Improve example so that we can demonstrate custom layout items.

Should show better how to reimplement setGeometry(), sizeHint()

3 files changed, 90 insertions, 27 deletions

diff --git a/doc/src/examples/basicgraphicslayouts.qdoc b/doc/src/examples/basicgraphicslayouts.qdoc
index 92571af..9696fb6 100644
--- a/doc/src/examples/basicgraphicslayouts.qdoc
+++ b/doc/src/examples/basicgraphicslayouts.qdoc
@@ -45,6 +45,7 @@
 
     The Basic Graphics Layouts example shows how to use the layout classes
     in QGraphicsView: QGraphicsLinearLayout and QGraphicsGridLayout.
+    In addition to that it shows how to write your own custom layout item.
 
     \image basicgraphicslayouts-example.png Screenshot of the Basic Layouts Example
 
@@ -115,26 +116,24 @@
 
     \section1 LayoutItem Class Definition
 
-    The \c LayoutItem class is a subclass of QGraphicsWidget. It has a
-    constructor, a destructor, and a reimplementation of the
-    {QGraphicsItem::paint()}{paint()} function.
+    The \c LayoutItem class is a subclass of QGraphicsLayoutItem and
+    QGraphicsItem. It has a constructor, a destructor, and some required
+    reimplementations.
+    Since it inherits QGraphicsLayoutItem it must reimplement
+    {QGraphicsLayoutItem::setGeometry()}{setGeometry()} and
+    {QGraphicsLayoutItem::sizeHint()}{sizeHint()}.
+    In addition to that it inherits QGraphicsItem, so it must reimplement
+    {QGraphicsItem::boundingRect()}{boundingRect()} and
+    {QGraphicsItem::paint()}{paint()}.
 
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.h 0
 
-    The \c LayoutItem class also has a private instance of QPixmap, \c pix.
-
-    \note We subclass QGraphicsWidget so that \c LayoutItem objects can
-    be automatically plugged into a layout, as QGraphicsWidget is a
-    specialization of QGraphicsLayoutItem.
+    The \c LayoutItem class also has a private instance of QPixmap, \c m_pix.
 
     \section1 LayoutItem Class Implementation
 
-    In \c{LayoutItem}'s constructor, \c pix is instantiated and the
-    \c{QT_original_R.png} image is loaded into it. We set the size of
-    \c LayoutItem to be slightly larger than the size of the pixmap as we
-    require some space around it for borders that we will paint later.
-    Alternatively, you could scale the pixmap to prevent the item from
-    becoming smaller than the pixmap.
+    In \c{LayoutItem}'s constructor, \c m_pix is instantiated and the
+    \c{block.png} image is loaded into it.
 
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 0
 
@@ -148,4 +147,32 @@
 
     \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 2
 
+    The reimplementation of {QGraphicsItem::boundingRect()}{boundingRect()}
+    will set the top left corner at (0,0), and the size of it will be
+    the size of the layout items
+    {QGraphicsLayoutItem::geometry()}{geometry()}. This is the area that
+    we paint within.
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 3
+
+
+    The reimplementation of {QGraphicsLayoutItem::setGeometry()}{setGeometry()}
+    simply calls its baseclass implementation. However, since this will change
+    the boundingRect we must also call
+    {QGraphicsItem::prepareGeometryChange()}{prepareGeometryChange()}.
+    Finally, we move the item according to \c geom.topLeft().
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 4
+
+
+    Since we don't want the size of the item to be smaller than the pixmap, we
+    must make sure that we return a size hint that is larger than \c m_pix.
+    We also add some extra space around for borders that we will paint later.
+    Alternatively, you could scale the pixmap to prevent the item from
+    becoming smaller than the pixmap.
+    The preferred size is the same as the minimum size hint, while we set
+    maximum to be a large value
+
+    \snippet examples/graphicsview/basicgraphicslayouts/layoutitem.cpp 5
+
 */
\ No newline at end of file
diff --git a/examples/graphicsview/basicgraphicslayouts/layoutitem.cpp b/examples/graphicsview/basicgraphicslayouts/layoutitem.cpp
index 8216b6e..7311b65 100644
--- a/examples/graphicsview/basicgraphicslayouts/layoutitem.cpp
+++ b/examples/graphicsview/basicgraphicslayouts/layoutitem.cpp
@@ -43,19 +43,18 @@
 
