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[Bug 14548] New: Grouping Content: algorithm for incrementing value (OL->LI @value) does not match any current user agent

From: <bugzilla@jessica.w3.org>
Date: Sun, 23 Oct 2011 14:03:43 +0000
To: public-html@w3.org
Message-ID: <bug-14548-2495@http.www.w3.org/Bugs/Public/>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=14548

           Summary: Grouping Content: algorithm for incrementing value
                    (OL->LI @value) does not match any current user agent
           Product: HTML WG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: HTML5 spec (editor: Ian Hickson)
        AssignedTo: ian@hixie.ch
        ReportedBy: theimp@iinet.net.au
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-wg-issue-tracking@w3.org,
                    public-html@w3.org


Created attachment 1036
  --> http://www.w3.org/Bugs/Public/attachment.cgi?id=1036
Initial post in HTML markup due to heavy pseudo-markup and tables

When I went to investigate this, I tested how a lot of user agents currently
handle their numbering rules, and none of them match the current spec. (and
very few come close to the spec. or each other, and no major ones match each
other exactly).

Results:
* Lynx comes the closest to what the HTML5 spec. currently says, but is the
only browser that performs incorrectly on the (invalid) initial positive sign
symbol (U+002B PLUS SIGN).
* Only Opera and Lynx support negative numbers at all (except through unhandled
overflows).
* IE and Webkit do not support the value 0.
* An empty string is treated according to the spec. by Gecko, Webkit, Presto
and Lynx. It always returns 0 for w3m and Dillo. It always returns 1 for IE.
* There's a three-way split between how invalid values that begin with valid
characters, are currently interpreted. Gecko ignores the entire value, treating
it as if no value was specified (incrementing the previous value by 1). IE
ignores the whole value but returns an absolute value of 1. The rest, per the
spec., read all valid characters up to the first invalid character, and use
that.
* As a special case of the above, all browsers will use a value that is
invalid, due to containing a whitespace character as the first invalid
character (that is, contains valid digits and then one or more whitespace
characters and then any other non-whitespace characters), using the characters
up to the first invalid character as above.
* As a special exception of the above, Gecko, if the first invalid character is
a period (U+002E FULL STOP) but there are valid numeric digit characters after
it, will use those digits as a number, ignoring the period.
* Presto, w3m and Dillo will treat invalid values as a 0. IE will treat invalid
values as a 1. All others treat invalid values as an increment of the previous
value.

                   Sample Ordered List Value Attributes                   
Markup                HTML5*  IE   Gecko  Webkit  Presto  Lynx  w3m  Dillo
<li            ></li>   1      1     1       1       1      1    1     1  
<li value="0"  ></li>   0      2     0       2       0      0    0     0  
<li value="1"  ></li>   1      1     1       1       1      1    1     1  
<li value="3a" ></li>   3      1     3       3       3      3    3     3  
<li value="3b" ></li>   3      1     4       3       3      3    3     3  
<li value="2  "></li>   2      2     2       2       2      2    2     2  
<li value="2 1"></li>   2      2     2       2       2      2    2     2  
<li value="2.1"></li>   2      2     2       2       2      2    2     2  
<li value=".2" ></li>   3      3     2       3       0      3    0     0  
<li value="-3" ></li>  -3      3     0       4      -3     -3    0     0  
<li value="+3" ></li>   3      3     3       3       3     -2    3     3  
<li value="-3" ></li>  -3      4     0       4      -3     -3    0     0  
<li value=""   ></li>  -2      1     1       5       0     -2    0     0  
<li            ></li>  -1      2     2       6       1     -1    1     1  
<li value=""   ></li>   0      1     3       7       0      0    0     0  
<li value="4"  ></li>   4      4     4       4       4      4    4     4  
<li value="5"  ></li>   5      5     5       5       5      5    5     5  
<li            ></li>   6      6     6       6       6      6    6     6  
<li value="c"  ></li>   7      1     7       7       0      7    0     0  
*The current HTML5 algorithm

Details:

IE
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return 2147483647
* Values less than 0 return an automatic increment of the previous number
* An empty string returns 1
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns 1
* Note: automatic increments of the previous value are 1 if there is no
previous value, but overflow to -2147483648 if the previous value was
2147483647

Webkit
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return an automatic increment of the previous
number
* Values less than 0 return an automatic increment of the previous number
* An empty string returns an automatic increment of the previous number
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns an automatic increment of the previous
number
* Note: automatic increments of the previous value are 1 if there is no
previous value, but overflow to -2147483648 if the previous value was
2147483647

Gecko
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return an automatic increment of the previous
number
* Values less than 0 return 0, unless it's also less than -2147483647, in which
case it returns an automatic increment of the previous number
* An empty string returns an automatic increment of the previous number
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns an automatic increment of the previous
number
* Note: strings beginning with U+002E FULL STOP ignore that character
* Note: automatic increments of the previous value are 1 if there is no
previous value, but overflow to -2147483648 if the previous value was
2147483647

Opera
* By default, the value is an automatic increment of the previous number
* Values greater than 536870911 return 536870911
* Values less than -536870912 return -536870912
* An empty string returns 0
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns 0
* Note: automatic increments of the previous value are 1 if there is no
previous value

Dillo
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return 2147483647
* Values less than 0 return 0
* An empty string returns 0
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns 0
* Note: automatic increments of the previous value are 1 if there is no
previous value

Lynx
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return 2147483647
* Values less than -29997 return -29997
* Note: This behavior is documented:
http://lynx.isc.org/current/lynx2-8-8/lynx_help/Lynx_users_guide.html#Lists
* An empty string returns an automatic increment of the previous number
* A string not beginning with any numeric characters (including U+002D
HYPHEN-MINUS) returns an automatic increment of the previous number
* Note: automatic increments of the previous value are 1 if there is no
previous value

w3m
* By default, the value is an automatic increment of the previous number
* Values greater than 2147483647 return 2147483647
* Values less than 0 return 0
* An empty string returns 0
* A string not beginning with any numeric characters (including U+002B PLUS
SIGN, U+002D HYPHEN-MINUS) returns 0
* Note: automatic increments of the previous value are 1 if there is no
previous value

Notes:

* Versions of user agents included the latest versions, all commonly-used
versions, and many others, including extremely old versions (for example, IE
was tested between versions 3 and 9). Occasional variations exist only in
extremely old versions (for example, IE version 2 has different behavior to all
other versions), however, no other browsers, or old versions of browsers, seem
to be worth reporting on due to the small number of active deployments.

* The value 2147483647 is the highest value that can be stored in a signed
32-bit integer. The value -2147483648 is the lowest value that can be stored in
a signed 32-bit integer. In principle, software compiled using a different int
width may have different, corresponding limits; although in practice this is
very rare.

* Also, note that the current HTML5 algorithms is slightly inconsistent with
CSS (which explicitly allows U+002B PLUS SIGN to indicate positive integers). I
don't know if mapping this attribute to CSS is a concern.

***

Personally, I don't have a solution to propose; this is purely informative.

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Received on Sunday, 23 October 2011 14:03:49 UTC

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