Re: [webcomponents] Imperative API for Insertion Points
On Mon, Feb 17, 2014 at 11:03 AM, Edward O'Connor eocon...@apple.comwrote: I think Ryosuke's content.add/remove are a better base layer than content select. In fact, content select is straightforwardly implementable / explainable on top of MO + content.add/remove, but there are several use cases that content.add/remove address that are difficult or impossible with content select (as described in Maciej's recent email on this thread). I agree. As a contributor to a major JS framework, I was shocked by the lack of an imperative API and that content select was even a thing. - Erik
Re: [webcomponents] Imperative API for Insertion Points
Hi Alex, You wrote: This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. I think Ryosuke's content.add/remove are a better base layer than content select. In fact, content select is straightforwardly implementable / explainable on top of MO + content.add/remove, but there are several use cases that content.add/remove address that are difficult or impossible with content select (as described in Maciej's recent email on this thread). Ted
Re: [webcomponents] Imperative API for Insertion Points
On Feb 15, 2014, at 11:30 PM, Alex Russell slightly...@google.com wrote: On Sat, Feb 15, 2014 at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. == Use Case == Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. == API Proposal == Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of *explicitly inserted nodes*. add(Element element) must act according to the following algorithm: If the content element's shadow host's node tree doesn't contain _element_, throw HierarchyRequestError. If element is already in some other content element's _explicitly inserted nodes_ then call remove with _element_ on that content element. Append _element_ to the end of _explicitly inserted nodes_. remove(Element element) must act according to the following algorithm: If the content element's _explicitly inserted nodes_ does not contain _element_, throw NotFoundError. Throwing exceptions is hostile to usability. If people are so inclined, we don’t have to throw an exception and silently fail. Remove _element_ from _explicitly inserted nodes_. The idea here is that _explicitly inserted nodes_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _explicitly inserted nodes_ should interact with select content attribute. I think the simplest model would be _explicitly inserted nodes_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: It doesn't require UA calling back to JS constantly to match elements Point 1 implies we don't expose when distribution happens for select content attribute. This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. We can imagine such a system for programmatic Shadow DOM with some sort of distribute(Element) callback that can be over-ridden and use add/remove methods to do final distribution. The problem here is that such a callback must be called on every node upon any state change because UAs have no way of knowing what causes redistribution for a given component. As as a matter of fact, some use cases may involve changing the node distributions based on some JS objects state. And having authors codify such conditions for UAs is much more cumbersome than letting them re-distribute nodes at their will. In terms of add/remove explaining “select” content attribute, we could describe node distribution as something that happens at the end of micro task via mutation observers. In fact, we should probably spec as such. I'm deeply skeptical of appeals to defeat/elide layering on the basis of performance arguments. Real-world systems often have fast-paths for common operations and we should note that a self-hosted DOM would feel no particular pain about calling back to JS. If your mental model is that the world is C++ and JS is bolt-on, you're bound to get this continuously wrong. Points 1 and 2 are mostly API advantages, not of performance. - R. Niwa
Re: [webcomponents] Imperative API for Insertion Points
On Feb 16, 2014, at 12:42 AM, Ryosuke Niwa rn...@apple.com wrote: On Feb 15, 2014, at 11:30 PM, Alex Russell slightly...@google.com wrote: On Sat, Feb 15, 2014 at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. == Use Case == Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. == API Proposal == Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of *explicitly inserted nodes*. add(Element element) must act according to the following algorithm: If the content element's shadow host's node tree doesn't contain _element_, throw HierarchyRequestError. If element is already in some other content element's _explicitly inserted nodes_ then call remove with _element_ on that content element. Append _element_ to the end of _explicitly inserted nodes_. remove(Element element) must act according to the following algorithm: If the content element's _explicitly inserted nodes_ does not contain _element_, throw NotFoundError. Throwing exceptions is hostile to usability. If people are so inclined, we don’t have to throw an exception and silently fail. Remove _element_ from _explicitly inserted nodes_. The idea here is that _explicitly inserted nodes_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _explicitly inserted nodes_ should interact with select content attribute. I think the simplest model would be _explicitly inserted nodes_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: It doesn't require UA calling back to JS constantly to match elements Point 1 implies we don't expose when distribution happens for select content attribute. This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. We can imagine such a system for programmatic Shadow DOM with some sort of distribute(Element) callback that can be over-ridden and use add/remove methods to do final distribution. The problem here is that such a callback must be called on every node upon any state change because UAs have no way of knowing what causes redistribution for a given component. As as a matter of fact, some use cases may involve changing the node distributions based on some JS objects state. And having authors codify such conditions for UAs is much more cumbersome than letting them re-distribute nodes at their will. To give you more concrete example, in the case of my random image element, how can UA notice that user clicking on the element should trigger reconstruction of the composed tree? Should the script call some method like redistribute() on the host upon click? But then, since the element needs to pick a child uniformly random, it probably needs to keep track of the number of children to be distributed and return true exactly when that node was passed into the callback. That’s an extremely cumbersome API at least for my use case. - R. Niwa
