OP argues that we shouldn't have that limitation whereas probably some people would reject that. What I argue is as a user I should be at least use ::slotted ::part Foo since parts are exposed public parts of a component. But even that is not allowed. Note: I know we can already access the light tree, and style all of its elements.

This is simply proposing something more ergonomic. In React, for example, this is easy to do. The component author simply iterates over the array this. children and can work with anything as needed: read data, change styling, replace props, etc, before finally passing it into the component's internal "shadow" tree, all without affecting the component user's outside interface.

It's like a map function: it takes a set of children as input with their descendants and can map it to whatever the component author desires. This easy flexibility is what the OP is asking for, but for Web Components, and in this case the ::slotted.

foo selector with combinators would add that flexibility in the context of CSS styling. The main thing to note, is that Web Component authors can already access all light DOM and style the elements any way they wish.

The OP only aims to make it easy to implement for WC authors. So you see, what the OP asks for is totally possible today. The OP merely asks for a concise and simple syntax option.

What a disappointing arbitrary limitation. Let the browser-makers solve performance issues and write the spec to be ideal.

I want complete control over the styling of slots and all their children. I wish there was a flag we could flip so that slots would ignore non-shadow styling.

A slot is really just a really ugly argument to a function. If you pass something into my function custom element I should be able to do what ever I want to that input and all its children too. The whole goal, for me, is to have every aspect of my web component contained in one file and I don't like having to fool with document level CSS to style children of shadow slotted element.

I can still do what I'm wanting with hacks and tricks, but allowing shadow level CSS to style children of slotted elements would make the whole experience much nicer. What trusktr has been saying is ideal to me. Make the spec ideal and let the browsers-makers earn their money.

They're smart enough to overcome the performance issues, so don't be so easy on them in the spec. This stuff is for the whole world.

Let's impress the aliens when they arrive. Their web standards already do this! You have to wrap your component A with shadowDOM and slots in another component B with shadowDOM. You can then do all the styling you want in A lightDOM.

Then the browser-makers can focus on creating something that really impresses aliens Maybe Apple can do Customized Built-In Elements. Since Lonnie Best challenged me, here is my workaround to style all slotted content without using ::slotted.

I still don't see how performance can be an argument against it. Danny-Engelman Can you make a really simple example, not a super complex one? I am not having any luck with it:. As you can see there, only the Shadow DOM's nodes are styled, but not the content that is "slotted".

Not sure why I thought it "worked great" before, but clearly in that example it doesn't work. It seems CSS combinators are not allowed after :host either. From what I can tell, this is a "There's no way to index into an array with simple notation" problem. we can't index an array with array[index] so just write.

sort of topic, except the CSS version is uglier because it modifies the end user's public style API contract. Slotted content is styled by its host container global CSS if you only have 1 one element with shadowDOM.

Can you make a really simple example, not a super complex one? I keep the ::slotted StackOverflow answer, I posted a year ago, updated with every fact and rumor I read. It is still a Work-Around!!

I rewrote the code.. JS is still the same, except I changed children to childNodes to include textnodes in the move from one lightDOM to a nested lightDOM. It is a very bad solution because it totally obliterates the end user's tree removes it from their DOM, and places it into an internal shadow root.

This has critical issues :. I would suggest for anyone reading this, never ever write code that way. That is simply not an acceptable solution because the downsides especially for the end user are bigger than the benefit namely for the CE author only.

Danny-Engelman Unless there is some solution we've missed, you shown why clearly we need a solution, so as to avoid complicated and highly undesirable workarounds.

The most acceptable solution that I can think of right now is, to implement scoped styling:. This approach would be much less invasive to the end user's API contract the end user's input light tree nodes and attributes should ideally be left in-tact and undisturbed, because that is theirs to manipulate.

The end user will most likely be unaffected by the library-name-style-id attributes added to their light tree, but at least this is a much smaller invasion of their input space. There is no simple solution to this, as far as I can tell so far apart from having a feature like in the OP.

