/**
* Copyright 2011 Google Inc.
*
* 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 org.waveprotocol.wave.client.scroll;
/**
* Defines UI scrolling actions on a scroll panel.
*
* @author hearnden@google.com (David Hearnden)
*/
public final class ScrollController {
private final ScrollPanel<?> scroller;
/**
* Creates a scroll controller.
*/
ScrollController(ScrollPanel<?> scroller) {
this.scroller = scroller;
}
void pageUp() {
Extent viewport = scroller.getViewport();
double target = Math.max(0, viewport.getStart() - viewport.getSize());
scroller.moveTo(target);
}
void pageDown() {
Extent viewport = scroller.getViewport();
double target = Math.min(scroller.getContent().getEnd(), viewport.getEnd());
scroller.moveTo(target);
}
void home() {
scroller.moveTo(0);
}
void end() {
Extent content = scroller.getContent();
Extent viewport = scroller.getViewport();
scroller.moveTo(content.getEnd() - viewport.getSize());
}
}