package at.bestsolution.efxclipse.runtime.example.photoedit.ui.control;
/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import javafx.scene.input.MouseEvent;
/**
* Helper for tracking the velocity of touch events, for implementing
* flinging and other such gestures. Use {@link #obtain} to retrieve a
* new instance of the class when you are going to begin tracking, put
* the motion events you receive into it with {@link #addMovement(MotionEvent)},
* and when you want to determine the velocity call
* {@link #computeCurrentVelocity(int)} and then {@link #getXVelocity()}
* and {@link #getXVelocity()}.
*/
public final class VelocityTracker {
private static final boolean DEBUG = false;
private static final boolean localLOGV = DEBUG;
private static final int NUM_PAST = 10;
private static final int MAX_AGE_MILLISECONDS = 200;
private static final int POINTER_POOL_CAPACITY = 20;
private static Pointer sRecycledPointerListHead;
private static int sRecycledPointerCount;
private static final class Pointer {
public Pointer next;
public int id;
public float xVelocity;
public float yVelocity;
public final float[] pastX = new float[NUM_PAST];
public final float[] pastY = new float[NUM_PAST];
public final long[] pastTime = new long[NUM_PAST]; // uses Long.MIN_VALUE as a sentinel
}
private Pointer mPointerListHead; // sorted by id in increasing order
private int mLastTouchIndex;
public VelocityTracker() {
clear();
}
/**
* Reset the velocity tracker back to its initial state.
*/
public void clear() {
releasePointerList(mPointerListHead);
mPointerListHead = null;
mLastTouchIndex = 0;
}
/**
* Add a user's movement to the tracker. You should call this for the
* initial {@link MotionEvent#ACTION_DOWN}, the following
* {@link MotionEvent#ACTION_MOVE} events that you receive, and the
* final {@link MotionEvent#ACTION_UP}. You can, however, call this
* for whichever events you desire.
*
* @param ev The MotionEvent you received and would like to track.
*/
public void addMovement(MouseEvent ev) {
final int historySize = 0;
final int lastTouchIndex = mLastTouchIndex;
final int nextTouchIndex = (lastTouchIndex + 1) % NUM_PAST;
final int finalTouchIndex = (nextTouchIndex + historySize) % NUM_PAST;
mLastTouchIndex = finalTouchIndex;
if (mPointerListHead == null) {
mPointerListHead = obtainPointer();
}
final float[] pastX = mPointerListHead.pastX;
final float[] pastY = mPointerListHead.pastY;
final long[] pastTime = mPointerListHead.pastTime;
pastX[finalTouchIndex] = (float)ev.getX();
pastY[finalTouchIndex] = (float)ev.getY();
pastTime[finalTouchIndex] = System.currentTimeMillis();
}
/**
* Equivalent to invoking {@link #computeCurrentVelocity(int, float)} with a maximum
* velocity of Float.MAX_VALUE.
*
* @see #computeCurrentVelocity(int, float)
*/
public void computeCurrentVelocity(int units) {
computeCurrentVelocity(units, Float.MAX_VALUE);
}
/**
* Compute the current velocity based on the points that have been
* collected. Only call this when you actually want to retrieve velocity
* information, as it is relatively expensive. You can then retrieve
* the velocity with {@link #getXVelocity()} and
* {@link #getYVelocity()}.
*
* @param units The units you would like the velocity in. A value of 1
* provides pixels per millisecond, 1000 provides pixels per second, etc.
* @param maxVelocity The maximum velocity that can be computed by this method.
* This value must be declared in the same unit as the units parameter. This value
* must be positive.
*/
public void computeCurrentVelocity(int units, float maxVelocity) {
final int lastTouchIndex = mLastTouchIndex;
for (Pointer pointer = mPointerListHead; pointer != null; pointer = pointer.next) {
final long[] pastTime = pointer.pastTime;
// Search backwards in time for oldest acceptable time.
