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