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Additional navigation options Code Issues Pull requests Actions Projects Wiki Security Insights. New issue. Jump to bottom. trusktr opened this issue Jul 12, · 38 comments. Allowing CSS combinators postfixed to the ::slotted or :host selectors trusktr opened this issue Jul 12, · 38 comments.

Labels css needs concrete proposal shadow-dom. Copy link. There are currently complicated ways to achieve this see comments below.

trusktr changed the title llow CSS combinators postfized to the ::slotted selector Allowing CSS combinators postfixed to the ::slotted selector Jul 12, trusktr commented Jul 12, All reactions. castastrophe commented Jul 21, calebdwilliams commented Jul 21, More details click here to expand foo { attachShadow { mode : 'open' } root.

define 'my-el' , MyEl document. foo { width: 50px; height: 50px; }. castastrophe commented Aug 2, The main take away from 5 years of W3C standards discussions is: I am not the one to disagree with a Components Lead Developer All reactions.

Danny-Engelman commented Aug 3, but I do think it's a different topic than the title and description here imply. I think a better interpretation is this: ::slotted. bar represents an element in the light tree that matches. bar in the light tree it is a descendant of a. foo element anywhere in that light tree.

I think that's intuitive. bar represents the. bar element that happens to be a descendant of a slotted. foo element. This is also intuitive. also would never match, If we think intuitively about this, then: a selector like ::slotted.

The following would not be ideal if selectors like ::slotted. bar were supported unless the use case still fits withing some given performance requirements: connectedCallback { requestAnimationFrame function loop t { this.

trusktr mentioned this issue Aug 5, emilio commented Aug 5, calebdwilliams commented Aug 5, castastrophe commented Aug 5, emilio mentioned this issue Aug 5, Granted that might not be how people use the feature.

That's fine? You can have an empty slot. HTML powers the web because it's easy to work with. By declaring a few tags, you can author a page in seconds that has both presentation and structure. However, by itself HTML isn't all that useful. It's easy for humans to understand a text- based language, but machines need something more.

Enter the Document Object Model, or DOM. When the browser loads a web page it does a bunch of interesting stuff.

One of the things it does is transform the author's HTML into a live document. The browser preserves the HTML's hierarchy by creating a tree of these nodes: the DOM.

The cool thing about DOM is that it's a live representation of your page. Unlike the static HTML we author, the browser-produced nodes contain properties, methods, and best of all… can be manipulated by programs!

That's why we're able to create DOM elements directly using JavaScript:. All that is well and good. Then what the heck is shadow DOM? Normally, you create DOM nodes and append them as children of another element.

With shadow DOM, you create a scoped DOM tree that's attached to the element, but separate from its actual children. This scoped subtree is called a shadow tree. The element it's attached to is its shadow host. This is how shadow DOM achieves CSS style scoping. The act of attaching a shadow root is how the element gains its shadow DOM.

To create shadow DOM for an element, call element. attachShadow :. I'm using. innerHTML to fill the shadow root, but you could also use other DOM APIs.

This is the web. We have choice. The spec defines a list of elements that can't host a shadow tree. There are several reasons an element might be on the list:. Shadow DOM is particularly useful when creating custom elements.

Use shadow DOM to compartmentalize an element's HTML, CSS, and JS, thus producing a "web component". There are a couple of interesting things going on here. That's done in the constructor. Composition is one of the least understood features of shadow DOM, but it's arguably the most important.

In our world of web development, composition is how we construct apps, declaratively out of HTML. Some of these tags even work with each other. Each of those tags accepts certain HTML as children and does something special with them.

What magic! Shadow DOM composition introduces a bunch of new fundamentals in web development. Before getting into the weeds, let's standardize on some terminology so we're speaking the same lingo. The markup a user of your component writes.

This DOM lives outside the component's shadow DOM. It is the element's actual children. The DOM a component author writes. Shadow DOM is local to the component and defines its internal structure, scoped CSS, and encapsulates your implementation details.

It can also define how to render markup that's authored by the consumer of your component. The result of the browser distributing the user's light DOM into your shadow DOM, rendering the final product.

