The Tor Browser: mobile/android/base/gfx/SimpleScaleGestureDetector.java@6474c204b198 (annotated)

mobile/android/base/gfx/SimpleScaleGestureDetector.java@6474c204b198 (annotated)

mobile/android/base/gfx/SimpleScaleGestureDetector.java

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 package org.mozilla.gecko.gfx;
 import org.json.JSONException;
 import android.graphics.PointF;
 import android.util.Log;
 import android.view.MotionEvent;
 import java.util.LinkedList;
 import java.util.ListIterator;
 import java.util.Stack;
 /**
  * A less buggy, and smoother, replacement for the built-in Android ScaleGestureDetector.
  *
  * This gesture detector is more reliable than the built-in ScaleGestureDetector because:
  *
  *   - It doesn't assume that pointer IDs are numbered 0 and 1.
  *
  *   - It doesn't attempt to correct for "slop" when resting one's hand on the device. On some
  *     devices (e.g. the Droid X) this can cause the ScaleGestureDetector to lose track of how many
  *     pointers are down, with disastrous results (bug 706684).
  *
  *   - Cancelling a zoom into a pan is handled correctly.
  *
  *   - Starting with three or more fingers down, releasing fingers so that only two are down, and
  *     then performing a scale gesture is handled correctly.
  *
  *   - It doesn't take pressure into account, which results in smoother scaling.
  */
 class SimpleScaleGestureDetector {
     private static final String LOGTAG = "GeckoSimpleScaleGestureDetector";
     private SimpleScaleGestureListener mListener;
     private long mLastEventTime;
     private boolean mScaleResult;
     /* Information about all pointers that are down. */
     private LinkedList<PointerInfo> mPointerInfo;
     /** Creates a new gesture detector with the given listener. */
     SimpleScaleGestureDetector(SimpleScaleGestureListener listener) {
         mListener = listener;
         mPointerInfo = new LinkedList<PointerInfo>();
     }
     /** Forward touch events to this function. */
     public void onTouchEvent(MotionEvent event) {
         switch (event.getAction() & MotionEvent.ACTION_MASK) {
         case MotionEvent.ACTION_DOWN:
             // If we get ACTION_DOWN while still tracking any pointers,
             // something is wrong.  Cancel the current gesture and start over.
             if (getPointersDown() > 0)
                 onTouchEnd(event);
             onTouchStart(event);
             break;
         case MotionEvent.ACTION_POINTER_DOWN:
             onTouchStart(event);
             break;
         case MotionEvent.ACTION_MOVE:
             onTouchMove(event);
             break;
         case MotionEvent.ACTION_POINTER_UP:
         case MotionEvent.ACTION_UP:
         case MotionEvent.ACTION_CANCEL:
             onTouchEnd(event);
             break;
         }
     }
     private int getPointersDown() {
         return mPointerInfo.size();
     }
     private int getActionIndex(MotionEvent event) {
         return (event.getAction() & MotionEvent.ACTION_POINTER_INDEX_MASK)
             >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
     }
     private void onTouchStart(MotionEvent event) {
         mLastEventTime = event.getEventTime();
         mPointerInfo.addFirst(PointerInfo.create(event, getActionIndex(event)));
         if (getPointersDown() == 2) {
             sendScaleGesture(EventType.BEGIN);
         }
     }
     private void onTouchMove(MotionEvent event) {
         mLastEventTime = event.getEventTime();
         for (int i = 0; i < event.getPointerCount(); i++) {
             PointerInfo pointerInfo = pointerInfoForEventIndex(event, i);
             if (pointerInfo != null) {
                 pointerInfo.populate(event, i);
             }
         }
         if (getPointersDown() == 2) {
             sendScaleGesture(EventType.CONTINUE);
         }
     }
     private void onTouchEnd(MotionEvent event) {
         mLastEventTime = event.getEventTime();
         int action = event.getAction() & MotionEvent.ACTION_MASK;
         boolean isCancel = (action == MotionEvent.ACTION_CANCEL ||
                             action == MotionEvent.ACTION_DOWN);
         int id = event.getPointerId(getActionIndex(event));
         ListIterator<PointerInfo> iterator = mPointerInfo.listIterator();
         while (iterator.hasNext()) {
             PointerInfo pointerInfo = iterator.next();
             if (!(isCancel || pointerInfo.getId() == id)) {
                 continue;
             }
             // One of the pointers we were tracking was lifted. Remove its info object from the
             // list, recycle it to avoid GC pauses, and send an onScaleEnd() notification if this
             // ended the gesture.
             iterator.remove();
             pointerInfo.recycle();
             if (getPointersDown() == 1) {
                 sendScaleGesture(EventType.END);
             }
         }
     }
     /**
      * Returns the X coordinate of the focus location (the midpoint of the two fingers). If only
      * one finger is down, returns the location of that finger.
      */
     public float getFocusX() {
         switch (getPointersDown()) {
         case 1:
             return mPointerInfo.getFirst().getCurrent().x;
         case 2:
             PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast();
             return (pointerA.getCurrent().x + pointerB.getCurrent().x) / 2.0f;
         }
         Log.e(LOGTAG, "No gesture taking place in getFocusX()!");
         return 0.0f;
     }
     /**
      * Returns the Y coordinate of the focus location (the midpoint of the two fingers). If only
      * one finger is down, returns the location of that finger.
      */
     public float getFocusY() {
         switch (getPointersDown()) {
