Add scrolling modes to web viewer

In addition to the default scrolling mode (vertical), this commit adds
horizontal, grid, and grid+cover scrolling, implemented primarily with
flexbox CSS.

l10n/en-US/viewer.properties

@@ -65,6 +65,15 @@ cursor_text_select_tool_label=Text Selection Tool
 cursor_hand_tool.title=Enable Hand Tool
 cursor_hand_tool_label=Hand Tool
 
+scroll_vertical.title=Use Vertical Scrolling
+scroll_vertical_label=Vertical Scrolling
+scroll_horizontal.title=Use Horizontal Scrolling
+scroll_horizontal_label=Horizontal Scrolling
+scroll_grid.title=Use Grid Scrolling
+scroll_grid_label=Grid Scrolling
+scroll_grid_cover.title=Use Grid Scrolling with a Cover Page
+scroll_grid_cover_label=Grid Scrolling with Cover Page
+
 # Document properties dialog box
 document_properties.title=Document Properties…
 document_properties_label=Document Properties…

web/app.js

@@ -1367,6 +1367,7 @@ let PDFViewerApplication = {
     eventBus.on('scalechanged', webViewerScaleChanged);
     eventBus.on('rotatecw', webViewerRotateCw);
     eventBus.on('rotateccw', webViewerRotateCcw);
+    eventBus.on('switchscrollmode', webViewerSwitchScrollMode);
     eventBus.on('documentproperties', webViewerDocumentProperties);
     eventBus.on('find', webViewerFind);
     eventBus.on('findfromurlhash', webViewerFindFromUrlHash);
@@ -1433,6 +1434,7 @@ let PDFViewerApplication = {
     eventBus.off('scalechanged', webViewerScaleChanged);
     eventBus.off('rotatecw', webViewerRotateCw);
     eventBus.off('rotateccw', webViewerRotateCcw);
+    eventBus.off('switchscrollmode', webViewerSwitchScrollMode);
     eventBus.off('documentproperties', webViewerDocumentProperties);
     eventBus.off('find', webViewerFind);
     eventBus.off('findfromurlhash', webViewerFindFromUrlHash);
@@ -1908,6 +1910,9 @@ function webViewerRotateCw() {
 function webViewerRotateCcw() {
   PDFViewerApplication.rotatePages(-90);
 }
+function webViewerSwitchScrollMode(evt) {
+  PDFViewerApplication.pdfViewer.setScrollMode(evt.mode);
+}
 function webViewerDocumentProperties() {
   PDFViewerApplication.pdfDocumentProperties.open();
 }

web/pdf_viewer.css

@@ -30,6 +30,7 @@
   background-clip: content-box;
   border-image: url(images/shadow.png) 9 9 repeat;
   background-color: white;
+  flex-shrink: 0;
 }
 
 .pdfViewer.removePageBorders .page {
@@ -46,6 +47,33 @@
   border: none;
 }
 
+.pdfViewer.scrollHorizontal, .pdfViewer.scrollGrid {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  margin-bottom: 8px;
+  min-width: -moz-min-content;
+  min-width: min-content;
+}
+
+.pdfViewer.scrollGrid {
+  flex-wrap: wrap;
+}
+
+.pdfViewer.scrollGrid.coverPage::before {
+  content: '';
+  width: 100%;
+}
+
+.pdfViewer.scrollHorizontal .page, .pdfViewer.scrollGrid .page {
+  margin-left: -4px;
+  margin-right: -4px;
+}
+
+.pdfViewer.scrollGrid.coverPage .page:first-child {
+  order: -1;
+}
+
 .pdfViewer .page canvas {
   margin: 0;
   display: block;
@@ -65,6 +93,15 @@
   background: url('images/loading-icon.gif') center no-repeat;
 }
 
+.pdfPresentationMode .pdfViewer {
+  display: block;
+}
+
+.pdfPresentationMode .pdfViewer .page {
+  margin-left: auto;
+  margin-right: auto;
+}
+
 .pdfPresentationMode:-webkit-full-screen .pdfViewer .page {
   margin-bottom: 100%;
   border: 0;

web/pdf_viewer.js

@@ -17,12 +17,22 @@ import { getVisibleElements, scrollIntoView } from './ui_utils';
 import { BaseViewer } from './base_viewer';
 import { shadow } from 'pdfjs-lib';
 
+const ScrollMode = {
+  VERTICAL: 0, // The default value.
+  HORIZONTAL: 1,
+  GRID: 2,
+  GRID_COVER: 3,
+};
+
 class PDFViewer extends BaseViewer {
   get _setDocumentViewerElement() {
     return shadow(this, '_setDocumentViewerElement', this.viewer);
   }
 