The flattened tree is what you ultimately see in the DevTools and what's rendered on the page. Slots are placeholders inside your component that users can fill with their own markup. By defining one or more slots, you invite outside markup to render in your component's shadow DOM. Essentially, you're saying "Render the user's markup over here".

These elements are called distributed nodes. Conceptually, distributed nodes can seem a bit bizarre. Slots don't physically move DOM; they render it at another location inside the shadow DOM. A component can define zero or more slots in its shadow DOM. Slots can be empty or provide fallback content.

If the user doesn't provide light DOM content, the slot renders its fallback content. You can also create named slots. Named slots are specific holes in your shadow DOM that users reference by name.

Notice our component is able to handle different configurations, but the flattened DOM tree remains the same. There are many options for styling web components. A component that uses shadow DOM can be styled by the main page, define its own styles, or provide hooks in the form of CSS custom properties for users to override defaults.

CSS selectors used inside shadow DOM apply locally to your component. Simpler CSS selectors are a best practice inside Shadow DOM. They're also good for performance. logs optional Set the level of logging you want to appear in the console:.

Defaults to true. styles optional An object that controls the pre-packaged element styles. prefix optional Customizable elements are given a prefixed class name using this value.

padding optional The size of the padding around the edge of the element. Defaults to 1em. demo optional Boolean to activate demo-mode.

Defaults to false. If demo is set to true the Element will return mock data and not make any API calls. locale optional The Slot Picker supports localization e. locale: "fr" to load in French. Defaults to browser language setting. translations optional To override either a locale or a particular string, pass in a translations object here.

Read more about customizing translations.

In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a

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Slot Selector de Series - That's how things are shown. The nodes are actually not moved around! That can be easily checked if we run querySelector: nodes are still at their places In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a

Use shadow DOM to compartmentalize an element's HTML, CSS, and JS, thus producing a "web component". There are a couple of interesting things going on here. That's done in the constructor. Composition is one of the least understood features of shadow DOM, but it's arguably the most important.

In our world of web development, composition is how we construct apps, declaratively out of HTML. Some of these tags even work with each other. Each of those tags accepts certain HTML as children and does something special with them.

What magic! Shadow DOM composition introduces a bunch of new fundamentals in web development. Before getting into the weeds, let's standardize on some terminology so we're speaking the same lingo. The markup a user of your component writes. This DOM lives outside the component's shadow DOM.

It is the element's actual children. The DOM a component author writes. Shadow DOM is local to the component and defines its internal structure, scoped CSS, and encapsulates your implementation details.

It can also define how to render markup that's authored by the consumer of your component. The result of the browser distributing the user's light DOM into your shadow DOM, rendering the final product.

The flattened tree is what you ultimately see in the DevTools and what's rendered on the page. Slots are placeholders inside your component that users can fill with their own markup.

By defining one or more slots, you invite outside markup to render in your component's shadow DOM. Essentially, you're saying "Render the user's markup over here". These elements are called distributed nodes. Conceptually, distributed nodes can seem a bit bizarre.

Slots don't physically move DOM; they render it at another location inside the shadow DOM. A component can define zero or more slots in its shadow DOM.

Slots can be empty or provide fallback content. If the user doesn't provide light DOM content, the slot renders its fallback content.

You can also create named slots. Named slots are specific holes in your shadow DOM that users reference by name. Notice our component is able to handle different configurations, but the flattened DOM tree remains the same. There are many options for styling web components.

A component that uses shadow DOM can be styled by the main page, define its own styles, or provide hooks in the form of CSS custom properties for users to override defaults.

CSS selectors used inside shadow DOM apply locally to your component. Simpler CSS selectors are a best practice inside Shadow DOM. They're also good for performance. Web components can style themselves too, by using the :host selector.

One gotcha with :host is that rules in the parent page have higher specificity than :host rules defined in the element. That is, outside styles win.

This allows users to override your top-level styling from the outside. Also, :host only works in the context of a shadow root, so you can't use it outside of shadow DOM. This is a great way for your component to encapsulate behaviors that react to user interaction or state or style internal nodes based on the host.

