package org.eclipse.swt.widgets; | |
/* | |
* (c) Copyright IBM Corp. 2000, 2001. | |
* All Rights Reserved | |
*/ | |
import org.eclipse.swt.*; | |
import org.eclipse.swt.graphics.*; | |
/** | |
* A layout controls the position and size | |
* of the children of a composite widget. | |
* This class is the abstract base class for | |
* layouts. | |
*/ | |
public abstract class Layout { | |
/** | |
* Computes and returns the size of the specified | |
* composite's client area according to this layout. | |
* <p> | |
* This method computes the minimum size that the | |
* client area of the composite must be in order to | |
* position all children at their minimum 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 minimum | |
* 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 minimum) | |
* @param hHint height (<code>SWT.DEFAULT</code> for minimum) | |
* @param flushCache <code>true</code> means flush cached layout values | |
* @return a point containing the computed size (width, height) | |
* @see #layout | |
*/ | |
protected abstract Point computeSize (Composite composite, int wHint, int hHint, boolean flushCache); | |
/** | |
* 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 layed 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); | |
} |