- Qt 5.5
- Qt Widgets
- Flow Layout Example
- flowlayout.cpp Example File
- Qt 5.5.1 Reference Documentation

# flowlayout.cpp Example File

layouts/flowlayout/flowlayout.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #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();
        }
    }