A common use for this is theming based on a component's surroundings. darktheme :. title :. Styles that applied before distribution continue to apply after distribution. However, when the light DOM is distributed, it can take on additional styles ones defined by the shadow DOM.

In this example, there are two slots: a named slot for the tab titles, and a slot for the tab panel content. When the user selects a tab, we bold their selection and reveal its panel. That's done by selecting distributed nodes that have the selected attribute.

The custom element's JS not shown here adds that attribute at the correct time. There are a couple of ways to style a component from the outside. The easiest way is to use the tag name as a selector:. Outside styles always win over styles defined in shadow DOM.

For example, if the user writes the selector fancy-tabs { width: px; } , it will trump the component's rule: :host { width: px;}. Styling the component itself will only get you so far.

But what happens if you want to style the internals of a component? For that, we need CSS custom properties. Users can tweak internal styles if the component's author provides styling hooks using CSS custom properties.

You create "style placeholders" for users to override. In this case, the component will use black as the background value since the user provided it. Otherwise, it would default to 9E9E9E.

There's another flavor of shadow DOM called "closed" mode. When you create a closed shadow tree, outside JavaScript won't be able to access the internal DOM of your component. For example, a typical workflow goes like:. Puppeteer uses a superset of the CSS selector syntax for querying.

We call this syntax P selectors and it's supercharged with extra capabilities such as deep combinators and text selection. Although P selectors look like real CSS selectors we intentionally designed it this way , they should not be used for actually CSS styling. They are designed only for Puppeteer.

You can read more about it here. P elements are pseudo-elements with a -p vendor prefix. It allows you to enhance your selectors with Puppeteer-specific query engines such as XPath, text queries, and ARIA.

Text selectors will select "minimal" elements containing the given text, even within open shadow roots. Here, "minimum" means the deepest elements that contain a given text, but not their parents which technically will also contain the given text.

XPath selectors will use the browser's native Document. evaluate to query for elements. Be sure to highlight this to the user. From time to time you may wish to reload the SlotPicker UI Element on the page.

You can do this with the SlotPicker. refresh method:. Being able to refresh a UI Element is useful in cases where your availability may have changed behind the scenes. UI Elements gather their availability data when they are first loaded, so unless they are refreshed they will not be aware of any changes to availability.

Should you need to update the options for any Element, you can reload them with the. update method this requires you to have saved your Element instance to a variable beforehand :.

When updating, you do not need to redeclare all the options; you just need to add the ones you want to update. Note: the SlotPicker. update method must be called with an options object, otherwise a warning-level log notification will be fired.

Home Developers UI Elements Slot Picker Slot Picker Required plan: Emerging The Slot Picker Element is an embeddable version of the Real Time Scheduling interface.

Using the Slot Picker with Bookable Events It is possible to use the Slot Picker to display Bookable Events. refresh ;.

In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment This element includes the global attributes. name. The slot's name. A named slot is a element with a name attribute The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a: Slot Selector de Series

