Flow Layout Example | Qt Widgets 5.13.0

Qt 5.13 | Qt Widgets | Flow Layout Example

Qt 5.13.0 Reference Documentation

# Flow Layout Example

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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);
          return nullptr;
      }

      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;
          for (const QLayoutItem *item : qAsConst(itemList))
              size = size.expandedTo(item->minimumSize());

          const QMargins margins = contentsMargins();
          size += QSize(margins.left() + margins.right(), margins.top() + margins.bottom());
          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;

          for (QLayoutItem *item : qAsConst(itemList)) {
              const 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, nullptr, pw);
          } else {
              return static_cast<QLayout *>(parent)->spacing();
          }
      }