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Follow-Up: Elliptical arc minimal syntax

From: Jeff Schiller <codedread@gmail.com>
Date: Sun, 11 Apr 2010 21:35:51 -0500
Message-ID: <g2sda131fde1004111935xe3c23f33hbb83da670ad3d03a@mail.gmail.com>
To: www-svg <www-svg@w3.org>

=== BEGIN SNIP ===

ed: We should allow for skipping of space and comma between
largeArcFlag and the sweepFlag
... Instead of ', *wsp' it should be ',wsp?'

<ed> so change elliptical-arc-argument to become this:

<ed> nonnegative-number comma-wsp? nonnegative-number comma-wsp?

<ed> number comma-wsp flag comma-wsp? flag comma-wsp coordinate-pair

=== END SNIP ===

Actually I don't believe this is good enough.  I have done some more
thorough research on this discrepancy.  Here are my results:

1) All browsers except for WebKit parse the elliptical-arc-argument
production as:

    nonnegative-number comma-wsp? nonnegative-number comma-wsp?
        number comma-wsp flag comma-wsp? flag comma-wsp? coordinate-pair

i.e. a comma-wsp? between the two flags and between the sweep-flag and
the coordinate-pair.

2) WebKit also accepts values for 'flag' other than "0" or "1" (and
interprets anything other than "1" as a "0").  I've looked at the

Here is my test case:

<?xml version="1.0"?>
<svg xmlns="http://www.w3.org/2000/svg">

    <!-- This tests parsing rules of the flags in the arc path command.
         No red should be visible, only green -->

    <!-- this tests that the two flags do not need whitespace between them -->
	<path fill="red" d="M200,200 h-150 a150,150 0 0,0 150,-150 z"/>
	<path fill="green" d="M200,200 h-150 a150,150 0 00 150,-150 z"/>

    <!-- this tests that the last flags does not need whitespace between it
         and the x-coordinate -->
	<path fill="red" d="M500,200 h-150 a150,150 0 0,1 150,-150 z"/>
	<path fill="green" d="M500,200 h-150 a150,150 0 01 150,-150 z"/>

    <!-- this tests that only flags with a 0 or 1 are valid, otherwise
the path is in error -->
	<path fill="green" d="M800,200 h-150 a150,150 0 0,0 150,-150 z"/>
	<path fill="red" d="M800,200 h-150 a150,150 0 0,8 150,-150 z"/>

    <!-- these two sub-tests test that the same rules apply when flags
are 0 or 1 -->
	<path fill="red" d="M200,500 h-150 a150,150 0 1,0 150,-150 z"/>
	<path fill="green" d="M200,500 h-150 a150,150 0 10 150,-150 z"/>

	<path fill="red" d="M700,650 h-150 a150,150 0 1,1 150,-150 z"/>
	<path fill="green" d="M700,650 h-150 a150,150 0 11 150,-150 z"/>


In Firefox, Opera, IE9 all paths are green.  In WebKit all paths are
red.  Batik reports an error when a flag value other than "0" or "1"
is present and refuses to render the entire file (boo!).  If I remove
the offending path, Batik renders the other four sub-tests as green.

Since Firefox, Opera, Batik and IE9 all support the above, I guess it
would make sense for WebKit to align with this for interoperability.
I will raise a bug against WebKit.  Is there a ruling on which spec
will be updated for this?  Can we get an official word from the SVG WG
so I can link to it?

Jeff Schiller

P.S.  I know I owe Chris Lilley a response on the points syntax too.
Received on Monday, 12 April 2010 02:36:25 UTC

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