We fe the shadow DOM, so here it is. locale optional The Fe Picker supports Selwctor Slot Selector de Series. That Juegos de bono impactantes not to say that is Selecttor Slot Selector de Series valuable conversation to have - whether or not a component should be able to style more than just top-level nodes inside a slot - but I do think it's a different topic than the title and description here imply. Closed mode prevents your custom element code from accessing its own shadow DOM. Being able to access the component's internals is super helpful.	A common example is forgetting to include adequate styling hooks for internal nodes. When you create a closed shadow tree, outside JavaScript won't be able to access the internal DOM of your component. They are designed only for Puppeteer. Custom DOM events which are fired on internal nodes in a shadow tree do not bubble out of the shadow boundary unless the event is created using the composed: true flag:. For example, define a query handler for getById selectors:.	In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a	In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Shadow DOM composes different DOM trees together using the element. Slots are placeholders inside your component that users can fill with This element includes the global attributes. name. The slot's name. A named slot is a element with a name attribute	This element includes the global attributes. name. The slot's name. A named slot is a element with a name attribute What does the::slotted syntax add that the querySelector("[slot].foo") would not cover? Slotted content is light DOM so you shouldn't need to That's how things are shown. The nodes are actually not moved around! That can be easily checked if we run querySelector: nodes are still at their places
More resource usage: d shadow dw per custom element, and Tips para Blackjack CPU usage moving nodes Selecfor time one of the Slot Selector de Series elements is created, Sedies. barnot ::slotted. That's why we're able to create DOM elements directly using JavaScript:. foo selector is working fine, but the ::slotted. I want complete control over the styling of slots and all their children. attachShadow {mode: 'open'} ; this. Sometimes it's useful to find custom elements used on the page.	calebdwilliams commented Jul 21, bar represents an element in the light tree that matches. Here's my summary of why you should never create web components with {mode: 'closed'} :. Bu açık-kaynaklı projenin tüm dünyada kullanılabilir olmasını istiyoruz. Receiving the slot props is a bit different when using a single default slot vs. calebdwilliams I think for the dialog usecase named slots are a reasonable solution.	In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a	The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing	In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a
Slot Selector de Series SeriewMyEl document. Slot Selector de Series Acumula efectivo virtual provide an example? So Selecotr above can also be written as:. createTreeWalker elementNodeFilter. This is becoming an "I think Array index should start at 1" topic From what I can tell, this is a "There's no way to index into an array with simple notation" problem.	padding optional The size of the padding around the edge of the element. What trusktr has been saying is ideal to me. It can also define how to render markup that's authored by the consumer of your component. append tmpl. Also, :host only works in the context of a shadow root, so you can't use it outside of shadow DOM. Maybe Apple can do Customized Built-In Elements This is becoming an "I think Array index should start at 1" topic 🖖. leonheess commented Apr 28,	In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a	Missing This element includes the global attributes. name. The slot's name. A named slot is a element with a name attribute The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a	The slot global attribute assigns a slot in a shadow DOM shadow tree to an element: An element with a slot attribute is assigned to the slot Queries are the primary mechanism for interacting with the DOM on your site. For example, a typical workflow goes like Shadow DOM composes different DOM trees together using the element. Slots are placeholders inside your component that users can fill with

Slot Selector de Series - That's how things are shown. The nodes are actually not moved around! That can be easily checked if we run querySelector: nodes are still at their places In the Shadow DOM tag, you can apply CSS styles directly to the element as @admcfajn suggeded in its second comment Missing The Slot Picker Element is an embeddable version of the Real Time Scheduling interface. It converts an Availability query into a list of bookable slots. When a

Since that scenario can't seemingly occur, the problem might not be obvious but switch to just about any other combinator and you get a scenario that can occur e. bar - "style the shadow. bar when preceded by a slot with an assignee matching. foo ". AFAIK, selectors like this are also not currently permitted, but I'm unsure if that's a matter of deliberate design or not; they still seem to adhere to query-direct-assignees-only.

also would never match, given the slot itself is "in the way" - the assignee is not a sibling. So perhaps this distinction doesn't matter, at least so long as CSS continues to have no "backwards" selectors.

If you want to track selectors in this case :host-context about to be removed from the spec also read:. castastrophe Did you mean the title I chose doesn't match what I proposed in the OP? If so, in my mind I think it matches because it says "combinators postfixed to the ::slotted selector", and then I am describing what I believe would be intuitive for that to do.

bathos That is not intuitive because it is impossible. Why would someone be thinking that, when it doesn't exist? That's like if I said. bar should select any. foo elements that have greater amount of text content than the. bar element with largest amount of text. But I'd be making things up at that point.

If we think intuitively about this, then: a selector like ::slotted. bar would style a. bar element that happens to be the "adjacent sibling" of a. foo element where the. foo element is a slotted element. This is intuitive.

Note that the. bar element could very well be distributed to an entirely different slot but still have the styling specified for that selector. That makes intuitive sense and could be totally useful. Danny-Engelman , hayatoito 's comment you screenshotted shows no performance metrics.