   _scrollIntoView({ pageDiv, pageSpot = null, }) {
+    if (!pageSpot && this._isHorizontallyScrolling) {
+      pageSpot = { left: 0, top: 0, };
+    }
     scrollIntoView(pageDiv, pageSpot);
   }
 
@@ -76,8 +86,28 @@ class PDFViewer extends BaseViewer {
       location: this._location,
     });
   }
+
+  setScrollMode(mode) {
+    this.viewer.classList.remove('scrollHorizontal', 'scrollGrid', 'coverPage');
+    this._isHorizontallyScrolling = false;
+    switch (mode) {
+      case ScrollMode.HORIZONTAL:
+        this._isHorizontallyScrolling = true;
+        this.viewer.classList.add('scrollHorizontal');
+        break;
+      case ScrollMode.GRID_COVER:
+        this.viewer.classList.add('coverPage');
+        // fallthrough
+      case ScrollMode.GRID:
+        this.viewer.classList.add('scrollGrid');
+        break;
+    }
+    this.eventBus.dispatch('scrollmodechanged', { mode, });
+    this.scrollPageIntoView({ pageNumber: this._currentPageNumber, });
+  }
 }
 
 export {
   PDFViewer,
+  ScrollMode,
 };

web/secondary_toolbar.js

@@ -15,6 +15,7 @@
 
 import { CursorTool } from './pdf_cursor_tools';
 import { SCROLLBAR_PADDING } from './ui_utils';
+import { ScrollMode } from './pdf_viewer';
 
 /**
  * @typedef {Object} SecondaryToolbarOptions
@@ -76,6 +77,14 @@ class SecondaryToolbar {
         eventDetails: { tool: CursorTool.SELECT, }, close: true, },
       { element: options.cursorHandToolButton, eventName: 'switchcursortool',
         eventDetails: { tool: CursorTool.HAND, }, close: true, },
+      { element: options.scrollVerticalButton, eventName: 'switchscrollmode',
+        eventDetails: { mode: ScrollMode.VERTICAL, }, close: true, },
+      { element: options.scrollHorizontalButton, eventName: 'switchscrollmode',
+        eventDetails: { mode: ScrollMode.HORIZONTAL, }, close: true, },
+      { element: options.scrollGridButton, eventName: 'switchscrollmode',
+        eventDetails: { mode: ScrollMode.GRID, }, close: true, },
+      { element: options.scrollGridCoverButton, eventName: 'switchscrollmode',
+        eventDetails: { mode: ScrollMode.GRID_COVER, }, close: true, },
       { element: options.documentPropertiesButton,
         eventName: 'documentproperties', close: true, },
     ];
@@ -95,9 +104,10 @@ class SecondaryToolbar {
 
     this.reset();
 
-    // Bind the event listeners for click and cursor tool actions.
+    // Bind the event listeners for click, cursor tool, and scroll mode actions.
     this._bindClickListeners();
     this._bindCursorToolsListener(options);
+    this._bindScrollModeListener(options);
 
     // Bind the event listener for adjusting the 'max-height' of the toolbar.
     this.eventBus.on('resize', this._setMaxHeight.bind(this));
@@ -172,6 +182,25 @@ class SecondaryToolbar {
     });
   }
 
+  _bindScrollModeListener(buttons) {
+    this.eventBus.on('scrollmodechanged', function(evt) {
+      const scrollModeButtons = [];
+      scrollModeButtons[ScrollMode.VERTICAL] = buttons.scrollVerticalButton;
+      scrollModeButtons[ScrollMode.HORIZONTAL] = buttons.scrollHorizontalButton;
+      scrollModeButtons[ScrollMode.GRID] = buttons.scrollGridButton;
+      scrollModeButtons[ScrollMode.GRID_COVER] = buttons.scrollGridCoverButton;
+
+      for (let i = 0; i < scrollModeButtons.length; i++) {
+        const { classList, } = scrollModeButtons[i];
+        if (i === evt.mode) {
+          classList.add('toggled');
+        } else {
+          classList.remove('toggled');
+        }
+      }
+    });
+  }
+
   open() {
     if (this.opened) {
       return;

web/ui_utils.js

@@ -153,7 +153,8 @@ function scrollIntoView(element, spot, skipOverflowHiddenElements = false) {
   }
   let offsetY = element.offsetTop + element.clientTop;
   let offsetX = element.offsetLeft + element.clientLeft;
-  while (parent.clientHeight === parent.scrollHeight ||
+  while ((parent.clientHeight === parent.scrollHeight &&
+         parent.clientWidth === parent.scrollWidth) ||
          (skipOverflowHiddenElements &&
           getComputedStyle(parent).overflow === 'hidden')) {
     if (parent.dataset._scaleY) {

web/viewer.css

@@ -1064,6 +1064,22 @@ html[dir="rtl"] .secondaryToolbarButton > span {
   content: url(images/secondaryToolbarButton-handTool.png);
 }
 
