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# flowlayout.cpp Example File
graphicsview/flowlayout/flowlayout.cpp

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     #include "flowlayout.h"
     #include <QtGui/qwidget.h>
     #include <QtCore/qmath.h>

     FlowLayout::FlowLayout()
     {
         m_spacing[0] = 6;
         m_spacing[1] = 6;
         QSizePolicy sp = sizePolicy();
         sp.setHeightForWidth(true);
         setSizePolicy(sp);
     }

     void FlowLayout::insertItem(int index, QGraphicsLayoutItem *item)
     {
         item->setParentLayoutItem(this);
         if (uint(index) > uint(m_items.count()))
             index = m_items.count();
         m_items.insert(index, item);
         invalidate();
     }

     int FlowLayout::count() const
     {
         return m_items.count();
     }

     QGraphicsLayoutItem *FlowLayout::itemAt(int index) const
     {
         return m_items.value(index);
     }

     void FlowLayout::removeAt(int index)
     {
         m_items.removeAt(index);
         invalidate();
     }

     qreal FlowLayout::spacing(Qt::Orientation o) const
     {
         return m_spacing[int(o) - 1];
     }

     void FlowLayout::setSpacing(Qt::Orientations o, qreal spacing)
     {
         if (o & Qt::Horizontal)
             m_spacing[0] = spacing;
         if (o & Qt::Vertical)
             m_spacing[1] = spacing;
     }

     void FlowLayout::setGeometry(const QRectF &geom)
     {
         QGraphicsLayout::setGeometry(geom);
         doLayout(geom, true);
     }

     qreal FlowLayout::doLayout(const QRectF &geom, bool applyNewGeometry) const
     {
         qreal left, top, right, bottom;
         getContentsMargins(&left, &top, &right, &bottom);
         const qreal maxw = geom.width() - left - right;

         qreal x = 0;
         qreal y = 0;
         qreal maxRowHeight = 0;
         QSizeF pref;
         for (int i = 0; i < m_items.count(); ++i) {
             QGraphicsLayoutItem *item = m_items.at(i);
             pref = item->effectiveSizeHint(Qt::PreferredSize);
             maxRowHeight = qMax(maxRowHeight, pref.height());

             qreal next_x;
             next_x = x + pref.width();
             if (next_x > maxw) {
                 if (x == 0) {
                     pref.setWidth(maxw);
                 } else {
                     x = 0;
                     next_x = pref.width();
                 }
                 y += maxRowHeight + spacing(Qt::Vertical);
                 maxRowHeight = 0;
             }

             if (applyNewGeometry)
                 item->setGeometry(QRectF(QPointF(left + x, top + y), pref));
             x = next_x + spacing(Qt::Horizontal);
         }
         maxRowHeight = qMax(maxRowHeight, pref.height());
         return top + y + maxRowHeight + bottom;
     }

     QSizeF FlowLayout::minSize(const QSizeF &constraint) const
     {
         QSizeF size(0, 0);
         qreal left, top, right, bottom;
         getContentsMargins(&left, &top, &right, &bottom);
         if (constraint.width() >= 0) {   // height for width
             const qreal height = doLayout(QRectF(QPointF(0,0), constraint), false);
             size = QSizeF(constraint.width(), height);
         } else if (constraint.height() >= 0) {  // width for height?
             // not supported
         } else {
             QGraphicsLayoutItem *item;
             foreach (item, m_items)
                 size = size.expandedTo(item->effectiveSizeHint(Qt::MinimumSize));
             size += QSize(left + right, top + bottom);
         }
         return size;
     }

     QSizeF FlowLayout::prefSize() const
     {
         qreal left, right;
         getContentsMargins(&left, 0, &right, 0);

         QGraphicsLayoutItem *item;
         qreal maxh = 0;
         qreal totalWidth = 0;
         foreach (item, m_items) {
             if (totalWidth > 0)
                 totalWidth += spacing(Qt::Horizontal);
             QSizeF pref = item->effectiveSizeHint(Qt::PreferredSize);
             totalWidth += pref.width();
             maxh = qMax(maxh, pref.height());
         }
         maxh += spacing(Qt::Vertical);

         const qreal goldenAspectRatio = 1.61803399;
         qreal w = qSqrt(totalWidth * maxh * goldenAspectRatio) + left + right;

         return minSize(QSizeF(w, -1));
     }

     QSizeF FlowLayout::maxSize() const
     {
         QGraphicsLayoutItem *item;
         qreal totalWidth = 0;
         qreal totalHeight = 0;
         foreach (item, m_items) {
             if (totalWidth > 0)
                 totalWidth += spacing(Qt::Horizontal);
             if (totalHeight > 0)
                 totalHeight += spacing(Qt::Vertical);
             QSizeF pref = item->effectiveSizeHint(Qt::PreferredSize);
             totalWidth += pref.width();
             totalHeight += pref.height();
         }

         qreal left, top, right, bottom;
         getContentsMargins(&left, &top, &right, &bottom);
         return QSizeF(left + totalWidth + right, top + totalHeight + bottom);
     }

     QSizeF FlowLayout::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const
     {
         QSizeF sh = constraint;
         switch (which) {
         case Qt::PreferredSize:
             sh = prefSize();
             break;
         case Qt::MinimumSize:
             sh = minSize(constraint);
             break;
         case Qt::MaximumSize:
             sh = maxSize();
             break;
         default:
             break;
         }
         return sh;
     }