/*******************************************************************************
 * Copyright (c) 2002, 2010 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
 *     EclipseSource - ongoing development
 ******************************************************************************/
package org.eclipse.swt.widgets;

import org.eclipse.swt.graphics.Rectangle;

/**
 * This class is the abstract superclass of all classes which
 * represent controls that have standard scroll bars.
 * <dl>
 * <dt><b>Styles:</b></dt>
 * <dd>H_SCROLL, V_SCROLL</dd>
 * <dt><b>Events:</b>
 * <dd>(none)</dd>
 * </dl>
 * <p>
 * IMPORTANT: This class is intended to be subclassed <em>only</em>
 * within the SWT implementation.
 * </p>
 * @since 1.0
 */
public abstract class Scrollable extends Control {

  Scrollable( final Composite parent ) {
    // prevent instantiation from outside this package
    super( parent );
  }

  /**
   * Constructs a new instance of this class given its parent
   * and a style value describing its behavior and appearance.
   * <p>
   * The style value is either one of the style constants defined in
   * class <code>SWT</code> which is applicable to instances of this
   * class, or must be built by <em>bitwise OR</em>'ing together
   * (that is, using the <code>int</code> "|" operator) two or more
   * of those <code>SWT</code> style constants. The class description
   * lists the style constants that are applicable to the class.
   * Style bits are also inherited from superclasses.
   * </p>
   *
   * @param parent a composite control which will be the parent of the new instance (cannot be null)
   * @param style the style of control to construct
   *
   * @exception IllegalArgumentException <ul>
   *    <li>ERROR_NULL_ARGUMENT - if the parent is null</li>
   * </ul>
   * @exception SWTException <ul>
   *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li>
   *    <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li>
   * </ul>
   *
   * @see SWT#H_SCROLL
   * @see SWT#V_SCROLL
   * @see Widget#checkSubclass
   * @see Widget#getStyle
   */
  public Scrollable( final Composite parent, final int style ) {
    super( parent, style );
  }

  /**
   * Returns a rectangle which describes the area of the
   * receiver which is capable of displaying data (that is,
   * not covered by the "trimmings").
   *
   * @return the client area
   *
   * @exception SWTException <ul>
   *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
   *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
   * </ul>
   *
   * @see #computeTrim
   */
  public Rectangle getClientArea() {
    checkWidget();
    Rectangle bounds = getBounds();
    int borderWidth = getBorderWidth();
    Rectangle padding = getPadding();
    int width
      = bounds.width - borderWidth * 2 - padding.width - getVScrollBarWidth();
    int height
      = bounds.height - borderWidth * 2 - padding.height - getHScrollBarHeight();
    return new Rectangle( padding.x, padding.y, width, height );
  }

  /**
   * Given a desired <em>client area</em> for the receiver
   * (as described by the arguments), returns the bounding
   * rectangle which would be required to produce that client
   * area.
   * <p>
   * In other words, it returns a rectangle such that, if the
   * receiver's bounds were set to that rectangle, the area
   * of the receiver which is capable of displaying data
   * (that is, not covered by the "trimmings") would be the
   * rectangle described by the arguments (relative to the
   * receiver's parent).
   * </p>
   *
   * @param x the desired x coordinate of the client area
   * @param y the desired y coordinate of the client area
   * @param width the desired width of the client area
   * @param height the desired height of the client area
   * @return the required bounds to produce the given client area
   *
   * @exception SWTException <ul>
   *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
   *    <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li>
   * </ul>
   *
   * @see #getClientArea
   */
  public Rectangle computeTrim( final int x,
                                final int y,
                                final int width,
                                final int height )
  {
    checkWidget();
    int borderWidth = getBorderWidth();
    Rectangle padding = getPadding();
    int newWidth
      = width + borderWidth * 2 + padding.width + getVScrollBarWidth();
    int newHeight
      = height + borderWidth * 2 + padding.height + getHScrollBarHeight();
    return new Rectangle( x - borderWidth - padding.x,
                          y - borderWidth - padding.y,
                          newWidth,
                          newHeight );
  }

  int getVScrollBarWidth() {
    //subclasses may override
    return 0;
  }

  int getHScrollBarHeight() {
    //subclasses may override
    return 0;
  }
}