简述

通过上一节内容，我们实现了窗体的缩放，功能很不错，但是很遗憾-不支持跨平台！如果对于多平台来说，这是一个硬伤，所以，我们急需要一个能够支持跨平台的实现方案。

在网上看到过很多不同的实现方式，多多少少会存在一些问题-要么融合度太高、要么不能很好地进行移动、缩放。基于前人的分享与总结，最后，我花了很长时间来完善。独乐乐不如众乐乐，既然纯开源-那就全部分享出来。

效果

窗体缩放

实现

frameless_helper.h

#ifndef FRAMELESS_HELPER_H
#define FRAMELESS_HELPER_H

#include <QObject>

class QWidget;
class FramelessHelperPrivate;

class FramelessHelper : public QObject
{
    Q_OBJECT

public:
    explicit FramelessHelper(QObject *parent = 0);
    ~FramelessHelper();
    // 激活窗体
    void activateOn(QWidget *topLevelWidget);
    // 移除窗体
    void removeFrom(QWidget *topLevelWidget);
    // 设置窗体移动
    void setWidgetMovable(bool movable);
    // 设置窗体缩放
    void setWidgetResizable(bool resizable);
    // 设置橡皮筋移动
    void setRubberBandOnMove(bool movable);
    // 设置橡皮筋缩放
    void setRubberBandOnResize(bool resizable);
    // 设置边框的宽度
    void setBorderWidth(uint width);
    // 设置标题栏高度
    void setTitleHeight(uint height);
    bool widgetResizable();
    bool widgetMovable();
    bool rubberBandOnMove();
    bool rubberBandOnResisze();
    uint borderWidth();
    uint titleHeight();

protected:
    // 事件过滤，进行移动、缩放等
    virtual bool eventFilter(QObject *obj, QEvent *event);

private:
    FramelessHelperPrivate *d;
};

#endif //FRAMELESS_HELPER_H

frameless_helper.cpp

FramelessHelperPrivate类

/*****
 * FramelessHelperPrivate
 * 存储界面对应的数据集合，以及是否可移动、可缩放属性
*****/
class FramelessHelperPrivate
{
public:
    QHash<QWidget*, WidgetData*> m_widgetDataHash;
    bool m_bWidgetMovable        : true;
    bool m_bWidgetResizable      : true;
    bool m_bRubberBandOnResize   : true;
    bool m_bRubberBandOnMove     : true;
};

CursorPosCalculator类

/*****
 * CursorPosCalculator
 * 计算鼠标是否位于左、上、右、下、左上角、左下角、右上角、右下角
*****/
class CursorPosCalculator
{
public:
    explicit CursorPosCalculator();
    void reset();
    void recalculate(const QPoint &globalMousePos, const QRect &frameRect);

public:
    bool m_bOnEdges              : true;
    bool m_bOnLeftEdge           : true;
    bool m_bOnRightEdge          : true;
    bool m_bOnTopEdge            : true;
    bool m_bOnBottomEdge         : true;
    bool m_bOnTopLeftEdge        : true;
    bool m_bOnBottomLeftEdge     : true;
    bool m_bOnTopRightEdge       : true;
    bool m_bOnBottomRightEdge    : true;

    static int m_nBorderWidth;
    static int m_nTitleHeight;
};

int CursorPosCalculator::m_nBorderWidth = 5;
int CursorPosCalculator::m_nTitleHeight = 30;

/***** CursorPosCalculator *****/
CursorPosCalculator::CursorPosCalculator()
{
    reset();
}

void CursorPosCalculator::reset()
{
    m_bOnEdges = false;
    m_bOnLeftEdge = false;
    m_bOnRightEdge = false;
    m_bOnTopEdge = false;
    m_bOnBottomEdge = false;
    m_bOnTopLeftEdge = false;
    m_bOnBottomLeftEdge = false;
    m_bOnTopRightEdge  = false;
    m_bOnBottomRightEdge = false;
}

void CursorPosCalculator::recalculate(const QPoint &gMousePos, const QRect &frameRect)
{
    int globalMouseX = gMousePos.x();
    int globalMouseY = gMousePos.y();

    int frameX = frameRect.x();
    int frameY = frameRect.y();

    int frameWidth = frameRect.width();
    int frameHeight = frameRect.height();

