Enable zoom through gamedpad trigger joystick

content/public/android/java/src/org/chromium/content/browser/input/JoystickZoomProvider.java

Index: content/public/android/java/src/org/chromium/content/browser/input/JoystickZoomProvider.java
diff --git a/content/public/android/java/src/org/chromium/content/browser/input/JoystickZoomProvider.java b/content/public/android/java/src/org/chromium/content/browser/input/JoystickZoomProvider.java
new file mode 100644
index 0000000000000000000000000000000000000000..489eb245759485ec628cb3a4616010d65ae15a99
--- /dev/null
+++ b/content/public/android/java/src/org/chromium/content/browser/input/JoystickZoomProvider.java
@@ -0,0 +1,131 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.content.browser.input;
+
+import android.view.InputDevice;
+import android.view.MotionEvent;
+
+import org.chromium.content.browser.ContentViewCore;
+
+/**
+ * This class controls page zoomin/out using trigger joystick events.
+ * Page Zoomin is proportional to RTRIGGER axis movement.
+ * Page Zoomout is proportional to LTRIGGER axis movement.
+ */
+public class JoystickZoomProvider {
+    private static final String TAG = "JoystickZoomProvider";
+
+    private static final float JOYSTICK_NOISE_THRESHOLD = 0.2f;
+
+    private static final float ZOOM_SPEED = 1.65f;
+
+    private long mLastAnimateTimeMillis;
+
+    private float mZoomInVelocity;
+
+    private float mZoomOutVelocity;
+
+    protected final ContentViewCore mContentViewCore;
+
+    protected float mDeviceScaleFactor;
+
+    private int mZoomXcoord;
+
+    private int mZoomYcoord;
+
+    protected Runnable mZoomRunnable;
+
+    private AnimationIntervalProvider mSystemAnimationIntervalProvider;
+
+    /**
+     * Constructs a new JoystickZoomProvider.
+     *
+     * @param cvc The ContentViewCore used to create this.
+     */
+    public JoystickZoomProvider(
+            ContentViewCore cvc, AnimationIntervalProvider animationTimeProvider) {
+        mContentViewCore = cvc;
+        mDeviceScaleFactor = mContentViewCore.getRenderCoordinates().getDeviceScaleFactor();
+        mZoomXcoord = mContentViewCore.getViewportWidthPix() / 2;
+        mZoomYcoord = mContentViewCore.getViewportHeightPix() / 2;
+        mSystemAnimationIntervalProvider = animationTimeProvider;
+    }
+
+    /**
+     * This function processes motion event and computes new
+     * page scale factor which is proportional to *_TRIGGER axes movement.
+     * It also starts runnable to update current page scale to new page scale.
+     *
+     * @param event Motion event to be processed for zooming.
+     * @return Whether zooming using *_TRIGGER axes is performed or not.
+     */
+    public boolean onMotion(MotionEvent event) {
+        if ((event.getSource() & InputDevice.SOURCE_CLASS_JOYSTICK) == 0) return false;
+
+        computeNewZoomVelocity(event);
+        if (mZoomInVelocity == 0 && mZoomOutVelocity == 0) {
+            stop();
+            return false;
+        }
+        if (mZoomRunnable == null) {
+            mZoomRunnable = new Runnable() {
+                @Override
+                public void run() {
+                    animateZoom();
+                }
+            };
+        }
+        if (mLastAnimateTimeMillis == 0) {
+            mLastAnimateTimeMillis =
+                    mSystemAnimationIntervalProvider.getLastAnimationFrameInterval();
+            mContentViewCore.getContainerView().postOnAnimation(mZoomRunnable);
+            mContentViewCore.pinchBegin(mZoomXcoord, mZoomYcoord);
+        }
+        return true;
+    }
+
+    protected void stop() {
+        if (mLastAnimateTimeMillis != 0) {
+            mContentViewCore.pinchEnd();
+            mLastAnimateTimeMillis = 0;
+        }
+    }
+
+    private void computeNewZoomVelocity(MotionEvent event) {
+        mZoomInVelocity = getFilteredAxisValue(event, MotionEvent.AXIS_RTRIGGER);
+        mZoomOutVelocity = getFilteredAxisValue(event, MotionEvent.AXIS_LTRIGGER);
+    }
+
+    protected void animateZoom() {
+        if (!mContentViewCore.getContainerView().hasFocus()) {
+            stop();
+            return;
+        }
+        if (mLastAnimateTimeMillis == 0) return;
+
+        final long timeMillis = mSystemAnimationIntervalProvider.getLastAnimationFrameInterval();
+        final long dt = timeMillis - mLastAnimateTimeMillis;
+        final float zoomFactor = (float) Math.pow(
+                ZOOM_SPEED, mDeviceScaleFactor * (mZoomInVelocity - mZoomOutVelocity) * dt / 1000f);
+        mContentViewCore.pinchBy(mZoomXcoord, mZoomYcoord, zoomFactor);
+        mLastAnimateTimeMillis = timeMillis;
+        mContentViewCore.getContainerView().postOnAnimation(mZoomRunnable);
+    }
+
+    /**
+     * This function removes noise from motion events.
+     * Joystick is very senstitive, it produces value (noise) along X/Y directions
+     * even if gamepad button is pressed which is not acceptable.
+     * Returns non-zero value only if event value is above noise threshold.
+     *
+     * @param event Motion event which needs noise processing.
+     * @param axis Joystick axis (whether X_AXIS of Y_AXIS)
+     * @return Processed joystick value.
+     */
+    private float getFilteredAxisValue(MotionEvent event, int axis) {
+        float axisValWithNoise = event.getAxisValue(axis);
+        return (axisValWithNoise > JOYSTICK_NOISE_THRESHOLD) ? axisValWithNoise : 0f;
+    }
+}