/*
* Copyright 2011 Vaadin Ltd.
*
* 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.
*/
package com.vaadin.terminal.gwt.client.ui;
import java.util.ArrayList;
import java.util.Date;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.dom.client.Node;
import com.google.gwt.dom.client.NodeList;
import com.google.gwt.dom.client.Style;
import com.google.gwt.dom.client.Touch;
import com.google.gwt.event.dom.client.TouchStartEvent;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
import com.google.gwt.user.client.Event.NativePreviewHandler;
import com.vaadin.terminal.gwt.client.VConsole;
/**
* Provides one finger touch scrolling for elements with once scrollable
* elements inside. One widget can have several of these scrollable elements.
* Scrollable elements are provided in the constructor. Users must pass
* touchStart events to this delegate, from there on the delegate takes over
* with an event preview. Other touch events needs to be sunken though.
* <p>
* This is bit similar as Scroller class in GWT expenses example, but ideas
* drawn from iscroll.js project:
* <ul>
* <li>uses GWT event mechanism.
* <li>uses modern CSS trick during scrolling for smoother experience:
* translate3d and transitions
* </ul>
* <p>
* Scroll event should only happen when the "touch scrolling actually ends".
* Later we might also tune this so that a scroll event happens if user stalls
* her finger long enought.
*
* TODO static getter for active touch scroll delegate. Components might need to
* prevent scrolling in some cases. Consider Table with drag and drop, or drag
* and drop in scrollable area. Optimal implementation might be to start the
* drag and drop only if user keeps finger down for a moment, otherwise do the
* scroll. In this case, the draggable component would need to cancel scrolling
* in a timer after touchstart event and take over from there.
*
* TODO support scrolling horizontally
*
* TODO cancel if user add second finger to the screen (user expects a gesture).
*
* TODO "scrollbars", see e.g. iscroll.js
*
* TODO write an email to sjobs ät apple dot com and beg for this feature to be
* built into webkit. Seriously, we should try to lobbying this to webkit folks.
* This sure ain't our business to implement this with javascript.
*
* TODO collect all general touch related constant to better place.
*
* @author Matti Tahvonen, Vaadin Ltd
*/
public class TouchScrollDelegate implements NativePreviewHandler {
private static final double FRICTION = 0.002;
private static final double DECELERATION = 0.002;
private static final int MAX_DURATION = 1500;
private int origX;
private int origY;
private Element[] scrollableElements;
private Element scrolledElement;
private int origScrollTop;
private HandlerRegistration handlerRegistration;
private int lastClientY;
private double pixxelsPerMs;
private boolean transitionPending = false;
private int deltaScrollPos;
private boolean transitionOn = false;
private int finalScrollTop;
private ArrayList<Element> layers;
private boolean moved;
private static TouchScrollDelegate activeScrollDelegate;
public TouchScrollDelegate(Element... elements) {
scrollableElements = elements;
}
public static TouchScrollDelegate getActiveScrollDelegate() {
return activeScrollDelegate;
}
/**
* Has user moved the touch.
*
* @return
*/
public boolean isMoved() {
return moved;
}
/**
* Forces the scroll delegate to cancels scrolling process. Can be called by
* users if they e.g. decide to handle touch event by themselves after all
* (e.g. a pause after touch start before moving touch -> interpreted as
* long touch/click or drag start).
*/
public void stopScrolling() {
handlerRegistration.removeHandler();
handlerRegistration = null;
if (moved) {
moveTransformationToScrolloffset();
} else {
activeScrollDelegate = null;
}
}
public void onTouchStart(TouchStartEvent event) {
if (activeScrollDelegate == null && event.getTouches().length() == 1) {
Touch touch = event.getTouches().get(0);
if (detectScrolledElement(touch)) {
VConsole.log("TouchDelegate takes over");
event.stopPropagation();
handlerRegistration = Event.addNativePreviewHandler(this);
activeScrollDelegate = this;
hookTransitionEndListener(scrolledElement
.getFirstChildElement());
origX = touch.getClientX();
origY = touch.getClientY();
yPositions[0] = origY;
eventTimeStamps[0] = new Date();
nextEvent = 1;
if (transitionOn) {
// TODO calculate current position of ongoing transition,
// fix to that and start scroll from there. Another option
// is to investigate if we can get even close the same
// framerate with scheduler based impl instead of using
// transitions (GWT examples has impl of this, with jsni
// though). This is very smooth on native ipad, now we
// ignore touch starts during animation.
origScrollTop = scrolledElement.getScrollTop();
} else {
origScrollTop = scrolledElement.getScrollTop();
}
moved = false;
// event.preventDefault();
// event.stopPropagation();
}
} else {
/*
* Touch scroll is currenly on (possibly bouncing). Ignore.