+.secondaryToolbarButton.scrollVertical::before {
+  content: url(images/secondaryToolbarButton-scrollVertical.png);
+}
+
+.secondaryToolbarButton.scrollHorizontal::before {
+  content: url(images/secondaryToolbarButton-scrollHorizontal.png);
+}
+
+.secondaryToolbarButton.scrollGrid::before {
+  content: url(images/secondaryToolbarButton-scrollGrid.png);
+}
+
+.secondaryToolbarButton.scrollGridCover::before {
+  content: url(images/secondaryToolbarButton-scrollGridCover.png);
+}
+
 .secondaryToolbarButton.documentProperties::before {
   content: url(images/secondaryToolbarButton-documentProperties.png);
 }
@@ -1798,6 +1814,22 @@ html[dir='rtl'] #documentPropertiesOverlay .row > * {
     content: url(images/secondaryToolbarButton-handTool@2x.png);
   }
 
+  .secondaryToolbarButton.scrollVertical::before {
+    content: url(images/secondaryToolbarButton-scrollVertical@2x.png);
+  }
+
+  .secondaryToolbarButton.scrollHorizontal::before {
+    content: url(images/secondaryToolbarButton-scrollHorizontal@2x.png);
+  }
+
+  .secondaryToolbarButton.scrollGrid::before {
+    content: url(images/secondaryToolbarButton-scrollGrid@2x.png);
+  }
+
+  .secondaryToolbarButton.scrollGridCover::before {
+    content: url(images/secondaryToolbarButton-scrollGridCover@2x.png);
+  }
+
   .secondaryToolbarButton.documentProperties::before {
     content: url(images/secondaryToolbarButton-documentProperties@2x.png);
   }

web/viewer.html

@@ -168,7 +168,22 @@
 
             <div class="horizontalToolbarSeparator"></div>
 
-            <button id="documentProperties" class="secondaryToolbarButton documentProperties" title="Document Properties…" tabindex="62" data-l10n-id="document_properties">
+            <button id="scrollVertical" class="secondaryToolbarButton scrollVertical toggled" title="Use Vertical Scrolling" tabindex="62" data-l10n-id="scroll_vertical">
+              <span data-l10n-id="scroll_vertical_label">Vertical Scrolling</span>
+            </button>
+            <button id="scrollHorizontal" class="secondaryToolbarButton scrollHorizontal" title="Use Horizontal Scrolling" tabindex="63" data-l10n-id="scroll_horizontal">
+              <span data-l10n-id="scroll_horizontal_label">Horizontal Scrolling</span>
+            </button>
+            <button id="scrollGrid" class="secondaryToolbarButton scrollGrid" title="Use Grid Scrolling" tabindex="64" data-l10n-id="scroll_grid">
+              <span data-l10n-id="scroll_grid_label">Grid Scrolling</span>
+            </button>
+            <button id="scrollGridCover" class="secondaryToolbarButton scrollGridCover" title="Use Grid Scrolling with a Cover Page" tabindex="65" data-l10n-id="scroll_grid_cover">
+              <span data-l10n-id="scroll_grid_cover_label">Grid Scrolling with Cover Page</span>
+            </button>
+
+            <div class="horizontalToolbarSeparator"></div>
+
+            <button id="documentProperties" class="secondaryToolbarButton documentProperties" title="Document Properties…" tabindex="66" data-l10n-id="document_properties">
               <span data-l10n-id="document_properties_label">Document Properties…</span>
             </button>
           </div>

web/viewer.js

@@ -95,6 +95,10 @@ function getViewerConfiguration() {
       pageRotateCcwButton: document.getElementById('pageRotateCcw'),
       cursorSelectToolButton: document.getElementById('cursorSelectTool'),
       cursorHandToolButton: document.getElementById('cursorHandTool'),
+      scrollVerticalButton: document.getElementById('scrollVertical'),
+      scrollHorizontalButton: document.getElementById('scrollHorizontal'),
+      scrollGridButton: document.getElementById('scrollGrid'),
+      scrollGridCoverButton: document.getElementById('scrollGridCover'),
       documentPropertiesButton: document.getElementById('documentProperties'),
     },
     fullscreen: {