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#include "qscrollarea.h"

#include "private/qscrollarea_p.h"

#ifndef QT_NO_SCROLLAREA

#include "qscrollbar.h"

#include "qlayout.h"

#include "qstyle.h"

#include "qapplication.h"

#include "qvariant.h"

#include "qdebug.h"

#include "private/qlayoutengine_p.h"

QT_BEGIN_NAMESPACE

/*!

    \class QScrollArea

    \brief The QScrollArea class provides a scrolling view onto

    another widget.

    \ingroup basicwidgets

    A scroll area is used to display the contents of a child widget

    within a frame. If the widget exceeds the size of the frame, the

    view can provide scroll bars so that the entire area of the child

    widget can be viewed. The child widget must be specified with

    setWidget(). For example:

    \snippet doc/src/snippets/code/src_gui_widgets_qscrollarea.cpp 0

    The code above creates a scroll area (shown in the images below)

    containing an image label. When scaling the image, the scroll area

    can provide the necessary scroll bars:

    \table

    \row

    \o \inlineimage qscrollarea-noscrollbars.png

    \o \inlineimage qscrollarea-onescrollbar.png

    \o \inlineimage qscrollarea-twoscrollbars.png

    \endtable

    The scroll bars appearance depends on the currently set \l

    {Qt::ScrollBarPolicy}{scroll bar policies}. You can control the

    appearance of the scroll bars using the inherited functionality

    from QAbstractScrollArea.

    For example, you can set the

    QAbstractScrollArea::horizontalScrollBarPolicy and

    QAbstractScrollArea::verticalScrollBarPolicy properties. Or if you

    want the scroll bars to adjust dynamically when the contents of

    the scroll area changes, you can use the \l

    {QAbstractScrollArea::horizontalScrollBar()}{horizontalScrollBar()}

    and \l

    {QAbstractScrollArea::verticalScrollBar()}{verticalScrollBar()}

    functions (which enable you to access the scroll bars) and set the

    scroll bars' values whenever the scroll area's contents change,

    using the QScrollBar::setValue() function.

    You can retrieve the child widget using the widget() function. The

    view can be made to be resizable with the setWidgetResizable()

    function. The alignment of the widget can be specified with

    setAlignment().

    Two convenience functions ensureVisible() and

    ensureWidgetVisible() ensure a certain region of the contents is

    visible inside the viewport, by scrolling the contents if

    necessary.

    \section1 Size Hints and Layouts

    When using a scroll area to display the contents of a custom

    widget, it is important to ensure that the

    \l{QWidget::sizeHint}{size hint} of the child widget is set to a

    suitable value. If a standard QWidget is used for the child

    widget, it may be necessary to call QWidget::setMinimumSize() to

    ensure that the contents of the widget are shown correctly within

    the scroll area.

    If a scroll area is used to display the contents of a widget that

    contains child widgets arranged in a layout, it is important to

    realise that the size policy of the layout will also determine the

    size of the widget. This is especially useful to know if you intend

    to dynamically change the contents of the layout. In such cases,

    setting the layout's \l{QLayout::sizeConstraint}{size constraint}

    property to one which provides constraints on the minimum and/or

    maximum size of the layout (e.g., QLayout::SetMinAndMaxSize) will

    cause the size of the scroll area to be updated whenever the

    contents of the layout changes.

    For a complete example using the QScrollArea class, see the \l

    {widgets/imageviewer}{Image Viewer} example. The example shows how

    to combine QLabel and QScrollArea to display an image.

    \sa QAbstractScrollArea, QScrollBar, {Image Viewer Example}

*/

/*!

    Constructs an empty scroll area with the given \a parent.

    \sa setWidget()

*/

QScrollArea::QScrollArea(QWidget *parent)

    : QAbstractScrollArea(*new QScrollAreaPrivate,parent)

{

    Q_D(QScrollArea);

    d->viewport->setBackgroundRole(QPalette::NoRole);

    d->vbar->setSingleStep(20);

    d->hbar->setSingleStep(20);

    d->layoutChildren();

}

/*!

