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IE compat with coords parsing

From: Simon Pieters <simonp@opera.com>
Date: Fri, 09 Jan 2009 16:08:08 +0100
To: public-html <public-html@w3.org>
Message-ID: <op.unhwbuozidj3kv@zcorpandell.linkoping.osa>

We implemented HTML5's parsing rules for coords=''. Hence I was interested  
in checking if the algorithm is compatible with IE, so I implemented it in  
javascript:

http://simon.html5.org/tools/js/coords-parsing.html

I found that HTML5 didn't quite match IE. For instance "1,2:3,4" gives "1"  
in HTML5 but "1,2,4" in IE (i.e. IE gives ':' the same treatment that the  
spec gives to '.').

So I wondered which characters other than ':' that IE treated this way:

http://software.hixie.ch/utilities/js/live-dom-viewer/?%3C!DOCTYPE%20html%3E%0D%0A%3Cmap%3E%3Carea%20shape%3D%22circle%22%3E%3C%2Fmap%3E%0D%0A%3Cscript%3E%0D%0Avar%20a%20%3D%20document.getElementsByTagName('area')%5B0%5D%3B%0D%0Afor%20(var%20i%20%3D%201%3B%20i%20%3C%200x3ff%3B%20%2B%2Bi)%20%7B%0D%0A%20%20a.coords%20%3D%20'1'%20%2B%20String.fromCharCode(i)%20%2B%20'2%2C3'%3B%0D%0A%20%20w('0x'%20%2B%20i.toString(16)%20%2B%20'%20('%20%2B%20String.fromCharCode(i)%20%2B%20')%3A%20'%20%2B%20a.coords)%3B%0D%0A%7D%0D%0A%3C%2Fscript%3E

...and it turns out to be quite a few (all lines that say "1,3,0").

Then I asked Philip` for a some data, and he kindly gave a list:

    http://philip.html5.org/data/coords-with-unusual-chars.txt

...from which I found three pages that would break with HTML5:

    http://www.psu.edu/ur/GSpanier/gallery/
    coords="157,5,233,20' href=" (apostrophe)

    http://www.motorsportforbundet.no/
    coords="615, 0, 768, 40	" (tab)

    http://www.kipwmi.com/
    coords="2,20', 87,38'" (apostrophe)

It's possible that there are similar pages that contain coords='1,2",3,4"'  
or coords=1,2',3,4', but Philip` only looked at double-quoted attributes.


On one hand it seems reasonable to say that 3 pages out of 130k isn't a  
big deal, but OTOH those pages work in today's browsers and changing the  
algorithm to fix them is simple.

Doing exactly what IE does might not be necessary for Web compat. IE gives  
different treatment to various non-ASCII characters (such as 0x3f3 and  
0x3f4).

For the time being we'll keep the HTML5 implementation but we might change  
to be more compatible.


(I note that Philip`'s data has an instance of  
COORDS="438,110,496,1ß2,496,156,438,159" which HTML5 and IE agree on  
although makes the link not work. If ß were to be treated as '.' then the  
page would work slightly better.)

(See http://krijnhoetmer.nl/irc-logs/whatwg/20090109#l-352 for discussion.)

-- 
Simon Pieters
Opera Software
Received on Friday, 9 January 2009 15:08:59 GMT

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