@polymer/lit-element/src/env.d.ts

Polymer based lit-html custom element

interface ShadyCSS {
  styleElement(host: Element, overrideProps?: {[key: string]: string}): void;
  getComputedStyleValue(element: Element, property: string): string;
  ScopingShim: {prepareAdoptedCssText(cssText: string[], name: string): void;};
  nativeShadow: boolean;
}

interface ShadyDOM {
  inUse: boolean;
}

interface Window {
  ShadyCSS?: ShadyCSS;
  ShadyDOM?: ShadyDOM;
  ShadowRoot: typeof ShadowRoot;
}

// Augment existing types with styling API
interface ShadowRoot {
  adoptedStyleSheets: CSSStyleSheet[];
}

declare var ShadowRoot: {prototype: ShadowRoot; new () : ShadowRoot;}

interface CSSStyleSheet {
  replaceSync(cssText: string): void;
  replace(cssText: string): Promise<unknown>;
}