Re: [whatwg] style sheet blocking scripts
This is false. WebKit will block the parser when it encounters an external script if there are pending stylesheet loads. However we have a speculative preloader that will continue to parse and load resources beyond that script (but the real parser will be blocked). dave On Dec 9, 2009, at 3:42 PM, tali garsiel wrote: 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. Date: Wed, 9 Dec 2009 17:01:30 + From: i...@hixie.ch To: t_gars...@hotmail.com; bzbar...@mit.edu CC: wha...@whatwg.org Subject: Re: [whatwg] style sheet blocking scripts On Wed, 28 Oct 2009, tali garsiel wrote: This is a quote from Section 4.2 of the spec: A style sheet in the context of the Document of an HTML parser or XML parser is said to be a style sheet blocking scripts if the element was created by that Document's parser, and the element is either a style element or a link element that was an external resource link that contributes to the styling processing model when the element was c reated by the parser, and the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document And the section about parsing - the script tag says that before executing a script the parser must: 3. Spin the event loop until there is no style sheet blocking scripts and the script's ready to be parser-executed flag is set. I have two questions: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. According to the spec the style sheet always blocks a script, am I right? 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document Does it mean the style sheet blocks scripts only if it's currently being parsed? On Wed, 28 Oct 2009, Boris Zbarsky wrote: On 10/28/09 2:59 AM, tali garsiel wrote: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. You know wrong, sorry. Firefox has the behavior the spec describes; webkit blocks the parser completely on stylesheets (the behavior Firefox used to have). Last I chec ked, at least. 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document The parts of that condition basically mean: 1) When the element was created by the parser, it was in the then-enabled stylesheet set (i.e. not an alternate stylesheet). 2) The stylesheet, or one of its @import descendants, is still loading. 3) The stylesheet linking element is still in the document (so the stylesheet still applies). Thanks Boris. Tali, does this answer your question to your satisfaction? -- Ian Hickson U+1047E )\._.,--,'``. fL http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.' Windows Live Hotmail: Your friends can get your Facebook updates, right from Hotmail®.
Re: [whatwg] style sheet blocking scripts
On Dec 9, 2009, at 4:10 PM, James Robinson wrote: 2009/12/9 tali garsiel t_gars...@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. - James This is accurate, although I'd add that we consider it a bug that we don't yet block the parser for inline scripts in addition to external scripts. dave
Re: [whatwg] style sheet blocking scripts
It is considered a bug. On Dec 9, 2009, at 4:57 PM, Jonas Sicking wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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? / Jonas
Re: [whatwg] style sheet blocking scripts
I understand now. Thank you for your answers. From: hy...@apple.com Date: Thu, 10 Dec 2009 12:15:50 -0600 To: jam...@google.com CC: wha...@whatwg.org; bzbar...@mit.edu; i...@hixie.ch; t_gars...@hotmail.com Subject: Re: [whatwg] style sheet blocking scripts On Dec 9, 2009, at 4:10 PM, James Robinson wrote:2009/12/9 tali garsiel t_gars...@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. - James This is accurate, although I'd add that we consider it a bug that we don't yet block the parser for inline scripts in addition to external scripts. dave _ Windows Live: Make it easier for your friends to see what you’re up to on Facebook. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_2:092009
Re: [whatwg] style sheet blocking scripts
On Wed, 28 Oct 2009, tali garsiel wrote: This is a quote from Section 4.2 of the spec: A style sheet in the context of the Document of an HTML parser or XML parser is said to be a style sheet blocking scripts if the element was created by that Document's parser, and the element is either a style element or a link element that was an external resource link that contributes to the styling processing model when the element was created by the parser, and the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document And the section about parsing - the script tag says that before executing a script the parser must: 3. Spin the event loop until there is no style sheet blocking scripts and the script's ready to be parser-executed flag is set. I have two questions: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. According to the spec the style sheet always blocks a script, am I right? 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document Does it mean the style sheet blocks scripts only if it's currently being parsed? On Wed, 28 Oct 2009, Boris Zbarsky wrote: On 10/28/09 2:59 AM, tali garsiel wrote: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. You know wrong, sorry. Firefox has the behavior the spec describes; webkit blocks the parser completely on stylesheets (the behavior Firefox used to have). Last I checked, at least. 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document The parts of that condition basically mean: 1) When the element was created by the parser, it was in the then-enabled stylesheet set (i.e. not an alternate stylesheet). 2) The stylesheet, or one of its @import descendants, is still loading. 3) The stylesheet linking element is still in the document (so the stylesheet still applies). Thanks Boris. Tali, does this answer your question to your satisfaction? -- Ian Hickson U+1047E)\._.,--,'``.fL http://ln.hixie.ch/ U+263A/, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.'
