qabstractscrollarea.cpp

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#include "qabstractscrollarea.h"

#ifndef QT_NO_SCROLLAREA

#include "qscrollbar.h"
#include "qapplication.h"
#include "qstyle.h"
#include "qstyleoption.h"
#include "qevent.h"
#include "qdebug.h"
#include "qboxlayout.h"
#include "qpainter.h"

#include "qabstractscrollarea_p.h"
#include <qwidget.h>

#ifdef Q_WS_MAC
#include <qmacstyle_mac.h>
#include <private/qt_mac_p.h>
#endif

/*!
    \class QAbstractScrollArea
    \brief The QAbstractScrollArea widget provides a scrolling area with
    on-demand scroll bars.

    \ingroup abstractwidgets

    QAbstractScrollArea is a low-level abstraction of a scrolling area. It gives
    you full control of the scroll bars, at the cost of simplicity. In
    most cases, using a QScrollArea is preferable.

    QAbstractScrollArea's central child widget is the scrolling area itself,
    called viewport(). The viewport widget uses all available
    space. Next to the viewport is a vertical scroll bar (accessible
    with verticalScrollBar()), and below a horizontal scroll bar
    (accessible with horizontalScrollBar()). Each scroll bar can be
    either visible or hidden, depending on the scroll bar's policy
    (see \l verticalScrollBarPolicy and \l horizontalScrollBarPolicy).
    When a scroll bar is hidden, the viewport expands in order to
    cover all available space. When a scroll bar becomes visible
    again, the viewport shrinks in order to make room for the scroll
    bar.

    With a scroll bar policy of Qt::ScrollBarAsNeeded (the default),
    QAbstractScrollArea shows scroll bars when those provide a non-zero
    scrolling range, and hides them otherwise. You control the range
    of each scroll bar with QAbstractSlider::setRange().

    In order to track scroll bar movements, reimplement the virtual
    function scrollContentsBy(). In order to fine-tune scrolling
    behavior, connect to a scroll bar's
    QAbstractSlider::actionTriggered() signal and adjust the \l
    QAbstractSlider::sliderPosition as you wish.

    It is possible to reserve a margin area around the viewport, see
    setViewportMargins(). The feature is mostly used to place a
    QHeaderView widget above or beside the scrolling area.

    For convenience, QAbstractScrollArea makes all viewport events available in
    the virtual viewportEvent() handler.  QWidget's specialized
    handlers are remapped to viewport events in the cases where this
    makes sense. The remapped specialized handlers are: paintEvent(),
    mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(),
    mouseMoveEvent(), wheelEvent(), dragEnterEvent(), dragMoveEvent(),
    dragLeaveEvent(), dropEvent(), contextMenuEvent().  and
    resizeEvent().

    \sa QScrollArea
*/

QAbstractScrollAreaPrivate::QAbstractScrollAreaPrivate()
    :hbar(0), vbar(0), vbarpolicy(Qt::ScrollBarAsNeeded), hbarpolicy(Qt::ScrollBarAsNeeded),
     viewport(0), cornerWidget(0), left(0), top(0), right(0), bottom(0),
     xoffset(0), yoffset(0), viewportFilter(0)
{
}

QAbstractScrollAreaScrollBarContainer::QAbstractScrollAreaScrollBarContainer(Qt::Orientation orientation, QWidget *parent)
    :QWidget(parent), scrollBar(new QScrollBar(orientation, this)),
     layout(new QBoxLayout(orientation == Qt::Horizontal ? QBoxLayout::LeftToRight : QBoxLayout::TopToBottom)),
     orientation(orientation)
{
    setLayout(layout);
    layout->setMargin(0);
    layout->setSpacing(0);
    layout->addWidget(scrollBar);
}

/*! \internal
    Adds a widget to the scroll bar container.
*/
void QAbstractScrollAreaScrollBarContainer::addWidget(QWidget *widget, LogicalPosition position)
{
    QSizePolicy policy = widget->sizePolicy();
    if (orientation == Qt::Vertical)
        policy.setHorizontalPolicy(QSizePolicy::Ignored);
    else
        policy.setVerticalPolicy(QSizePolicy::Ignored);
    widget->setSizePolicy(policy);
    widget->setParent(this);

    const int insertIndex = (position & LogicalLeft) ? 0 : scrollBarLayoutIndex() + 1;
    layout->insertWidget(insertIndex, widget);
}

/*! \internal
    Retuns a list of scroll bar widgets for the given position. The scroll bar
    itself is not returned.
*/
QWidgetList QAbstractScrollAreaScrollBarContainer::widgets(LogicalPosition position)
{
    QWidgetList list;
    const int scrollBarIndex = scrollBarLayoutIndex();
    if (position == LogicalLeft) {
        for (int i = 0; i < scrollBarIndex; ++i)
            list.append(layout->itemAt(i)->widget());
    } else if (position == LogicalRight) {
        const int layoutItemCount = layout->count();
        for (int i = scrollBarIndex + 1; i < layoutItemCount; ++i)
            list.append(layout->itemAt(i)->widget());
    }
    return list;
}