// Stop at the beginning of the trace as indicated by the sentinel time Long.MIN_VALUE.
int oldestTouchIndex = lastTouchIndex;
int numTouches = 1;
final long minTime = pastTime[lastTouchIndex] - MAX_AGE_MILLISECONDS;
while (numTouches < NUM_PAST) {
final int nextOldestTouchIndex = (oldestTouchIndex + NUM_PAST - 1) % NUM_PAST;
final long nextOldestTime = pastTime[nextOldestTouchIndex];
if (nextOldestTime < minTime) { // also handles end of trace sentinel
break;
}
oldestTouchIndex = nextOldestTouchIndex;
numTouches += 1;
}
// If we have a lot of samples, skip the last received sample since it is
// probably pretty noisy compared to the sum of all of the traces already acquired.
if (numTouches > 3) {
numTouches -= 1;
}
// Kind-of stupid.
final float[] pastX = pointer.pastX;
final float[] pastY = pointer.pastY;
final float oldestX = pastX[oldestTouchIndex];
final float oldestY = pastY[oldestTouchIndex];
final long oldestTime = pastTime[oldestTouchIndex];
float accumX = 0;
float accumY = 0;
for (int i = 1; i < numTouches; i++) {
final int touchIndex = (oldestTouchIndex + i) % NUM_PAST;
final int duration = (int)(pastTime[touchIndex] - oldestTime);
if (duration == 0) continue;
float delta = pastX[touchIndex] - oldestX;
float velocity = (delta / duration) * units; // pixels/frame.
accumX = (accumX == 0) ? velocity : (accumX + velocity) * .5f;
delta = pastY[touchIndex] - oldestY;
velocity = (delta / duration) * units; // pixels/frame.
accumY = (accumY == 0) ? velocity : (accumY + velocity) * .5f;
}
if (accumX < -maxVelocity) {
accumX = - maxVelocity;
} else if (accumX > maxVelocity) {
accumX = maxVelocity;
}
if (accumY < -maxVelocity) {
accumY = - maxVelocity;
} else if (accumY > maxVelocity) {
accumY = maxVelocity;
}
pointer.xVelocity = accumX;
pointer.yVelocity = accumY;
if (localLOGV) {
System.out.println("Pointer " + pointer.id + ": Y velocity=" + accumX +" X velocity=" + accumY + " N=" + numTouches);
}
}
}
/**
* Retrieve the last computed X velocity. You must first call
* {@link #computeCurrentVelocity(int)} before calling this function.
*
* @return The previously computed X velocity.
*/
public float getXVelocity() {
Pointer pointer = getPointer(0);
return pointer != null ? pointer.xVelocity : 0;
}
/**
* Retrieve the last computed Y velocity. You must first call
* {@link #computeCurrentVelocity(int)} before calling this function.
*
* @return The previously computed Y velocity.
*/
public float getYVelocity() {
Pointer pointer = getPointer(0);
return pointer != null ? pointer.yVelocity : 0;
}
/**
* Retrieve the last computed X velocity. You must first call
* {@link #computeCurrentVelocity(int)} before calling this function.
*
* @param id Which pointer's velocity to return.
* @return The previously computed X velocity.
*/
public float getXVelocity(int id) {
Pointer pointer = getPointer(id);
return pointer != null ? pointer.xVelocity : 0;
}
/**
* Retrieve the last computed Y velocity. You must first call
* {@link #computeCurrentVelocity(int)} before calling this function.
*
* @param id Which pointer's velocity to return.
* @return The previously computed Y velocity.
*/
public float getYVelocity(int id) {
Pointer pointer = getPointer(id);
return pointer != null ? pointer.yVelocity : 0;
}
private final Pointer getPointer(int id) {
for (Pointer pointer = mPointerListHead; pointer != null; pointer = pointer.next) {
if (pointer.id == id) {
return pointer;
}
}
return null;
}
private static final Pointer obtainPointer() {
if (sRecycledPointerCount != 0) {
Pointer element = sRecycledPointerListHead;
sRecycledPointerCount -= 1;
sRecycledPointerListHead = element.next;
element.next = null;
return element;
}
return new Pointer();
}
private static final void releasePointer(Pointer pointer) {
if (sRecycledPointerCount < POINTER_POOL_CAPACITY) {
pointer.next = sRecycledPointerListHead;
sRecycledPointerCount += 1;
sRecycledPointerListHead = pointer;
}
}
private static final void releasePointerList(Pointer pointer) {
if (pointer != null) {
int count = sRecycledPointerCount;
if (count >= POINTER_POOL_CAPACITY) {
return;
}
Pointer tail = pointer;
for (;;) {
count += 1;
if (count >= POINTER_POOL_CAPACITY) {
break;
}
Pointer next = tail.next;
if (next == null) {
break;
}
tail = next;
}
tail.next = sRecycledPointerListHead;
sRecycledPointerCount = count;
sRecycledPointerListHead = pointer;
}
}
}
