path: root/src/gui/graphicsview/qgraphicsanchorlayout.cpp

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/*!
    \class QGraphicsAnchorLayout
    \brief The QGraphicsAnchorLayout class provides a layout where one can anchor widgets
    together in Graphics View.
    \since 4.6
    \ingroup appearance
    \ingroup geomanagement
    \ingroup graphicsview-api

    The anchor layout is a layout where one can specify how widgets should be placed relative to
    each other. The specification is called an anchor, and it is set up by calling anchor().
    Anchors are always set up between edges of an item, where the "center" is also considered to
    be an edge. Considering this example:
    \code
        QGraphicsAnchorLayout *l = new QGraphicsAnchorLayout;
        QGraphicsWidget *a = new QGraphicsWidget;
        QGraphicsWidget *b = new QGraphicsWidget;
        l->anchor(a, Qt::AnchorRight, b, Qt::AnchorLeft);
    \endcode

    Here is the right edge of item A anchored to the left edge of item B, with the result that
    item B will be placed to the right of item A, with a spacing between A and B. If the
    spacing is negative, the items will overlap to some extent. Items that are anchored are
    automatically added to the layout, and if items are removed, all their anchors will be
    automatically removed

    \section1 Size Hints and Size Policies in QGraphicsAnchorLayout

    QGraphicsAnchorLayout respects each item's size hints and size policies. However it does
    not respect stretch factors currently. This might change in the future, so please refrain
    from using stretch factors in anchor layout to avoid any future regressions.

    \section1 Spacing within QGraphicsAnchorLayout

    Between the items, the layout can distribute some space. If the spacing has not been
    explicitly specified, the actual amount of space will usually be 0, but if the first edge
    is the "opposite" of the second edge (i.e. Right is anchored to Left or vice-versa), the
    size of the anchor will be queried from the style through the pixelMetric
    PM_LayoutHorizontalSpacing (or PM_LayoutVerticalSpacing for vertical anchors).
*/

#include "qgraphicsanchorlayout_p.h"

QT_BEGIN_NAMESPACE

QGraphicsAnchor::QGraphicsAnchor(QGraphicsAnchorLayout *parentLayout)
    : QObject(*(new QGraphicsAnchorPrivate))
{
    Q_D(QGraphicsAnchor);
    Q_ASSERT(parentLayout);
    d->layoutPrivate = parentLayout->d_func();
}

/*!
    Removes the QGraphicsAnchor object from the layout and destroys it.
*/
QGraphicsAnchor::~QGraphicsAnchor()
{
}

/*!
    Set the spacing for the anchor to \a spacing.

    \sa spacing(), unsetSpacing()
*/
void QGraphicsAnchor::setSpacing(qreal spacing)
{
    Q_D(QGraphicsAnchor);
    d->setSpacing(spacing);
}

/*!
    Returns the spacing for the anchor

    \sa setSpacing()
*/
qreal QGraphicsAnchor::spacing() const
{
    Q_D(const QGraphicsAnchor);
    return d->spacing();
}

/*!
    Resets the spacing of the anchor point to be the default spacing. Depending on the anchor type,
    the default spacing is either 0 or a value returned from the style.

    \sa setSpacing(), spacing(), QGraphicsAnchorLayout::anchor()
*/
void QGraphicsAnchor::unsetSpacing()
{
    Q_D(QGraphicsAnchor);
    d->unsetSpacing();
}

/*!
    Constructs a QGraphicsAnchorLayout instance.  \a parent is passed to
    QGraphicsLayout's constructor.
  */
QGraphicsAnchorLayout::QGraphicsAnchorLayout(QGraphicsLayoutItem *parent)
    : QGraphicsLayout(*new QGraphicsAnchorLayoutPrivate(), parent)
{
    Q_D(QGraphicsAnchorLayout);
    d->createLayoutEdges();
}

/*!
    Destroys the QGraphicsAnchorLayout object.
*/
QGraphicsAnchorLayout::~QGraphicsAnchorLayout()
{
    Q_D(QGraphicsAnchorLayout);

    for (int i = count() - 1; i >= 0; --i) {
        QGraphicsLayoutItem *item = d->items.at(i);
        removeAt(i);
        if (item) {
            if (item->ownedByLayout())
                delete item;
        }
    }

    d->removeCenterConstraints(this, QGraphicsAnchorLayoutPrivate::Horizontal);
    d->removeCenterConstraints(this, QGraphicsAnchorLayoutPrivate::Vertical);
    d->deleteLayoutEdges();