/*! \internal
    Returns the layout index for the scroll bar. This needs to be
    recalculated by a linear search for each use, since items in
    the layout can be removed at any time (i.e. when a widget is
    deleted or re-parented).
*/
int QAbstractScrollAreaScrollBarContainer::scrollBarLayoutIndex() const
{
    const int layoutItemCount = layout->count();
    for (int i = 0; i < layoutItemCount; ++i) {
        if (qobject_cast<QScrollBar *>(layout->itemAt(i)->widget()))
            return i;
    }
    return -1;
}

/*! \internal
*/
void QAbstractScrollAreaPrivate::replaceScrollBar(QScrollBar *scrollBar,
                                                  Qt::Orientation orientation)
{
    Q_Q(QAbstractScrollArea);

    QAbstractScrollAreaScrollBarContainer *container = scrollBarContainers[orientation];
    bool horizontal = (orientation == Qt::Horizontal);
    QScrollBar *oldBar = horizontal ? hbar : vbar;
    if (horizontal)
        hbar = scrollBar;
    else
        vbar = scrollBar;
    scrollBar->setParent(container);
    container->scrollBar = scrollBar;
    container->layout->removeWidget(oldBar);
    container->layout->insertWidget(0, scrollBar);
    scrollBar->setVisible(oldBar->isVisibleTo(oldBar->window()));
    scrollBar->setInvertedAppearance(oldBar->invertedAppearance());
    scrollBar->setInvertedControls(oldBar->invertedControls());
    scrollBar->setRange(oldBar->minimum(), oldBar->maximum());
    scrollBar->setOrientation(oldBar->orientation());
    scrollBar->setPageStep(oldBar->pageStep());
    scrollBar->setSingleStep(oldBar->singleStep());
    scrollBar->setSliderDown(oldBar->isSliderDown());
    scrollBar->setSliderPosition(oldBar->sliderPosition());
    scrollBar->setTracking(oldBar->hasTracking());
    scrollBar->setValue(oldBar->value());
    delete oldBar;

    QObject::connect(scrollBar, SIGNAL(valueChanged(int)),
                     q, horizontal ? SLOT(_q_hslide(int)) : SLOT(_q_vslide(int)));
    QObject::connect(scrollBar, SIGNAL(rangeChanged(int,int)),
                     q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
}

void QAbstractScrollAreaPrivate::init()
{
    Q_Q(QAbstractScrollArea);
    scrollBarContainers[Qt::Horizontal] = new QAbstractScrollAreaScrollBarContainer(Qt::Horizontal, q);
    hbar = scrollBarContainers[Qt::Horizontal]->scrollBar;
    hbar->setRange(0,0);
    scrollBarContainers[Qt::Horizontal]->setVisible(false);
    QObject::connect(hbar, SIGNAL(valueChanged(int)), q, SLOT(_q_hslide(int)));
    QObject::connect(hbar, SIGNAL(rangeChanged(int,int)), q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
    scrollBarContainers[Qt::Vertical] = new QAbstractScrollAreaScrollBarContainer(Qt::Vertical, q);
    vbar = scrollBarContainers[Qt::Vertical]->scrollBar;
    vbar->setRange(0,0);
    scrollBarContainers[Qt::Vertical]->setVisible(false);
    QObject::connect(vbar, SIGNAL(valueChanged(int)), q, SLOT(_q_vslide(int)));
    QObject::connect(vbar, SIGNAL(rangeChanged(int,int)), q, SLOT(_q_showOrHideScrollBars()), Qt::QueuedConnection);
    viewportFilter = new QAbstractScrollAreaFilter(this);
    viewport = new QWidget(q);
    viewport->setObjectName(QLatin1String("qt_scrollarea_viewport"));
    viewport->setBackgroundRole(QPalette::Base);
    viewport->setAutoFillBackground(true);
    viewport->installEventFilter(viewportFilter);
    viewport->setFocusProxy(q);
    q->setFocusPolicy(Qt::WheelFocus);
    q->setFrameStyle(QFrame::StyledPanel | QFrame::Sunken);
    q->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    layoutChildren();
}

void QAbstractScrollAreaPrivate::layoutChildren()
{
    Q_Q(QAbstractScrollArea);
    bool needh = (hbarpolicy == Qt::ScrollBarAlwaysOn
                  || (hbarpolicy == Qt::ScrollBarAsNeeded && hbar->minimum() < hbar->maximum()));

    bool needv = (vbarpolicy == Qt::ScrollBarAlwaysOn
                  || (vbarpolicy == Qt::ScrollBarAsNeeded && vbar->minimum() < vbar->maximum()));

    const int hsbExt = hbar->sizeHint().height();
    const int vsbExt = vbar->sizeHint().width();
    const QPoint extPoint(vsbExt, hsbExt);
    const QSize extSize(vsbExt, hsbExt);

    const QRect widgetRect = q->rect();
    QStyleOption opt(0);
    opt.init(q);

    const bool hasCornerWidget = (cornerWidget != 0);

