com.vaadin.v7.client.widget.grid.AutoScroller Maven / Gradle / Ivy
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/*
* Copyright (C) 2000-2023 Vaadin Ltd
*
* This program is available under Vaadin Commercial License and Service Terms.
*
* See for the full
* license.
*/
package com.vaadin.v7.client.widget.grid;
import com.google.gwt.animation.client.AnimationScheduler;
import com.google.gwt.animation.client.AnimationScheduler.AnimationCallback;
import com.google.gwt.animation.client.AnimationScheduler.AnimationHandle;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.dom.client.TableElement;
import com.google.gwt.dom.client.TableSectionElement;
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.client.WidgetUtil;
import com.vaadin.v7.client.widgets.Grid;
/**
* A class for handling automatic scrolling vertically / horizontally in the
* Grid when the cursor is close enough the edge of the body of the grid,
* depending on the scroll direction chosen.
*
* @since 7.5.0
* @author Vaadin Ltd
*/
public class AutoScroller {
/**
* Callback that notifies when the cursor is on top of a new row or column
* because of the automatic scrolling.
*/
public interface AutoScrollerCallback {
/**
* Triggered when doing automatic scrolling.
*
* Because the auto scroller currently only supports scrolling in one
* axis, this method is used for both vertical and horizontal scrolling.
*
* @param scrollDiff
* the amount of pixels that have been auto scrolled since
* last call
*/
void onAutoScroll(int scrollDiff);
/**
* Triggered when the grid scroll has reached the minimum scroll
* position. Depending on the scroll axis, either scrollLeft or
* scrollTop is 0.
*/
void onAutoScrollReachedMin();
/**
* Triggered when the grid scroll has reached the max scroll position.
* Depending on the scroll axis, either scrollLeft or scrollTop is at
* its maximum value.
*/
void onAutoScrollReachedMax();
}
public enum ScrollAxis {
VERTICAL, HORIZONTAL
}
/** The maximum number of pixels per second to autoscroll. */
private static final int SCROLL_TOP_SPEED_PX_SEC = 500;
/**
* The minimum area where the grid doesn't scroll while the pointer is
* pressed.
*/
private static final int MIN_NO_AUTOSCROLL_AREA_PX = 50;
/** The size of the autoscroll area, both top/left and bottom/right. */
private int scrollAreaPX = 100;
/**
* This class's main objective is to listen when to stop autoscrolling, and
* make sure everything stops accordingly.
*/
private class TouchEventHandler implements NativePreviewHandler {
@Override
public void onPreviewNativeEvent(final NativePreviewEvent event) {
/*
* Remember: targetElement is always where touchstart started, not
* where the finger is pointing currently.
*/
switch (event.getTypeInt()) {
case Event.ONTOUCHSTART: {
if (event.getNativeEvent().getTouches().length() == 1) {
/*
* Something has dropped a touchend/touchcancel and the
* scroller is most probably running amok. Let's cancel it
* and pretend that everything's going as expected
*
* Because this is a preview, this code is run before start
* event can be passed to the start(...) method.
*/
stop();
/*
* Related TODO: investigate why iOS seems to ignore a
* touchend/touchcancel when frames are dropped, and/or if
* something can be done about that.
*/
}
break;
}
case Event.ONTOUCHMOVE:
event.cancel();
break;
case Event.ONTOUCHEND:
case Event.ONTOUCHCANCEL:
// TODO investigate if this works as desired
stop();
break;
}
}
}
/**
* This class's responsibility is to scroll the table while a pointer is
* kept in a scrolling zone.
*
* Techical note: This class is an AnimationCallback because we
* need a timer: when the finger is kept in place while the grid scrolls, we
* still need to be able to make new selections. So, instead of relying on
* events (which won't be fired, since the pointer isn't necessarily
* moving), we do this check on each frame while the pointer is "active"
* (mouse is pressed, finger is on screen).
*/
private class AutoScrollingFrame implements AnimationCallback {
/**
* If the acceleration gradient area is smaller than this, autoscrolling
* will be disabled (it becomes too quick to accelerate to be usable).
*/
private static final int GRADIENT_MIN_THRESHOLD_PX = 10;
/**
* The speed at which the gradient area recovers, once scrolling in that
* direction has started.