    m_bOnLeftEdge = (globalMouseX >= frameX &&
                  globalMouseX <= frameX + m_nBorderWidth );


    m_bOnRightEdge = (globalMouseX >= frameX + frameWidth - m_nBorderWidth &&
                   globalMouseX <= frameX + frameWidth);

    m_bOnTopEdge = (globalMouseY >= frameY &&
                 globalMouseY <= frameY + m_nBorderWidth );

    m_bOnBottomEdge = (globalMouseY >= frameY + frameHeight - m_nBorderWidth &&
                    globalMouseY <= frameY + frameHeight);

    m_bOnTopLeftEdge = m_bOnTopEdge && m_bOnLeftEdge;
    m_bOnBottomLeftEdge = m_bOnBottomEdge && m_bOnLeftEdge;
    m_bOnTopRightEdge = m_bOnTopEdge && m_bOnRightEdge;
    m_bOnBottomRightEdge = m_bOnBottomEdge && m_bOnRightEdge;

    m_bOnEdges = m_bOnLeftEdge || m_bOnRightEdge || m_bOnTopEdge || m_bOnBottomEdge;
}

WidgetData类

/*****
 * WidgetData
 * 更新鼠标样式、移动窗体、缩放窗体
*****/
class WidgetData
{
public:
    explicit WidgetData(FramelessHelperPrivate *d, QWidget *pTopLevelWidget);
    ~WidgetData();
    QWidget* widget();
    // 处理鼠标事件-划过、按下、释放、移动
    void handleWidgetEvent(QEvent *event);
    // 更新橡皮筋状态
    void updateRubberBandStatus();

private:
    // 更新鼠标样式
    void updateCursorShape(const QPoint &gMousePos);
    // 重置窗体大小
    void resizeWidget(const QPoint &gMousePos);
    // 移动窗体
    void moveWidget(const QPoint &gMousePos);
    // 处理鼠标按下
    void handleMousePressEvent(QMouseEvent *event);
    // 处理鼠标释放
    void handleMouseReleaseEvent(QMouseEvent *event);
    // 处理鼠标移动
    void handleMouseMoveEvent(QMouseEvent *event);
    // 处理鼠标离开
    void handleLeaveEvent(QEvent *event);
    // 处理鼠标进入
    void handleHoverMoveEvent(QHoverEvent *event);

private:
    FramelessHelperPrivate *d;
    QRubberBand *m_pRubberBand;
    QWidget *m_pWidget;
    QPoint m_ptDragPos;
    CursorPosCalculator m_pressedMousePos;
    CursorPosCalculator m_moveMousePos;
    bool m_bLeftButtonPressed;
    bool m_bCursorShapeChanged;
    bool m_bLeftButtonTitlePressed;
    Qt::WindowFlags m_windowFlags;
};

/***** WidgetData *****/
WidgetData::WidgetData(FramelessHelperPrivate *_d, QWidget *pTopLevelWidget)
{
    d = _d;
    m_pWidget = pTopLevelWidget;
    m_bLeftButtonPressed = false;
    m_bCursorShapeChanged = false;
    m_bLeftButtonTitlePressed = false;
    m_pRubberBand = NULL;

    m_windowFlags = m_pWidget->windowFlags();
    m_pWidget->setMouseTracking(true);
    m_pWidget->setAttribute(Qt::WA_Hover, true);

    updateRubberBandStatus();
}

WidgetData::~WidgetData()
{
    m_pWidget->setMouseTracking(false);
    m_pWidget->setWindowFlags(m_windowFlags);
    m_pWidget->setAttribute(Qt::WA_Hover, false);

    delete m_pRubberBand;
    m_pRubberBand = NULL;
}

QWidget* WidgetData::widget()
{
    return m_pWidget;
}

void WidgetData::handleWidgetEvent(QEvent *event)
{
    switch (event->type())
    {
    default:
        break;
    case QEvent::MouseButtonPress:
        handleMousePressEvent(static_cast<QMouseEvent*>(event));
        break;
    case QEvent::MouseButtonRelease:
        handleMouseReleaseEvent(static_cast<QMouseEvent*>(event));
        break;
    case QEvent::MouseMove:
        handleMouseMoveEvent(static_cast<QMouseEvent*>(event));
        break;
    case QEvent::Leave:
        handleLeaveEvent(static_cast<QMouseEvent*>(event));
        break;
    case QEvent::HoverMove:
        handleHoverMoveEvent(static_cast<QHoverEvent*>(event));
        break;
    }
}

