[whatwg] style sheet blocking scripts

[Jonas Sicking]

On Wed, Dec 9, 2009 at 3:06 PM, James Robinson <jamesr at google.com> wrote:
> On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking <jonas at sicking.cc> wrote:
>>
>> On Wed, Dec 9, 2009 at 2:10 PM, James Robinson <jamesr at google.com> wrote:
>> > 2009/12/9 tali garsiel <t_garsiel at hotmail.com>
>> >>
>> >> Well, not completely.
>> >> Regarding the first question- Webkit guys told me (on their IRC
>> >> channel)
>> >> that the don't block the parser and only block scripts that request
>> >> visual
>> >> information, so I'm still  confused.
>> >
>> > Here's my understanding of the implementation inside WebKit currently:
>> > During parsing, WebKit does not block the parser on stylesheet loads,
>> > but
>> > does block external scripts from running until previously-encountered
>> > stylesheets have loaded.  WebKit does not suspend script execution on
>> > requests for visual information if stylesheets have not loaded (for
>> > example
>> > for inline scripts or in the case of stylesheets added dynamically after
>> > parsing has completed).  WebKit does suspend parsing of the document on
>> > script loads, but has a speculative preloader to attempt to start
>> > fetches
>> > for resources past the <script> tag.
>>
>> Why does webkit treat external scripts different from inline scripts
>> here? I.e. why is an inline script allowed to run even if there are
>> pending stylesheet loads, but external scripts not? That seems
>> inconsistent and confusing.
>>
>> Is this considered a bug or desired behavior?
>
> The
> former: http://trac.webkit.org/browser/trunk/WebCore/html/HTMLTokenizer.cpp#L2017
> I'm not sure how much this matters in practice.  In theory, this is
> unobservable to the page unless it queries the loaded stylesheets directly
> or a property derived from layout both of which should suspend script
> execution.

Why is this more "in theory" for inline scripts than for external scripts?

/ Jonas