Bug 731779: Integrate the Add-on SDK loader and API libraries into Firefox (uplifting from addon-sdk a16bbd5772880b578a939eeb65102bca6560d494)

addon-sdk/source/lib/sdk/content/thumbnail.js

@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+'use strict';
+
+module.metadata = {
+  'stability': 'unstable'
+};
+
+const { Cc, Ci, Cu } = require('chrome');
+const AppShellService = Cc['@mozilla.org/appshell/appShellService;1'].
+                        getService(Ci.nsIAppShellService);
+
+const NS = 'http://www.w3.org/1999/xhtml';
+const COLOR = 'rgb(255,255,255)';
+
+/**
+ * Creates canvas element with a thumbnail of the passed window.
+ * @param {Window} window
+ * @returns {Element}
+ */
+function getThumbnailCanvasForWindow(window) {
+  let aspectRatio = 0.5625; // 16:9
+  let thumbnail = AppShellService.hiddenDOMWindow.document
+                    .createElementNS(NS, 'canvas');
+  thumbnail.mozOpaque = true;
+  thumbnail.width = Math.ceil(window.screen.availWidth / 5.75);
+  thumbnail.height = Math.round(thumbnail.width * aspectRatio);
+  let ctx = thumbnail.getContext('2d');
+  let snippetWidth = window.innerWidth * .6;
+  let scale = thumbnail.width / snippetWidth;
+  ctx.scale(scale, scale);
+  ctx.drawWindow(window, window.scrollX, window.scrollY, snippetWidth,
+                snippetWidth * aspectRatio, COLOR);
+  return thumbnail;
+}
+exports.getThumbnailCanvasForWindow = getThumbnailCanvasForWindow;
+
+/**
+ * Creates Base64 encoded data URI of the thumbnail for the passed window.
+ * @param {Window} window
+ * @returns {String}
+ */
+exports.getThumbnailURIForWindow = function getThumbnailURIForWindow(window) {
+  return getThumbnailCanvasForWindow(window).toDataURL()
+};