Local NTP: prevent tiles from reloading on resize by moving them into single <div>.

chrome/browser/resources/local_ntp/local_ntp.js

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 /**
  * @fileoverview The local InstantExtended NTP.
  */
 
 
@@ skipping 21 matching lines @@
   // Applies drag focus style to the fakebox
   FAKEBOX_DRAG_FOCUS: 'fakebox-drag-focused',
   FAVICON: 'mv-favicon',
   HIDE_BLACKLIST_BUTTON: 'mv-x-hide', // hides blacklist button during animation
   HIDE_FAKEBOX_AND_LOGO: 'hide-fakebox-logo',
   HIDE_NOTIFICATION: 'mv-notice-hide',
   // Vertically centers the most visited section for a non-Google provided page.
   NON_GOOGLE_PAGE: 'non-google-page',
   PAGE: 'mv-page', // page tiles
   PAGE_READY: 'mv-page-ready',  // page tile when ready
-  ROW: 'mv-row',  // tile row
   RTL: 'rtl',  // Right-to-left language text.
   THUMBNAIL: 'mv-thumb',
   THUMBNAIL_MASK: 'mv-mask',
   TILE: 'mv-tile',
   TITLE: 'mv-title'
 };
 
 
 /**
  * Enum for HTML element ids.
@@ skipping 145 matching lines @@
 
 
 /**
  * The state of the NTP when a query is entered into the Fakebox.
  * @type {NTP_DISPOSE_STATE}
  */
 var fakeboxInputBehavior = NTP_DISPOSE_STATE.HIDE_FAKEBOX_AND_LOGO;
 
 
 /**
+ * A counter to control the visibility of tile elements.
+ * @type {number}
+ */
+var tileVisibilityCounter = 0;

[beaudoin, 2014/07/24 15:24:36]

I'd prefer numHiddenTiles with a matching comment.

[huangs, 2014/07/24 19:33:11]

Per discussion, numHiddenTiles will be off by one because we need to increment
before creating tiles to guard against race condition.

Using Barrier to do this.

+
+
+/**
  * Total tile width. Should be equal to mv-tile's width + 2 * border-width.
  * @private {number}
  * @const
  */
 var TILE_WIDTH = 140;
 
 
 /**
  * Margin between tiles. Should be equal to mv-tile's -webkit-margin-start.
  * @private {number}
@@ skipping 104 matching lines @@
 
   var background = [convertToRGBAColor(info.backgroundColorRgba),
                     info.imageUrl,
                     info.imageTiling,
                     info.imageHorizontalAlignment,
                     info.imageVerticalAlignment].join(' ').trim();
   document.body.style.background = background;
   document.body.classList.toggle(CLASSES.ALTERNATE_LOGO, info.alternateLogo);
   updateThemeAttribution(info.attributionUrl);
   setCustomThemeStyle(info);
+
   renderTiles();
 }
 
 
 /**
  * Updates the NTP style according to theme.
  * @param {Object=} opt_themeInfo The information about the theme. If it is
  * omitted the style will be reverted to the default.
  * @private
  */
@@ skipping 83 matching lines @@
 function convertToRGBAColor(color) {
   return 'rgba(' + color[0] + ',' + color[1] + ',' + color[2] + ',' +
                     color[3] / 255 + ')';
 }
 
 
 /**
  * Handles a new set of Most Visited page data.
  */
 function onMostVisitedChange() {
-  var pages = ntpApiHandle.mostVisited;
-
   if (isBlacklisting) {
-    // Trigger the blacklist animation and re-render the tiles when it
-    // completes.
+    // Trigger the blacklist animation. On completion, the handler will call
+    // reloadAllTiles().
     var lastBlacklistedTileElement = lastBlacklistedTile.elem;
     lastBlacklistedTileElement.addEventListener(
         'webkitTransitionEnd', blacklistAnimationDone);
     lastBlacklistedTileElement.classList.add(CLASSES.BLACKLIST);
 

[Mathieu, 2014/07/24 15:11:25]

remove extra new line

[huangs, 2014/07/24 19:33:11]

Done.

