Re: Should IE drop currentStyle/ runtimeStyle?

On Tue, Sep 22, 2009 at 7:07 AM, Travis Leithead <travil@microsoft.com> wrote:
> We (the IE team) are _considering_ dropping support for currentStyle and
> runtimeStyle in our next most "standards compliant" mode. However, because
> there is interest in this space (via the CSSOM spec [1], we wanted to get a
> feel for whether other browsers are considering implementing these APIs or
> not. (We see that Opera has an implementation.)
>
[...]

>
>
> _IF_ we are to drop support for these, we'd want to provide a more
> "standards compliant" replacement, for which:
>
> runtimeStyle -> getOverrideStyle
>
> currentStyle -> ??
>
>
>
> Given existing API design precedent, it seems logical to create a
> "getCascadedStyle" API that would replace "currentStyle" in the future--it
> can handle pseudo-elements and would be similar to related style APIs of
> which web developers are already familiar.
>

document.defaultView.getCascadedStyle?
As in:
http://lists.w3.org/Archives/Public/www-dom/2000AprJun/0112.html

?

>
>
> Any strong opinions on this matter?
>

A strong opinion can be formed by making observations. Using google
code search to find existing code can reveal usage patterns. When
analyzing existing code, one can formally or informally write a
program with the new feature. Often it is obvious just from looking at
the code.

Dropping support for currentStyle and runtimeStyle would break
Microsoft-only sites and applications.

Gecko, Webkit, Opera, IE all have no implementation of
document.defaultView.getCascadedStyle. It would just make more work
for all involved. Those involved included: Microsoft, for working to
implement getCascadedStyle, Microsoft's business customers, for having
to update their code, the w3c (who would presumably write up a spec),
and the rest of the web, .

Consider how existing code that uses currentStyle (only) would have to
change to still try to function:-

var value = "";
if(document.defaultView) {

 /// this fails in IE9 and Safari 1 (Safari 1 had a broken implementation).
  value = document.defaultView.getComputedStyle(el, "").height;
} else if(el.currentStyle) {
  value = el.currentStyle.height;
  }
}

to:-

var value = "";
if(document.defaultView) {
  if(document.defaultView.getComputedStyle) {
    value = document.defaultView.getComputedStyle(el, "").height;
  } else if(document.defaultView.getCascadedStyle) {
    value = document.defaultView.getCascadedStyle(el, "").height;
} else if(el.currentStyle) {
    value = el.currentStyle.height;
  }
}


Benefits:
Officially part of a new standard.

Drawbacks:
Breaks many sites in ways that probably cannot be easily fixed.
Makes developing cross-browser applications a lot more work.

Dropping both runtimeStyle would make it harder for code that attempts
to make conversion between em|ex|pt|in| to px.

Garrett