/*
* Copyright 2009 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 com.google.gwt.user.client.ui;
import com.google.gwt.event.logical.shared.ResizeEvent;
import com.google.gwt.event.logical.shared.ResizeHandler;
import com.google.gwt.user.client.Window;
/**
* A singleton implementation of {@link LayoutPanel} that always attaches itself
* to the document body (i.e. {@link RootPanel#get()}).
*
* <p>
* This panel automatically calls {@link RequiresResize#onResize()} on itself
* when initially created, and whenever the window is resized.
* </p>
*
* <p>
* NOTE: This widget will <em>only</em> work in standards mode, which requires
* that the HTML page in which it is run have an explicit <!DOCTYPE>
* declaration.
* </p>
*
* <p>
* NOTE: This class is still very new, and its interface may change without
* warning. Use at your own risk.
* </p>
*
* <p>
* <h3>Example</h3>
* {@example com.google.gwt.examples.LayoutPanelExample}
* </p>
*/
public class RootLayoutPanel extends LayoutPanel {
private static RootLayoutPanel singleton;
/**
* Gets the singleton instance of RootLayoutPanel. This instance will always
* be attached to the document body via {@link RootPanel#get()}.
*
* <p>
* Note that, unlike {@link RootPanel#get(String)}, this class provides no way
* to get an instance for any element on the page other than the document
* body. This is because we know of no way to get resize events for anything
* but the window.
* </p>
*/
public static RootLayoutPanel get() {
if (singleton == null) {
singleton = new RootLayoutPanel();
RootPanel.get().add(singleton);
}
return singleton;
}
private RootLayoutPanel() {
Window.addResizeHandler(new ResizeHandler() {
public void onResize(ResizeEvent event) {
RootLayoutPanel.this.onResize();
}
});
// TODO(jgw): We need notification of font-size changes as well.
// I believe there's a hidden iframe trick that we can use to get
// a font-size-change event (really an em-definition-change event).
}
@Override
protected void onLoad() {
getLayout().onAttach();
getLayout().fillParent();
}
}