// If the scroll bars are at the very right and bottom of the window we
// move their positions to be aligned with the size grip.
#ifdef Q_WS_MAC
    QWidget * const window = q->window();
    // Check if a native sizegrip is present.
    bool hasMacReverseSizeGrip = false;
    bool hasMacSizeGrip = false;
    HIViewRef nativeSizeGrip;
    HIViewFindByID(HIViewGetRoot(HIViewGetWindow(HIViewRef(q->winId()))), kHIViewWindowGrowBoxID, &nativeSizeGrip);
    if (nativeSizeGrip) {
        // Look for a native size grip at the visual window bottom right and at the
        // absolute window bottom right. In reverse mode, the native size grip does not
        // swich side, so we need to check if it is on the "wrong side".
        const QPoint scrollAreaBottomRight = q->mapTo(window, widgetRect.bottomRight() - QPoint(frameWidth, frameWidth));
        const QPoint windowBottomRight = window->rect().bottomRight();
        const QPoint visualWindowBottomRight = QStyle::visualPos(opt.direction, opt.rect, windowBottomRight);
        const QPoint offset = windowBottomRight - scrollAreaBottomRight;
        const QPoint visualOffset = visualWindowBottomRight - scrollAreaBottomRight;
        hasMacSizeGrip = (visualOffset.manhattanLength() < vsbExt);
        hasMacReverseSizeGrip = (hasMacSizeGrip == false && (offset.manhattanLength() < hsbExt));
    }

    // Use small scroll bars for tool windows, if the window has a native size grip.
    const QMacStyle::WidgetSizePolicy hpolicy = QMacStyle::widgetSizePolicy(hbar);
    const QMacStyle::WidgetSizePolicy vpolicy = QMacStyle::widgetSizePolicy(vbar);
    const Qt::WindowType windowType = window->windowType();
    if (windowType == Qt::Tool && (hasMacSizeGrip || hasMacReverseSizeGrip)) {
        if (hpolicy != QMacStyle::SizeSmall)
            QMacStyle::setWidgetSizePolicy(hbar, QMacStyle::SizeSmall);
        if (vpolicy != QMacStyle::SizeSmall)
            QMacStyle::setWidgetSizePolicy(vbar, QMacStyle::SizeSmall);
    } else {
        if (hpolicy != QMacStyle::SizeDefault)
            QMacStyle::setWidgetSizePolicy(hbar, QMacStyle::SizeDefault);
        if (vpolicy != QMacStyle::SizeDefault)
            QMacStyle::setWidgetSizePolicy(vbar, QMacStyle::SizeDefault);
    }
#endif
    QPoint cornerOffset(needv ? vsbExt : 0, needh ? hsbExt : 0);
    QRect controlsRect;
    QRect viewportRect;

    // In FrameOnlyAroundContents mode the frame is drawn between the controls and
    // the viewport, else the frame rect is equal to the widget rect.
    if (q->style()->styleHint(QStyle::SH_ScrollView_FrameOnlyAroundContents, &opt, q)) {
        controlsRect = widgetRect;
        const int extra = q->style()->pixelMetric(QStyle::PM_DefaultFrameWidth) * 2;
        const QPoint cornerExtra(needv ? extra : 0, needh ? extra : 0);
        QRect frameRect = widgetRect;
        frameRect.adjust(0, 0, -cornerOffset.x() - cornerExtra.x(), -cornerOffset.y() - cornerExtra.y());
        q->setFrameRect(frameRect);
        viewportRect = q->contentsRect();
    } else {
        q->setFrameRect(QStyle::visualRect(opt.direction, opt.rect, widgetRect));
        controlsRect = q->contentsRect();
        viewportRect = QRect(controlsRect.topLeft(), controlsRect.bottomRight() - cornerOffset);
    }

    // If we have a corner widget and are only showing one scroll bar, we need to move it
    // to make room for the corner widget.
    if (hasCornerWidget && (needv || needh))
        cornerOffset =  extPoint;

#ifdef Q_WS_MAC
    // Also move the scroll bars if they are covered by the native Mac size grip.
    if (hasMacSizeGrip)
        cornerOffset =  extPoint;
#endif

    // The corner point is where the scroll bar rects, the corner widget rect and the
    // viewport rect meets.
    const QPoint cornerPoint(controlsRect.bottomRight() + QPoint(1, 1) - cornerOffset);

    // Some styles paints the corner if both scorllbars are showing and there is
    // no corner widget. Also, on the Mac we paint if there is a native
    // (transparent) sizegrip in the area where a corner widget would be.
    if (needv && needh && hasCornerWidget == false
#ifdef Q_WS_MAC
        || ((needv || needh) && hasMacSizeGrip)
#endif
    ) {
        cornerPaintingRect = QStyle::visualRect(opt.direction, opt.rect, QRect(cornerPoint, extSize));
    } else {
        cornerPaintingRect = QRect();
    }

