Bug 807990 - Scroll reader mode page by one page on double tap. r=lucasr,cwiiis

mobile/android/base/gfx/JavaPanZoomController.java

@@ -1373,9 +1373,7 @@ class JavaPanZoomController
 
     @Override
     public boolean onDoubleTap(MotionEvent motionEvent) {
-        if (mTarget.getZoomConstraints().getAllowDoubleTapZoom()) {
-            sendPointToGecko("Gesture:DoubleTap", motionEvent);
-        }
+        sendPointToGecko("Gesture:DoubleTap", motionEvent);
         return true;
     }
 

mobile/android/chrome/content/aboutReader.js

@@ -35,6 +35,7 @@ let AboutReader = function(doc, win) {
   Services.obs.addObserver(this, "Reader:Add", false);
   Services.obs.addObserver(this, "Reader:Remove", false);
   Services.obs.addObserver(this, "Reader:ListStatusReturn", false);
+  Services.obs.addObserver(this, "Gesture:DoubleTap", false);
 
   this._article = null;
 
@@ -223,6 +224,19 @@ AboutReader.prototype = {
         }
         break;
       }
+
+      case "Gesture:DoubleTap": {
+        let args = JSON.parse(aData);
+        let scrollBy;
+        // Arbitary choice of innerHeight - 50 to give some context after scroll
+        if (args.y < (this._win.innerHeight / 2)) {
+          scrollBy = -this._win.innerHeight + 50;
+        } else {
+          scrollBy = this._win.innerHeight - 50;
+        }
+        this._scrollPage(scrollBy);
+        break;
+      }
     }
   },
 
@@ -261,10 +275,21 @@ AboutReader.prototype = {
         Services.obs.removeObserver(this, "Reader:Add");
         Services.obs.removeObserver(this, "Reader:Remove");
         Services.obs.removeObserver(this, "Reader:ListStatusReturn");
+        Services.obs.removeObserver(this, "Gesture:DoubleTap");
         break;
     }
   },
 
+  _scrollPage: function Reader_scrollPage(scrollByPixels) {
+    let viewport = BrowserApp.selectedTab.getViewport();
+    let newY = Math.min(Math.max(viewport.cssY + scrollByPixels, viewport.cssPageTop), viewport.cssPageBottom);
+    let newRect = new Rect(viewport.cssX, newY, viewport.cssWidth, viewport.cssHeight);
+
+    this._setToolbarVisibility(false);
+    this._scrolled  = true;
+    ZoomHelper.zoomToRect(newRect, -1, false, false);
+  },
+
   _updateToggleButton: function Reader_updateToggleButton() {
     let classes = this._doc.getElementById("toggle-button").classList;
 

mobile/android/chrome/content/browser.js

@@ -4878,6 +4878,11 @@ var BrowserEventHandler = {
   },
 
   onDoubleTap: function(aData) {
+    let metadata = BrowserApp.selectedTab.metadata;
+    if (!metadata.allowDoubleTapZoom) {
+      return;
+    }
+
     let data = JSON.parse(aData);
     let element = ElementTouchHelper.anyElementFromPoint(data.x, data.y);