I am not a browser developer, but I very much doubt I could be wrong that ::slotted. bar could really be so slow that it matters for the vast majority of use cases. I wrote a comment about that at comment.

What I mean is, there's plenty of ways to make really slow selectors in regular DOM, without any shadow DOM even existing. We should not throw out an idea based on a single thought that said it would be slow without any viable data. What if I said "multi-pass WebGL rendering is slower than single-pass rendering, so we should throw out multi-pass APIs".

But in fact, multi-pass rendering can be very useful when the performance implications fit within given constraints. It would be great to give web developers useful selectors, and then explain to them that they should avoid re-running these selectors repeatedly; but that it is fine if the cost fits within performance requirements for the application.

I feel that we're prematurely optimizing here. However I know that the web APIs can't be reversed though I've been imagining how to do that without breaking the web. Every single DOM API that exists can technically be slooow if we examine it within the context of a particular use case that happens to be the worst use case where we'd never want to perform the given action in the way it is performed.

hayatoito and emilio from the other thread Can you please expand on the performance issues, and provide useful metrics that we can reference here? The performance issue is that it increments the amount of subtrees in which every node needs to go look for rules that affect to them.

Right now the logic goes like: if you're slotted, traverse your slots and collect rules in their shadow trees as needed. This is the code fwiw. This is nice because the complexity of styling the element depends directly on the complexity of the shadow trees that you're building, and it only affects slotted nodes.

If you want to allow combinators past slotted then every node would need to look at its ancestor and prev-sibling chain and look at which ones of them are slotted, then do that process for all their slots.

Then, on top, you also need to change the general selector-matching code so that selectors that do not contain slotted selectors don't match if you're not in the right shadow tree. That's a cost that you pay for all elements, regardless of whether you use Shadow DOM or ::slotted , and is probably just not going to fly.

emilio wpuld something like I described in work better, which is essentially inverting part? querySelector '::slotted. I'm just not sure that referencing slotted content inside the ShadowRoot is possible or makes logical sense if we consider the main benefit of web components: scope.

The ShadowRoot does not know what it's slotted content looks like, only that it has slots. The slots point to the light DOM. If you want to capture the light DOM on a component, you use: this. querySelector ". If you want to make sure. foo is assigned to a slot, you query for: this.

querySelector "[slot]. foo" or even this. foo" if you want to make sure it's in a specific slot. There is no need for the ::slotted selector inside the querySelector. Most light DOM styles will overwrite anything the component tries to apply to a ::slotted style unless that component uses!

important to beat it. tldr; Scope is the primary discussion here imo. A component is tightly scoped to see it's own template and it's top-level nodes assigned to a slot, no deeper and no higher.

That scope is a powerful tool that can be leveraged. calebdwilliams I think for the dialog usecase named slots are a reasonable solution. Introducing a particular part-like attribute definitely mitigates the "now all elements need to look at all their ancestors for slots", for sure at the cost of adding one more part-like attribute, which is also a bit of an annoyance because it involves one extra branch in all attribute mutations, but probably not a huge issue.

That being said, allowing arbitrary access to the slotted DOM is a bit fishy. That way you start depending on the shape of your slotted DOM tree and that reintroduces the same issue that you're trying to solve with shadow DOM in the first place, which is making an isolated, reusable component.

I think that's the point that catastrophe is making, which I agree with. emilio , yeah, I wrestled with that but I keep coming back to the idea that the slotted content is not or should not be necessarily required. A dialog without a cancel button is potentially fine. emilio In some ways, I feel you both on that sentiment.

But there are other possibilities too. The idea is that we allow custom element authors to be more inventive by giving them flexibility. For example, a custom element author may describe certain usage requirements in the component documentation, and it could require a user to nest elements like follows, where the foo- prefix denotes the elements from the component author's foo- lib:.