#ifdef Q_WS_MAC
    if (hasMacReverseSizeGrip)
        reverseCornerPaintingRect = QRect(controlsRect.bottomRight() + QPoint(1, 1) - extPoint, extSize);
    else
        reverseCornerPaintingRect = QRect();
#endif

    if (needh) {
        QRect horizontalScrollBarRect(QPoint(controlsRect.left(), cornerPoint.y()), QPoint(cornerPoint.x() - 1, controlsRect.bottom()));
#ifdef Q_WS_MAC
        if (hasMacReverseSizeGrip)
            horizontalScrollBarRect.adjust(vsbExt, 0, 0, 0);
#endif
        scrollBarContainers[Qt::Horizontal]->setGeometry(QStyle::visualRect(opt.direction, opt.rect, horizontalScrollBarRect));
        scrollBarContainers[Qt::Horizontal]->raise();
    }

    if (needv) {
        const QRect verticalScrollBarRect  (QPoint(cornerPoint.x(), controlsRect.top()),  QPoint(controlsRect.right(), cornerPoint.y() - 1));
        scrollBarContainers[Qt::Vertical]->setGeometry(QStyle::visualRect(opt.direction, opt.rect, verticalScrollBarRect));
        scrollBarContainers[Qt::Vertical]->raise();
    }

    if (cornerWidget) {
        const QRect cornerWidgetRect(cornerPoint, controlsRect.bottomRight());
        cornerWidget->setGeometry(QStyle::visualRect(opt.direction, opt.rect, cornerWidgetRect));
    }

    scrollBarContainers[Qt::Horizontal]->setVisible(needh);
    scrollBarContainers[Qt::Vertical]->setVisible(needv);

    // Existing code expect to have to account for reverse mode when calling
    // setViewportMargins(), so we undo that here to preserve the behavior.
    // ### Qt 5: Consider changing the behavior.
    if (QApplication::isRightToLeft())
        viewportRect.adjust(right, top, -left, -bottom);
    else
        viewportRect.adjust(left, top, -right, -bottom);

    viewport->setGeometry(QStyle::visualRect(opt.direction, opt.rect, viewportRect)); // resize the viewport last
}

/*!
    \internal

    Creates a new QAbstractScrollAreaPrivate, \a dd with the given \a parent.
*/
00383 QAbstractScrollArea::QAbstractScrollArea(QAbstractScrollAreaPrivate &dd, QWidget *parent)
    :QFrame(dd, parent)
{
    Q_D(QAbstractScrollArea);
    d->init();
}

/*!
    Constructs a viewport.

    The \a parent arguments is sent to the QWidget constructor.
*/
00395 QAbstractScrollArea::QAbstractScrollArea(QWidget *parent)
    :QFrame(*new QAbstractScrollAreaPrivate, parent)
{
    Q_D(QAbstractScrollArea);
    d->init();
}


/*!
  Destroys the viewport.
 */
00406 QAbstractScrollArea::~QAbstractScrollArea()
{
    Q_D(QAbstractScrollArea);
    delete d->viewportFilter;
}


/*!
  \since 4.2
  Sets the viewport to be the given \a widget.
  The QAbstractScrollArea will take ownership of the given \a widget.

  If \a widget is 0, QAbstractScrollArea will assign a new QWidget instance
  for the viewport.

  \sa viewport()
*/
00423 void QAbstractScrollArea::setViewport(QWidget *widget)
{
    Q_D(QAbstractScrollArea);
    if (widget != d->viewport) {
        QWidget *oldViewport = d->viewport;
        if (!widget)
            widget = new QWidget;
        d->viewport = widget;
        d->viewport->setParent(this);
        d->viewport->setFocusProxy(this);
        d->viewport->installEventFilter(d->viewportFilter);
        d->layoutChildren();
        if (isVisible())
            d->viewport->show();
        QMetaObject::invokeMethod(this, "setupViewport", Q_ARG(QWidget *, widget));
        delete oldViewport;
    }
}

/*!
    Returns the viewport widget.

    Use the QScrollArea::widget() function to retrieve the contents of
    the viewport widget.

    \sa QScrollArea::widget()
*/
00450 QWidget *QAbstractScrollArea::viewport() const
{
    Q_D(const QAbstractScrollArea);
    return d->viewport;
}


/*!
Returns the size of the viewport as if the scroll bars had no valid
scrolling range.
*/
// ### still thinking about the name
00462 QSize QAbstractScrollArea::maximumViewportSize() const
{
    Q_D(const QAbstractScrollArea);
    int hsbExt = d->hbar->sizeHint().height();
    int vsbExt = d->vbar->sizeHint().width();

    int f = 2 * d->frameWidth;
    QSize max = size() - QSize(f + d->left + d->right, f + d->top + d->bottom);
    if (d->vbarpolicy == Qt::ScrollBarAlwaysOn)
        max.rwidth() -= vsbExt;
    if (d->hbarpolicy == Qt::ScrollBarAlwaysOn)
        max.rheight() -= hsbExt;
    return max;
}

/*!
    \property QAbstractScrollArea::verticalScrollBarPolicy
    \brief the policy for the vertical scroll bar

    The default policy is Qt::ScrollBarAsNeeded.

    \sa horizontalScrollBarPolicy
*/

Qt::ScrollBarPolicy QAbstractScrollArea::verticalScrollBarPolicy() const
{
    Q_D(const QAbstractScrollArea);
    return d->vbarpolicy;
}

void QAbstractScrollArea::setVerticalScrollBarPolicy(Qt::ScrollBarPolicy policy)
{
    Q_D(QAbstractScrollArea);
    d->vbarpolicy = policy;
    if (isVisible())
        d->layoutChildren();
}


/*!
  Returns the vertical scroll bar.