    \internal

*/

QScrollArea::QScrollArea(QScrollAreaPrivate &dd, QWidget *parent)

    : QAbstractScrollArea(dd, parent)

{

    Q_D(QScrollArea);

    d->viewport->setBackgroundRole(QPalette::NoRole);

    d->vbar->setSingleStep(20);

    d->hbar->setSingleStep(20);

    d->layoutChildren();

}

/*!

    Destroys the scroll area and its child widget.

    \sa setWidget()

*/

QScrollArea::~QScrollArea()

{

}

void QScrollAreaPrivate::updateWidgetPosition()

{

    Q_Q(QScrollArea);

    Qt::LayoutDirection dir = q->layoutDirection();

    QRect scrolled = QStyle::visualRect(dir, viewport->rect(), QRect(QPoint(-hbar->value(), -vbar->value()), widget->size()));

    QRect aligned = QStyle::alignedRect(dir, alignment, widget->size(), viewport->rect());

    widget->move(widget->width() < viewport->width() ? aligned.x() : scrolled.x(),

                 widget->height() < viewport->height() ? aligned.y() : scrolled.y());

}

void QScrollAreaPrivate::updateScrollBars()

{

    Q_Q(QScrollArea);

    if (!widget)

        return;

    QSize p = viewport->size();

    QSize m = q->maximumViewportSize();

    QSize min = qSmartMinSize(widget);

    QSize max = qSmartMaxSize(widget);

    if (resizable) {

        if ((widget->layout() ? widget->layout()->hasHeightForWidth() : widget->sizePolicy().hasHeightForWidth())) {

            QSize p_hfw = p.expandedTo(min).boundedTo(max);

            int h = widget->heightForWidth( p_hfw.width() );

            min = QSize(p_hfw.width(), qMax(p_hfw.height(), h));

        }

    }

    if ((resizable && m.expandedTo(min) == m && m.boundedTo(max) == m)

        || (!resizable && m.expandedTo(widget->size()) == m))

        p = m; // no scroll bars needed

    if (resizable)

        widget->resize(p.expandedTo(min).boundedTo(max));

    QSize v = widget->size();

    hbar->setRange(0, v.width() - p.width());

    hbar->setPageStep(p.width());

    vbar->setRange(0, v.height() - p.height());

    vbar->setPageStep(p.height());

    updateWidgetPosition();

}

/*!

    Returns the scroll area's widget, or 0 if there is none.

    \sa setWidget()

*/

QWidget *QScrollArea::widget() const

{

    Q_D(const QScrollArea);

    return d->widget;

}

/*!

    \fn void QScrollArea::setWidget(QWidget *widget)

    Sets the scroll area's \a widget.

    The \a widget becomes a child of the scroll area, and will be

    destroyed when the scroll area is deleted or when a new widget is

    set.

    The widget's \l{QWidget::setAutoFillBackground()}{autoFillBackground}

    property will be set to \c{true}.

    If the scroll area is visible when the \a widget is

    added, you must \l{QWidget::}{show()} it explicitly.

    Note that You must add the layout of \a widget before you call

    this function; if you add it later, the \a widget will not be

    visible - regardless of when you \l{QWidget::}{show()} the scroll

    area. In this case, you can also not \l{QWidget::}{show()} the \a

    widget later.

    \sa widget()

*/

void QScrollArea::setWidget(QWidget *widget)

{

    Q_D(QScrollArea);

    if (widget == d->widget || !widget)

        return;

    delete d->widget;

    d->widget = 0;

    d->hbar->setValue(0);

    d->vbar->setValue(0);

    if (widget->parentWidget() != d->viewport)

        widget->setParent(d->viewport);

    if (!widget->testAttribute(Qt::WA_Resized))

        widget->resize(widget->sizeHint());

    d->widget = widget;

    d->widget->setAutoFillBackground(true);

    widget->installEventFilter(this);

    d->widgetSize = QSize();

    d->updateScrollBars();

    d->widget->show();

}

/*!

