flowlayout.cpp Example File

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  #include <QtWidgets>

  #include "flowlayout.h"
  FlowLayout::FlowLayout(QWidget *parent, int margin, int hSpacing, int vSpacing)
      : QLayout(parent), m_hSpace(hSpacing), m_vSpace(vSpacing)
  {
      setContentsMargins(margin, margin, margin, margin);
  }

  FlowLayout::FlowLayout(int margin, int hSpacing, int vSpacing)
      : m_hSpace(hSpacing), m_vSpace(vSpacing)
  {
      setContentsMargins(margin, margin, margin, margin);
  }

  FlowLayout::~FlowLayout()
  {
      QLayoutItem *item;
      while ((item = takeAt(0)))
          delete item;
  }

  void FlowLayout::addItem(QLayoutItem *item)
  {
      itemList.append(item);
  }

  int FlowLayout::horizontalSpacing() const
  {
      if (m_hSpace >= 0) {
          return m_hSpace;
      } else {
          return smartSpacing(QStyle::PM_LayoutHorizontalSpacing);
      }
  }

  int FlowLayout::verticalSpacing() const
  {
      if (m_vSpace >= 0) {
          return m_vSpace;
      } else {
          return smartSpacing(QStyle::PM_LayoutVerticalSpacing);
      }
  }

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

  QLayoutItem *FlowLayout::itemAt(int index) const
  {
      return itemList.value(index);
  }

  QLayoutItem *FlowLayout::takeAt(int index)
  {
      if (index >= 0 && index < itemList.size())
          return itemList.takeAt(index);
      else
          return 0;
  }

  Qt::Orientations FlowLayout::expandingDirections() const
  {
      return 0;
  }

  bool FlowLayout::hasHeightForWidth() const
  {
      return true;
  }

  int FlowLayout::heightForWidth(int width) const
  {
      int height = doLayout(QRect(0, 0, width, 0), true);
      return height;
  }

  void FlowLayout::setGeometry(const QRect &rect)
  {
      QLayout::setGeometry(rect);
      doLayout(rect, false);
  }

  QSize FlowLayout::sizeHint() const
  {
      return minimumSize();
  }

  QSize FlowLayout::minimumSize() const
  {
      QSize size;
      QLayoutItem *item;
      foreach (item, itemList)
          size = size.expandedTo(item->minimumSize());

      size += QSize(2*margin(), 2*margin());
      return size;
  }

  int FlowLayout::doLayout(const QRect &rect, bool testOnly) const
  {
      int left, top, right, bottom;
      getContentsMargins(&left, &top, &right, &bottom);
      QRect effectiveRect = rect.adjusted(+left, +top, -right, -bottom);
      int x = effectiveRect.x();
      int y = effectiveRect.y();
      int lineHeight = 0;

      QLayoutItem *item;
      foreach (item, itemList) {
          QWidget *wid = item->widget();
          int spaceX = horizontalSpacing();
          if (spaceX == -1)
              spaceX = wid->style()->layoutSpacing(
                  QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
          int spaceY = verticalSpacing();
          if (spaceY == -1)
              spaceY = wid->style()->layoutSpacing(
                  QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
          int nextX = x + item->sizeHint().width() + spaceX;
          if (nextX - spaceX > effectiveRect.right() && lineHeight > 0) {
              x = effectiveRect.x();
              y = y + lineHeight + spaceY;
              nextX = x + item->sizeHint().width() + spaceX;
              lineHeight = 0;
          }

          if (!testOnly)
              item->setGeometry(QRect(QPoint(x, y), item->sizeHint()));

          x = nextX;
          lineHeight = qMax(lineHeight, item->sizeHint().height());
      }
      return y + lineHeight - rect.y() + bottom;
  }
  int FlowLayout::smartSpacing(QStyle::PixelMetric pm) const
  {
      QObject *parent = this->parent();
      if (!parent) {
          return -1;
      } else if (parent->isWidgetType()) {
          QWidget *pw = static_cast<QWidget *>(parent);
          return pw->style()->pixelMetric(pm, 0, pw);
      } else {
          return static_cast<QLayout *>(parent)->spacing();
      }
  }