         case 1:
             return mPointerInfo.getFirst().getCurrent().y;
         case 2:
             PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast();
             return (pointerA.getCurrent().y + pointerB.getCurrent().y) / 2.0f;
         }
         Log.e(LOGTAG, "No gesture taking place in getFocusY()!");
         return 0.0f;
     }
     /** Returns the most recent distance between the two pointers. */
     public float getCurrentSpan() {
         if (getPointersDown() != 2) {
             Log.e(LOGTAG, "No gesture taking place in getCurrentSpan()!");
             return 0.0f;
         }
         PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast();
         return PointUtils.distance(pointerA.getCurrent(), pointerB.getCurrent());
     }
     /** Returns the second most recent distance between the two pointers. */
     public float getPreviousSpan() {
         if (getPointersDown() != 2) {
             Log.e(LOGTAG, "No gesture taking place in getPreviousSpan()!");
             return 0.0f;
         }
         PointerInfo pointerA = mPointerInfo.getFirst(), pointerB = mPointerInfo.getLast();
         PointF a = pointerA.getPrevious(), b = pointerB.getPrevious();
         if (a == null || b == null) {
             a = pointerA.getCurrent();
             b = pointerB.getCurrent();
         }
         return PointUtils.distance(a, b);
     }
     /** Returns the time of the last event related to the gesture. */
     public long getEventTime() {
         return mLastEventTime;
     }
     /** Returns true if the scale gesture is in progress and false otherwise. */
     public boolean isInProgress() {
         return getPointersDown() == 2;
     }
     /* Sends the requested scale gesture notification to the listener. */
     private void sendScaleGesture(EventType eventType) {
         switch (eventType) {
         case BEGIN:
             mScaleResult = mListener.onScaleBegin(this);
             break;
         case CONTINUE:
             if (mScaleResult) {
                 mListener.onScale(this);
             }
             break;
         case END:
             if (mScaleResult) {
                 mListener.onScaleEnd(this);
             }
             break;
         }
     }
     /*
      * Returns the pointer info corresponding to the given pointer index, or null if the pointer
      * isn't one that's being tracked.
      */
     private PointerInfo pointerInfoForEventIndex(MotionEvent event, int index) {
         int id = event.getPointerId(index);
         for (PointerInfo pointerInfo : mPointerInfo) {
             if (pointerInfo.getId() == id) {
                 return pointerInfo;
             }
         }
         return null;
     }
     private enum EventType {
         BEGIN,
         CONTINUE,
         END,
     }
     /* Encapsulates information about one of the two fingers involved in the gesture. */
     private static class PointerInfo {
         /* A free list that recycles pointer info objects, to reduce GC pauses. */
         private static Stack<PointerInfo> sPointerInfoFreeList;
         private int mId;
         private PointF mCurrent, mPrevious;
         private PointerInfo() {
             // External users should use create() instead.
         }
         /* Creates or recycles a new PointerInfo instance from an event and a pointer index. */
         public static PointerInfo create(MotionEvent event, int index) {
             if (sPointerInfoFreeList == null) {
                 sPointerInfoFreeList = new Stack<PointerInfo>();
             }
             PointerInfo pointerInfo;
             if (sPointerInfoFreeList.empty()) {
                 pointerInfo = new PointerInfo();
             } else {
                 pointerInfo = sPointerInfoFreeList.pop();
             }
             pointerInfo.populate(event, index);
             return pointerInfo;
         }
         /*
          * Fills in the fields of this instance from the given motion event and pointer index
          * within that event.
          */
         public void populate(MotionEvent event, int index) {
             mId = event.getPointerId(index);
             mPrevious = mCurrent;
             mCurrent = new PointF(event.getX(index), event.getY(index));
         }
         public void recycle() {
             mId = -1;
             mPrevious = mCurrent = null;
             sPointerInfoFreeList.push(this);
         }
         public int getId() { return mId; }
         public PointF getCurrent() { return mCurrent; }
         public PointF getPrevious() { return mPrevious; }
         @Override
         public String toString() {
             if (mId == -1) {
                 return "(up)";
             }
             try {
                 String prevString;
                 if (mPrevious == null) {
                     prevString = "n/a";
                 } else {
                     prevString = PointUtils.toJSON(mPrevious).toString();
                 }
                 // The current position should always be non-null.
                 String currentString = PointUtils.toJSON(mCurrent).toString();
                 return "id=" + mId + " cur=" + currentString + " prev=" + prevString;
             } catch (JSONException e) {
                 throw new RuntimeException(e);
             }
         }
     }
     public static interface SimpleScaleGestureListener {
         public boolean onScale(SimpleScaleGestureDetector detector);
         public boolean onScaleBegin(SimpleScaleGestureDetector detector);
         public void onScaleEnd(SimpleScaleGestureDetector detector);
     }
 }

The Tor Browser / annotate

mobile/android/base/gfx/SimpleScaleGestureDetector.java@6474c204b198 (annotated)

mobile/android/base/gfx/SimpleScaleGestureDetector.java