Issue 3532 - Generate animation images at runtime

lib/icon.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /** @module icon */
 
-const numberOfFrames = 10;
+"use strict";
 
+const frameOpacities =  [0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9,
+                         1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0,
+                         0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.0];
+const numberOfFrames = frameOpacities.length;
+
+let stopAnimation = null;
+let animationPlaying = false;
 let whitelistedState = new ext.PageMap();
-let notificationType = null;
-let animationInterval = null;
-let animationStep = 0;
 
-function getIconPath(whitelisted)
+let loadImageAsCanvas =
+/**
+ * Loads an image and draws it onto a canvas.
+ *
+ * @param {string} url  URL string of the image to load
+ * @return {Promise}
+ */
+exports.loadImageAsCanvas = function(url)
 {
+  return new Promise((resolve, reject) => {
+    let image = new Image();
+    image.src = url;
+    image.addEventListener("load", () =>
+    {
+      let canvas = document.createElement("canvas");
+      let context = canvas.getContext("2d");
+      canvas.height = image.height;
+      canvas.width = image.width;
+      context.drawImage(image, 0, 0);
+      resolve(canvas);
+    });
+    image.addEventListener("error", () => {
+      reject("Failed to load image " + url);
+    });
+  });
+};
+
+function getImageData(baseIcon, overlayIcon, opacity, animationStep, frameCache)
+{
+  let cacheIndex = baseIcon + overlayIcon + opacity;
+
+  if (frameCache && frameCache[cacheIndex])
+    return frameCache[cacheIndex];
+
+  let imageData = Promise.all(
+    [loadImageAsCanvas(baseIcon),
+     overlayIcon && loadImageAsCanvas(overlayIcon) || Promise.resolve(null)]
+  ).then(icons =>
+  {
+    let baseIconCanvas = icons[0];
+    let overlayIconCanvas = icons[1];
+    let context = baseIconCanvas.getContext("2d");
+
+    if (overlayIconCanvas && opacity)
+    {
+      context.globalAlpha = opacity;
+      context.drawImage(overlayIconCanvas, 0, 0);
+    }
+
+    return context.getImageData(0, 0, baseIconCanvas.width,
+                                baseIconCanvas.height);
+  });
+  if (frameCache)
+    frameCache[cacheIndex] = imageData;
+  return imageData;
+}
+
+function setIcon(page, animationType, animationStep, frameCache)
+{
+  let safari = require("info").platform == "safari";
+  let opacity = animationType ? frameOpacities[animationStep] : 0;
+  let greyed = whitelistedState.get(page) && !safari;
+  let blending = (animationType && opacity > 0 && opacity < 1);
+
   let filename = "icons/abp-$size";
+  let baseIcon = filename + (greyed ? "-whitelisted" : "") + ".png";
+  let overlayIcon = animationType && (filename + "-notification-" +
+                                      animationType + ".png");
 
-  // If the current page is whitelisted, pick an icon that indicates that
-  // Adblock Plus is disabled, however not when the notification icon has
-  // full opacity, or on Safari where icons are genrally grayscale-only.
-  if (whitelisted && animationStep < numberOfFrames && require("info").platform != "safari")
-    filename += "-whitelisted";
 
-  // If the icon is currently animating to indicate a pending notification,
-  // pick the icon for the corresponing notification type and animation frame.
-  if (notificationType && animationStep > 0)
+  // If the icon doesn't need any modifications, or the platform doesn't support
+  // data URLs, we can just use the image's filename with the $size placeholder.
+  if (!blending || safari)
+    if (overlayIcon && opacity > 0.5)
+      return page.browserAction.setIcon(overlayIcon);
+    else
+      return page.browserAction.setIcon(baseIcon);
+
+  // Otherwise we must process the images using a canvas and return a data URL
+  // of the result for each size that's required. (19px and 38px are required by
+  // Chrome/Opera.)
+  let imageData = [19, 38].map(size =>
   {
-    filename += "-notification-" + notificationType;
+    return getImageData(baseIcon.replace("$size", size.toString()),
+                        overlayIcon.replace("$size", size.toString()),
+                        opacity, animationStep, frameCache);
+  });
+  Promise.all(imageData).then(imageData =>
+  {
+    chrome.browserAction.setIcon({tabId: page._id,
+                                  imageData: {19: imageData[0],
+                                              38: imageData[1]}});
+  });
+}
 
