1 files changed, 354 insertions, 0 deletions
diff --git a/toolkit/components/thumbnails/PageThumbUtils.jsm b/toolkit/components/thumbnails/PageThumbUtils.jsm
new file mode 100644
index 000000000..dda3a81b3
--- /dev/null
+++ b/toolkit/components/thumbnails/PageThumbUtils.jsm
@@ -0,0 +1,354 @@
+/* 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/. */
+
+/*
+ * Common thumbnailing routines used by various consumers, including
+ * PageThumbs and backgroundPageThumbsContent.
+ */
+
+this.EXPORTED_SYMBOLS = ["PageThumbUtils"];
+
+const { classes: Cc, interfaces: Ci, utils: Cu } = Components;
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm", this);
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://gre/modules/Promise.jsm", this);
+Cu.import("resource://gre/modules/AppConstants.jsm");
+
+XPCOMUtils.defineLazyModuleGetter(this, "BrowserUtils",
+  "resource://gre/modules/BrowserUtils.jsm");
+
+this.PageThumbUtils = {
+  // The default background color for page thumbnails.
+  THUMBNAIL_BG_COLOR: "#fff",
+  // The namespace for thumbnail canvas elements.
+  HTML_NAMESPACE: "http://www.w3.org/1999/xhtml",
+
+  /**
+   * Creates a new canvas element in the context of aWindow, or if aWindow
+   * is undefined, in the context of hiddenDOMWindow.
+   *
+   * @param aWindow (optional) The document of this window will be used to
+   *  create the canvas.  If not given, the hidden window will be used.
+   * @param aWidth (optional) width of the canvas to create
+   * @param aHeight (optional) height of the canvas to create
+   * @return The newly created canvas.
+   */
+  createCanvas: function (aWindow, aWidth = 0, aHeight = 0) {
+    let doc = (aWindow || Services.appShell.hiddenDOMWindow).document;
+    let canvas = doc.createElementNS(this.HTML_NAMESPACE, "canvas");
+    canvas.mozOpaque = true;
+    canvas.imageSmoothingEnabled = true;
+    let [thumbnailWidth, thumbnailHeight] = this.getThumbnailSize(aWindow);
+    canvas.width = aWidth ? aWidth : thumbnailWidth;
+    canvas.height = aHeight ? aHeight : thumbnailHeight;
+    return canvas;
+  },
+
+  /**
+   * Calculates a preferred initial thumbnail size based based on newtab.css
+   * sizes or a preference for other applications. The sizes should be the same
+   * as set for the tile sizes in newtab.
+   *
+   * @param aWindow (optional) aWindow that is used to calculate the scaling size.
+   * @return The calculated thumbnail size or a default if unable to calculate.
+   */
+  getThumbnailSize: function (aWindow = null) {
+    if (!this._thumbnailWidth || !this._thumbnailHeight) {
+      let screenManager = Cc["@mozilla.org/gfx/screenmanager;1"]
+                            .getService(Ci.nsIScreenManager);
+      let left = {}, top = {}, screenWidth = {}, screenHeight = {};
+      screenManager.primaryScreen.GetRectDisplayPix(left, top, screenWidth, screenHeight);
+
+      /** *
+       * The system default scale might be different than
+       * what is reported by the window. For example,
+       * retina displays have 1:1 system scales, but 2:1 window
+       * scale as 1 pixel system wide == 2 device pixels.
+       * To get the best image quality, query both and take the highest one.
+       */
+      let systemScale = screenManager.systemDefaultScale;
+      let windowScale = aWindow ? aWindow.devicePixelRatio : systemScale;
+      let scale = Math.max(systemScale, windowScale);
+
+      /** *
+       * On retina displays, we can sometimes go down this path
+       * without a window object. In those cases, force 2x scaling
+       * as the system scale doesn't represent the 2x scaling
+       * on OS X.
+       */
+      if (AppConstants.platform == "macosx" && !aWindow) {
+        scale = 2;
+      }
+
+      /** *
+       * THESE VALUES ARE DEFINED IN newtab.css and hard coded.
+       * If you change these values from the prefs,
+       * ALSO CHANGE THEM IN newtab.css
+       */
+      let prefWidth = Services.prefs.getIntPref("toolkit.pageThumbs.minWidth");
+      let prefHeight = Services.prefs.getIntPref("toolkit.pageThumbs.minHeight");
+      let divisor = Services.prefs.getIntPref("toolkit.pageThumbs.screenSizeDivisor");
+
+      prefWidth *= scale;
+      prefHeight *= scale;
+
+      this._thumbnailWidth = Math.max(Math.round(screenWidth.value / divisor), prefWidth);
+      this._thumbnailHeight = Math.max(Math.round(screenHeight.value / divisor), prefHeight);
+    }
+
+    return [this._thumbnailWidth, this._thumbnailHeight];
+  },
+
+  /** *
+   * Given a browser window, return the size of the content
+   * minus the scroll bars.