Re: [webcomponents] Imperative API for Insertion Points
On Sun, Feb 16, 2014 at 12:52 AM, Ryosuke Niwa rn...@apple.com wrote: On Feb 16, 2014, at 12:42 AM, Ryosuke Niwa rn...@apple.com wrote: On Feb 15, 2014, at 11:30 PM, Alex Russell slightly...@google.com wrote: On Sat, Feb 15, 2014 at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. *== Use Case ==* Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. *== API Proposal ==* Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of **explicitly inserted nodes* *. add(Element element) must act according to the following algorithm: 1. If the content element's shadow host's node tree doesn't contain _ *element*_, throw HierarchyRequestError. 2. If element is already in some other content element's _*explicitly inserted nodes*_ then call remove with _*element*_ on that content element. 3. Append _*element*_ to the end of _*explicitly inserted nodes*_. remove(Element element) must act according to the following algorithm: 1. If the content element's _*explicitly inserted nodes*_ does not contain _*element*_, throw NotFoundError. Throwing exceptions is hostile to usability. If people are so inclined, we don’t have to throw an exception and silently fail. 1. Remove _*element*_ from _*explicitly inserted nodes*_. The idea here is that _*explicitly inserted nodes*_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _*explicitly inserted nodes*_ should interact with select content attribute. I think the simplest model would be _*explicitly inserted nodes*_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: 1. It doesn't require UA calling back to JS constantly to match elements 2. Point 1 implies we don't expose when distribution happens for select content attribute. This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. We can imagine such a system for programmatic Shadow DOM with some sort of distribute(Element) callback that can be over-ridden and use add/remove methods to do final distribution. The problem here is that such a callback must be called on every node upon any state change because UAs have no way of knowing what causes redistribution for a given component. As as a matter of fact, some use cases may involve changing the node distributions based on some JS objects state. And having authors codify such conditions for UAs is much more cumbersome than letting them re-distribute nodes at their will. To give you more concrete example, in the case of my random image element, how can UA notice that user clicking on the element should trigger reconstruction of the composed tree? Isn't the stated design of the custom element that it re-constructs the composed tree with a random image every time it's clicked? It's not actually clear what you wanted here because there isn't any example code to go on. Should the script call some method like redistribute() on the host upon click? But then, since the element needs to pick a child uniformly random, it probably needs to keep track of the number of children to be distributed and return true exactly when that node was passed into the callback. That’s an extremely cumbersome API at least for my use case. I have the sense that if you produced example code you'd be able to make a better guess about what's onerous and what isn't. As it is, we're debating hypotheticals. Here's a version of your component
Re: [webcomponents] Imperative API for Insertion Points
On Feb 15, 2014, at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. == Use Case == Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. == API Proposal == Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of *explicitly inserted nodes*. add(Element element) must act according to the following algorithm: If the content element's shadow host's node tree doesn't contain _element_, throw HierarchyRequestError. If element is already in some other content element's _explicitly inserted nodes_ then call remove with _element_ on that content element. Append _element_ to the end of _explicitly inserted nodes_. remove(Element element) must act according to the following algorithm: If the content element's _explicitly inserted nodes_ does not contain _element_, throw NotFoundError. Remove _element_ from _explicitly inserted nodes_. The idea here is that _explicitly inserted nodes_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _explicitly inserted nodes_ should interact with select content attribute. I think the simplest model would be _explicitly inserted nodes_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: It doesn't require UA calling back to JS constantly to match elements Point 1 implies we don't expose when distribution happens for select content attribute. I'm sorry I don't know what was reading. The strawman proposal on the bug is basically what I'm proposing. add/remove are simply on distributedChildren instead. In fact, the stated design is probably better than what I have here now that we have getDistributedNodes() on content element. I think we just need to turn that into a Static/Live NodeList with add/remove. I would prefer the name distributedNodes. One important implication of adding this API surface is that the node distribution from declarative syntax also needs to happen at the end of each micro task as opposed to happen implicitly after each DOM mutation if we wanted to formulate the mutation observer as a way of implementing select content attribute. Since this is visible to the scripts, it's important to take it into the account in the level 1 specification. - R. Niwa