   } else {
-    // Otherwise render the tiles using the new data without animation.
-    tiles = [];
-    for (var i = 0; i < MAX_NUM_TILES_TO_SHOW; ++i) {
-      tiles.push(createTile(pages[i], i));
-    }
     if (!userInitiatedMostVisitedChange) {
       tilesContainer.hidden = true;
       window.setTimeout(function() {
         if (tilesContainer) {
           tilesContainer.hidden = false;
         }
       }, MOST_VISITED_PAINT_TIMEOUT_MSEC);
     }
-    renderTiles();
+    reloadAllTiles();
   }
 }
 
 
 /**
- * Renders the current set of tiles.
+ * Fetches new data, creates, and renders tiles.
+ */
+function reloadAllTiles() {
+  var pages = ntpApiHandle.mostVisited;
+
+  tiles = [];
+  deltaMostVisitedVisibility(1);

[beaudoin, 2014/07/24 15:24:36]

I'd use just a ++ here and call the other 
  decrementNumberOfVisibleTiles();

[huangs, 2014/07/24 19:33:12]

Changed to Barrier.

+  for (var i = 0; i < MAX_NUM_TILES_TO_SHOW; ++i) {
+    tiles.push(createTile(pages[i], i));
+  }
+  renderTiles();
+  deltaMostVisitedVisibility(-1);
+}
+
+
+/**
+ * Adds the current list of tiles to DOM.
  */
 function renderTiles() {
-  var rows = tilesContainer.children;
-  for (var i = 0; i < rows.length; ++i) {
-    removeChildren(rows[i]);
-  }
-
-  for (var i = 0, length = tiles.length;
-       i < Math.min(length, numColumnsShown * NUM_ROWS); ++i) {
-    rows[Math.floor(i / numColumnsShown)].appendChild(tiles[i].elem);
+  removeChildren(tilesContainer);
+  var renderedList = tilesContainer.querySelectorAll('.mv-tile');
+  var size = Math.min(tiles.length, numColumnsShown * NUM_ROWS);
+  for (var i = 0; i < size; ++i) {
+    tilesContainer.appendChild(tiles[i].elem);
   }
 }
 
 
 /**
- * Shows most visited tiles if all child iframes are loaded, and hides them
+ * Shows or hides rendered tiles, depending on the number of columns shown.
+ */
+function showTiles() {
+  var renderedList = tilesContainer.querySelectorAll('.mv-tile');
+  var numVisible = Math.min(tiles.length, numColumnsShown * NUM_ROWS);
+  for (var i = 0; i < renderedList.length; ++i) {
+    renderedList[i].style.display = i < numVisible ? 'inline-block' : 'none';
+  }
+}
+
+
+/**
+ * Changes the visibility counter for most visited tiles by |delta|, and

[Mathieu, 2014/07/24 15:11:25]

*Most Visited

[huangs, 2014/07/24 19:33:11]

Done.

+ * makes the tiles visible once the count decreases to 0.
  * otherwise.

[Mathieu, 2014/07/24 15:11:25]

fix comment

[huangs, 2014/07/24 19:33:11]

Done.

+ * @param {number} delta The amount to change counter by, usually 1 or -1.
  */
-function updateMostVisitedVisibility() {
-  var iframes = tilesContainer.querySelectorAll('iframe');
-  var ready = true;
-  for (var i = 0, numIframes = iframes.length; i < numIframes; i++) {
-    if (iframes[i].hidden) {
-      ready = false;
-      break;
-    }
-  }
-  if (ready) {
+function deltaMostVisitedVisibility(delta) {

[Mathieu, 2014/07/24 15:11:25]

As discussed offline, reconsider if this function is needed.

[huangs, 2014/07/24 19:33:11]

This function is needed: in onMostVisitedChange(), the container gets hidden for
0.5s before being shown.  This flow preempts the wait when all the tiles have
been loaded.  Updating comment.

