/*******************************************************************************

 * Copyright (c) 2000, 2007 IBM Corporation and others.

 * Portion Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).

 * 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:

 *     IBM Corporation - initial API and implementation

 *     Nokia Corporation - Qt implementation

 *******************************************************************************/

package org.eclipse.swt.widgets;

import org.eclipse.swt.SWT;

import org.eclipse.swt.SWTException;

import org.eclipse.swt.events.SelectionEvent;

import org.eclipse.swt.events.SelectionListener;

import org.eclipse.swt.graphics.Point;

import org.eclipse.swt.internal.qt.OS;

import org.eclipse.swt.internal.qt.WidgetState;

/**

 * Instances of this class are selectable user interface objects that represent

 * a range of positive, numeric values.

 * <p>

 * At any given moment, a given scroll bar will have a single 'selection' that

 * is considered to be its value, which is constrained to be within the range of

 * values the scroll bar represents (that is, between its <em>minimum</em> and

 * <em>maximum</em> values).

 * </p>

 * <p>

 * Typically, scroll bars will be made up of five areas:

 * <ol>

 * <li>an arrow button for decrementing the value</li>

 * <li>a page decrement area for decrementing the value by a larger amount</li>

 * <li>a <em>thumb</em> for modifying the value by mouse dragging</li>

 * <li>a page increment area for incrementing the value by a larger amount</li>

 * <li>an arrow button for incrementing the value</li>

 * </ol>

 * Based on their style, scroll bars are either <code>HORIZONTAL</code> (which

 * have a left facing button for decrementing the value and a right facing

 * button for incrementing it) or <code>VERTICAL</code> (which have an upward

 * facing button for decrementing the value and a downward facing buttons for

 * incrementing it).

 * </p>

 * <p>

 * On some platforms, the size of the scroll bar's thumb can be varied relative

 * to the magnitude of the range of values it represents (that is, relative to

 * the difference between its maximum and minimum values). Typically, this is

 * used to indicate some proportional value such as the ratio of the visible

 * area of a document to the total amount of space that it would take to display

 * it. SWT supports setting the thumb size even if the underlying platform does

 * not, but in this case the appearance of the scroll bar will not change.

 * </p>

 * <p>

 * Scroll bars are created by specifying either <code>H_SCROLL</code>,

 * <code>V_SCROLL</code> or both when creating a <code>Scrollable</code>. They

 * are accessed from the <code>Scrollable</code> using

 * <code>getHorizontalBar</code> and <code>getVerticalBar</code>.

 * </p>

 * <p>

 * Note: Scroll bars are not Controls. On some platforms, scroll bars that

 * appear as part of some standard controls such as a text or list have no

 * operating system resources and are not children of the control. For this

 * reason, scroll bars are treated specially. To create a control that looks

 * like a scroll bar but has operating system resources, use <code>Slider</code>

 * .

 * </p>

 * <dl>

 * <dt><b>Styles:</b></dt>

 * <dd>HORIZONTAL, VERTICAL</dd>

 * <dt><b>Events:</b></dt>

 * <dd>Selection</dd>

 * </dl>

 * <p>

 * Note: Only one of the styles HORIZONTAL and VERTICAL may be specified.

 * </p>

 * <p>

 * IMPORTANT: This class is <em>not</em> intended to be subclassed.

 * </p>

 * 

 * @see Slider

 * @see Scrollable

 * @see Scrollable#getHorizontalBar

 * @see Scrollable#getVerticalBar

 */

public class ScrollBar extends Widget {

    Scrollable parent;

    /*

     * In QT, thumb'size and page increment are the same thing. Setting page

     * increment with a value other than thumb's size would ruins the

     * consistency of scrollbar. So, page increment value is only stored in java

     * side and does not affect native scrollbar

     */

    int pageIncrement = 1;

    int eventDetail = SWT.NONE;

    ScrollBar(Scrollable parent, int style) {

        super(parent,

                checkBits(style, SWT.HORIZONTAL, SWT.VERTICAL, 0, 0, 0, 0));

        this.parent = parent;

        checkOrientation(parent);

        createWidget(0);

    }

    void createHandle_pp(int index) {

        if (parent.scrollAreaHandle == 0)

