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Re: Minutes, Monday 4 May 2009 SVG WG telcon

From: Erik Dahlström <ed@opera.com>
Date: Mon, 04 May 2009 14:17:17 +0200
To: anthony.grasso@cisra.canon.com.au, public-svg-wg@w3.org
Message-ID: <op.utem23ppgqiacl@gnorps.linkoping.osa>
On Mon, 04 May 2009 10:11:13 +0200, Anthony Grasso <anthony.grasso@cisra.canon.com.au> wrote:

...
> Tighten up the implicit lineto commands in the path syntax
>
>     <heycam> ISSUE-2268?
>
>     <trackbot> ISSUE-2268 -- Tighten up the implicit lineto commands in
>     the path syntax -- RAISED
>
>     <trackbot> [13]http://www.w3.org/Graphics/SVG/WG/track/issues/2268
>
>       [13] http://www.w3.org/Graphics/SVG/WG/track/issues/2268
>
>     <heycam> DS: I think there are two sensible answers to this
>
>     <heycam> ... one, they're always absolute
>
>     <heycam> ... (or relative, but absolute makes more sense)
>
>     <heycam> ED: i tested a few implementations
>
>     <heycam> ... if you have a relative 'm', then you have relative 'l's
>
>     <heycam> ... and if you have an absolute 'M', then you have absolute
>     'L's
>
>     <heycam> DS: that's the second sensible one
>
>     CM: Erik, you were saying that the first line to is absolute?
>
>     ED: Even if it's lower case 'm' it will be absolute
>
>     CM: All the subsequent implicit line-to's
>
>     ED: That's what the test cases showed
>
>     CM: I guess that makes sense
>     ... You can always not use implicit lines if you want particular
>     behavior
>
>     ED: I couldn't find any implementation that behaved differently
>     ... but I didn't test ASV
>
>     DS: Implementations, the first 'm' whether capital is not is always
>     absolute then everything after is absolute
>     ... need to have a lower case 'm' after the first to make line-to
>     commands relative
>
>     CM: Are we going to errata this for 1.1F and 1.2T?
>
>     ED: Yes we should
>
>     <scribe> ACTION: Anthony to Create an errata of the implicit line to
>     problem mentioned on the list [recorded in
>     [14]http://www.w3.org/2009/05/04-svg-minutes.html#action01]
>
>     <trackbot> Created ACTION-2542 - Create an errata of the implicit
>     line to problem mentioned on the list [on Anthony Grasso - due
>     2009-05-11].

My memory was a bit hazy there (the inverse of what was claimed in the telcon seems to hold though):

  - implicit lineto commands will be relative if the moveto is relative, and absolute if the moveto is absolute.
  - if the first moveto in @d is relative the implicit lineto's will be relative even though the moveto will be interpreted as an absolute moveto

Sorry for the confusion.

Simple testcase:

<svg xmlns="http://www.w3.org/2000/svg" stroke="black" viewBox="0 0 50 50">
  <g stroke="none" fill="blue">
    <circle cx="30" cy="10" r="2"/>
    <circle cx="30" cy="20" r="2"/>
    <circle cx="30" cy="30" r="2"/>
    <circle cx="30" cy="40" r="2"/>
  </g>
  <g stroke="none" fill="lime">
    <circle cx="20" cy="10" r="2"/>
    <circle cx="20" cy="20" r="2"/>
    <circle cx="20" cy="30" r="2"/>
    <circle cx="20" cy="40" r="2"/>
  </g>
  <g text-anchor="middle" font-size="2" stroke="none">
    <text x="20" y="5">Absolute</text>
    <text x="30" y="5">Relative</text>
  </g>
  
  <path d="m10 10 20 0" />
  <path d="m0 0m10 20 20 0" />

  <path d="M10 30 20 30" />
  <path d="M0 0M10 40 20 40" />
</svg>

-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Monday, 4 May 2009 12:16:05 GMT

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