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 dab584d9d0bdc9afb6d3a68f1631627bba6bd8ac..41d9b59ec4043d73abbe3803c3224b9a6563d160 100644
--- a/chrome/browser/resources/pdf/pdf.js
+++ b/chrome/browser/resources/pdf/pdf.js
@@ -217,6 +217,46 @@ 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 browser
+  // 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', function(ev) {
+    this.pinchZoomStart(ev);
+  }.bind(this.viewport_));
+
+  this.hammertime_.on('pinch', function(ev) {
+    if(!this.didPinch_) {
+      this.didPinch_ = true;
+      window.requestAnimationFrame(function() {
+        this.didPinch_ = false;
+        this.pinchZoom(ev);
+      }.bind(this));
+    }
+  }.bind(this.viewport_));
+
+  this.hammertime_.on('pinchend', function(ev) {
+    if(!this.didPinchEnd_) {
+      this.didPinchEnd_ = true;
+      window.requestAnimationFrame(function() {

[bokan, 2016/05/12 14:57:57]

I don't think we need to rAF the PinchEnd event.

+        this.didPinchEnd_ = false;
+        this.pinchZoomEnd(ev);
+      }.bind(this));
+    }
+  }.bind(this.viewport_));
+
   if (toolbarEnabled) {
     this.toolbar_ = $('toolbar');
     this.toolbar_.hidden = false;
@@ -687,11 +727,24 @@ 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 doRender = this.viewport.doRender_;
+
+    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,
+      render: doRender,  // Render or not

[bokan, 2016/05/12 14:57:57]

I think a better name here would be needsReraster

+      px: pinchCenter.x,
+      py: pinchCenter.y,
+      pinchVectorX: pinchVector.x,
+      pinchVectorY: pinchVector.y
     });
     this.zoomManager_.onPdfZoomChange();
   },