    Q_ASSERT(d->itemCenterConstraints[0].isEmpty());
    Q_ASSERT(d->itemCenterConstraints[1].isEmpty());
    Q_ASSERT(d->items.isEmpty());
    Q_ASSERT(d->m_vertexList.isEmpty());
}

/*!
 * Creates an anchor between the edge \a firstEdge of item \a firstItem and the edge \a secondEdge
 * of item \a secondItem. The magnitude of the anchor is picked up from the style. Anchors
 * between a layout edge and an item edge will have a size of 0.
 * If there is already an anchor between the edges, the the new anchor will replace the old one.
 *
 * \a firstItem and \a secondItem are automatically added to the layout if they are not part
 * of the layout. This means that count() can increase with up to 2.
 *
 * The spacing an anchor will get depends on the type of anchor. For instance, anchors from the
 * Right edge of one item to the Left edge of another (or vice versa) will use the default
 * horizontal spacing. The same behaviour applies to Bottom to Top anchors, (but they will use
 * the default vertical spacing). For all other anchor combinations, the spacing will be 0.
 * All anchoring functions will follow this rule.
 *
 * The spacing can also be set manually by using QGraphicsAnchor::setSpacing() method.
 *
 * \sa addCornerAnchors(), addAnchors()
 */
QGraphicsAnchor *
QGraphicsAnchorLayout::addAnchor(QGraphicsLayoutItem *firstItem, Qt::AnchorPoint firstEdge,
                                 QGraphicsLayoutItem *secondItem, Qt::AnchorPoint secondEdge)
{
    Q_D(QGraphicsAnchorLayout);
    QGraphicsAnchor *a = d->anchor(firstItem, firstEdge, secondItem, secondEdge);
    invalidate();
    return a;
}

/*!
  Returns the anchor between the anchor points defined by \a firstItem and \a firstEdge and
  \a secondItem and \a secondEdge. If there is no such anchor, the function will return 0.
*/
QGraphicsAnchor *
QGraphicsAnchorLayout::anchor(QGraphicsLayoutItem *firstItem, Qt::AnchorPoint firstEdge,
                              QGraphicsLayoutItem *secondItem, Qt::AnchorPoint secondEdge)
{
    Q_D(QGraphicsAnchorLayout);
    return d->getAnchor(firstItem, firstEdge, secondItem, secondEdge);
}

/*!
 * Creates two anchors between \a firstItem and \a secondItem, where one is for the horizontal
 * edge and another one for the vertical edge that the corners \a firstCorner and \a
 * secondCorner specifies.
 * The magnitude of the anchors is picked up from the style.
 *
 * This is a convenience function, since anchoring corners can be expressed as anchoring two edges.
 * For instance,
 * \code
 *  layout->addAnchor(layout, Qt::AnchorTop, b, Qt::AnchorTop);
 *  layout->addAnchor(layout, Qt::AnchorLeft, b, Qt::AnchorLeft);
 * \endcode
 *
 * has the same effect as
 *
 * \code
 * layout->addCornerAnchors(layout, Qt::TopLeft, b, Qt::TopLeft);
 * \endcode
 *
 * If there is already an anchor between the edge pairs, it will be replaced by the anchors that
 * this function specifies.
 *
 * \a firstItem and \a secondItem are automatically added to the layout if they are not part
 * of the layout. This means that count() can increase with up to 2.
 */
void QGraphicsAnchorLayout::addCornerAnchors(QGraphicsLayoutItem *firstItem,
                                             Qt::Corner firstCorner,
                                             QGraphicsLayoutItem *secondItem,
                                             Qt::Corner secondCorner)
{
    Q_D(QGraphicsAnchorLayout);

    // Horizontal anchor
    Qt::AnchorPoint firstEdge = (firstCorner & 1 ? Qt::AnchorRight: Qt::AnchorLeft);
    Qt::AnchorPoint secondEdge = (secondCorner & 1 ? Qt::AnchorRight: Qt::AnchorLeft);
    d->anchor(firstItem, firstEdge, secondItem, secondEdge);

    // Vertical anchor
    firstEdge = (firstCorner & 2 ? Qt::AnchorBottom: Qt::AnchorTop);
    secondEdge = (secondCorner & 2 ? Qt::AnchorBottom: Qt::AnchorTop);
    d->anchor(firstItem, firstEdge, secondItem, secondEdge);

    invalidate();
}

/*!
    Anchors two or four edges of \a firstItem with the corresponding edges of \secondItem,
    so that \a firstItem has the same size as \a secondItem in the dimensions specified by
    \a orientation.