*/
}
}
private native void hookTransitionEndListener(Element element)
/*-{
if(!element.hasTransitionEndListener) {
var that = this;
element.addEventListener("webkitTransitionEnd",function(event){
that.@com.vaadin.terminal.gwt.client.ui.TouchScrollDelegate::onTransitionEnd()();
},false);
element.hasTransitionEndListener = true;
}
}-*/;
private void onTransitionEnd() {
if (finalScrollTop < 0) {
animateToScrollPosition(0, finalScrollTop);
finalScrollTop = 0;
} else if (finalScrollTop > getMaxFinalY()) {
animateToScrollPosition(getMaxFinalY(), finalScrollTop);
finalScrollTop = getMaxFinalY();
} else {
moveTransformationToScrolloffset();
}
transitionOn = false;
}
private void animateToScrollPosition(int to, int from) {
int dist = Math.abs(to - from);
int time = getAnimationTimeForDistance(dist);
if (time <= 0) {
time = 1; // get animation and transition end event
}
translateTo(time, -to + origScrollTop);
}
private int getAnimationTimeForDistance(int dist) {
return 350; // 350ms seems to work quite fine for all distances
// if (dist < 0) {
// dist = -dist;
// }
// return MAX_DURATION * dist / (scrolledElement.getClientHeight() * 3);
}
/**
* Called at the end of scrolling. Moves possible translate values to
* scrolltop, causing onscroll event.
*/
private void moveTransformationToScrolloffset() {
for (Element el : layers) {
Style style = el.getStyle();
style.setProperty("webkitTransitionProperty", "none");
style.setProperty("webkitTransform", "translate3d(0,0,0)");
}
scrolledElement.setScrollTop(finalScrollTop);
activeScrollDelegate = null;
handlerRegistration.removeHandler();
handlerRegistration = null;
}
/**
* Detects if a touch happens on a predefined element and the element has
* something to scroll.
*
* @param touch
* @return
*/
private boolean detectScrolledElement(Touch touch) {
Element target = touch.getTarget().cast();
for (Element el : scrollableElements) {
if (el.isOrHasChild(target)
&& el.getScrollHeight() > el.getClientHeight()) {
scrolledElement = el;
NodeList<Node> childNodes = scrolledElement.getChildNodes();
layers = new ArrayList<Element>();
for (int i = 0; i < childNodes.getLength(); i++) {
Node item = childNodes.getItem(i);
if (item.getNodeType() == Node.ELEMENT_NODE) {
layers.add((Element) item);
}
}
return true;
}
}
return false;
}
private void onTouchMove(NativeEvent event) {
if (!moved) {
Date date = new Date();
long l = (date.getTime() - eventTimeStamps[0].getTime());
VConsole.log(l + " ms from start to move");
}
boolean handleMove = readPositionAndSpeed(event);
if (handleMove) {
int deltaScrollTop = origY - lastClientY;
int finalPos = origScrollTop + deltaScrollTop;
if (finalPos > getMaxFinalY()) {
// spring effect at the end
int overscroll = (deltaScrollTop + origScrollTop)
- getMaxFinalY();
overscroll = overscroll / 2;
if (overscroll > scrolledElement.getClientHeight() / 2) {
overscroll = scrolledElement.getClientHeight() / 2;
}
deltaScrollTop = getMaxFinalY() + overscroll - origScrollTop;
} else if (finalPos < 0) {
// spring effect at the beginning
int overscroll = finalPos / 2;
if (-overscroll > scrolledElement.getClientHeight() / 2) {
overscroll = -scrolledElement.getClientHeight() / 2;
}
deltaScrollTop = overscroll - origScrollTop;
}
quickSetScrollPosition(0, deltaScrollTop);
moved = true;
event.preventDefault();
event.stopPropagation();
}
}
private void quickSetScrollPosition(int deltaX, int deltaY) {
deltaScrollPos = deltaY;
translateTo(0, -deltaScrollPos);
}
private static final int EVENTS_FOR_SPEED_CALC = 3;
public static final int SIGNIFICANT_MOVE_THRESHOLD = 3;
private int[] yPositions = new int[EVENTS_FOR_SPEED_CALC];
private Date[] eventTimeStamps = new Date[EVENTS_FOR_SPEED_CALC];
private int nextEvent = 0;
private Date transitionStart;
private Date transitionDuration;
/**
*
* @param event
* @return
*/
private boolean readPositionAndSpeed(NativeEvent event) {
Date now = new Date();
Touch touch = event.getChangedTouches().get(0);
lastClientY = touch.getClientY();
int eventIndx = nextEvent++;
eventIndx = eventIndx % EVENTS_FOR_SPEED_CALC;
eventTimeStamps[eventIndx] = now;
yPositions[eventIndx] = lastClientY;
return isMovedSignificantly();
}
private boolean isMovedSignificantly() {
return moved ? moved
: Math.abs(origY - lastClientY) >= SIGNIFICANT_MOVE_THRESHOLD;
}
private void onTouchEnd(NativeEvent event) {
if (!moved) {
activeScrollDelegate = null;
handlerRegistration.removeHandler();
