[whatwg] Quirks Mode Standard

Boris Zbarsky bzbarsky at MIT.EDU
Fri Feb 10 07:37:24 PST 2012

On 2/10/12 2:57 AM, Simon Pieters wrote:
>> 1) I'm fairly certain the "Images (img elements) without alt
>> attributes sometimes display placeholder icons in quirks mode." quirk
>> cannot be dropped.
> The HTML specification specifies this quirk in the Rendering section.
> http://www.whatwg.org/specs/web-apps/current-work/multipage/rendering.html#images-0

Ah, excellent.  ;)

>> 4) The CSS parsing quirks need to define behavior for shorthands.
> Other than the behavior for 'font' (assuming 'font-size' is on the
> list), what's missing? (My idea was that shorthands that reference other
> properties (or value productions from other properties) in their
> "Value:" specification would automatically support unitless lengths,
> e.g. 'background' where only <position> gets rewritten to use
> <quirklength> because 'background-position' is in the list but
> 'background-size' is not.)

I agree that having the list for lengths reduces the scope of the 
problem somewhat.  But the color quirk means that any shorthand that 
includes colors will run into ambiguity issues if any keywords for any 
subproperty only use letters in the range a-f.  I _think_ we can't hit 
that case now, but going forward that will either place a restriction on 
keyword values or we'll need to define how to resolve the ambiguity somehow.

Even for lengths, if we ever add any new subproperties to border, say, 
that happen to take numbers we would run into trouble.  I'd rather not 
overconstrain future development of CSS by how we define quirks 
behavior.  So I would prefer to avoid the problem as Gecko does, 
frankly.  Of course I'm biased.  ;)

This discussion is probably worth taking to www-style.

>> It's interesting that 'font-size' is not in the list....
> I trusted https://developer.mozilla.org/en/Mozilla_Quirks_Mode_Behavior
> which says "The CSS parser interprets unitless numbers as px (except for
> font-size because that was what Netscape Navigator 4 did...". :-)

Huh.  That's a blatant lie!  I fixed the page.

> Now added, but I'm not sure right now how to spec how the 'font' shorthand
> is handled.

Exactly.  My proposal, again, is that neither of these quirks apply 
inside a shorthand.


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