source: trunk/src/gui/graphicsview/qgraphicsanchorlayout.cpp@ 704

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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 allows developers to specify how widgets should be placed relative to
    each other, and to the layout itself. The specification is made by adding anchors to the
    layout by calling addAnchor(), addAnchors() or addCornerAnchors().

    Existing anchors in the layout can be accessed with the anchor() function.
    Items that are anchored are automatically added to the layout, and if items
    are removed, all their anchors will be automatically removed.

    \beginfloatleft
    \inlineimage simpleanchorlayout-example.png Using an anchor layout to align simple colored widgets.
    \endfloat

    Anchors are always set up between edges of an item, where the "center" is also considered to
    be an edge. Consider the following example:

    \snippet examples/graphicsview/simpleanchorlayout/main.cpp adding anchors

    Here, the right edge of item \c a is anchored to the left edge of item \c b and the bottom
    edge of item \c a is anchored to the top edge of item \c b, with the result that
    item \c b will be placed diagonally to the right and below item \c b.

    The addCornerAnchors() function provides a simpler way of anchoring the corners
    of two widgets than the two individual calls to addAnchor() shown in the code
    above. Here, we see how a widget can be anchored to the top-left corner of the enclosing
    layout:

    \snippet examples/graphicsview/simpleanchorlayout/main.cpp adding a corner anchor

    In cases where anchors are used to match the widths or heights of widgets, it is
    convenient to use the addAnchors() function. As with the other functions for specifying
    anchors, it can also be used to anchor a widget to a layout.

    \clearfloat
    \section1 Size Hints and Size Policies in an Anchor Layout

    QGraphicsAnchorLayout respects each item's size hints and size policies.
    Note that there are some properties of QSizePolicy that are \l{Known issues}{not respected}.

    \section1 Spacing within an Anchor Layout

    The layout may distribute some space between the items. If the spacing has not been
    explicitly specified, the actual amount of space will usually be 0.

    However, if the first edge is the \e opposite of the second edge (e.g., the right edge
    of the first widget is anchored to the left edge of the second widget), the size of the
    anchor will be queried from the style through a pixel metric:
    \l{QStyle::}{PM_LayoutHorizontalSpacing} for horizontal anchors and
    \l{QStyle::}{PM_LayoutVerticalSpacing} for vertical anchors.

    If the spacing is negative, the items will overlap to some extent.


    \section1 Known issues
    There are some features that QGraphicsAnchorLayout currently does not support.
    This might change in the future, so avoid using these features if you want to
    avoid any future regressions in behaviour:
    \list

    \o Stretch factors are not respected.

    \o QSizePolicy::ExpandFlag is not respected.

    \o Height for width is not respected.

    \endlist

    \sa QGraphicsLinearLayout, QGraphicsGridLayout, QGraphicsLayout
*/

/*!
    \class QGraphicsAnchor
    \brief The QGraphicsAnchor class represents an anchor between two items in a
           QGraphicsAnchorLayout.
    \since 4.6
    \ingroup appearance
    \ingroup geomanagement
    \ingroup graphicsview-api

    The graphics anchor provides an API that enables you to query and manipulate the
    properties an anchor has. When an anchor is added to the layout with
    QGraphicsAnchorLayout::addAnchor(), a QGraphicsAnchor instance is returned where the properties
    are initialized to their default values. The properties can then be further changed, and they
    will be picked up the next time the layout is activated.

    \sa QGraphicsAnchorLayout::anchor()

*/
#include "qgraphicsanchorlayout_p.h"
#ifndef QT_NO_GRAPHICSVIEW
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()
{
}

/*!
    \property QGraphicsAnchor::sizePolicy
    \brief the size policy for the QGraphicsAnchor.

    By setting the size policy on an anchor you can configure how the anchor can resize itself
    from its preferred spacing. For instance, if the anchor has the size policy
    QSizePolicy::Minimum, the spacing is the minimum size of the anchor. However, its size
    can grow up to the anchors maximum size. If the default size policy is QSizePolicy::Fixed,
    the anchor can neither grow or shrink, which means that the only size the anchor can have
    is the spacing. QSizePolicy::Fixed is the default size policy.
    QGraphicsAnchor always has a minimum spacing of 0 and a very large maximum spacing.

    \sa QGraphicsAnchor::spacing
*/

void QGraphicsAnchor::setSizePolicy(QSizePolicy::Policy policy)
{
    Q_D(QGraphicsAnchor);
    d->setSizePolicy(policy);
}

QSizePolicy::Policy QGraphicsAnchor::sizePolicy() const
{
    Q_D(const QGraphicsAnchor);