  \sa verticalScrollBarPolicy, horizontalScrollBar()
 */
00506 QScrollBar *QAbstractScrollArea::verticalScrollBar() const
{
    Q_D(const QAbstractScrollArea);
    return d->vbar;
}

/*!
   \since 4.2
   Replaces the existing vertical scroll bar with \a scrollBar, and sets all
   the former scroll bar's slider properties on the new scroll bar. The former
   scroll bar is then deleted.

   QAbstractScrollArea already provides vertical and horizontal scroll bars by
   default. You can call this function to replace the default vertical
   scroll bar with your own custom scroll bar.

   \sa verticalScrollBar(), setHorizontalScrollBar()
*/
00524 void QAbstractScrollArea::setVerticalScrollBar(QScrollBar *scrollBar)
{
    Q_D(QAbstractScrollArea);
    if (!scrollBar) {
        qWarning("QAbstractScrollArea::setVerticalScrollBar: Cannot set a null scroll bar");
        return;
    }

    d->replaceScrollBar(scrollBar, Qt::Vertical);
}

/*!
    \property QAbstractScrollArea::horizontalScrollBarPolicy
    \brief the policy for the horizontal scroll bar

    The default policy is Qt::ScrollBarAsNeeded.

    \sa verticalScrollBarPolicy
*/

Qt::ScrollBarPolicy QAbstractScrollArea::horizontalScrollBarPolicy() const
{
    Q_D(const QAbstractScrollArea);
    return d->hbarpolicy;
}

void QAbstractScrollArea::setHorizontalScrollBarPolicy(Qt::ScrollBarPolicy policy)
{
    Q_D(QAbstractScrollArea);
    d->hbarpolicy = policy;
    if (isVisible())
        d->layoutChildren();
}

/*!
  Returns the horizontal scroll bar.

  \sa horizontalScrollBarPolicy, verticalScrollBar()
 */
00563 QScrollBar *QAbstractScrollArea::horizontalScrollBar() const
{
    Q_D(const QAbstractScrollArea);
    return d->hbar;
}

/*!
    \since 4.2

    Replaces the existing horizontal scroll bar with \a scrollBar, and sets all
    the former scroll bar's slider properties on the new scroll bar. The former
    scroll bar is then deleted.

    QAbstractScrollArea already provides horizontal and vertical scroll bars by
    default. You can call this function to replace the default horizontal
    scroll bar with your own custom scroll bar.

    \sa horizontalScrollBar(), setVerticalScrollBar()
*/
00582 void QAbstractScrollArea::setHorizontalScrollBar(QScrollBar *scrollBar)
{
    Q_D(QAbstractScrollArea);
    if (!scrollBar) {
        qWarning("QAbstractScrollArea::setHorizontalScrollBar: Cannot set a null scroll bar");
        return;
    }

    d->replaceScrollBar(scrollBar, Qt::Horizontal);
}

/*!
    \since 4.2

    Returns the widget in the corner between the two scroll bars.

    By default, no corner widget is present.
*/
00600 QWidget *QAbstractScrollArea::cornerWidget() const
{
    Q_D(const QAbstractScrollArea);
    return d->cornerWidget;
}

/*!
    \since 4.2

    Sets the widget in the corner between the two scroll bars to be
    \a widget.

    You will probably also want to set at least one of the scroll bar
    modes to \c AlwaysOn.

    Passing 0 shows no widget in the corner.

    Any previous corner widget is hidden.

    You may call setCornerWidget() with the same widget at different
    times.

    All widgets set here will be deleted by the scroll area when it is
    destroyed unless you separately reparent the widget after setting
    some other corner widget (or 0).

    Any \e newly set widget should have no current parent.

    By default, no corner widget is present.

    \sa horizontalScrollBarPolicy, horizontalScrollBarPolicy
*/
00632 void QAbstractScrollArea::setCornerWidget(QWidget *widget)
{
    Q_D(QAbstractScrollArea);
    QWidget* oldWidget = d->cornerWidget;
    if (oldWidget != widget) {
        if (oldWidget)
            oldWidget->hide();
        d->cornerWidget = widget;

        if (widget && widget->parentWidget() != this)
            widget->setParent(this);

        d->layoutChildren();
        if (widget)
            widget->show();
    } else {
        d->cornerWidget = widget;
        d->layoutChildren();
    }
}

/*!
    \since 4.2
    Adds \a widget as a scroll bar widget in the location specified
    by \a alignment.

    Scroll bar widgets are shown next to the horizontal or vertical
    scroll bar, and can be placed on either side of it. If you want
    the scroll bar widgets to be always visible, set the
    scrollBarPolicy for the corresponding scroll bar to \c AlwaysOn.

    \a alignment must be one of Qt::Alignleft and Qt::AlignRight,
    which maps to the horizontal scroll bar, or Qt::AlignTop and
    Qt::AlignBottom, which maps to the vertical scroll bar.

    A scroll bar widget can be removed by either re-parenting the
    widget or deleting it. It's also possible to hide a widget with
    QWidget::hide()

    The scroll bar widget will be resized to fit the scroll bar
    geometry for the current style. The following describes the case
    for scroll bar widgets on the horizontal scroll bar:

    The height of the widget will be set to match the height of the
    scroll bar. To control the width of the widget, use
    QWidget::setMinimumWidth and QWidget::setMaximumWidth, or
    implement QWidget::sizeHint() and set a horizontal size policy.
    If you want a square widget, call
    QStyle::pixelMetric(QStyle::PM_ScrollBarExtent) and set the
    width to this value.

