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RE: FW: In a quick glance, all of the whitespace test file are invalid tests that don't prove anything

From: Arron Eicholz <Arron.Eicholz@microsoft.com>
Date: Tue, 2 Mar 2010 17:23:02 +0000
To: "css21testsuite@gtalbot.org" <css21testsuite@gtalbot.org>, Melissa Newman <melissa@newmanfamily.org>
CC: "public-css-testsuite@w3.org" <public-css-testsuite@w3.org>
Message-ID: <651D2A831D17C040B828D62270386CE92C10753E@TK5EX14MBXC137.redmond.corp.microsoft.com>
Gérard Talbot wrote:
> 
> > how
> > can anybody realistically tell the difference, with the naked eye,
> > between a tab, 8 single white spaces, 16 half white spaces, or 4
> > double white spaces?
> > You can't,
> 
> I agree with you. Testcases should avoid relying on/expecting the tester
> counting and figuring out how many white spaces (of various kinds) there is.
> 

Next update to the Microsoft tests will correct the white space tests. Though it might be into next week since I just got back from vacation and I have a bit of a back log.

> This is the same problem with testcases which expect the tester to be able to
> see, measure (or compare) a 9px (or 12px or 18px) difference between 2
> objects with the naked eye.

I don't know of any cases that you are referring to here but I would be happy to address those cases if you call them out (note I haven't gotten a chance to address any issues since 2/9 so I am a bit behind on feedback if you already called them out).

> 
> > Plus, we should have images that are exact measurements.  One for mm,
> > one for inches, etc.  So if an end result of a test is supposed to
> > have a space of 10mm, the tester can clearly see that the end results
> > are 10 mm.
> 
> Creating custom (vertical and horizontal) measurement rulers (for in, mm,
> cm, px, etc.) is rather easy to do. I have submitted 2 for the test suite.
> 

Rulers are a great idea but you forget a couple major issues with using images. Zooming and HighDPI. These two features do not have any guidelines on how they should react on images. Are they required to scale the images? I say yes but that then can possibly change image rendering a 1px line into 2px or more. That is problematic. Using rulers restricts us from testing zooming and HighDPI scenarios with the same tests that we have already created. This is one reason why the '96dpi' flag was created because of this particular issue. That flag defines that the tests is only valid in that specific DPI setting and may not work in other DPI settings.

> What is unacceptable is that a few testcases expect user agents to be able to
> render distance like 2.54mm (9.6px) or 15.24mm (or 57.6px) precisely and
> then ask/invite the tester to check if there is red in the page.
> 
> There is no normative restraint or requirement regarding how fraction of a
> pixel is supposed to be handled by user agents. Each/all user agents have
> implementation limits and various capability limitations.

If there are cases that have this fractional pixel problem let me know. I know I have been trying to track all of them down and fix them.
Received on Tuesday, 2 March 2010 17:23:49 GMT

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