    Calling this convenience function with the following arguments
    \code
    l->addAnchors(firstItem, secondItem, Qt::Horizontal)
    \endcode

    is the same as

    \code
    l->addAnchor(firstItem, Qt::AnchorLeft, secondItem, Qt::AnchorLeft);
    l->addAnchor(firstItem, Qt::AnchorRight, secondItem, Qt::AnchorRight);
    \endcode
*/
void QGraphicsAnchorLayout::addAnchors(QGraphicsLayoutItem *firstItem,
                                       QGraphicsLayoutItem *secondItem,
                                       Qt::Orientations orientations)
{
    if (orientations & Qt::Horizontal) {
        addAnchor(secondItem, Qt::AnchorLeft, firstItem, Qt::AnchorLeft);
        addAnchor(firstItem, Qt::AnchorRight, secondItem, Qt::AnchorRight);
    }
    if (orientations & Qt::Vertical) {
        addAnchor(secondItem, Qt::AnchorTop, firstItem, Qt::AnchorTop);
        addAnchor(firstItem, Qt::AnchorBottom, secondItem, Qt::AnchorBottom);
    }
}

/*!
    \fn QGraphicsAnchorLayout::addLeftAndRightAnchors(QGraphicsLayoutItem *firstItem, QGraphicsLayoutItem *secondItem)

    Anchors the left and right edges of \a firstItem to the same edges of
    \a secondItem.

    This convenience function is equivalent to calling
    \code
    l->addAnchor(firstItem, Qt::AnchorLeft, secondItem, Qt::AnchorLeft);
    l->addAnchor(firstItem, Qt::AnchorRight, secondItem, Qt::AnchorRight);
    \endcode
*/

/*!
    \fn QGraphicsAnchorLayout::addTopAndBottomAnchors(QGraphicsLayoutItem *firstItem, QGraphicsLayoutItem *secondItem)

    Anchors the top and bottom edges of \a firstItem to the same edges of
    \a secondItem.

    This convenience function is equivalent to calling
    \code
    l->addAnchor(firstItem, Qt::AnchorTop, secondItem, Qt::AnchorTop);
    l->addAnchor(firstItem, Qt::AnchorBottom, secondItem, Qt::AnchorBottom);
    \endcode
*/

/*!
    \fn QGraphicsAnchorLayout::addAllAnchors(QGraphicsLayoutItem *firstItem, QGraphicsLayoutItem *secondItem)

    Anchors all edges (left, right, top and bottom) of \a firstItem to the same edges of
    \a secondItem.

    This convenience function is equivalent to calling
    \code
    l->addLeftAndRightAnchors(firstItem, secondItem);
    l->addTopAndBottomAnchors(firstItem, secondItem);
    \endcode
*/

/*!
    Sets the default horizontal spacing for the anchor layout to \a spacing.

    \sa horizontalSpacing(), setVerticalSpacing(), setSpacing()
*/
void QGraphicsAnchorLayout::setHorizontalSpacing(qreal spacing)
{
    Q_D(QGraphicsAnchorLayout);
    d->spacings[0] = spacing;
    invalidate();
}

/*!
    Sets the default vertical spacing for the anchor layout to \a spacing.

    \sa verticalSpacing(), setHorizontalSpacing(), setSpacing()
*/
void QGraphicsAnchorLayout::setVerticalSpacing(qreal spacing)
{
    Q_D(QGraphicsAnchorLayout);
    d->spacings[1] = spacing;
    invalidate();
}

/*!
    Sets the default horizontal and the default vertical spacing for the anchor layout to \a spacing.