-    if (animationStep < numberOfFrames)
-      filename += "-" + animationStep;
+function runAnimation(animationType)
+{
+  let frameCache = {};
+  let frameInterval;
+
+  function playAnimation()
+  {
+    animationPlaying = true;
+    let animationStep = 0;
+    ext.pages.query({active: true}, pages =>
+    {
+      function refreshActivePages()
+      {
+        ext.pages.query({active: true}, newPages => {
+          pages.forEach(page => { setIcon(page); });
+          pages = newPages;
+        });
+      }
+      chrome.tabs.onActivated.addListener(refreshActivePages);
+      chrome.tabs.onRemoved.addListener(refreshActivePages);
+
+      frameInterval = setInterval(() =>
+      {
+        pages.forEach(page => {
+          setIcon(page, animationType, animationStep++, frameCache);
+        });
+        if (animationStep >= numberOfFrames)
+        {
+          animationStep = 0;
+          clearInterval(frameInterval);
+          animationPlaying = false;
+          chrome.tabs.onActivated.removeListener(refreshActivePages);
+          chrome.tabs.onRemoved.removeListener(refreshActivePages);
+        }
+      }, 100);
+    });
   }
 
-  return filename + ".png";
-}
-
-function setIcon(page)
-{
-  page.browserAction.setIcon(getIconPath(whitelistedState.get(page)));
-}
-
-function runAnimation()
-{
-  return setInterval(function()
+  playAnimation();
+  let animationInterval = setInterval(playAnimation, 10000);
+  return () =>
   {
-    ext.pages.query({active: true}, function(pages)
-    {
-      let fadeInInterval = setInterval(function()
-      {
-        animationStep++;
-        pages.forEach(setIcon);
-
-        if (animationStep < numberOfFrames)
-          return;
-
-        setTimeout(function()
-        {
-          let fadeOutInterval = setInterval(function()
-          {
-            animationStep--;
-            pages.forEach(setIcon);
-
-            if (animationStep > 0)
-              return;
-
-            clearInterval(fadeOutInterval);
-          }, 100);
-        },1000);
-
-        clearInterval(fadeInInterval);
-      }, 100);
-    });
-  }, 10000);
+    clearInterval(frameInterval);
+    clearInterval(animationInterval);
+    animationPlaying = false;
+  };
 }
 
 /**
  * Set the browser action icon for the given page, indicating whether
  * adblocking is active there, and considering the icon animation.
  *
  * @param {Page}    page         The page to set the browser action icon for
  * @param {Boolean} whitelisted  Whether the page has been whitelisted
  */
 exports.updateIcon = function(page, whitelisted)
 {
-  page.browserAction.setIcon(getIconPath(whitelisted));
   whitelistedState.set(page, whitelisted);
+  if (!animationPlaying)
+    setIcon(page);
 };
 
 /**
  * Starts to animate the browser action icon to indicate a pending notifcation.
  *
  * @param {string} type  The notification type (i.e: "information" or "critical")
  */
 exports.startIconAnimation = function(type)
 {
-  notificationType = type;
-
-  if (animationInterval == null)
-    animationInterval = runAnimation();
+  stopAnimation && stopAnimation();
+  stopAnimation = runAnimation(type);
 };
 
 /**
  * Stops to animate the browser action icon.
  */
 exports.stopIconAnimation = function()
 {
-  if (animationInterval != null)
-  {
-    clearInterval(animationInterval);
-    animationInterval = null;
-  }
-
-  notificationType  = null;
+  stopAnimation && stopAnimation();
 };