    \sa scrollBarWidgets()
*/
00685 void QAbstractScrollArea::addScrollBarWidget(QWidget *widget, Qt::Alignment alignment)
{
    Q_D(QAbstractScrollArea);

    if (widget == 0)
        return;

    const Qt::Orientation scrollBarOrientation
        = ((alignment & Qt::AlignLeft) || (alignment & Qt::AlignRight)) ? Qt::Horizontal : Qt::Vertical;
    const QAbstractScrollAreaScrollBarContainer::LogicalPosition position
        = ((alignment & Qt::AlignRight) || (alignment & Qt::AlignBottom))
          ? QAbstractScrollAreaScrollBarContainer::LogicalRight : QAbstractScrollAreaScrollBarContainer::LogicalLeft;
    d->scrollBarContainers[scrollBarOrientation]->addWidget(widget, position);
    d->layoutChildren();
    if (isHidden() == false)
        widget->show();
}

/*!
    \since 4.2
    Returns a list of the currently set scroll bar widgets. \a alignment
    can be any combination of the four location flags.

    \sa addScrollBarWidget()
*/
00710 QWidgetList QAbstractScrollArea::scrollBarWidgets(Qt::Alignment alignment)
{
    Q_D(QAbstractScrollArea);

    QWidgetList list;

    if (alignment & Qt::AlignLeft)
        list += d->scrollBarContainers[Qt::Horizontal]->widgets(QAbstractScrollAreaScrollBarContainer::LogicalLeft);
    if (alignment & Qt::AlignRight)
        list += d->scrollBarContainers[Qt::Horizontal]->widgets(QAbstractScrollAreaScrollBarContainer::LogicalRight);
    if (alignment & Qt::AlignTop)
        list += d->scrollBarContainers[Qt::Vertical]->widgets(QAbstractScrollAreaScrollBarContainer::LogicalLeft);
    if (alignment & Qt::AlignBottom)
        list += d->scrollBarContainers[Qt::Vertical]->widgets(QAbstractScrollAreaScrollBarContainer::LogicalRight);

    return list;
}

/*!
    Sets the margins around the scrolling area to \a left, \a top, \a
    right and \a bottom. This is useful for applications such as
    spreadsheets with "locked" rows and columns. The marginal space is
    is left blank; put widgets in the unused area.

    By default all margins are zero.

*/
00737 void QAbstractScrollArea::setViewportMargins(int left, int top, int right, int bottom)
{
    Q_D(QAbstractScrollArea);
    d->left = left;
    d->top = top;
    d->right = right;
    d->bottom = bottom;
    d->layoutChildren();
}

/*!
    \fn bool QAbstractScrollArea::event(QEvent *event)

    \reimp

    This is the main event handler for the QAbstractScrollArea widget (\e not
    the scrolling area viewport()). The specified \a event is a general event
    object that may need to be cast to the appropriate class depending on its
    type.

    \sa QEvent::type()
*/
00759 bool QAbstractScrollArea::event(QEvent *e)
{
    Q_D(QAbstractScrollArea);
    switch (e->type()) {
    case QEvent::AcceptDropsChange:
        d->viewport->setAcceptDrops(acceptDrops());
        break;
    case QEvent::MouseTrackingChange:
        d->viewport->setMouseTracking(hasMouseTracking());
        break;
    case QEvent::Resize:
            d->layoutChildren();
            break;
    case QEvent::Paint:
        if (d->cornerPaintingRect.isValid()) {
            QStyleOption option;
            option.rect = d->cornerPaintingRect;
            QPainter p(this);
            style()->drawPrimitive(QStyle::PE_PanelScrollAreaCorner, &option, &p, this);
        }
#ifdef Q_WS_MAC
        if (d->reverseCornerPaintingRect.isValid()) {
            QStyleOption option;
            option.rect = d->reverseCornerPaintingRect;
            QPainter p(this);
            style()->drawPrimitive(QStyle::PE_PanelScrollAreaCorner, &option, &p, this);
        }
#endif
        QFrame::paintEvent((QPaintEvent*)e);
        break;
    case QEvent::ContextMenu:
        if (static_cast<QContextMenuEvent *>(e)->reason() == QContextMenuEvent::Keyboard)
           return QFrame::event(e);
        e->ignore();
        break;
    case QEvent::MouseButtonPress:
    case QEvent::MouseButtonRelease:
    case QEvent::MouseButtonDblClick:
    case QEvent::MouseMove:
    case QEvent::Wheel:
#ifndef QT_NO_DRAGANDDROP
    case QEvent::Drop:
    case QEvent::DragEnter:
    case QEvent::DragMove:
    case QEvent::DragLeave:
#endif
        return false;
    case QEvent::StyleChange:
        d->layoutChildren();
        // fall through
    default:
        return QFrame::event(e);
    }
    return true;
}

/*!
  \fn bool QAbstractScrollArea::viewportEvent(QEvent *event)

  The main event handler for the scrolling area (the viewport() widget).
  It handles the \a event specified, and can be called by subclasses to
  provide reasonable default behavior.

