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Re: Missing test assertion, reconstructing (searchRange, entrySelector and rangeShift).

From: Chris Lilley <chris@w3.org>
Date: Tue, 29 Nov 2011 22:55:00 +0100
Message-ID: <1995363499.20111129225500@w3.org>
To: Tal Leming <tal@typesupply.com>
CC: www-font@w3.org
On Tuesday, November 29, 2011, 7:37:07 PM, Tal wrote:

TL> On Nov 29, 2011, at 1:21 PM, Chris Lilley wrote:

>> On Tuesday, November 29, 2011, 3:56:13 PM, Tal wrote:

>> TL> On Nov 29, 2011, at 8:49 AM, Chris Lilley wrote:

>>>> On a third hand, the assertion could be broadened to include authoring tools which perform round-trip or bidirectional conversion,and would be testable (perhaps the bitwise-identical authoring tool tests already cover this).

>> TL> The Authoring Tool cases invalidsfnt-searchrange-001,
>> TL> invalidsfnt-entryselector-001 and invalidsfnt-rangeshift-001 have
>> TL> invalid values for these fields for SFNT input testing.

>> Good, but that seems to be a different test. Its about conversion from sfnt to woff.

>> The quoted spec text is about conversion from woff (which does not explicitly store these values) to sfnt (so they need to be correctly calculated).

TL> Ah, yes. I can't think of a way to provide test cases for this
TL> conversion. The only thing that I have come up with so far is to
TL> generate WOFFs from an SFNT that has one of the fields set
TL> incorrectly and has a head checkSumAdjustment that is calculated
TL> with the invalid field value. When a UA recreates the SFNT data
TL> from the WOFF, it would set the fields correctly and thereby
TL> create SFNT data that is a mismatch against the head
TL> checkSumAdjustment. But, we don't require UAs to check the head
TL> checkSumAdjustment so this won't work. Any other ideas?

For authoring tools, the test would be a woff, to be converted to sfnt, and a check would be that

- the values exist in the sfnt
- the values are correct

For ua's I can't think of a suitable test. I wonder therefore if the MUST is better replaced by a SHOULD.



-- 
 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups
Received on Tuesday, 29 November 2011 21:55:02 UTC

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