@jupyterlab/apputils/lib/printing.js

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.
import { ServerConnection } from '@jupyterlab/services';
/**
 * Any object is "printable" if it implements the `IPrintable` interface.
 *
 * To do this it, it must have a method called `Printing.symbol` which returns either a function
 * to print the object or null if it cannot be printed.
 *
 * One way of printing is to use the `printWidget` function, which creates a hidden iframe
 * and copies the DOM nodes from your widget to that iframe and printing just that iframe.
 *
 * Another way to print is to use the `printURL` function, which takes a URL and prints that page.
 */
export var Printing;
(function (Printing) {
    /**
     * Symbol to use for a method that returns a function to print an object.
     */
    Printing.symbol = Symbol('printable');
    /**
     * Returns whether an object implements a print method.
     */
    function isPrintable(a) {
        if (typeof a !== 'object' || !a) {
            return false;
        }
        return Printing.symbol in a;
    }
    Printing.isPrintable = isPrintable;
    /**
     * Returns the print function for an object, or null if it does not provide a handler.
     */
    function getPrintFunction(val) {
        if (isPrintable(val)) {
            return val[Printing.symbol]();
        }
        return null;
    }
    Printing.getPrintFunction = getPrintFunction;
    /**
     * Prints a widget by copying it's DOM node
     * to a hidden iframe and printing that iframe.
     */
    function printWidget(widget) {
        return printContent(widget.node);
    }
    Printing.printWidget = printWidget;
    /**
     * Prints a URL by loading it into an iframe.
     *
     * @param url URL to load into an iframe.
     */
    async function printURL(url) {
        const settings = ServerConnection.makeSettings();
        const text = await (await ServerConnection.makeRequest(url, {}, settings)).text();
        return printContent(text);
    }
    Printing.printURL = printURL;
    /**
     * Prints a URL or an element in an iframe and then removes the iframe after printing.
     */
    async function printContent(textOrEl) {
        const isText = typeof textOrEl === 'string';
        const iframe = createIFrame();
        const parent = window.document.body;
        parent.appendChild(iframe);
        if (isText) {
            iframe.srcdoc = textOrEl;
            await resolveWhenLoaded(iframe);
        }
        else {
            iframe.src = 'about:blank';
            await resolveWhenLoaded(iframe);
            setIFrameNode(iframe, textOrEl);
        }
        const printed = resolveAfterEvent();
        launchPrint(iframe.contentWindow);
        // Once the print dialog has been dismissed, we regain event handling,
        // and it should be safe to discard the hidden iframe.
        await printed;
        parent.removeChild(iframe);
    }
    /**
     * Creates a new hidden iframe and appends it to the document
     *
     * Modified from
     * https://github.com/joseluisq/printd/blob/eb7948d602583c055ab6dee3ee294b6a421da4b6/src/index.ts#L24
     */
    function createIFrame() {
        const el = window.document.createElement('iframe');
        // We need both allow-modals and allow-same-origin to be able to
        // call print in the iframe.
        // We intentionally do not allow scripts:
        // https://github.com/jupyterlab/jupyterlab/pull/5850#pullrequestreview-230899790
        el.setAttribute('sandbox', 'allow-modals allow-same-origin');
        const css = 'visibility:hidden;width:0;height:0;position:absolute;z-index:-9999;bottom:0;';
        el.setAttribute('style', css);
        el.setAttribute('width', '0');
        el.setAttribute('height', '0');
        return el;
    }
    /**
     * Copies a node from the base document to the iframe.
     */
    function setIFrameNode(iframe, node) {
        iframe.contentDocument.body.appendChild(node.cloneNode(true));
        iframe.contentDocument.close();
    }
    /**
     * Promise that resolves when all resources are loaded in the window.
     */
    function resolveWhenLoaded(iframe) {
        return new Promise(resolve => {
            iframe.onload = () => resolve();
        });
    }
    /**
     * A promise that resolves after the next mousedown, mousemove, or
     * keydown event. We use this as a proxy for determining when the
     * main window has regained control after the print dialog is removed.
     *
     * We can't use the usual window.onafterprint handler because we
     * disallow Javascript execution in the print iframe.
     */
    function resolveAfterEvent() {
        return new Promise(resolve => {
            const onEvent = () => {
                document.removeEventListener('mousemove', onEvent, true);
                document.removeEventListener('mousedown', onEvent, true);
                document.removeEventListener('keydown', onEvent, true);
                resolve();
            };
            document.addEventListener('mousemove', onEvent, true);
            document.addEventListener('mousedown', onEvent, true);
            document.addEventListener('keydown', onEvent, true);
        });
    }
    /**
     * Prints a content window.
     */
    function launchPrint(contentWindow) {
        const result = contentWindow.document.execCommand('print', false);
        // execCommand won't work in firefox so we call the `print` method instead if it fails
        // https://github.com/joseluisq/printd/blob/eb7948d602583c055ab6dee3ee294b6a421da4b6/src/index.ts#L148
        if (!result) {
            contentWindow.print();
        }
    }
})(Printing || (Printing = {}));
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