  Returns true to indicate to the event system that the event has been
  handled, and needs no further processing; otherwise returns false to
  indicate that the event should be propagated further.

  You can reimplement this function in a subclass, but we recommend
  using one of the specialized event handlers instead.

  Specialised handlers for viewport events are: paintEvent(),
  mousePressEvent(), mouseReleaseEvent(), mouseDoubleClickEvent(),
  mouseMoveEvent(), wheelEvent(), dragEnterEvent(), dragMoveEvent(),
  dragLeaveEvent(), dropEvent(), contextMenuEvent(), and
  resizeEvent().
*/
00835 bool QAbstractScrollArea::viewportEvent(QEvent *e)
{
    switch (e->type()) {
    case QEvent::Resize:
    case QEvent::Paint:
    case QEvent::MouseButtonPress:
    case QEvent::MouseButtonRelease:
    case QEvent::MouseButtonDblClick:
    case QEvent::MouseMove:
    case QEvent::ContextMenu:
#ifndef QT_NO_WHEELEVENT
    case QEvent::Wheel:
#endif
#ifndef QT_NO_DRAGANDDROP
    case QEvent::Drop:
    case QEvent::DragEnter:
    case QEvent::DragMove:
    case QEvent::DragLeave:
#endif
        return QFrame::event(e);
    case QEvent::LayoutRequest:
        return event(e);
    default:
        break;
    }
    return false; // let the viewport widget handle the event
}

/*!
    \fn void QAbstractScrollArea::resizeEvent(QResizeEvent *event)

    This event handler can be reimplemented in a subclass to receive
    resize events (passed in \a event), for the viewport() widget.

    When resizeEvent() is called, the viewport already has its new
    geometry: Its new size is accessible through the
    QResizeEvent::size() function, and the old size through
    QResizeEvent::oldSize().

    \sa QWidget::resizeEvent()
 */
00876 void QAbstractScrollArea::resizeEvent(QResizeEvent *)
{
}

/*!
    \fn void QAbstractScrollArea::paintEvent(QPaintEvent *event)

    This event handler can be reimplemented in a subclass to receive
    paint events (passed in \a event), for the viewport() widget.

    Note: If you open a painter, make sure to open it on the
    viewport().

    \sa QWidget::paintEvent()
*/
00891 void QAbstractScrollArea::paintEvent(QPaintEvent*)
{
}

/*!
    This event handler can be reimplemented in a subclass to receive
    mouse press events for the viewport() widget. The event is passed
    in \a e.

    \sa QWidget::mousePressEvent()
*/
00902 void QAbstractScrollArea::mousePressEvent(QMouseEvent *e)
{
    e->ignore();
}

/*!
    This event handler can be reimplemented in a subclass to receive
    mouse release events for the viewport() widget. The event is
    passed in \a e.

    \sa QWidget::mouseReleaseEvent()
*/
00914 void QAbstractScrollArea::mouseReleaseEvent(QMouseEvent *e)
{
    e->ignore();
}

/*!
    This event handler can be reimplemented in a subclass to receive
    mouse double click events for the viewport() widget. The event is
    passed in \a e.

    \sa QWidget::mouseDoubleClickEvent()
*/
00926 void QAbstractScrollArea::mouseDoubleClickEvent(QMouseEvent *e)
{
    e->ignore();
}

/*!
    This event handler can be reimplemented in a subclass to receive
    mouse move events for the viewport() widget. The event is passed
    in \a e.

    \sa QWidget::mouseMoveEvent()
*/
00938 void QAbstractScrollArea::mouseMoveEvent(QMouseEvent *e)
{
    e->ignore();
}

/*!
    This event handler can be reimplemented in a subclass to receive
    wheel events for the viewport() widget. The event is passed in \a
    e.

    \sa QWidget::wheelEvent()
*/
#ifndef QT_NO_WHEELEVENT
00951 void QAbstractScrollArea::wheelEvent(QWheelEvent *e)
{
    Q_D(QAbstractScrollArea);
    if (static_cast<QWheelEvent*>(e)->orientation() == Qt::Horizontal)
        QApplication::sendEvent(d->hbar, e);
    else
        QApplication::sendEvent(d->vbar, e);
}
#endif

/*!
    This event handler can be reimplemented in a subclass to receive
    context menu events for the viewport() widget. The event is passed
    in \a e.

    \sa QWidget::contextMenuEvent()
*/
00968 void QAbstractScrollArea::contextMenuEvent(QContextMenuEvent *e)
{
    e->ignore();
}

/*!
    This function is called with key event \a e when key presses
    occur. It handles PageUp, PageDown, Up, Down, Left, and Right, and
    ignores all other key presses.
*/
00978 void QAbstractScrollArea::keyPressEvent(QKeyEvent * e)
{
    Q_D(QAbstractScrollArea);
    if (false){
#ifndef QT_NO_SHORTCUT
    } else if (e == QKeySequence::MoveToPreviousPage) {
        d->vbar->triggerAction(QScrollBar::SliderPageStepSub);
    } else if (e == QKeySequence::MoveToNextPage) {
        d->vbar->triggerAction(QScrollBar::SliderPageStepAdd);
#endif
    } else {
        switch (e->key()) {
        case Qt::Key_Up:
            d->vbar->triggerAction(QScrollBar::SliderSingleStepSub);
            break;
        case Qt::Key_Down:
            d->vbar->triggerAction(QScrollBar::SliderSingleStepAdd);
            break;
        case Qt::Key_Left:
            d->hbar->triggerAction(QScrollBar::SliderSingleStepSub);
            break;
        case Qt::Key_Right:
            d->hbar->triggerAction(QScrollBar::SliderSingleStepAdd);
            break;
        default:
            e->ignore();
            return;
        }
    }
    e->accept();
}


#ifndef QT_NO_DRAGANDDROP
/*!
    \fn void QAbstractScrollArea::dragEnterEvent(QDragEnterEvent *event)

    This event handler can be reimplemented in a subclass to receive
    drag enter events (passed in \a event), for the viewport() widget.