Now, the foo- lib author needs to style the slotted elements, as well as the nested foo- elements in a certain way for this layout f. positioning, or depending on which slot they are slotted into. In my mind, this sort of nesting is a totally valid thing that a library author could document as a requirement, and therefore should have some easy way to perform the styling.

The most important thing to note is that performing the styling is entirely possible today, the feature I ask for only makes it easier with less code. That of course is less ideal, but completely doable, and more error prone.

If the author was able to use ::slotted foo-open-left , it would keep the styling co-located with the components it is meant to accompany without extra complication and maintenance burden.

If the foo-interesting-layout author has selectors like ::slotted foo-whatever , they can write simpler code, and rely on web APIs like adoptedStyleSheets to handle de-duplication of stylesheets. emilio catastrophe If the custom element author relies on certain slotted DOM structure without documenting that, of course that's bad.

It isn't to say a custom element author can't make good documentation to describe what an end user should do. Secondly, without any documentation, the end user will have a hard time guessing what the structure should be anyway, so they probably wouldn't even bother to use that custom element.

People generally don't like to guess how an API works. So that point, though fully valid, doesn't have as high of a significance in my humble opinion as the proposed feature does, in that the proposed feature would allow CE authors to achieve things more easily and usage of those things should be documented for end users.

But it is easy to imagine use cases where a CE author asks end users to supply DOM trees with certain structures, or even just certain elements anywhere inside the tree; it's a valid use case.

A CE author could be fairly strict with the requirements, f. Or, the well-documented requirements could be less strict while the author would use selectors like ::slotted bar to allow lose tree structure. One feature in particular that relies on lose structure is CSS transforms.

CSS transform causes absolutely-positioned transformed elements to escape from their DOM hierarchy layout, and they enter into their own 3D layout hierarchy within the nearest position:relative element. In order to perform the proper styling with CSS transform s in a slotted tree, a CE author would document less-strict requirements f.

Imagine the 3D possibilities: imagine how a custom element wrapping a DOM tree, relying on selectors post-fixed to ::slotted could make certain elements break out into 3D space, and the only thing the end user has to do is wrap the tree with the custom element, then apply names classes or attributes, or something to elements that should break out into a 3D layout.

The wrapper custom element would enforce a scope where the 3D effects are applied thanks to ShadowDOM , and would do other things under the hood like use a canvas for WebGL effects added to the elements. io , but I have a lot left to do There are many possibilities. What we've just imagined is doable today, but ::slotted foo could make it simply easier.

OnurGumus From reading that, I'm not sure what is being proposed there or how that's an alternative to the OP. Could you provide an example? Is it to say that the light DOM author could specify parts, then the Custom Element author or ShadowDOM author could style those ::part s even if they are nested any level deep inside of a slotted node?

If that's what is meant the light DOM author specifies stylable ::part s , I see how that can satisfy some of the scenerios discussed above, but with some limitations. Namely, the above would allow a custom element author to style any elements in the light DOM without the light DOM author having to explicitly label all of them with part.

trusktr What we know is slotted is limited to the "public surface" of the component for performance reasons. OP argues that we shouldn't have that limitation whereas probably some people would reject that. What I argue is as a user I should be at least use ::slotted ::part Foo since parts are exposed public parts of a component.

But even that is not allowed. Note: I know we can already access the light tree, and style all of its elements. This is simply proposing something more ergonomic. In React, for example, this is easy to do. The component author simply iterates over the array this. children and can work with anything as needed: read data, change styling, replace props, etc, before finally passing it into the component's internal "shadow" tree, all without affecting the component user's outside interface.

It's like a map function: it takes a set of children as input with their descendants and can map it to whatever the component author desires. This easy flexibility is what the OP is asking for, but for Web Components, and in this case the ::slotted.

foo selector with combinators would add that flexibility in the context of CSS styling. The main thing to note, is that Web Component authors can already access all light DOM and style the elements any way they wish. The OP only aims to make it easy to implement for WC authors. So you see, what the OP asks for is totally possible today.

The OP merely asks for a concise and simple syntax option. What a disappointing arbitrary limitation. Let the browser-makers solve performance issues and write the spec to be ideal. I want complete control over the styling of slots and all their children.