+  tileVisibilityCounter += delta;
+  if (tileVisibilityCounter === 0) {
     tilesContainer.hidden = false;
     userInitiatedMostVisitedChange = false;
   }
 }
 
 
 /**
  * Builds a URL to display a most visited tile component in an iframe.
  * @param {string} filename The desired most visited component filename.
  * @param {number} rid The restricted ID.
@@ skipping 52 matching lines @@
     // begins loading RIDs n, n+1, ..., n+k-1; after the second event, these get
     // destroyed and a new set begins loading RIDs n+k, n+k+1, ..., n+2k-1.
     // Now due to crbug.com/68841, Chrome incorrectly loads the content for the
     // first set of iframes into the most recent set of iframes.
     //
     // Giving iframes distinct ids seems to cause some invalidation and prevent
     // associating the incorrect data.
     //
     // TODO(jered): Find and fix the root (probably Blink) bug.
 
+    // Keep this id here. See comment above.
+    titleElement.id = 'title-' + rid;
+    titleElement.className = CLASSES.TITLE;
+    titleElement.hidden = true;
+    deltaMostVisitedVisibility(1);

[beaudoin, 2014/07/24 15:24:36]

++

[huangs, 2014/07/24 19:33:11]

Acknowledged.

+    titleElement.onload = function() {
+      titleElement.hidden = false;
+      deltaMostVisitedVisibility(-1);

[beaudoin, 2014/07/24 15:24:36]

decrementNumberOfVisibleTiles();

[huangs, 2014/07/24 19:33:11]

Acknowledged.

+    };
     titleElement.src = getMostVisitedIframeUrl(
         MOST_VISITED_TITLE_IFRAME, rid, MOST_VISITED_COLOR,
         MOST_VISITED_FONT_FAMILY, MOST_VISITED_FONT_SIZE, position);
-
-    // Keep this id here. See comment above.
-    titleElement.id = 'title-' + rid;
-    titleElement.hidden = true;
-    titleElement.onload = function() {
-      titleElement.hidden = false;
-      updateMostVisitedVisibility();
-    };
-    titleElement.className = CLASSES.TITLE;
     tileElement.appendChild(titleElement);
 
     // The iframe which renders either a thumbnail or domain element.
     var thumbnailElement = document.createElement('iframe');
     thumbnailElement.tabIndex = '-1';
+    // Keep this id here. See comment above.
+    thumbnailElement.id = 'thumb-' + rid;
+    thumbnailElement.className = CLASSES.THUMBNAIL;
+    thumbnailElement.hidden = true;
+    deltaMostVisitedVisibility(1);

[beaudoin, 2014/07/24 15:24:37]

Same.

[huangs, 2014/07/24 19:33:12]

Acknowledged.

+    thumbnailElement.onload = function() {
+      thumbnailElement.hidden = false;
+      tileElement.classList.add(CLASSES.PAGE_READY);
+      deltaMostVisitedVisibility(-1);
+    };
     thumbnailElement.src = getMostVisitedIframeUrl(
         MOST_VISITED_THUMBNAIL_IFRAME, rid, MOST_VISITED_COLOR,
         MOST_VISITED_FONT_FAMILY, MOST_VISITED_FONT_SIZE, position);
-
-    // Keep this id here. See comment above.
-    thumbnailElement.id = 'thumb-' + rid;
-    thumbnailElement.hidden = true;
-    thumbnailElement.onload = function() {
-      thumbnailElement.hidden = false;
-      tileElement.classList.add(CLASSES.PAGE_READY);
-      updateMostVisitedVisibility();
-    };
-    thumbnailElement.className = CLASSES.THUMBNAIL;
     tileElement.appendChild(thumbnailElement);
 
     // A mask to darken the thumbnail on focus.
     var maskElement = createAndAppendElement(
         tileElement, 'div', CLASSES.THUMBNAIL_MASK);
 
     // The button used to blacklist this page.
     var blacklistButton = createAndAppendElement(
         tileElement, 'div', CLASSES.BLACKLIST_BUTTON);
     var blacklistFunction = generateBlacklistFunction(rid);
@@ skipping 63 matching lines @@
  */
 function blacklistAnimationDone() {
   showNotification();
   isBlacklisting = false;
   tilesContainer.classList.remove(CLASSES.HIDE_BLACKLIST_BUTTON);
   lastBlacklistedTile.elem.removeEventListener(
       'webkitTransitionEnd', blacklistAnimationDone);
   // Need to call explicitly to re-render the tiles, since the initial
   // onmostvisitedchange issued by the blacklist function only triggered
   // the animation.
-  onMostVisitedChange();
+  reloadAllTiles();
 }
 
