source: trunk/src/gui/graphicsview/qgraphicsgridlayout.cpp

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/*!
    \class QGraphicsGridLayout
    \brief The QGraphicsGridLayout class provides a grid layout for managing
    widgets in Graphics View.
    \since 4.4

    \ingroup graphicsview-api

    The most common way to use QGraphicsGridLayout is to construct an object
    on the heap with no parent, add widgets and layouts by calling addItem(),
    and finally assign the layout to a widget by calling
    QGraphicsWidget::setLayout(). QGraphicsGridLayout automatically computes
    the dimensions of the grid as you add items.

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

    The layout takes ownership of the items. In some cases when the layout
    item also inherits from QGraphicsItem (such as QGraphicsWidget) there will be a
    ambiguity in ownership because the layout item belongs to two ownership hierarchies.
    See the documentation of QGraphicsLayoutItem::setOwnedByLayout() how to handle
    this.
    You can access each item in the layout by calling count() and itemAt(). Calling
    removeAt() will remove an item from the layout, without
    destroying it.

    \section1 Size Hints and Size Policies in QGraphicsGridLayout

    QGraphicsGridLayout respects each item's size hints and size policies,
    and when a cell in the grid has more space than the items can fill, each item
    is arranged according to the layout's alignment for that item. You can set
    an alignment for each item by calling setAlignment(), and check the
    alignment for any item by calling alignment(). You can also set the alignment
    for an entire row or column by calling setRowAlignment() and setColumnAlignment()
    respectively.  By default, items are aligned to the top left.


    \sa QGraphicsLinearLayout, QGraphicsWidget
*/

#include "qglobal.h"

#ifndef QT_NO_GRAPHICSVIEW

#include "qapplication.h"
#include "qwidget.h"
#include "qgraphicslayout_p.h"
#include "qgraphicslayoutitem.h"
#include "qgraphicsgridlayout.h"
#include "qgraphicswidget.h"
#include "qgridlayoutengine_p.h"
#include <QtCore/qdebug.h>

QT_BEGIN_NAMESPACE

class QGraphicsGridLayoutPrivate : public QGraphicsLayoutPrivate
{
public:
    QGraphicsGridLayoutPrivate() { }
    QLayoutStyleInfo styleInfo() const;

    QGridLayoutEngine engine;
#ifdef QT_DEBUG
    void dump(int indent) const;
#endif
};

Q_GLOBAL_STATIC(QWidget, globalStyleInfoWidget);

QLayoutStyleInfo QGraphicsGridLayoutPrivate::styleInfo() const
{
    QGraphicsItem *item = parentItem();
    QStyle *style = (item && item->isWidget()) ? static_cast<QGraphicsWidget*>(item)->style() : QApplication::style();
    return QLayoutStyleInfo(style, globalStyleInfoWidget());
}

/*!
    Constructs a QGraphicsGridLayout instance.  \a parent is passed to
    QGraphicsLayout's constructor.
*/
QGraphicsGridLayout::QGraphicsGridLayout(QGraphicsLayoutItem *parent)
    : QGraphicsLayout(*new QGraphicsGridLayoutPrivate(), parent)
{
}

/*!
    Destroys the QGraphicsGridLayout object.
*/
QGraphicsGridLayout::~QGraphicsGridLayout()
{
    for (int i = count() - 1; i >= 0; --i) {
        QGraphicsLayoutItem *item = itemAt(i);
        // The following lines can be removed, but this removes the item
        // from the layout more efficiently than the implementation of
        // ~QGraphicsLayoutItem.
        removeAt(i);
        if (item) {
            item->setParentLayoutItem(0);
            if (item->ownedByLayout())
                delete item;
        }
    }
}

/*!
    Adds \a item to the grid on \a row and \a column. You can specify a
    \a rowSpan and \a columnSpan and an optional \a alignment.
*/
void QGraphicsGridLayout::addItem(QGraphicsLayoutItem *item, int row, int column,
                                  int rowSpan, int columnSpan, Qt::Alignment alignment)
{
    Q_D(QGraphicsGridLayout);
    if (row < 0 || column < 0) {
        qWarning("QGraphicsGridLayout::addItem: invalid row/column: %d",
                 row < 0 ? row : column);
        return;
    }
    if (columnSpan < 1 || rowSpan < 1) {
        qWarning("QGraphicsGridLayout::addItem: invalid row span/column span: %d",
                 rowSpan < 1 ? rowSpan : columnSpan);
        return;
    }
    if (!item) {
        qWarning("QGraphicsGridLayout::addItem: cannot add null item");
        return;
    }
    if (item == this) {
        qWarning("QGraphicsGridLayout::addItem: cannot insert itself");
        return;
    }

    d->addChildLayoutItem(item);

    new QGridLayoutItem(&d->engine, item, row, column, rowSpan, columnSpan, alignment);
    invalidate();
}

/*!
    \fn QGraphicsGridLayout::addItem(QGraphicsLayoutItem *item, int row, int column, Qt::Alignment alignment = 0)

    Adds \a item to the grid on \a row and \a column. You can specify
    an optional \a alignment for \a item.
*/

/*!
    Sets the default horizontal spacing for the grid layout to \a spacing.
*/
void QGraphicsGridLayout::setHorizontalSpacing(qreal spacing)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setSpacing(spacing, Qt::Horizontal);
    invalidate();
}

/*!
    Returns the default horizontal spacing for the grid layout.
*/
qreal QGraphicsGridLayout::horizontalSpacing() const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.spacing(d->styleInfo(), Qt::Horizontal);
}

/*!
    Sets the default vertical spacing for the grid layout to \a spacing.
*/
void QGraphicsGridLayout::setVerticalSpacing(qreal spacing)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setSpacing(spacing, Qt::Vertical);
    invalidate();
}

/*!
    Returns the default vertical spacing for the grid layout.
*/
qreal QGraphicsGridLayout::verticalSpacing() const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.spacing(d->styleInfo(), Qt::Vertical);
}

/*!
    Sets the grid layout's default spacing, both vertical and
    horizontal, to \a spacing.