*/
private static final int SCROLL_AREA_REBOUND_PX_PER_SEC = 1;
private static final double SCROLL_AREA_REBOUND_PX_PER_MS = SCROLL_AREA_REBOUND_PX_PER_SEC
/ 1000.0d;
/**
* The lowest y/x-coordinate on the {@link Event#getClientY() client-y}
* or {@link Event#getClientX() client-x} from where we need to start
* scrolling towards the top/left.
*/
private int startBound = -1;
/**
* The highest y/x-coordinate on the {@link Event#getClientY() client-y}
* or {@link Event#getClientX() client-x} from where we need to
* scrolling towards the bottom.
*/
private int endBound = -1;
/**
* The area where the selection acceleration takes place. If <
* {@link #GRADIENT_MIN_THRESHOLD_PX}, autoscrolling is disabled
*/
private final int gradientArea;
/**
* The number of pixels per seconds we currently are scrolling (negative
* is towards the top/left, positive is towards the bottom/right).
*/
private double scrollSpeed = 0;
private double prevTimestamp = 0;
/**
* This field stores fractions of pixels to scroll, to make sure that
* we're able to scroll less than one px per frame.
*/
private double pixelsToScroll = 0.0d;
/** Should this animator be running. */
private boolean running = false;
/** The handle in which this instance is running. */
private AnimationHandle handle;
/**
* The pointer's pageY (VERTICAL) / pageX (HORIZONTAL) coordinate
* depending on scrolling axis.
*/
private int scrollingAxisPageCoordinate;
/** @see #doScrollAreaChecks(int) */
private int finalStartBound;
/** @see #doScrollAreaChecks(int) */
private int finalEndBound;
private boolean scrollAreaShouldRebound = false;
public AutoScrollingFrame(final int startBound, final int endBound,
final int gradientArea) {
finalStartBound = startBound;
finalEndBound = endBound;
this.gradientArea = gradientArea;
}
@Override
public void execute(final double timestamp) {
final double timeDiff = timestamp - prevTimestamp;
prevTimestamp = timestamp;
reboundScrollArea(timeDiff);
pixelsToScroll += scrollSpeed * (timeDiff / 1000.0d);
final int intPixelsToScroll = (int) pixelsToScroll;
pixelsToScroll -= intPixelsToScroll;
if (intPixelsToScroll != 0) {
double scrollPos;
double maxScrollPos;
double newScrollPos;
if (scrollDirection == ScrollAxis.VERTICAL) {
scrollPos = grid.getScrollTop();
maxScrollPos = getMaxScrollTop();
} else {
scrollPos = grid.getScrollLeft();
maxScrollPos = getMaxScrollLeft();
}
if (intPixelsToScroll > 0 && scrollPos < maxScrollPos
|| intPixelsToScroll < 0 && scrollPos > 0) {
newScrollPos = scrollPos + intPixelsToScroll;
if (scrollDirection == ScrollAxis.VERTICAL) {
grid.setScrollTop(newScrollPos);
} else {
grid.setScrollLeft(newScrollPos);
}
callback.onAutoScroll(intPixelsToScroll);
if (newScrollPos <= 0) {
callback.onAutoScrollReachedMin();
} else if (newScrollPos >= maxScrollPos) {
callback.onAutoScrollReachedMax();
}
}
}
reschedule();
}
/**
* If the scroll are has been offset by the pointer starting out there,
* move it back a bit
*/
private void reboundScrollArea(double timeDiff) {
if (!scrollAreaShouldRebound) {
return;
}
int reboundPx = (int) Math
.ceil(SCROLL_AREA_REBOUND_PX_PER_MS * timeDiff);
if (startBound < finalStartBound) {
startBound += reboundPx;
startBound = Math.min(startBound, finalStartBound);
updateScrollSpeed(scrollingAxisPageCoordinate);
} else if (endBound > finalEndBound) {
endBound -= reboundPx;
endBound = Math.max(endBound, finalEndBound);
updateScrollSpeed(scrollingAxisPageCoordinate);
}
}
private void updateScrollSpeed(final int pointerPageCordinate) {
final double ratio;
if (pointerPageCordinate < startBound) {
final double distance = pointerPageCordinate - startBound;
ratio = Math.max(-1, distance / gradientArea);
} else if (pointerPageCordinate > endBound) {
final double distance = pointerPageCordinate - endBound;
ratio = Math.min(1, distance / gradientArea);
} else {
ratio = 0;
}
scrollSpeed = ratio * SCROLL_TOP_SPEED_PX_SEC;
}
public void start() {
running = true;
reschedule();
}
public void stop() {
running = false;
if (handle != null) {
handle.cancel();
handle = null;
}
}
private void reschedule() {
if (running && gradientArea >= GRADIENT_MIN_THRESHOLD_PX) {
handle = AnimationScheduler.get().requestAnimationFrame(this,
grid.getElement());
}
}
public void updatePointerCoords(int pageX, int pageY) {
final int pageCordinate;
if (scrollDirection == ScrollAxis.VERTICAL) {
pageCordinate = pageY;
} else {
pageCordinate = pageX;
}
doScrollAreaChecks(pageCordinate);
updateScrollSpeed(pageCordinate);
scrollingAxisPageCoordinate = pageCordinate;
}
/**
* This method checks whether the first pointer event started in an area
* that would start scrolling immediately, and does some actions
* accordingly.