    Removes the scroll area's widget, and passes ownership of the

    widget to the caller.

    \sa widget()

 */

QWidget *QScrollArea::takeWidget()

{

    Q_D(QScrollArea);

    QWidget *w = d->widget;

    d->widget = 0;

    if (w)

        w->setParent(0);

    return w;

}

/*!

    \reimp

 */

bool QScrollArea::event(QEvent *e)

{

    Q_D(QScrollArea);

    if (e->type() == QEvent::StyleChange || e->type() == QEvent::LayoutRequest) {

        d->updateScrollBars();

    }

#ifdef QT_KEYPAD_NAVIGATION

    else if (QApplication::keypadNavigationEnabled()) {

        if (e->type() == QEvent::Show)

            QApplication::instance()->installEventFilter(this);

        else if (e->type() == QEvent::Hide)

            QApplication::instance()->removeEventFilter(this);

    }

#endif

    return QAbstractScrollArea::event(e);

}

/*!

    \reimp

 */

bool QScrollArea::eventFilter(QObject *o, QEvent *e)

{

    Q_D(QScrollArea);

#ifdef QT_KEYPAD_NAVIGATION

    if (d->widget && o != d->widget && e->type() == QEvent::FocusIn

            && QApplication::keypadNavigationEnabled()) {

        if (o->isWidgetType())

            ensureWidgetVisible(static_cast<QWidget *>(o));

    }

#endif

    if (o == d->widget && e->type() == QEvent::Resize)

        d->updateScrollBars();

    return false;

}

/*!

    \reimp

 */

void QScrollArea::resizeEvent(QResizeEvent *)

{

    Q_D(QScrollArea);

    d->updateScrollBars();

}

/*!\reimp

 */

void QScrollArea::scrollContentsBy(int, int)

{

    Q_D(QScrollArea);

    if (!d->widget)

        return;

    d->updateWidgetPosition();

}

/*!

    \property QScrollArea::widgetResizable

    \brief whether the scroll area should resize the view widget

    If this property is set to false (the default), the scroll area

    honors the size of its widget. Regardless of this property, you

    can programmatically resize the widget using widget()->resize(),

    and the scroll area will automatically adjust itself to the new

    size.

    If this property is set to true, the scroll area will

    automatically resize the widget in order to avoid scroll bars

    where they can be avoided, or to take advantage of extra space.

*/

bool QScrollArea::widgetResizable() const

{

    Q_D(const QScrollArea);

    return d->resizable;

}

void QScrollArea::setWidgetResizable(bool resizable)

{

    Q_D(QScrollArea);

    d->resizable = resizable;

    updateGeometry();

    d->updateScrollBars();

}

/*!

    \reimp

 */

QSize QScrollArea::sizeHint() const

{

    Q_D(const QScrollArea);

    int f = 2 * d->frameWidth;

    QSize sz(f, f);

    int h = fontMetrics().height();

    if (d->widget) {

        if (!d->widgetSize.isValid())

            d->widgetSize = d->resizable ? d->widget->sizeHint() : d->widget->size();

        sz += d->widgetSize;

    } else {

        sz += QSize(12 * h, 8 * h);

    }

    if (d->vbarpolicy == Qt::ScrollBarAlwaysOn)

        sz.setWidth(sz.width() + d->vbar->sizeHint().width());

    if (d->hbarpolicy == Qt::ScrollBarAlwaysOn)

        sz.setHeight(sz.height() + d->hbar->sizeHint().height());

    return sz.boundedTo(QSize(36 * h, 24 * h));

}

/*!

