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Proposed erratum text for ISSUE-2216

From: Cameron McCormack <cam@mcc.id.au>
Date: Mon, 6 Apr 2009 15:50:59 +1000
To: public-svg-wg@w3.org
Message-ID: <20090406055059.GA10500@arc.mcc.id.au>
SVG Working Group Issue Tracker:
> When assigning to SVGLength.valueAsString (or SVGAngle.valueAsString),
> the unitType should be changed to whatever was parsed from the given
> string. For example:
>
>   var l = /* an SVGLength object */;
>   l.valueAsString = '1em';
>   assert(l.unitType == SVGLength.SVG_LENGTHTYPE_EMS);
>   assert(l.valueInSpecifiedUnits == 1);
> 
> But the current text describing valueAsString says:
> 
>   The value as a string value, in the units expressed by unitType. Setting this
>   attribute will cause value and valueInSpecifiedUnits to be updated
>   automatically to reflect this setting.
> 
> which doesn't make this clear.
>
> There's also no indication of what exception would be thrown if the
> given SVGLength string couldn't be parsed, or what exactly is the
> acceptable syntax.

Here is proposed erratum replacement text for the description of
valueAsString:

  DOMString valueAsString
    The length value as a string, in the units expressed by unitType.
    Setting this attribute will cause value, valueInSpecifiedUnits
    and unitType to be updated automatically to reflect this setting.
    Exceceptions on setting
      DOMException NO_MODIFICATION_ALLOWED_ERR: Raised on an attempt to
        change the value of a readonly attribute.
      DOMException SYNTAX_ERR: Raised if valueAsString cannot be parsed
        as a valid <length>.

> Similarly, there are no exceptions declared for the
> newValueSpecifiedUnits() or convertToSpecifiedUnits() methods.  I’d
> expect exceptions to be thrown if an invalid unitType were given.

Proposed replacement text for those two methods:

  newValueSpecifiedUnits
    …
    Exceptions
      DOMException NOT_SUPPORTED_ERR: Raised if unitType is not a valid
        unit type constant (one of the SVG_LENGTHTYPE_* constants
        defined on this interface).

  convertToSpecifiedUnits
    …
    Exceptions
      DOMException NOT_SUPPORTED_ERR: Raised if unitType is not a valid
        unit type constant (one of the SVG_LENGTHTYPE_* constants
        defined on this interface).

(Aside: I’m not sure why the convertToSpecifiedUnits() method is needed.
Why not just make unitType a read-write attribute?)

-- 
Cameron McCormack ≝ http://mcc.id.au/
Received on Monday, 6 April 2009 05:51:50 GMT

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