@polymer/lit-element/lib/css-tag.js

/**
@license
Copyright (c) 2019 The Polymer Project Authors. All rights reserved.
This code may only be used under the BSD style license found at
http://polymer.github.io/LICENSE.txt The complete set of authors may be found at
http://polymer.github.io/AUTHORS.txt The complete set of contributors may be
found at http://polymer.github.io/CONTRIBUTORS.txt Code distributed by Google as
part of the polymer project is also subject to an additional IP rights grant
found at http://polymer.github.io/PATENTS.txt
*/
export const supportsAdoptingStyleSheets = ('adoptedStyleSheets' in Document.prototype);
export class CSSResult {
    constructor(cssText) { this.cssText = cssText; }
    // Note, this is a getter so that it's lazy. In practice, this means
    // stylesheets are not created until the first element instance is made.
    get styleSheet() {
        if (this._styleSheet === undefined) {
            // Note, if `adoptedStyleSheets` is supported then we assume CSSStyleSheet
            // is constructable.
            if (supportsAdoptingStyleSheets) {
                this._styleSheet = new CSSStyleSheet();
                this._styleSheet.replaceSync(this.cssText);
            }
            else {
                this._styleSheet = null;
            }
        }
        return this._styleSheet;
    }
}
const textFromCSSResult = (value) => {
    if (value instanceof CSSResult) {
        return value.cssText;
    }
    else {
        throw new Error(`Value passed to 'css' function must be a 'css' function result: ${value}.`);
    }
};
export const css = (strings, ...values) => {
    const cssText = values.reduce((acc, v, idx) => acc + textFromCSSResult(v) + strings[idx + 1], strings[0]);
    return new CSSResult(cssText);
};
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