Re: Cross Referencing Between Elements

Note, in recursive cross-reference chains, the first reference parsed has
precedence.  Subsequent references are pushed onto a chain for the user
agent to follow down, looking for a fallback.




On Wed, Jun 11, 2014 at 4:48 PM, Brian Blakely <anewpage.media@gmail.com>
wrote:

> Because the reference chain resolves back to the element being defined,
> the selector is invalid.
>
> Although the conditions for recursion should be refined to include the
> property in our figurings.
>
>
> In the below example, the element can safely reference itself.  Both
> .foo's width and margin-right are 100px.
>
> Safe Recursion Example
> ===
>
> .foo {
>   width: $(.foo margin-right 50px);
>   margin-right: 100px;
> }
>
>
> In the next example, the first cross-reference selector resolves back to
> the element being defined AND the property being defined.  Therefore, the
> selector fails and the fallback argument is used.  Both .foo's width and
> margin-right resolve to 50px.
>
> Unsafe Recursion Example With Fallback
> ===
>
> .foo {
>   width: $(.foo margin-right 50px);
>   margin-right: $(.foo width 100px);
> }
>
>
> In the following example, the first cross-reference does not possess a
> fallback, and so the next cross-reference up the chain is asked for one,
> which it provides.  Both .foo's width and margin-right resolve to 100px.
>
> Unsafe Recursion Example Without Fallback
> ===
>
> .foo {
>   width: $(.foo margin-right);
>   margin-right: $(.foo width 100px);
> }
>
> Finally, in the example below, neither cross-reference supplies a valid
> fallback.  They are both considered "tainted" and both values are invalid.
>
> Tainted Recursion Example
> ===
>
> .foo {
>   width: $(.foo margin-right);
>   margin-right: $(.foo width);
> }
>
>
>
>
> On Wed, Jun 11, 2014 at 3:38 PM, Boris Zbarsky <bzbarsky@mit.edu> wrote:
>
>> On 6/11/14, 3:36 PM, Brian Blakely wrote:
>>
>>> In an instance where the cross-reference ends up selecting the element
>>> being defined
>>>
>>
>> What if it selects some other element that itself cross-referenced the
>> original element?
>>
>>
>>  2) Arbitrarily deep cross-reference nesting.
>>>
>>
>> This is not just a problem for the fallback.
>>
>> -Boris
>>
>
>