handlerRegistration = null;
return;
}
int currentY = origScrollTop + deltaScrollPos;
int maxFinalY = getMaxFinalY();
int pixelsToMove;
int finalY;
int duration = -1;
if (currentY > maxFinalY) {
// we are over the max final pos, animate to end
pixelsToMove = maxFinalY - currentY;
finalY = maxFinalY;
} else if (currentY < 0) {
// we are below the max final pos, animate to beginning
pixelsToMove = -currentY;
finalY = 0;
} else {
double pixelsPerMs = calculateSpeed();
// we are currently within scrollable area, calculate pixels that
// we'll move due to momentum
VConsole.log("pxPerMs" + pixelsPerMs);
pixelsToMove = (int) (0.5 * pixelsPerMs * pixelsPerMs / FRICTION);
if (pixelsPerMs < 0) {
pixelsToMove = -pixelsToMove;
}
// VConsole.log("pixels to move" + pixelsToMove);
finalY = currentY + pixelsToMove;
if (finalY > maxFinalY + getMaxOverScroll()) {
// VConsole.log("To max overscroll");
finalY = getMaxFinalY() + getMaxOverScroll();
int fixedPixelsToMove = finalY - currentY;
pixelsPerMs = pixelsPerMs * pixelsToMove / fixedPixelsToMove
/ FRICTION;
pixelsToMove = fixedPixelsToMove;
} else if (finalY < 0 - getMaxOverScroll()) {
// VConsole.log("to min overscroll");
finalY = -getMaxOverScroll();
int fixedPixelsToMove = finalY - currentY;
pixelsPerMs = pixelsPerMs * pixelsToMove / fixedPixelsToMove
/ FRICTION;
pixelsToMove = fixedPixelsToMove;
} else {
duration = (int) (Math.abs(pixelsPerMs / DECELERATION));
}
}
if (duration == -1) {
// did not keep in side borders or was outside borders, calculate
// a good enough duration based on pixelsToBeMoved.
duration = getAnimationTimeForDistance(pixelsToMove);
}
if (duration > MAX_DURATION) {
VConsole.log("Max animation time. " + duration);
duration = MAX_DURATION;
}
finalScrollTop = finalY;
if (Math.abs(pixelsToMove) < 3 || duration < 20) {
VConsole.log("Small 'momentum' " + pixelsToMove + " | " + duration
+ " Skipping animation,");
moveTransformationToScrolloffset();
return;
}
int translateY = -finalY + origScrollTop;
translateTo(duration, translateY);
}
private double calculateSpeed() {
if (nextEvent < EVENTS_FOR_SPEED_CALC) {
VConsole.log("Not enough data for speed calculation");
// not enough data for decent speed calculation, no momentum :-(
return 0;
}
int idx = nextEvent % EVENTS_FOR_SPEED_CALC;
final int firstPos = yPositions[idx];
final Date firstTs = eventTimeStamps[idx];
idx += EVENTS_FOR_SPEED_CALC;
idx--;
idx = idx % EVENTS_FOR_SPEED_CALC;
final int lastPos = yPositions[idx];
final Date lastTs = eventTimeStamps[idx];
// speed as in change of scrolltop == -speedOfTouchPos
return (firstPos - lastPos)
/ (double) (lastTs.getTime() - firstTs.getTime());
}
/**
* Note positive scrolltop moves layer up, positive translate moves layer
* down.
*
* @param duration
* @param translateY
*/
private void translateTo(int duration, int translateY) {
for (Element el : layers) {
final Style style = el.getStyle();
if (duration > 0) {
style.setProperty("webkitTransitionDuration", duration + "ms");
style.setProperty("webkitTransitionTimingFunction",
"cubic-bezier(0,0,0.25,1)");
style.setProperty("webkitTransitionProperty",
"-webkit-transform");
transitionOn = true;
transitionStart = new Date();
transitionDuration = new Date();
} else {
style.setProperty("webkitTransitionProperty", "none");
}
style.setProperty("webkitTransform", "translate3d(0px,"
+ translateY + "px,0px)");
}
}
private int getMaxOverScroll() {
return scrolledElement.getClientHeight() / 4;
}
private int getMaxFinalY() {
return scrolledElement.getScrollHeight()
- scrolledElement.getClientHeight();
}
public void onPreviewNativeEvent(NativePreviewEvent event) {
if (transitionOn) {
/*
* TODO allow starting new events. See issue in onTouchStart
*/
event.cancel();
return;
}
int typeInt = event.getTypeInt();
switch (typeInt) {
case Event.ONTOUCHMOVE:
if (!event.isCanceled()) {
onTouchMove(event.getNativeEvent());
if (moved) {
event.cancel();
}
}
break;
case Event.ONTOUCHEND:
case Event.ONTOUCHCANCEL:
if (!event.isCanceled()) {
if (moved) {
event.cancel();
}
onTouchEnd(event.getNativeEvent());
}
break;
case Event.ONMOUSEMOVE:
if (moved) {
// no debug message, mobile safari generates these for some
// compatibility purposes.
event.cancel();
}
break;
default:
VConsole.log("Non touch event:" + event.getNativeEvent().getType());
event.cancel();
break;
}
}
public void setElements(com.google.gwt.user.client.Element[] elements) {
scrollableElements = elements;
}
}