Re: [webcomponents] Imperative API for Insertion Points
On Feb 15, 2014, at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote:Hi all,I’d like to propose one solution for[Shadow]: Specify imperative API for node distributionhttps://www.w3.org/Bugs/Public/show_bug.cgi?id=18429because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates,and doesn’t satisfy my random image element use case below.== Use Case ==Random image element is a custom element that shows one of child img elements chosen uniformally random.e.g. the markup of a document that uses random-image-element may look like this:random-image-element img src="" img src="" img src=""/random-image-elementrandom-image-element displays one out of the three img child elements when a user clicks on it.As an author of this element, I could modify the DOM and add style content attribute directly on those elementsbut I would rather use shadow DOM to encapsulate the implementation.I wanted to mention that this handles other use cases besides selecting a random child which are impossible (or at least very awkward) with contentselect="" as presently defined:(1) A container component that can hold an arbitrary number of children, and wraps each of its light DOM children in a piece of markup inside the ShadowDOM. Consider a buttonbar component that placed each child into a button, and styled them all specially:buttonbar i _onclick_="execCommand('italic')"I/i b _onclick_="execCommand('bold')B/b u _onclick_="execCommand('underline')U/ubuttonImagine it would render like this (explaining why separate individual button elements won't cut it).(2) A component that expects alternate labels and corresponding items, wants to parent them into different boxes, but wants to make sure they remaincorresponding.tabview tabtitlePuppies/tabtitle tabpane lots of pictures of puppies /tabpane tabtitleKittens/tabtitle tabpane lots of pictures of kittens /tabpane tabtitleSadness/tabtitle !-- no tab pane provided for this title yet -- tabtitleBunnies/tabtitle tabpane lots of pictures of bunnies .../tabpane/tabviewThe component author would like this to render as a tabview with 4 tab labels at the top ("Puppies", "Kittens", "Sadness", "Bunnies") and 3 actual tab paneswith one placeholder inserted: (the puppy pane, the kitten pane, a blank placeholder, the bunny pane).But if my shadow DOM looks like this:div class=tab-label-barcontent select="tabtitle"/divdiv class=tab-holdercontent select="tabpane"/divThen the pictures of bunnies would line up with the "Sadness" label, and I don't have an easy way to add the placeholder anywhere but at the beginning or theend of the tab panes.(3) An element that selects some of its children conditionally. Let's say you have an element that will select different children depending on what features thebrowser supports:cond case condition="Modernizr.webgl"Spiffy WebGL view goes here!/case case condition="Modernizr.canvas"Passable 2-D canvas view goes here/case case defaultOh noes! You need more browser features to use this site!/case/condThe idea is to select in only exactly one of the cases - the first that matches. The others don't go into the shadow DOM. There isn't a great way to select only one of the "case" elements here (after having run the JS to evaluate which applies).The SVG "switch" element does something similar, as does Modernizr's normal class-based mode of operation.I hope these examples give more motivation for why programmatically binding an insertion point may be useful.Regards,Maciej
Re: [webcomponents] Imperative API for Insertion Points
On Feb 16, 2014, at 1:21 AM, Alex Russell slightly...@google.com wrote: On Sun, Feb 16, 2014 at 12:52 AM, Ryosuke Niwa rn...@apple.com wrote: On Feb 16, 2014, at 12:42 AM, Ryosuke Niwa rn...@apple.com wrote: On Feb 15, 2014, at 11:30 PM, Alex Russell slightly...@google.com wrote: On Sat, Feb 15, 2014 at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. == Use Case == Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. == API Proposal == Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of *explicitly inserted nodes*. add(Element element) must act according to the following algorithm: If the content element's shadow host's node tree doesn't contain _element_, throw HierarchyRequestError. If element is already in some other content element's _explicitly inserted nodes_ then call remove with _element_ on that content element. Append _element_ to the end of _explicitly inserted nodes_. remove(Element element) must act according to the following algorithm: If the content element's _explicitly inserted nodes_ does not contain _element_, throw NotFoundError. Throwing exceptions is hostile to usability. If people are so inclined, we don’t have to throw an exception and silently fail. Remove _element_ from _explicitly inserted nodes_. The idea here is that _explicitly inserted nodes_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _explicitly inserted nodes_ should interact with select content attribute. I think the simplest model would be _explicitly inserted nodes_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: It doesn't require UA calling back to JS constantly to match elements Point 1 implies we don't expose when distribution happens for select content attribute. This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. We can imagine such a system for programmatic Shadow DOM with some sort of distribute(Element) callback that can be over-ridden and use add/remove methods to do final distribution. The problem here is that such a callback must be called on every node upon any state change because UAs have no way of knowing what causes redistribution for a given component. As as a matter of fact, some use