michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 'use strict';
michael@0: 
michael@0: module.metadata = {
michael@0:   'stability': 'unstable'
michael@0: };
michael@0: 
michael@0: const { Cc, Ci, Cu } = require('chrome');
michael@0: const AppShellService = Cc['@mozilla.org/appshell/appShellService;1'].
michael@0:                         getService(Ci.nsIAppShellService);
michael@0: 
michael@0: const NS = 'http://www.w3.org/1999/xhtml';
michael@0: const COLOR = 'rgb(255,255,255)';
michael@0: 
michael@0: /**
michael@0:  * Creates canvas element with a thumbnail of the passed window.
michael@0:  * @param {Window} window
michael@0:  * @returns {Element}
michael@0:  */
michael@0: function getThumbnailCanvasForWindow(window) {
michael@0:   let aspectRatio = 0.5625; // 16:9
michael@0:   let thumbnail = AppShellService.hiddenDOMWindow.document
michael@0:                     .createElementNS(NS, 'canvas');
michael@0:   thumbnail.mozOpaque = true;
michael@0:   thumbnail.width = Math.ceil(window.screen.availWidth / 5.75);
michael@0:   thumbnail.height = Math.round(thumbnail.width * aspectRatio);
michael@0:   let ctx = thumbnail.getContext('2d');
michael@0:   let snippetWidth = window.innerWidth * .6;
michael@0:   let scale = thumbnail.width / snippetWidth;
michael@0:   ctx.scale(scale, scale);
michael@0:   ctx.drawWindow(window, window.scrollX, window.scrollY, snippetWidth,
michael@0:                 snippetWidth * aspectRatio, COLOR);
michael@0:   return thumbnail;
michael@0: }
michael@0: exports.getThumbnailCanvasForWindow = getThumbnailCanvasForWindow;
michael@0: 
michael@0: /**
michael@0:  * Creates Base64 encoded data URI of the thumbnail for the passed window.
michael@0:  * @param {Window} window
michael@0:  * @returns {String}
michael@0:  */
michael@0: exports.getThumbnailURIForWindow = function getThumbnailURIForWindow(window) {
michael@0:   return getThumbnailCanvasForWindow(window).toDataURL()
michael@0: };