 //! [0]
 LayoutItem::LayoutItem(QGraphicsItem *parent/* = 0*/)
-    : QGraphicsWidget(parent)
+    : QGraphicsLayoutItem(), QGraphicsItem(parent)
 {
-    pix = new QPixmap(QLatin1String(":/images/block.png"));
-    // Do not allow a size smaller than the pixmap with two frames around it.
-    setMinimumSize(pix->size() + QSize(12, 12));
+    m_pix = new QPixmap(QLatin1String(":/images/block.png"));
+    setGraphicsItem(this);
 }
 //! [0]
 
 LayoutItem::~LayoutItem()
 {
-    delete pix;
+    delete m_pix;
 }
- 
+
 //! [1]
 void LayoutItem::paint(QPainter *painter,
     const QStyleOptionGraphicsItem *option, QWidget *widget /*= 0*/)
@@ -64,8 +63,8 @@ void LayoutItem::paint(QPainter *painter,
     Q_UNUSED(option);
 
     QRectF frame(QPointF(0,0), geometry().size());
-    qreal w = pix->width();
-    qreal h = pix->height();
+    qreal w = m_pix->width();
+    qreal h = m_pix->height();
     QGradientStops stops;
 //! [1]
 
@@ -94,6 +93,39 @@ void LayoutItem::paint(QPainter *painter,
     gradient.setStops(stops);
     painter->setBrush(QBrush(gradient));
     painter->drawRoundedRect(innerFrame, 10.0, 10.0);
-    painter->drawPixmap(pixpos, *pix);
+    painter->drawPixmap(pixpos, *m_pix);
 }
 //! [2]
+
+//! [3]
+QRectF LayoutItem::boundingRect() const
+{
+    return QRectF(QPointF(0,0), geometry().size());
+}
+//! [3]
+
+//! [4]
+void LayoutItem::setGeometry(const QRectF &geom)
+{
+    prepareGeometryChange();
+    QGraphicsLayoutItem::setGeometry(geom);
+    setPos(geom.topLeft());
+}
+//! [4]
+
+//! [5]
+QSizeF LayoutItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const
+{
+    switch (which) {
+    case Qt::MinimumSize:
+    case Qt::PreferredSize:
+        // Do not allow a size smaller than the pixmap with two frames around it.
+        return m_pix->size() + QSize(12, 12);
+    case Qt::MaximumSize:
+        return QSizeF(1000,1000);
+    default:
+        break;
+    }
+    return constraint;
+}
+//! [5]
diff --git a/examples/graphicsview/basicgraphicslayouts/layoutitem.h b/examples/graphicsview/basicgraphicslayouts/layoutitem.h
index cbda636..8ec9038 100644
--- a/examples/graphicsview/basicgraphicslayouts/layoutitem.h
+++ b/examples/graphicsview/basicgraphicslayouts/layoutitem.h
@@ -44,18 +44,22 @@
 #include <QtGui>
 
 //! [0]
-class LayoutItem : public QGraphicsWidget
+class LayoutItem : public QGraphicsLayoutItem, public QGraphicsItem
 {
-    Q_OBJECT
-
 public:
     LayoutItem(QGraphicsItem *parent = 0);
     ~LayoutItem();
+    // Inherited from QGraphicsLayoutItem
+    void setGeometry(const QRectF &geom);
+    QSizeF sizeHint(Qt::SizeHint which, const QSizeF &constraint = QSizeF()) const;
+
+    // Inherited from QGraphicsItem
+    QRectF boundingRect() const;
     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option,
         QWidget *widget = 0);
 
 private:
-    QPixmap *pix;
+    QPixmap *m_pix;
 };
 //! [0]