    \sa rowSpacing(), columnSpacing()
*/
void QGraphicsGridLayout::setSpacing(qreal spacing)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setSpacing(spacing, Qt::Horizontal | Qt::Vertical);
    invalidate();
}

/*!
    Sets the spacing for \a row to \a spacing.
*/
void QGraphicsGridLayout::setRowSpacing(int row, qreal spacing)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSpacing(row, spacing, Qt::Vertical);
    invalidate();
}

/*!
    Returns the row spacing for \a row.
*/
qreal QGraphicsGridLayout::rowSpacing(int row) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSpacing(row, Qt::Vertical);
}

/*!
    Sets the spacing for \a column to \a spacing.
*/
void QGraphicsGridLayout::setColumnSpacing(int column, qreal spacing)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSpacing(column, spacing, Qt::Horizontal);
    invalidate();
}

/*!
    Returns the column spacing for \a column.
*/
qreal QGraphicsGridLayout::columnSpacing(int column) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSpacing(column, Qt::Horizontal);
}

/*!
    Sets the stretch factor for \a row to \a stretch.
*/
void QGraphicsGridLayout::setRowStretchFactor(int row, int stretch)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowStretchFactor(row, stretch, Qt::Vertical);
    invalidate();
}

/*!
    Returns the stretch factor for \a row.
*/
int QGraphicsGridLayout::rowStretchFactor(int row) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowStretchFactor(row, Qt::Vertical);
}

/*!
    Sets the stretch factor for \a column to \a stretch.
*/
void QGraphicsGridLayout::setColumnStretchFactor(int column, int stretch)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowStretchFactor(column, stretch, Qt::Horizontal);
    invalidate();
}

/*!
    Returns the stretch factor for \a column.
*/
int QGraphicsGridLayout::columnStretchFactor(int column) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowStretchFactor(column, Qt::Horizontal);
}

/*!
    Sets the minimum height for row, \a row, to \a height.
*/
void QGraphicsGridLayout::setRowMinimumHeight(int row, qreal height)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::MinimumSize, row, height, Qt::Vertical);
    invalidate();
}

/*!
    Returns the minimum height for row, \a row.
*/
qreal QGraphicsGridLayout::rowMinimumHeight(int row) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSizeHint(Qt::MinimumSize, row, Qt::Vertical);
}

/*!
    Sets the preferred height for row, \a row, to \a height.
*/
void QGraphicsGridLayout::setRowPreferredHeight(int row, qreal height)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::PreferredSize, row, height, Qt::Vertical);
    invalidate();
}

/*!
    Returns the preferred height for row, \a row.
*/
qreal QGraphicsGridLayout::rowPreferredHeight(int row) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSizeHint(Qt::PreferredSize, row, Qt::Vertical);
}

/*!
    Sets the maximum height for row, \a row, to \a height.
*/
void QGraphicsGridLayout::setRowMaximumHeight(int row, qreal height)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::MaximumSize, row, height, Qt::Vertical);
    invalidate();
}

/*!
    Returns the maximum height for row, \a row.
*/
qreal QGraphicsGridLayout::rowMaximumHeight(int row) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSizeHint(Qt::MaximumSize, row, Qt::Vertical);
}

/*!
    Sets the fixed height for row, \a row, to \a height.
*/
void QGraphicsGridLayout::setRowFixedHeight(int row, qreal height)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::MinimumSize, row, height, Qt::Vertical);
    d->engine.setRowSizeHint(Qt::MaximumSize, row, height, Qt::Vertical);
    invalidate();
}

/*!
    Sets the minimum width for \a column to \a width.
*/
void QGraphicsGridLayout::setColumnMinimumWidth(int column, qreal width)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::MinimumSize, column, width, Qt::Horizontal);
    invalidate();
}

/*!
    Returns the minimum width for \a column.
*/
qreal QGraphicsGridLayout::columnMinimumWidth(int column) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSizeHint(Qt::MinimumSize, column, Qt::Horizontal);
}

/*!
    Sets the preferred width for \a column to \a width.
*/
void QGraphicsGridLayout::setColumnPreferredWidth(int column, qreal width)
{
    Q_D(QGraphicsGridLayout);
    d->engine.setRowSizeHint(Qt::PreferredSize, column, width, Qt::Horizontal);
    invalidate();
}

/*!
    Returns the preferred width for \a column.
*/
qreal QGraphicsGridLayout::columnPreferredWidth(int column) const
{
    Q_D(const QGraphicsGridLayout);
    return d->engine.rowSizeHint(Qt::PreferredSize, column, Qt::Horizontal);
}