/*******************************************************************************
* Copyright (c) 2002, 2007 Innoopract Informationssysteme GmbH.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Innoopract Informationssysteme GmbH - initial API and implementation
******************************************************************************/
package org.eclipse.swt.widgets;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.internal.SerializableCompatibility;
/**
* A layout controls the position and size of the children of a composite
* widget. This class is the abstract base class for layouts.
*
* @see Composite#setLayout(Layout)
*/
public abstract class Layout implements SerializableCompatibility {
/**
* Lays out the children of the specified composite according to this
* layout.
* <p>
* This method positions and sizes the children of a composite using the
* layout algorithm encoded by this layout. Children of the composite are
* positioned in the client area of the composite. The position of the
* composite is not altered by this method.
* </p>
* <p>
* When the flush cache hint is true, the layout is instructed to flush any
* cached values associated with the children. Typically, a layout will
* cache the preferred sizes of the children to avoid the expense of
* computing these values each time the widget is laid out.
* </p>
* <p>
* When layout is triggered explicitly by the programmer the flush cache
* hint is true. When layout is triggered by a resize, either caused by the
* programmer or by the user, the hint is false.
* </p>
*
* @param composite
* a composite widget using this layout
* @param flushCache
* <code>true</code> means flush cached layout values
*/
protected abstract void layout(Composite composite, boolean flushCache);
/**
* Instruct the layout to flush any cached values
* associated with the control specified in the argument
* <code>control</code>.
*
* @param control a control managed by this layout
* @return true if the Layout has flushed all cached information associated with control
*/
protected boolean flushCache (Control control) {
return false;
}
/**
* Computes and returns the size of the specified composite's client area
* according to this layout.
* <p>
* This method computes the size that the client area of the composite must
* be in order to position all children at their preferred size inside the
* composite according to the layout algorithm encoded by this layout.
* </p>
* <p>
* When a width or height hint is supplied, it is used to constrain the
* result. For example, if a width hint is provided that is less than the
* width of the client area, the layout may choose to wrap and increase
* height, clip, overlap, or otherwise constrain the children.
* </p>
*
* @param composite
* a composite widget using this layout
* @param wHint
* width (<code>SWT.DEFAULT</code> for preferred size)
* @param hHint
* height (<code>SWT.DEFAULT</code> for preferred size)
* @param flushCache
* <code>true</code> means flush cached layout values
* @return a point containing the computed size (width, height)
*
* @see #layout
* @see Control#getBorderWidth
* @see Control#getBounds
* @see Control#getSize
* @see Control#pack(boolean)
* @see "computeTrim, getClientArea for controls that implement them"
*/
protected abstract Point computeSize(Composite composite, int wHint,
int hHint, boolean flushCache);
}