            SWT.error(SWT.ERROR_NULL_ARGUMENT);

        if ((style & SWT.H_SCROLL) != 0) {

            handle = OS.QAbstractScrollArea_horizontalScrollBar(parent.scrollAreaHandle);

        } else {

            handle = OS.QAbstractScrollArea_verticalScrollBar(parent.scrollAreaHandle);

        }

        if (handle == 0) {

            SWT.error(SWT.ERROR_UNSPECIFIED);

        }

        topHandle = handle;

        state |= WidgetState.HANDLE;

    }

    void releaseParent_pp() {

        super.releaseParent_pp();

        if (parent.horizontalBar == this) {

            OS.QAbstractScrollArea_setHorizontalScrollBarPolicy(

                    parent.scrollAreaHandle, OS.QT_SCROLLBARALWAYSOFF);

            parent.horizontalBar = null;

        } else if (parent.verticalBar == this) {

            OS.QAbstractScrollArea_setVerticalScrollBarPolicy(

                    parent.scrollAreaHandle, OS.QT_SCROLLBARALWAYSOFF);

            parent.verticalBar = null;

        }

    }

    void destroyWidget() {

        releaseHandle_pp();

        /*

         * no need to delete native scrollbar since ScrollBar does not own

         * native scrollbar

         */

    }

    void releaseWidget_pp() {

        super.releaseWidget_pp();

        parent = null;

    }

    /**

     * Adds the listener to the collection of listeners who will be notified

     * when the user changes the receiver's value, by sending it one of the

     * messages defined in the <code>SelectionListener</code> interface.

     * <p>

     * When <code>widgetSelected</code> is called, the event object detail field

     * contains one of the following values: <code>SWT.NONE</code> - for the end

     * of a drag. <code>SWT.DRAG</code>. <code>SWT.HOME</code>.

     * <code>SWT.END</code>. <code>SWT.ARROW_DOWN</code>.

     * <code>SWT.ARROW_UP</code>. <code>SWT.PAGE_DOWN</code>.

     * <code>SWT.PAGE_UP</code>. <code>widgetDefaultSelected</code> is not

     * called.

     * </p>

     * 

     * @param listener

     *            the listener which should be notified when the user changes

     *            the receiver's value

     * 

     * @exception IllegalArgumentException

     *                <ul>

     *                <li>ERROR_NULL_ARGUMENT - if the listener is null</li>

     *                </ul>

     * @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 SelectionListener

     * @see #removeSelectionListener

     * @see SelectionEvent

     */

    public void addSelectionListener(SelectionListener listener) {

        checkWidget();

        if (listener == null)

            error(SWT.ERROR_NULL_ARGUMENT);

        TypedListener typedListener = new TypedListener(listener);

        addListener(SWT.Selection, typedListener);

        addListener(SWT.DefaultSelection, typedListener);

    }

    /**

     * Removes the listener from the collection of listeners who will be

     * notified when the user changes the receiver's value.

     * 

     * @param listener

     *            the listener which should no longer be notified

     * 

     * @exception IllegalArgumentException

     *                <ul>

     *                <li>ERROR_NULL_ARGUMENT - if the listener is null</li>

     *                </ul>

     * @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 SelectionListener

     * @see #addSelectionListener

     */

    public void removeSelectionListener(SelectionListener listener) {

        checkWidget();

        if (listener == null)

            error(SWT.ERROR_NULL_ARGUMENT);

        if (eventTable == null)

            return;

        eventTable.unhook(SWT.Selection, listener);

        eventTable.unhook(SWT.DefaultSelection, listener);

    }

    /**

     * Returns the amount that the receiver's value will be modified by when the

     * up/down (or right/left) arrows are pressed.

     * 

     * @return the increment

     * 

     * @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>

     */

    public int getIncrement() {

        checkWidget();

        return OS.QAbstractSlider_singleStep(handle);

    }

    /**

     * Returns the maximum value which the receiver will allow.

     * 

     * @return the maximum

     * 

     * @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>

     */

    public int getMaximum() {

        checkWidget();

        return OS.QAbstractSlider_maximum(handle)

                + OS.QAbstractSlider_pageStep(handle);

    }

    /**

     * Returns the minimum value which the receiver will allow.

     * 

     * @return the minimum

     * 

     * @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>

     */

    public int getMinimum() {

        checkWidget();

        return OS.QAbstractSlider_minimum(handle);

    }

    /**

     * Returns the amount that the receiver's value will be modified by when the

     * page increment/decrement areas are selected.

