Allow outline to be collapsed / shown via icon.

- This commit adds a '>' before every outline item that has subitems.
- Click on the '>' to collapse all subitems under that item (which turns
  the '>' in a 'v').
- Shift + click expands/collapses all descendant items under that tree.
- Double-clicking on the "Show Document Outline" button in the toolbar
  expands/collapses all outline items.

web/pdf_outline_view.js

@@ -36,6 +36,7 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
     this.container = options.container;
     this.outline = options.outline;
     this.linkService = options.linkService;
+    this.lastToggleIsShow = true;
   }
 
   PDFOutlineView.prototype = {
@@ -44,6 +45,7 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
       while (container.firstChild) {
         container.removeChild(container.firstChild);
       }
+      this.lastToggleIsShow = true;
     },
 
     /**
@@ -69,6 +71,51 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
       };
     },
 
+    /**
+     * Prepend a button before an outline item which allows the user to toggle
+     * the visibility of all outline items at that level.
+     *
+     * @private
+     */
+    _addToggleButton: function PDFOutlineView_addToggleButton(div) {
+      var toggler = document.createElement('div');
+      toggler.className = 'outlineItemToggler';
+      toggler.onclick = function(event) {
+        event.stopPropagation();
+        toggler.classList.toggle('outlineItemsHidden');
+
+        if (event.shiftKey) {
+          var shouldShowAll = !toggler.classList.contains('outlineItemsHidden');
+          this._toggleOutlineItem(div, shouldShowAll);
+        }
+      }.bind(this);
+      div.insertBefore(toggler, div.firstChild);
+    },
+
+    /**
+     * Toggle the visibility of the subtree of an outline item.
+     *
+     * @param {Element} root - the root of the outline (sub)tree.
+     * @param {boolean} state - whether to show the outline (sub)tree. If false,
+     *   the outline subtree rooted at |root| will be collapsed.
+     *
+     * @private
+     */
+    _toggleOutlineItem: function PDFOutlineView_toggleOutlineItem(root, show) {
+      this.lastToggleIsShow = show;
+      var togglers = root.querySelectorAll('.outlineItemToggler');
+      for (var i = 0, ii = togglers.length; i < ii; ++i) {
+        togglers[i].classList[show ? 'remove' : 'add']('outlineItemsHidden');
+      }
+    },
+
+    /**
+     * Collapse or expand all subtrees of the outline.
+     */
+    toggleOutlineTree: function PDFOutlineView_toggleOutlineTree() {
+      this._toggleOutlineItem(this.container, !this.lastToggleIsShow);
+    },
+
     render: function PDFOutlineView_render() {
       var outline = this.outline;
       var outlineCount = 0;
@@ -80,7 +127,9 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
         return;
       }
 
-      var queue = [{ parent: this.container, items: this.outline }];
+      var fragment = document.createDocumentFragment();
+      var queue = [{ parent: fragment, items: this.outline }];
+      var hasAnyNesting = false;
       while (queue.length > 0) {
         var levelData = queue.shift();
         for (var i = 0, len = levelData.items.length; i < len; i++) {
@@ -93,6 +142,9 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
           div.appendChild(element);
 
           if (item.items.length > 0) {
+            hasAnyNesting = true;
+            this._addToggleButton(div);
+
             var itemsDiv = document.createElement('div');
             itemsDiv.className = 'outlineItems';
             div.appendChild(itemsDiv);
@@ -103,6 +155,11 @@ var PDFOutlineView = (function PDFOutlineViewClosure() {
           outlineCount++;
         }
       }
+      if (hasAnyNesting) {
+        this.container.classList.add('outlineWithDeepNesting');
+      }
+
+      this.container.appendChild(fragment);
 
       this._dispatchEvent(outlineCount);
     }

web/viewer.css

@@ -1190,10 +1190,12 @@ a:focus > .thumbnail > .thumbnailSelectionRing,
   padding: 3px 4px 0;
 }
 
+html[dir='ltr'] .outlineWithDeepNesting > .outlineItem,
 html[dir='ltr'] .outlineItem > .outlineItems {
   margin-left: 20px;
 }
 
+html[dir='rtl'] .outlineWithDeepNesting > .outlineItem,
 html[dir='rtl'] .outlineItem > .outlineItems {
   margin-right: 20px;
 }
@@ -1221,7 +1223,7 @@ html[dir='rtl'] .outlineItem > .outlineItems {
 }
 
 html[dir='ltr'] .outlineItem > a {
-  padding: 2px 0 5px 10px;
+  padding: 2px 0 5px 4px;
 }
 html[dir='ltr'] .attachmentsItem > button {
   padding: 2px 0 3px 7px;
@@ -1229,13 +1231,46 @@ html[dir='ltr'] .attachmentsItem > button {
 }
 
 html[dir='rtl'] .outlineItem > a {
-  padding: 2px 10px 5px 0;
+  padding: 2px 4px 5px 0;
 }
 html[dir='rtl'] .attachmentsItem > button {
   padding: 2px 7px 3px 0;
   text-align: right;
 }
 
+.outlineItemToggler {
+  position: relative;
+  height: 0;
+  width: 0;
+  color: hsla(0,0%,100%,.5);
+}
+.outlineItemToggler::before {
+  content: url(images/treeitem-collapsed.png);
+  display: inline-block;
+  position: absolute;
+}
+.outlineItemToggler.outlineItemsHidden::before {
+  content: url(images/treeitem-expanded.png);
+}
+.outlineItemToggler.outlineItemsHidden ~ .outlineItems {
+  display: none;
+}
+html[dir='ltr'] .outlineItemToggler {
+  float: left;
+}
+html[dir='rtl'] .outlineItemToggler {
+  float: right;
+}
+html[dir='ltr'] .outlineItemToggler::before {
+  right: 4px;
+}
+html[dir='rtl'] .outlineItemToggler::before {
+  left: 4px;
+}
+
+.outlineItemToggler:hover,
+.outlineItemToggler:hover + a,
+.outlineItemToggler:hover ~ .outlineItems,
 .outlineItem > a:hover,
 .attachmentsItem > button:hover {
   background-color: hsla(0,0%,100%,.02);

web/viewer.js

@@ -1401,6 +1401,11 @@ function webViewerInitialized() {
       PDFViewerApplication.switchSidebarView('outline');
     });
 
+  document.getElementById('viewOutline').addEventListener('dblclick',
+    function() {
+      PDFViewerApplication.outline.toggleOutlineTree();
+    });
+
   document.getElementById('viewAttachments').addEventListener('click',
     function() {
       PDFViewerApplication.switchSidebarView('attachments');