+   */
+  getContentSize: function(aWindow) {
+    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                       .getInterface(Ci.nsIDOMWindowUtils);
+    // aWindow may be a cpow, add exposed props security values.
+    let sbWidth = {}, sbHeight = {};
+
+    try {
+      utils.getScrollbarSize(false, sbWidth, sbHeight);
+    } catch (e) {
+      // This might fail if the window does not have a presShell.
+      Cu.reportError("Unable to get scrollbar size in determineCropSize.");
+      sbWidth.value = sbHeight.value = 0;
+    }
+
+    // Even in RTL mode, scrollbars are always on the right.
+    // So there's no need to determine a left offset.
+    let width = aWindow.innerWidth - sbWidth.value;
+    let height = aWindow.innerHeight - sbHeight.value;
+
+    return [width, height];
+  },
+
+  /** *
+   * Given a browser window, this creates a snapshot of the content
+   * and returns a canvas with the resulting snapshot of the content
+   * at the thumbnail size. It has to do this through a two step process:
+   *
+   * 1) Render the content at the window size to a canvas that is 2x the thumbnail size
+   * 2) Downscale the canvas from (1) down to the thumbnail size
+   *
+   * This is because the thumbnail size is too small to render at directly,
+   * causing pages to believe the browser is a small resolution. Also,
+   * at that resolution, graphical artifacts / text become very jagged.
+   * It's actually better to the eye to have small blurry text than sharp
+   * jagged pixels to represent text.
+   *
+   * @params aWindow - the window to create a snapshot of.
+   * @params aDestCanvas destination canvas to draw the final
+   *   snapshot to. Can be null.
+   * @param aArgs (optional) Additional named parameters:
+   *   fullScale - request that a non-downscaled image be returned.
+   * @return Canvas with a scaled thumbnail of the window.
+   */
+  createSnapshotThumbnail: function(aWindow, aDestCanvas, aArgs) {
+    if (Cu.isCrossProcessWrapper(aWindow)) {
+      throw new Error('Do not pass cpows here.');
+    }
+    let fullScale = aArgs ? aArgs.fullScale : false;
+    let [contentWidth, contentHeight] = this.getContentSize(aWindow);
+    let [thumbnailWidth, thumbnailHeight] = aDestCanvas ?
+                                            [aDestCanvas.width, aDestCanvas.height] :
+                                            this.getThumbnailSize(aWindow);
+
+    // If the caller wants a fullscale image, set the desired thumbnail dims
+    // to the dims of content and (if provided) size the incoming canvas to
+    // support our results.
+    if (fullScale) {
+      thumbnailWidth = contentWidth;
+      thumbnailHeight = contentHeight;
+      if (aDestCanvas) {
+        aDestCanvas.width = contentWidth;
+        aDestCanvas.height = contentHeight;
+      }
+    }
+
+    let intermediateWidth = thumbnailWidth * 2;
+    let intermediateHeight = thumbnailHeight * 2;
+    let skipDownscale = false;
+
+    // If the intermediate thumbnail is larger than content dims (hiDPI
+    // devices can experience this) or a full preview is requested render
+    // at the final thumbnail size.
+    if ((intermediateWidth >= contentWidth ||
+         intermediateHeight >= contentHeight) || fullScale) {
+      intermediateWidth = thumbnailWidth;
+      intermediateHeight = thumbnailHeight;
+      skipDownscale = true;
+    }
+
+    // Create an intermediate surface
+    let snapshotCanvas = this.createCanvas(aWindow, intermediateWidth,
+                                           intermediateHeight);
+
+    // Step 1: capture the image at the intermediate dims. For thumbnails
+    // this is twice the thumbnail size, for fullScale images this is at
+    // content dims.
+    // Also by default, canvas does not draw the scrollbars, so no need to
+    // remove the scrollbar sizes.
+    let scale = Math.min(Math.max(intermediateWidth / contentWidth,
+                                  intermediateHeight / contentHeight), 1);
+
+    let snapshotCtx = snapshotCanvas.getContext("2d");
+    snapshotCtx.save();
+    snapshotCtx.scale(scale, scale);
+    snapshotCtx.drawWindow(aWindow, 0, 0, contentWidth, contentHeight,
+                           PageThumbUtils.THUMBNAIL_BG_COLOR,
+                           snapshotCtx.DRAWWINDOW_DO_NOT_FLUSH);
+    snapshotCtx.restore();
+
+    // Part 2: Downscale from our intermediate dims to the final thumbnail
+    // dims and copy the result to aDestCanvas. If the caller didn't
+    // provide a target canvas, create a new canvas and return it.
