer if it explicitly used two different types of
units, like "coordinate units" and "transformed coordinate units".
It's pretty confusing right now.

> (I don't think it's clear exactly *how* the stroke will be scaled, or
> rotated or translated or skewed etc - I'd like it more if everything
> was specified in precise geometric algorithms, rather than fluffy
> prose, but it seems like implementations interoperate anyway and test
> cases can tell when they get it wrong so there's probably not much
> practical benefit in rewriting everything much more precisely.)

Ideally, we shouldn't be relying on test-cases here.  If it can be
specified more precisely, it should be, if someone is willing and able
to write the text.  It's already been pointed out that some browsers
aren't interoperable on some points.

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