[whatwg] Canvas "coordinate space units"

Philip Taylor excors+whatwg at gmail.com
Thu Jul 15 03:11:18 PDT 2010

On Wed, Jul 14, 2010 at 10:33 PM, Aryeh Gregor <Simetrical+w3c at gmail.com> wrote:
> On Wed, Jul 14, 2010 at 3:03 PM, David Flanagan <david at davidflanagan.com> wrote:
> [...]
>> It is used in the definition of the lineWidth attribute as well. Chrome,
>> Firefox and Opera all scaled lineWidth and Phillip Taylor's test suite
>> expects this behavior as well.
> I can't find where it says lineWidth should be scaled . . .

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.

(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.)

Philip Taylor
excors at gmail.com

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