    \sa QWidget::dragEnterEvent()
*/
01020 void QAbstractScrollArea::dragEnterEvent(QDragEnterEvent *)
{
}

/*!
    \fn void QAbstractScrollArea::dragMoveEvent(QDragMoveEvent *event)

    This event handler can be reimplemented in a subclass to receive
    drag move events (passed in \a event), for the viewport() widget.

    \sa QWidget::dragMoveEvent()
*/
01032 void QAbstractScrollArea::dragMoveEvent(QDragMoveEvent *)
{
}

/*!
    \fn void QAbstractScrollArea::dragLeaveEvent(QDragLeaveEvent *event)

    This event handler can be reimplemented in a subclass to receive
    drag leave events (passed in \a event), for the viewport() widget.

    \sa QWidget::dragLeaveEvent()
*/
01044 void QAbstractScrollArea::dragLeaveEvent(QDragLeaveEvent *)
{
}

/*!
    \fn void QAbstractScrollArea::dropEvent(QDropEvent *event)

    This event handler can be reimplemented in a subclass to receive
    drop events (passed in \a event), for the viewport() widget.

    \sa QWidget::dropEvent()
*/
01056 void QAbstractScrollArea::dropEvent(QDropEvent *)
{
}


#endif

/*!
    This virtual handler is called when the scroll bars are moved by
    \a dx, \a dy, and consequently the viewport's contents should be
    scrolled accordingly.

    The default implementation simply calls update() on the entire
    viewport(), subclasses can reimplement this handler for
    optimization purposes, or - like QScrollArea - to move a contents
    widget. The parameters \a dx and \a dy are there for convenience,
    so that the class knows how much should be scrolled (useful
    e.g. when doing pixel-shifts). You may just as well ignore these
    values and scroll directly to the position the scroll bars
    indicate.

    Calling this function in order to scroll programmatically is an
    error, use the scroll bars instead (e.g. by calling
    QScrollBar::setValue() directly).
*/
01081 void QAbstractScrollArea::scrollContentsBy(int, int)
{
    viewport()->update();
}

void QAbstractScrollAreaPrivate::_q_hslide(int x)
{
    Q_Q(QAbstractScrollArea);
    int dx = xoffset - x;
    xoffset = x;
    q->scrollContentsBy(dx, 0);
}

void QAbstractScrollAreaPrivate::_q_vslide(int y)
{
    Q_Q(QAbstractScrollArea);
    int dy = yoffset - y;
    yoffset = y;
    q->scrollContentsBy(0, dy);
}

void QAbstractScrollAreaPrivate::_q_showOrHideScrollBars()
{
    layoutChildren();
}

QPoint QAbstractScrollAreaPrivate::contentsOffset() const
{
    Q_Q(const QAbstractScrollArea);
    QPoint offset;
    if (vbar->isVisible())
        offset.setY(vbar->value());
    if (hbar->isVisible()) {
        if (q->isRightToLeft())
            offset.setX(hbar->maximum() - hbar->value());
        else
            offset.setX(hbar->value());
    }
    return offset;
}

/*!
    \reimp

*/
01126 QSize QAbstractScrollArea::minimumSizeHint() const
{
    Q_D(const QAbstractScrollArea);
    int hsbExt = d->hbar->sizeHint().height();
    int vsbExt = d->vbar->sizeHint().width();
    int extra = 2 * d->frameWidth;
    return QSize(d->scrollBarContainers[Qt::Horizontal]->sizeHint().width() + vsbExt + extra,
                 d->scrollBarContainers[Qt::Vertical]->sizeHint().height() + hsbExt + extra);
}

/*!
    \reimp
*/
01139 QSize QAbstractScrollArea::sizeHint() const
{
    return QSize(256, 192);
#if 0
    Q_D(const QAbstractScrollArea);
    int h = qMax(10, fontMetrics().height());
    int f = 2 * d->frameWidth;
    return QSize((6 * h) + f, (4 * h) + f);
#endif
}

/*!
    This slot is called by QAbstractScrollArea after setViewport(\a
    viewport) has been called. Reimplement this function in a
    subclass of QAbstractScrollArea to initialize the new \a viewport
    before it is used.

    \sa setViewport()
*/
01158 void QAbstractScrollArea::setupViewport(QWidget *viewport)
{
    Q_UNUSED(viewport);
}

#include "moc_qabstractscrollarea.cpp"
#include "moc_qabstractscrollarea_p.cpp"
#endif // QT_NO_SCROLLAREA