     * 

     * @return the page increment

     * 

     * @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>

     */

    public int getPageIncrement() {

        checkWidget();

        return pageIncrement;

    }

    /**

     * Returns the receiver's parent, which must be a Scrollable.

     * 

     * @return the receiver's parent

     * 

     * @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>

     */

    public Scrollable getParent() {

        checkWidget();

        return parent;

    }

    /**

     * Returns the single 'selection' that is the receiver's value.

     * 

     * @return the selection

     * 

     * @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>

     */

    public int getSelection() {

        checkWidget();

        return OS.QAbstractSlider_value(handle);

    }

    /**

     * Returns a point describing the receiver's size. The x coordinate of the

     * result is the width of the receiver. The y coordinate of the result is

     * the height of the receiver.

     * 

     * @return the receiver's size

     * 

     * @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>

     */

    public Point getSize() {

        checkWidget();

        if(!isVisible()) parent.updateQLayouts();

        return OS.QWidget_frameSize(handle);

    }

    /**

     * Returns the size of the receiver's thumb relative to the difference

     * between its maximum and minimum values.

     * 

     * @return the thumb value

     * 

     * @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 ScrollBar

     */

    public int getThumb() {

        checkWidget();

        return OS.QAbstractSlider_pageStep(handle);

    }

    /**

     * Returns <code>true</code> if the receiver is enabled, and

     * <code>false</code> otherwise. A disabled control is typically not

     * selectable from the user interface and draws with an inactive or "grayed"

     * look.

     * 

     * @return the receiver's enabled state

     * 

     * @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 #isEnabled

     */

    public boolean getEnabled() {

        checkWidget();

        return OS.QWidget_isEnabled(handle);

    }

    /**

     * Returns <code>true</code> if the receiver is visible, and

     * <code>false</code> otherwise.

     * <p>

     * If one of the receiver's ancestors is not visible or some other condition

     * makes the receiver not visible, this method may still indicate that it is

     * considered visible even though it may not actually be showing.

     * </p>

     * 

     * @return the receiver's visibility state

     * 

     * @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>

     */

    public boolean getVisible() {

        checkWidget();

        return OS.QWidget_isVisible(handle);

    }

    /**

     * Returns <code>true</code> if the receiver is enabled and all of the

     * receiver's ancestors are enabled, and <code>false</code> otherwise. A

     * disabled control is typically not selectable from the user interface and

     * draws with an inactive or "grayed" look.

     * 

     * @return the receiver's enabled state

     * 

     * @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 #getEnabled

     */

    public boolean isEnabled() {

        checkWidget();

        return OS.QWidget_isEnabled(handle) && parent.isEnabled();

    }

    /**

     * Returns <code>true</code> if the receiver is visible and all of the

     * receiver's ancestors are visible and <code>false</code> otherwise.

     * 

     * @return the receiver's visibility state

     * 

     * @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 #getVisible

     */

    public boolean isVisible() {

        checkWidget();

        return OS.QWidget_isVisible(handle) && parent.isVisible();

    }

    /**

     * Enables the receiver if the argument is <code>true</code>, and disables

     * it otherwise. A disabled control is typically not selectable from the

     * user interface and draws with an inactive or "grayed" look.

     * 

     * @param enabled

     *            the new enabled state

     * 

     * @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>

     */

    public void setEnabled(boolean enabled) {

        checkWidget();

        if (enabled) {

            state &= ~WidgetState.DISABLED;

        } else {

            state |= WidgetState.DISABLED;

        }

        OS.QWidget_setEnabled(handle, enabled);

    }

    /**

     * Sets the amount that the receiver's value will be modified by when the

     * up/down (or right/left) arrows are pressed to the argument, which must be

     * at least one.

     * 

     * @param value

     *            the new increment (must be greater than zero)

     * 

     * @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>

     */

    public void setIncrement(int value) {

        checkWidget();

        if (value < 1) {

            return;

        }

        OS.QAbstractSlider_setSingleStep(handle, value);

    }

    /**

     * Sets the maximum. If this value is negative or less than or equal to the

     * minimum, the value is ignored. If necessary, the selection are adjusted

     * to fit within the new range.

     * 

     * @param value

     *            the new maximum

     *