+    let finalCanvas = aDestCanvas ||
+      this.createCanvas(aWindow, thumbnailWidth, thumbnailHeight);
+
+    let finalCtx = finalCanvas.getContext("2d");
+    finalCtx.save();
+    if (!skipDownscale) {
+      finalCtx.scale(0.5, 0.5);
+    }
+    finalCtx.drawImage(snapshotCanvas, 0, 0);
+    finalCtx.restore();
+
+    return finalCanvas;
+  },
+
+  /**
+   * Determine a good thumbnail crop size and scale for a given content
+   * window.
+   *
+   * @param aWindow The content window.
+   * @param aCanvas The target canvas.
+   * @return An array containing width, height and scale.
+   */
+  determineCropSize: function (aWindow, aCanvas) {
+    if (Cu.isCrossProcessWrapper(aWindow)) {
+      throw new Error('Do not pass cpows here.');
+    }
+    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
+                       .getInterface(Ci.nsIDOMWindowUtils);
+    // aWindow may be a cpow, add exposed props security values.
+    let sbWidth = {}, sbHeight = {};
+
+    try {
+      utils.getScrollbarSize(false, sbWidth, sbHeight);
+    } catch (e) {
+      // This might fail if the window does not have a presShell.
+      Cu.reportError("Unable to get scrollbar size in determineCropSize.");
+      sbWidth.value = sbHeight.value = 0;
+    }
+
+    // Even in RTL mode, scrollbars are always on the right.
+    // So there's no need to determine a left offset.
+    let width = aWindow.innerWidth - sbWidth.value;
+    let height = aWindow.innerHeight - sbHeight.value;
+
+    let {width: thumbnailWidth, height: thumbnailHeight} = aCanvas;
+    let scale = Math.min(Math.max(thumbnailWidth / width, thumbnailHeight / height), 1);
+    let scaledWidth = width * scale;
+    let scaledHeight = height * scale;
+
+    if (scaledHeight > thumbnailHeight)
+      height -= Math.floor(Math.abs(scaledHeight - thumbnailHeight) * scale);
+
+    if (scaledWidth > thumbnailWidth)
+      width -= Math.floor(Math.abs(scaledWidth - thumbnailWidth) * scale);
+
+    return [width, height, scale];
+  },
+
+  shouldStoreContentThumbnail: function (aDocument, aDocShell) {
+    if (BrowserUtils.isToolbarVisible(aDocShell, "findbar")) {
+      return false;
+    }
+
+    // FIXME Bug 720575 - Don't capture thumbnails for SVG or XML documents as
+    //       that currently regresses Talos SVG tests.
+    if (aDocument instanceof Ci.nsIDOMXMLDocument) {
+      return false;
+    }
+
+    let webNav = aDocShell.QueryInterface(Ci.nsIWebNavigation);
+
+    // Don't take screenshots of about: pages.
+    if (webNav.currentURI.schemeIs("about")) {
+      return false;
+    }
+
+    // There's no point in taking screenshot of loading pages.
+    if (aDocShell.busyFlags != Ci.nsIDocShell.BUSY_FLAGS_NONE) {
+      return false;
+    }
+
+    let channel = aDocShell.currentDocumentChannel;
+
+    // No valid document channel. We shouldn't take a screenshot.
+    if (!channel) {
+      return false;
+    }
+
+    // Don't take screenshots of internally redirecting about: pages.
+    // This includes error pages.
+    let uri = channel.originalURI;
+    if (uri.schemeIs("about")) {
+      return false;
+    }
+
+    let httpChannel;
+    try {
+      httpChannel = channel.QueryInterface(Ci.nsIHttpChannel);
+    } catch (e) { /* Not an HTTP channel. */ }
+
+    if (httpChannel) {
+      // Continue only if we have a 2xx status code.
+      try {
+        if (Math.floor(httpChannel.responseStatus / 100) != 2) {
+        return false;
+        }
+      } catch (e) {
+        // Can't get response information from the httpChannel
+        // because mResponseHead is not available.
+        return false;
+      }
+
+      // Cache-Control: no-store.
+      if (httpChannel.isNoStoreResponse()) {
+        return false;
+      }
+
+      // Don't capture HTTPS pages unless the user explicitly enabled it.
+      if (uri.schemeIs("https") &&
+          !Services.prefs.getBoolPref("browser.cache.disk_cache_ssl")) {
+        return false;
+      }
+    } // httpChannel
+    return true;
+  },
+
+  /**
+   * Given a channel, returns true if it should be considered an "error
+   * response", false otherwise.
+   */
+  isChannelErrorResponse: function(channel) {
+    // No valid document channel sounds like an error to me!
+    if (!channel)
+      return true;
+    if (!(channel instanceof Ci.nsIHttpChannel))
+      // it might be FTP etc, so assume it's ok.
+      return false;
+    try {
+      return !channel.requestSucceeded;
+    } catch (_) {
+      // not being able to determine success is surely failure!
+      return true;
+    }
+  },
+};