*
* If it is, that scroll area will be offset "beyond" the pointer (above
* if pointer is towards the top/left, otherwise below/right).
*/
private void doScrollAreaChecks(int pageCordinate) {
/*
* The first run makes sure that neither scroll position is
* underneath the finger, but offset to either direction from
* underneath the pointer.
*/
if (startBound == -1) {
startBound = Math.min(finalStartBound, pageCordinate);
endBound = Math.max(finalEndBound, pageCordinate);
} else {
/*
* Subsequent runs make sure that the scroll area grows (but
* doesn't shrink) with the finger, but no further than the
* final bound.
*/
int oldTopBound = startBound;
if (startBound < finalStartBound) {
startBound = Math.max(startBound,
Math.min(finalStartBound, pageCordinate));
}
int oldBottomBound = endBound;
if (endBound > finalEndBound) {
endBound = Math.min(endBound,
Math.max(finalEndBound, pageCordinate));
}
final boolean startDidNotMove = oldTopBound == startBound;
final boolean endDidNotMove = oldBottomBound == endBound;
final boolean wasMovement = pageCordinate != scrollingAxisPageCoordinate;
scrollAreaShouldRebound = (startDidNotMove && endDidNotMove
&& wasMovement);
}
}
}
/**
* This handler makes sure that pointer movements are handled.
*
* Essentially, a native preview handler is registered (so that selection
* gestures can happen outside of the selection column). The handler itself
* makes sure that it's detached when the pointer is "lifted".
*/
private final NativePreviewHandler scrollPreviewHandler = new NativePreviewHandler() {
@Override
public void onPreviewNativeEvent(final NativePreviewEvent event) {
if (autoScroller == null) {
stop();
return;
}
final NativeEvent nativeEvent = event.getNativeEvent();
int pageY = 0;
int pageX = 0;
switch (event.getTypeInt()) {
case Event.ONMOUSEMOVE:
case Event.ONTOUCHMOVE:
pageY = WidgetUtil.getTouchOrMouseClientY(nativeEvent);
pageX = WidgetUtil.getTouchOrMouseClientX(nativeEvent);
autoScroller.updatePointerCoords(pageX, pageY);
break;
case Event.ONMOUSEUP:
case Event.ONTOUCHEND:
case Event.ONTOUCHCANCEL:
stop();
break;
}
}
};
/** The registration info for {@link #scrollPreviewHandler} */
private HandlerRegistration handlerRegistration;
/**
* The top/left bound, as calculated from the {@link Event#getClientY()
* client-y} or {@link Event#getClientX() client-x} coordinates.
*/
private double startingBound = -1;
/**
* The bottom/right bound, as calculated from the {@link Event#getClientY()
* client-y} or or {@link Event#getClientX() client-x} coordinates.
*/
private int endingBound = -1;
/** The size of the autoscroll acceleration area. */
private int gradientArea;
private Grid grid;
private HandlerRegistration nativePreviewHandlerRegistration;
private ScrollAxis scrollDirection;
private AutoScrollingFrame autoScroller;
private AutoScrollerCallback callback;
/**
* Creates a new instance for scrolling the given grid.
*
* @param grid
* the grid to auto scroll
*/
public AutoScroller(Grid grid) {
this.grid = grid;
}
/**
* Starts the automatic scrolling detection.
*
* @param startEvent
* the event that starts the automatic scroll
* @param scrollAxis
* the axis along which the scrolling should happen
* @param callback
* the callback for getting info about the automatic scrolling
*/
public void start(final NativeEvent startEvent, ScrollAxis scrollAxis,
AutoScrollerCallback callback) {
scrollDirection = scrollAxis;
this.callback = callback;
injectNativeHandler();
start();
startEvent.preventDefault();
startEvent.stopPropagation();
}
/**
* Stops the automatic scrolling.