cases may involve changing the node distributions based on some JS objects state. And having authors codify such conditions for UAs is much more cumbersome than letting them re-distribute nodes at their will. To give you more concrete example, in the case of my random image element, how can UA notice that user clicking on the element should trigger reconstruction of the composed tree? Isn't the stated design of the custom element that it re-constructs the composed tree with a random image every time it's clicked? It's not actually clear what you wanted here because there isn't any example code to go on. Should the script call some method like redistribute() on the host upon click? But then, since the element needs to pick a child uniformly random, it probably needs to keep track of the number of children to be distributed and return true exactly when that node was passed into the callback. That’s an extremely cumbersome API at least for my use case. I have the sense that if you produced example code you'd be able to make a better guess about what's onerous and what isn't. As it is, we're debating
[webcomponents] Imperative API for Insertion Points
Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. == Use Case == Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. == API Proposal == Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of *explicitly inserted nodes*. add(Element element) must act according to the following algorithm: If the content element's shadow host's node tree doesn't contain _element_, throw HierarchyRequestError. If element is already in some other content element's _explicitly inserted nodes_ then call remove with _element_ on that content element. Append _element_ to the end of _explicitly inserted nodes_. remove(Element element) must act according to the following algorithm: If the content element's _explicitly inserted nodes_ does not contain _element_, throw NotFoundError. Remove _element_ from _explicitly inserted nodes_. The idea here is that _explicitly inserted nodes_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _explicitly inserted nodes_ should interact with select content attribute. I think the simplest model would be _explicitly inserted nodes_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: It doesn't require UA calling back to JS constantly to match elements Point 1 implies we don't expose when distribution happens for select content attribute. - R. Niwa
Re: [webcomponents] Imperative API for Insertion Points
On Sat, Feb 15, 2014 at 4:57 PM, Ryosuke Niwa rn...@apple.com wrote: Hi all, I’d like to propose one solution for [Shadow]: Specify imperative API for node distribution https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429 because select content attribute doesn’t satisfy the needs of framework/library authors to support conditionals in their templates, and doesn’t satisfy my random image element use case below. *== Use Case ==* Random image element is a custom element that shows one of child img elements chosen uniformally random. e.g. the markup of a document that uses random-image-element may look like this: random-image-element img src=kitten.jpg img src=cat.jpg img src=webkitten.jpg /random-image-element random-image-element displays one out of the three img child elements when a user clicks on it. As an author of this element, I could modify the DOM and add style content attribute directly on those elements but I would rather use shadow DOM to encapsulate the implementation. *== API Proposal ==* Add two methods void add(Element) and void remove(Element) to content element. (We can give them more descriptive names. I matched select element for now). Each content element has an ordered list of **explicitly inserted nodes**. add(Element element) must act according to the following algorithm: 1. If the content element's shadow host's node tree doesn't contain _ *element*_, throw HierarchyRequestError. 2. If element is already in some other content element's _*explicitly inserted nodes*_ then call remove with _*element*_ on that content element. 3. Append _*element*_ to the end of _*explicitly inserted nodes*_. remove(Element element) must act according to the following algorithm: 1. If the content element's _*explicitly inserted nodes*_ does not contain _*element*_, throw NotFoundError. Throwing exceptions is hostile to usability. 1. Remove _*element*_ from _*explicitly inserted nodes*_. The idea here is that _*explicitly inserted nodes*_ of an insertion point A would be the list of distributed nodes of A but I haven't figured out exactly how _*explicitly inserted nodes*_ should interact with select content attribute. I think the simplest model would be _*explicitly inserted nodes*_ simply overriding whatever select content attribute was trying to do but I don't have a strong opinion about how they should interact yet. I don't think it makes sense to support redistributions, etc... at least in the initial API. This proposal has an advantage over the existing proposal on https://www.w3.org/Bugs/Public/show_bug.cgi?id=18429: 1. It doesn't require UA calling back to JS constantly to match elements 2. Point 1 implies we don't expose when distribution happens for select content attribute. This doesn't seem like progress. I'd hope an imperative API would, instead, be used to explain how the existing system works and then propose layering that both accommodates the existing system and opens new areas for programmatic use. We can imagine such a system for programmatic Shadow DOM with some sort of distribute(Element) callback that can be over-ridden and use add/remove methods to do final distribution. I'm deeply skeptical of appeals to defeat/elide layering on the basis of performance arguments. Real-world systems often have fast-paths for common operations and we should note that a self-hosted DOM would feel no particular pain about calling back to JS. If your mental model is that the world is C++ and JS is bolt-on, you're bound to get this continuously wrong. Regards