 
 /**
  * Handles a click on the notification undo link by hiding the notification and
  * informing Chrome.
  */
 function onUndo() {
   userInitiatedMostVisitedChange = true;
   hideNotification();
@@ skipping 17 matching lines @@
 /**
  * Re-renders the tiles if the number of columns has changed.  As a temporary
  * fix for crbug/240510, updates the width of the fakebox and most visited tiles
  * container.
  */
 function onResize() {
   // If innerWidth is zero, then use the maximum snap size.
   var innerWidth = window.innerWidth || 820;
 
   // These values should remain in sync with local_ntp.css.
   // TODO(jeremycho): Delete once the root cause of crbug/240510 is resolved.

[Mathieu, 2014/07/24 15:11:25]

this bug as been marked as fixed, I wonder if this is still needed?

[huangs, 2014/07/24 19:33:11]

Updated the routine and added comments.

   var setWidths = function(tilesContainerWidth) {
     tilesContainer.style.width = tilesContainerWidth + 'px';
     if (fakebox)
-      fakebox.style.width = (tilesContainerWidth - 2) + 'px';
+      fakebox.style.width = (tilesContainerWidth - 22) + 'px';
   };
   if (innerWidth >= 820)
-    setWidths(620);
+    setWidths(640);
   else if (innerWidth >= 660)
-    setWidths(460);
+    setWidths(480);
   else
-    setWidths(300);
+    setWidths(320);
 
   var tileRequiredWidth = TILE_WIDTH + TILE_MARGIN_START;
   // Adds margin-start to the available width to compensate the extra margin
   // counted above for the first tile (which does not have a margin-start).
   var availableWidth = innerWidth + TILE_MARGIN_START -
       MIN_TOTAL_HORIZONTAL_PADDING;
   var numColumnsToShow = Math.floor(availableWidth / tileRequiredWidth);
   numColumnsToShow = Math.max(MIN_NUM_COLUMNS,
                               Math.min(MAX_NUM_COLUMNS, numColumnsToShow));
   if (numColumnsToShow != numColumnsShown) {
     numColumnsShown = numColumnsToShow;
-    renderTiles();
+    showTiles();
   }
 }
 
 
 /**
  * Returns the tile corresponding to the specified page RID.
  * @param {number} rid The page RID being looked up.
  * @return {Tile} The corresponding tile.
  */
 function getTileByRid(rid) {
@@ skipping 166 matching lines @@
  * Prepares the New Tab Page by adding listeners, rendering the current
  * theme, the most visited pages section, and Google-specific elements for a
  * Google-provided page.
  */
 function init() {
   tilesContainer = $(IDS.TILES);
   notification = $(IDS.NOTIFICATION);
   attribution = $(IDS.ATTRIBUTION);
   ntpContents = $(IDS.NTP_CONTENTS);
 
-  for (var i = 0; i < NUM_ROWS; i++) {
-    var row = document.createElement('div');
-    row.classList.add(CLASSES.ROW);
-    tilesContainer.appendChild(row);
-  }
-
   if (configData.isGooglePage) {
     var logo = document.createElement('div');
     logo.id = IDS.LOGO;
 
     fakebox = document.createElement('div');
     fakebox.id = IDS.FAKEBOX;
     fakebox.innerHTML =
         '<input id="' + IDS.FAKEBOX_INPUT +
             '" autocomplete="off" tabindex="-1" aria-hidden="true">' +
-        '<div id=cursor></div>';
+        '<div id="cursor"></div>';
 
     ntpContents.insertBefore(fakebox, ntpContents.firstChild);
     ntpContents.insertBefore(logo, ntpContents.firstChild);
   } else {
     document.body.classList.add(CLASSES.NON_GOOGLE_PAGE);
   }
 
   var notificationMessage = $(IDS.NOTIFICATION_MESSAGE);
   notificationMessage.textContent =
       configData.translatedStrings.thumbnailRemovedNotification;
@@ skipping 87 matching lines @@
 
 return {
   init: init,
   listen: listen
 };
 }
 
 if (!window.localNTPUnitTest) {
   LocalNTP().listen();
 }