*/
public void stop() {
if (handlerRegistration != null) {
handlerRegistration.removeHandler();
handlerRegistration = null;
}
if (autoScroller != null) {
autoScroller.stop();
autoScroller = null;
}
removeNativeHandler();
}
/**
* Set the auto scroll area height or width depending on the scrolling axis.
* This is the amount of pixels from the edge of the grid that the scroll is
* triggered.
*
* Defaults to 100px.
*
* @param px
* the pixel height/width for the auto scroll area depending on
* direction
*/
public void setScrollArea(int px) {
scrollAreaPX = px;
}
/**
* Returns the size of the auto scroll area in pixels.
*
* Defaults to 100px.
*
* @return size in pixels
*/
public int getScrollArea() {
return scrollAreaPX;
}
private void start() {
/*
* bounds are updated whenever the autoscroll cycle starts, to make sure
* that the widget hasn't changed in size, moved around, or whatnot.
*/
updateScrollBounds();
assert handlerRegistration == null : "handlerRegistration was not null";
assert autoScroller == null : "autoScroller was not null";
handlerRegistration = Event
.addNativePreviewHandler(scrollPreviewHandler);
autoScroller = new AutoScrollingFrame((int) Math.ceil(startingBound),
endingBound, gradientArea);
autoScroller.start();
}
private void updateScrollBounds() {
double startBorder = getBodyClientStart();
final int endBorder = getBodyClientEnd();
startBorder += getFrozenColumnsWidth();
startingBound = startBorder + scrollAreaPX;
endingBound = endBorder - scrollAreaPX;
gradientArea = scrollAreaPX;
// modify bounds if they're too tightly packed
if (endingBound - startingBound < MIN_NO_AUTOSCROLL_AREA_PX) {
double adjustment = MIN_NO_AUTOSCROLL_AREA_PX
- (endingBound - startingBound);
startingBound -= adjustment / 2;
endingBound += adjustment / 2;
gradientArea -= adjustment / 2;
}
}
private void injectNativeHandler() {
removeNativeHandler();
nativePreviewHandlerRegistration = Event
.addNativePreviewHandler(new TouchEventHandler());
}
private void removeNativeHandler() {
if (nativePreviewHandlerRegistration != null) {
nativePreviewHandlerRegistration.removeHandler();
nativePreviewHandlerRegistration = null;
}
}
private TableElement getTableElement() {
final Element root = grid.getElement();
final Element tablewrapper = Element.as(root.getChild(2));
if (tablewrapper != null) {
return TableElement.as(tablewrapper.getFirstChildElement());
} else {
return null;
}
}
private TableSectionElement getTheadElement() {
TableElement table = getTableElement();
if (table != null) {
return table.getTHead();
} else {
return null;
}
}
private TableSectionElement getTfootElement() {
TableElement table = getTableElement();
if (table != null) {
return table.getTFoot();
} else {
return null;
}
}
private int getBodyClientEnd() {
if (scrollDirection == ScrollAxis.VERTICAL) {
return getTfootElement().getAbsoluteTop() - 1;
} else {
return getTableElement().getAbsoluteRight();
}
}
private int getBodyClientStart() {
if (scrollDirection == ScrollAxis.VERTICAL) {
return getTheadElement().getAbsoluteBottom() + 1;
} else {
return getTableElement().getAbsoluteLeft();
}
}
public double getFrozenColumnsWidth() {
double value = 0;
for (int i = 0; i < getRealFrozenColumnCount(); i++) {
value += grid.getColumn(i).getWidthActual();
}
return value;
}
private int getRealFrozenColumnCount() {
if (grid.getFrozenColumnCount() < 0) {
return 0;
} else if (grid.getSelectionModel()
.getSelectionColumnRenderer() != null) {
// includes the selection column
return grid.getFrozenColumnCount() + 1;
} else {
return grid.getFrozenColumnCount();
}
}
private double getMaxScrollLeft() {
return grid.getScrollWidth()
- (getTableElement().getParentElement().getOffsetWidth()
- getFrozenColumnsWidth());
}
private double getMaxScrollTop() {
return grid.getScrollHeight() - getTfootElement().getOffsetHeight()
- getTheadElement().getOffsetHeight();
}
}