I wish there was a flag we could flip so that slots would ignore non-shadow styling. A slot is really just a really ugly argument to a function.

If you pass something into my function custom element I should be able to do what ever I want to that input and all its children too. The whole goal, for me, is to have every aspect of my web component contained in one file and I don't like having to fool with document level CSS to style children of shadow slotted element.

I can still do what I'm wanting with hacks and tricks, but allowing shadow level CSS to style children of slotted elements would make the whole experience much nicer. What trusktr has been saying is ideal to me.

Make the spec ideal and let the browsers-makers earn their money. They're smart enough to overcome the performance issues, so don't be so easy on them in the spec. This stuff is for the whole world.

Let's impress the aliens when they arrive. Their web standards already do this! You have to wrap your component A with shadowDOM and slots in another component B with shadowDOM. You can then do all the styling you want in A lightDOM.

Then the browser-makers can focus on creating something that really impresses aliens Maybe Apple can do Customized Built-In Elements. Since Lonnie Best challenged me, here is my workaround to style all slotted content without using ::slotted.

I still don't see how performance can be an argument against it. Danny-Engelman Can you make a really simple example, not a super complex one? I am not having any luck with it:. As you can see there, only the Shadow DOM's nodes are styled, but not the content that is "slotted".

Not sure why I thought it "worked great" before, but clearly in that example it doesn't work. It seems CSS combinators are not allowed after :host either. From what I can tell, this is a "There's no way to index into an array with simple notation" problem. we can't index an array with array[index] so just write.

sort of topic, except the CSS version is uglier because it modifies the end user's public style API contract. Slotted content is styled by its host container global CSS if you only have 1 one element with shadowDOM.

Can you make a really simple example, not a super complex one? I keep the ::slotted StackOverflow answer, I posted a year ago, updated with every fact and rumor I read.

It is still a Work-Around!! I rewrote the code.. JS is still the same, except I changed children to childNodes to include textnodes in the move from one lightDOM to a nested lightDOM. It is a very bad solution because it totally obliterates the end user's tree removes it from their DOM, and places it into an internal shadow root.

This has critical issues :. I would suggest for anyone reading this, never ever write code that way. That is simply not an acceptable solution because the downsides especially for the end user are bigger than the benefit namely for the CE author only.

Danny-Engelman Unless there is some solution we've missed, you shown why clearly we need a solution, so as to avoid complicated and highly undesirable workarounds. The most acceptable solution that I can think of right now is, to implement scoped styling:. This approach would be much less invasive to the end user's API contract the end user's input light tree nodes and attributes should ideally be left in-tact and undisturbed, because that is theirs to manipulate.

The end user will most likely be unaffected by the library-name-style-id attributes added to their light tree, but at least this is a much smaller invasion of their input space. There is no simple solution to this, as far as I can tell so far apart from having a feature like in the OP. Related: To do so, use a Bookable Events availability query in place of a standard query.

Event IDs may not be found either because the events do not exist or because the Slot Picker element token does not have the correct permissions to view the events. The function to be called when an action has occurred within the Element.

Receives an object in the format:. The object will always include a notification object with a type attribute to allow you to determine how to handle it. Your application should ignore notifications it does not understand as new ones may be added in the future. config optional Use this object to add further configuration to the Element:.

When in confirm mode, clicking a slot displays a confirmation view that allows a user to confirm their selection or return to the list of slots. logs optional Set the level of logging you want to appear in the console:.

Defaults to true. styles optional An object that controls the pre-packaged element styles. prefix optional Customizable elements are given a prefixed class name using this value.

padding optional The size of the padding around the edge of the element. Defaults to 1em. demo optional Boolean to activate demo-mode. Defaults to false. If demo is set to true the Element will return mock data and not make any API calls.

locale optional The Slot Picker supports localization e. locale: "fr" to load in French. Defaults to browser language setting.

translations optional To override either a locale or a particular string, pass in a translations object here. Read more about customizing translations.