    \reimp

 */

bool QScrollArea::focusNextPrevChild(bool next)

{

    if (QWidget::focusNextPrevChild(next)) {

        if (QWidget *fw = focusWidget())

            ensureWidgetVisible(fw);

        return true;

    }

    return false;

}

/*!

    Scrolls the contents of the scroll area so that the point (\a x, \a y) is visible

    inside the region of the viewport with margins specified in pixels by \a xmargin and

    \a ymargin. If the specified point cannot be reached, the contents are scrolled to

    the nearest valid position. The default value for both margins is 50 pixels.

*/

void QScrollArea::ensureVisible(int x, int y, int xmargin, int ymargin)

{

    Q_D(QScrollArea);

    int logicalX = QStyle::visualPos(layoutDirection(), d->viewport->rect(), QPoint(x, y)).x();

    if (logicalX - xmargin < d->hbar->value()) {

        d->hbar->setValue(qMax(0, logicalX - xmargin));

    } else if (logicalX > d->hbar->value() + d->viewport->width() - xmargin) {

        d->hbar->setValue(qMin(logicalX - d->viewport->width() + xmargin, d->hbar->maximum()));

    }

    if (y - ymargin < d->vbar->value()) {

        d->vbar->setValue(qMax(0, y - ymargin));

    } else if (y > d->vbar->value() + d->viewport->height() - ymargin) {

        d->vbar->setValue(qMin(y - d->viewport->height() + ymargin, d->vbar->maximum()));

    }

}

/*!

    \since 4.2

    Scrolls the contents of the scroll area so that the \a childWidget

    of QScrollArea::widget() is visible inside the viewport with

    margins specified in pixels by \a xmargin and \a ymargin. If the

    specified point cannot be reached, the contents are scrolled to

    the nearest valid position. The default value for both margins is

    50 pixels.

*/

void QScrollArea::ensureWidgetVisible(QWidget *childWidget, int xmargin, int ymargin)

{

    Q_D(QScrollArea);

    if (!d->widget->isAncestorOf(childWidget))

        return;

    const QRect microFocus = childWidget->inputMethodQuery(Qt::ImMicroFocus).toRect();

    const QRect defaultMicroFocus =

        childWidget->QWidget::inputMethodQuery(Qt::ImMicroFocus).toRect();

    QRect focusRect = (microFocus != defaultMicroFocus)

        ? QRect(childWidget->mapTo(d->widget, microFocus.topLeft()), microFocus.size())

        : QRect(childWidget->mapTo(d->widget, QPoint(0,0)), childWidget->size());

    const QRect visibleRect(-d->widget->pos(), d->viewport->size());

    if (visibleRect.contains(focusRect))

        return;

    focusRect.adjust(-xmargin, -ymargin, xmargin, ymargin);

    if (focusRect.width() > visibleRect.width())

        d->hbar->setValue(focusRect.center().x() - d->viewport->width() / 2);

    else if (focusRect.right() > visibleRect.right())

        d->hbar->setValue(focusRect.right() - d->viewport->width());

    else

        d->hbar->setValue(focusRect.left());

    if (focusRect.height() > visibleRect.height())

        d->vbar->setValue(focusRect.center().y() - d->viewport->height() / 2);

    else if (focusRect.bottom() > visibleRect.bottom())

        d->vbar->setValue(focusRect.bottom() - d->viewport->height());

    else

        d->vbar->setValue(focusRect.top());

}

/*!

    \property QScrollArea::alignment

    \brief the alignment of the scroll area's widget

    \since 4.2

    By default, the widget stays rooted to the top-left corner of the

    scroll area.

*/

void QScrollArea::setAlignment(Qt::Alignment alignment)

{

    Q_D(QScrollArea);

    d->alignment = alignment;

    if (d->widget)

        d->updateWidgetPosition();

}

Qt::Alignment QScrollArea::alignment() const

{

    Q_D(const QScrollArea);

    return d->alignment;

}

QT_END_NAMESPACE

#endif // QT_NO_SCROLLAREA