Re: [whatwg] style sheet blocking scripts
2009/12/9 tali garsiel t_gars...@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. - James Date: Wed, 9 Dec 2009 17:01:30 + From: i...@hixie.ch To: t_gars...@hotmail.com; bzbar...@mit.edu CC: wha...@whatwg.org Subject: Re: [whatwg] style sheet blocking scripts On Wed, 28 Oct 2009, tali garsiel wrote: This is a quote from Section 4.2 of the spec: A style sheet in the context of the Document of an HTML parser or XML parser is said to be a style sheet blocking scripts if the element was created by that Document's parser, and the element is either a style element or a link element that was an external resource link that contributes to the styling processing model when the element was c reated by the parser, and the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document And the section about parsing - the script tag says that before executing a script the parser must: 3. Spin the event loop until there is no style sheet blocking scripts and the script's ready to be parser-executed flag is set. I have two questions: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. According to the spec the style sheet always blocks a script, am I right? 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document Does it mean the style sheet blocks scripts only if it's currently being parsed? On Wed, 28 Oct 2009, Boris Zbarsky wrote: On 10/28/09 2:59 AM, tali garsiel wrote: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. You know wrong, sorry. Firefox has the behavior the spec describes; webkit blocks the parser completely on stylesheets (the behavior Firefox used to have). Last I chec ked, at least. 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document The parts of that condition basically mean: 1) When the element was created by the parser, it was in the then-enabled stylesheet set (i.e. not an alternate stylesheet). 2) The stylesheet, or one of its @import descendants, is still loading. 3) The stylesheet linking element is still in the document (so the stylesheet still applies). Thanks Boris. Tali, does this answer your question to your satisfaction? -- Ian Hickson U+1047E )\._.,--,'``. fL http://ln.hixie.ch/ U+263A /, _.. \ _\ ;`._ ,. Things that are impossible just take longer. `._.-(,_..'--(,_..'`-.;.' -- Windows Live Hotmail: Your friends can get your Facebook updates, right from Hotmail®.http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_4:092009
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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? / Jonas
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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 http://trac.webkit.org/browser/trunk/WebCore/html/HTMLTokenizer.cpp#L2017I'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. - James / Jonas
Re: [whatwg] style sheet blocking scripts
On 12/9/09 3:06 PM, James Robinson wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com mailto:jam...@google.com wrote: WebKit does not suspend script execution on requests for visual information if stylesheets have not loaded 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. I'm having a hard time reconciling the above two claims. -Boris
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 3:06 PM, James Robinson jam...@google.com wrote: On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 3:18 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 3:06 PM, James Robinson jam...@google.com wrote: On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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? Or rather, why is this more unobservable for inline scripts than for external scripts? / Jonas
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 3:18 PM, Boris Zbarsky bzbar...@mit.edu wrote: On 12/9/09 3:06 PM, James Robinson wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com mailto:jam...@google.com wrote: WebKit does not suspend script execution on requests for visual information if stylesheets have not loaded 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. I'm having a hard time reconciling the above two claims. Hence the in theory. If WebKit did suspend script execution on requests for information that pending stylesheets might influence, then theory would match practice. It currently does not (which I believe is contrary to what the spec says). I'm curious if this actually negatively impacts anyone in the wild, as suspending script execution in the middle of a block to wait for a network load is generally not ideal. - James -Boris
Re: [whatwg] style sheet blocking scripts
On Wed, Dec 9, 2009 at 3:19 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 3:18 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 3:06 PM, James Robinson jam...@google.com wrote: On Wed, Dec 9, 2009 at 2:57 PM, Jonas Sicking jo...@sicking.cc wrote: On Wed, Dec 9, 2009 at 2:10 PM, James Robinson jam...@google.com wrote: 2009/12/9 tali garsiel t_gars...@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? Or rather, why is this more unobservable for inline scripts than for external scripts? You're right, there's no real difference in the observability of this behavior for inline vs external scripts. - James / Jonas
Re: [whatwg] style sheet blocking scripts
On 12/9/09 3:53 PM, James Robinson wrote: Hence the in theory. If WebKit did suspend script execution on requests for information that pending stylesheets might influence, then theory would match practice. It currently does not (which I believe is contrary to what the spec says). I'm curious if this actually negatively impacts anyone in the wild, as suspending script execution in the middle of a block to wait for a network load is generally not ideal. Sure. The Gecko behavior is to not run the inline script until the stylesheets have loaded, just like webkit (and Gecko) does for non-inline scripts. Any inline script that asks for layout information is affected, right? Good question on how much this is a problem in practice. I don't have data on that -Boris
[whatwg] style sheet blocking scripts
Hi, This is a quote from Section 4.2 of the spec: A style sheet in the context of the Document of an HTML parser or XML parser is said to be a style sheet blocking scripts if the element was created by that Document's parser, and the element is either a style element or a link element that was an external resource link that contributes to the styling processing model when the element was created by the parser, and the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document And the section about parsing - the script tag says that before executing a script the parser must: 3. Spin the event loop until there is no style sheet blocking scripts and the script's ready to be parser-executed flag is set. I have two questions: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. According to the spec the style sheet always blocks a script, am I right? 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document Does it mean the style sheet blocks scripts only if it's currently being parsed? Tali _ Windows Live: Make it easier for your friends to see what you’re up to on Facebook. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_2:092009
Re: [whatwg] style sheet blocking scripts
On 10/28/09 2:59 AM, tali garsiel wrote: 1. As far as I know, Firefox and Webkit have a stall on demand behavior, where a stylesheet blocks a script only if the script asks from style information. You know wrong, sorry. Firefox has the behavior the spec describes; webkit blocks the parser completely on stylesheets (the behavior Firefox used to have). Last I checked, at least. 2. Can you clarify the condition - the element's style sheet was enabled when the element was created by the parser, and the element's style sheet ready flag is not yet set, and, the last time the event loop reached step 1, the element was in that Document The parts of that condition basically mean: 1) When the element was created by the parser, it was in the then-enabled stylesheet set (i.e. not an alternate stylesheet). 2) The stylesheet, or one of its @import descendants, is still loading. 3) The stylesheet linking element is still in the document (so the stylesheet still applies). -Boris
