Improved Pinch-Zoom for PDF.

chrome/browser/resources/pdf/pdf.js

Index: chrome/browser/resources/pdf/pdf.js
diff --git a/chrome/browser/resources/pdf/pdf.js b/chrome/browser/resources/pdf/pdf.js
index 9805660b562c34e82cae189e4670abaace68eb8e..a14745df931fae4eca9cfc7d2a46c5a0f00684d3 100644
--- a/chrome/browser/resources/pdf/pdf.js
+++ b/chrome/browser/resources/pdf/pdf.js
@@ -191,6 +191,46 @@ function PDFViewer(browserApi) {
   this.zoomToolbar_.addEventListener('zoom-out',
       this.viewport_.zoomOut.bind(this.viewport_));
 
+  // We add Hammer.js in order to handle touch events like pinch-zoom.
+  this.hammertime_ = new Hammer($('plugin'));
+
+  // We must preventDefault if there is a two finger touch. By doing so native
+  // pinch-zoom does not interfere with our way of handling the event.
+  this.plugin_.addEventListener('touchstart', function(e) {
+    if (e.touches.length >= 2) {
+      e.preventDefault();
+      this.hammertime_.get('pinch').set({enable: true});
+    }
+  }.bind(this));
+
+  this.plugin_.addEventListener('touchend', function(e) {
+    this.hammertime_.get('pinch').set({enable: false});
+  }.bind(this));
+
+  this.hammertime_.on('pinchstart',
+      this.viewport_.pinchZoomStart.bind(this.viewport_));
+
+  // Throttle number of pinch events to one per frame.
+  this.sentPinchEvent_ = false;
+
+  this.hammertime_.on('pinch', function(ev) {
+    if (!this.sentPinchEvent_) {
+      this.sentPinchEvent_ = true;
+      window.requestAnimationFrame(function() {
+        this.sentPinchEvent_ = false;
+        this.viewport_.pinchZoom(ev);
+      }.bind(this));
+    }
+  }.bind(this));
+
+  this.hammertime_.on('pinchend', function(ev) {
+    // Using rAF for pinch end prevents pinch updates scheduled by rAF getting
+    // sent after the pinch end.
+    window.requestAnimationFrame(function() {
+      this.viewport_.pinchZoomEnd(ev);
+    }.bind(this));
+  }.bind(this));
+
   if (toolbarEnabled) {
     this.toolbar_ = $('toolbar');
     this.toolbar_.hidden = false;
@@ -659,6 +699,19 @@ PDFViewer.prototype = {
     this.plugin_.postMessage({
       type: 'stopScrolling'
     });
+
+    if (this.viewport_.pinchPhase == Viewport.PinchPhase.PINCH_START) {
+      var position = this.viewport_.position;
+      var zoom = this.viewport_.zoom;
+      var pinchPhase = this.viewport_.pinchPhase;
+      this.plugin_.postMessage({
+        type: 'viewport',
+        zoom: zoom,
+        xOffset: position.x,
+        yOffset: position.y,
+        pinchPhase: pinchPhase
+      });
+    }
   },
 
   /**
@@ -669,11 +722,24 @@ PDFViewer.prototype = {
   afterZoom_: function() {
     var position = this.viewport_.position;
     var zoom = this.viewport_.zoom;
+    var pinchVector = this.viewport_.pinchPanVector;
+    var pinchCenter = this.viewport_.pinchCenter;
+    var pinchPhase = this.viewport_.pinchPhase;
+
+    if (!pinchVector)
+      pinchVector = {x: 0, y: 0};
+    if (!pinchCenter)
+      pinchCenter = {x: 0, y: 0};
     this.plugin_.postMessage({
       type: 'viewport',
       zoom: zoom,
       xOffset: position.x,
-      yOffset: position.y
+      yOffset: position.y,
+      pinchPhase: pinchPhase,
+      pinchX: pinchCenter.x,
+      pinchY: pinchCenter.y,
+      pinchVectorX: pinchVector.x,
+      pinchVectorY: pinchVector.y
     });
     this.zoomManager_.onPdfZoomChange();
   },