Qt 5.11 | Qt Widgets | Graphics View Flow Layout Example | flowlayout.cpp Example File

Qt 5.11.3 Reference Documentation

# flowlayout.cpp Example File

graphicsview/flowlayout/flowlayout.cpp

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      #include "flowlayout.h"

      #include <qmath.h>

      #include <QWidget>

      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;
      }