Extension to the standard
render method which supports rendering to ShadowRoots when the ShadyDOM (https://github.com/webcomponents/shadydom) and ShadyCSS (https://github.com/webcomponents/shadycss) polyfills are used or when the webcomponentsjs (https://github.com/webcomponents/webcomponentsjs) polyfill is used.
render(result, container, options): void
scopeName option which is used to scope element DOM and stylesheets when native ShadowDOM is unavailable. The
scopeName will be added to the class attribute of all rendered DOM. In addition, any style elements will be automatically re-written with this
scopeName selector and moved out of the rendered DOM and into the document
It is common to use this render method in conjunction with a custom element which renders a shadowRoot. When this is done, typically the element's
localName should be used as the
In addition to DOM scoping, ShadyCSS also supports a basic shim for css custom properties (needed only on older browsers like IE11) and a shim for a deprecated feature called
@apply that supports applying a set of css custom properties to a given location.
Part values in
<style>elements are only applied the first time a given
scopeNamerenders. Subsequent changes to parts in style elements will have no effect. Because of this, parts in style elements should only be used for values that will never change, for example parts that set scope-wide theme values or parts which render shared style elements.
Note, due to a limitation of the ShadyDOM polyfill, rendering in a custom element's
constructoris not supported. Instead rendering should either done asynchronously, for example at microtask timing (for example
Promise.resolve()), or be deferred until the first time the element's
Usage considerations when using shimmed custom properties or
Whenever any dynamic changes are made which affect css custom properties,
ShadyCSS.styleElement(element)must be called to update the element. There are two cases when this is needed: (1) the element is connected to a new parent, (2) a class is added to the element that causes it to match different custom properties. To address the first case when rendering a custom element,
styleElementshould be called in the element's
Shimmed custom properties may only be defined either for an entire shadowRoot (for example, in a
:hostrule) or via a rule that directly matches an element with a shadowRoot. In other words, instead of flowing from parent to child as do native css custom properties, shimmed custom properties flow only from shadowRoots to nested shadowRoots.
@applymixing css shorthand property names with non-shorthand names (for example
border-width) is not supported.
Template factory which scopes template DOM using ShadyCSS.