    If an item is anchored with no spacing associated with the anchor, it will use the default
    spacing.
    \sa setHorizontalSpacing(), setVerticalSpacing()
*/
void QGraphicsAnchorLayout::setSpacing(qreal spacing)
{
    Q_D(QGraphicsAnchorLayout);
    d->spacings[0] = d->spacings[1] = spacing;
    invalidate();
}

/*!
    Returns the default horizontal spacing for the anchor layout.

    \sa verticalSpacing(), setHorizontalSpacing()
*/
qreal QGraphicsAnchorLayout::horizontalSpacing() const
{
    Q_D(const QGraphicsAnchorLayout);
    return d->effectiveSpacing(QGraphicsAnchorLayoutPrivate::Horizontal);
}

/*!
    Returns the default vertical spacing for the anchor layout.

    \sa horizontalSpacing(), setVerticalSpacing()
*/
qreal QGraphicsAnchorLayout::verticalSpacing() const
{
    Q_D(const QGraphicsAnchorLayout);
    return d->effectiveSpacing(QGraphicsAnchorLayoutPrivate::Vertical);
}

/*!
  \reimp
*/
void QGraphicsAnchorLayout::setGeometry(const QRectF &geom)
{
    Q_D(QGraphicsAnchorLayout);

    QGraphicsLayout::setGeometry(geom);
    d->calculateVertexPositions(QGraphicsAnchorLayoutPrivate::Horizontal);
    d->calculateVertexPositions(QGraphicsAnchorLayoutPrivate::Vertical);
    d->setItemsGeometries(geom);
}

/*!
    Removes the layout item at \a index without destroying it. Ownership of
    the item is transferred to the caller.

    Removing an item will also remove any of the anchors associated with it.

    \sa itemAt(), count()
*/
void QGraphicsAnchorLayout::removeAt(int index)
{
    Q_D(QGraphicsAnchorLayout);
    QGraphicsLayoutItem *item = d->items.value(index);

    if (!item)
        return;

    // Removing an item affects both horizontal and vertical graphs
    d->restoreSimplifiedGraph(QGraphicsAnchorLayoutPrivate::Horizontal);
    d->restoreSimplifiedGraph(QGraphicsAnchorLayoutPrivate::Vertical);

    d->removeCenterConstraints(item, QGraphicsAnchorLayoutPrivate::Horizontal);
    d->removeCenterConstraints(item, QGraphicsAnchorLayoutPrivate::Vertical);
    d->removeAnchors(item);
    d->items.remove(index);

    item->setParentLayoutItem(0);
    invalidate();
}

/*!
    \reimp
*/
int QGraphicsAnchorLayout::count() const
{
    Q_D(const QGraphicsAnchorLayout);
    return d->items.size();
}

/*!
    \reimp
*/
QGraphicsLayoutItem *QGraphicsAnchorLayout::itemAt(int index) const
{
    Q_D(const QGraphicsAnchorLayout);
    return d->items.value(index);
}

/*!
    \reimp
*/
void QGraphicsAnchorLayout::invalidate()
{
    Q_D(QGraphicsAnchorLayout);
    QGraphicsLayout::invalidate();
    d->calculateGraphCacheDirty = 1;
}

/*!
    \reimp
*/
QSizeF QGraphicsAnchorLayout::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const
{
    Q_UNUSED(which);
    Q_UNUSED(constraint);
    Q_D(const QGraphicsAnchorLayout);

    // Some setup calculations are delayed until the information is
    // actually needed, avoiding unnecessary recalculations when
    // adding multiple anchors.

    // sizeHint() / effectiveSizeHint() already have a cache
    // mechanism, using invalidate() to force recalculation. However
    // sizeHint() is called three times after invalidation (for max,
    // min and pref), but we just need do our setup once.

    const_cast<QGraphicsAnchorLayoutPrivate *>(d)->calculateGraphs();

    // ### apply constraint!
    QSizeF engineSizeHint(
        d->sizeHints[QGraphicsAnchorLayoutPrivate::Horizontal][which],
        d->sizeHints[QGraphicsAnchorLayoutPrivate::Vertical][which]);

    qreal left, top, right, bottom;
    getContentsMargins(&left, &top, &right, &bottom);

    return engineSizeHint + QSizeF(left + right, top + bottom);
}

QT_END_NAMESPACE