void WidgetData::updateRubberBandStatus()
{
    if (d->m_bRubberBandOnMove || d->m_bRubberBandOnResize)
    {
        if (NULL == m_pRubberBand)
            m_pRubberBand = new QRubberBand(QRubberBand::Rectangle);
    }
    else
    {
        delete m_pRubberBand;
        m_pRubberBand = NULL;
    }
}

void WidgetData::updateCursorShape(const QPoint &gMousePos)
{
    if (m_pWidget->isFullScreen() || m_pWidget->isMaximized())
    {
        if (m_bCursorShapeChanged)
        {
            m_pWidget->unsetCursor();
        }
        return;
    }

    m_moveMousePos.recalculate(gMousePos, m_pWidget->frameGeometry());

    if(m_moveMousePos.m_bOnTopLeftEdge || m_moveMousePos.m_bOnBottomRightEdge)
    {
        m_pWidget->setCursor( Qt::SizeFDiagCursor );
        m_bCursorShapeChanged = true;
    }
    else if(m_moveMousePos.m_bOnTopRightEdge || m_moveMousePos.m_bOnBottomLeftEdge)
    {
        m_pWidget->setCursor( Qt::SizeBDiagCursor );
        m_bCursorShapeChanged = true;
    }
    else if(m_moveMousePos.m_bOnLeftEdge || m_moveMousePos.m_bOnRightEdge)
    {
        m_pWidget->setCursor( Qt::SizeHorCursor );
        m_bCursorShapeChanged = true;
    }
    else if(m_moveMousePos.m_bOnTopEdge || m_moveMousePos.m_bOnBottomEdge)
    {
        m_pWidget->setCursor( Qt::SizeVerCursor );
        m_bCursorShapeChanged = true;
    }
    else
    {
        if (m_bCursorShapeChanged)
        {
            m_pWidget->unsetCursor();
            m_bCursorShapeChanged = false;
        }
    }
}

void WidgetData::resizeWidget(const QPoint &gMousePos)
{
    QRect origRect;

    if (d->m_bRubberBandOnResize)
        origRect = m_pRubberBand->frameGeometry();
    else
        origRect = m_pWidget->frameGeometry();

    int left = origRect.left();
    int top = origRect.top();
    int right = origRect.right();
    int bottom = origRect.bottom();
    origRect.getCoords(&left, &top, &right, &bottom);

    int minWidth = m_pWidget->minimumWidth();
    int minHeight = m_pWidget->minimumHeight();

    if (m_pressedMousePos.m_bOnTopLeftEdge)
    {
        left = gMousePos.x();
        top = gMousePos.y();
    }
    else if (m_pressedMousePos.m_bOnBottomLeftEdge)
    {
        left = gMousePos.x();
        bottom = gMousePos.y();
    }
    else if (m_pressedMousePos.m_bOnTopRightEdge)
    {
        right = gMousePos.x();
        top = gMousePos.y();
    }
    else if (m_pressedMousePos.m_bOnBottomRightEdge)
    {
        right = gMousePos.x();
        bottom = gMousePos.y();
    }
    else if (m_pressedMousePos.m_bOnLeftEdge)
    {
        left = gMousePos.x();
    }
    else if (m_pressedMousePos.m_bOnRightEdge)
    {
        right = gMousePos.x();
    }
    else if (m_pressedMousePos.m_bOnTopEdge)
    {
        top = gMousePos.y();
    }
    else if (m_pressedMousePos.m_bOnBottomEdge)
    {
        bottom = gMousePos.y();
    }

    QRect newRect(QPoint(left, top), QPoint(right, bottom));

    if (newRect.isValid())
    {
        if (minWidth > newRect.width())
        {
            if (left != origRect.left())
                newRect.setLeft(origRect.left());
            else
                newRect.setRight(origRect.right());
        }
        if (minHeight > newRect.height())
        {
            if (top != origRect.top())
                newRect.setTop(origRect.top());
            else
                newRect.setBottom(origRect.bottom());
        }

        if (d->m_bRubberBandOnResize)
        {
            m_pRubberBand->setGeometry(newRect);
        }
        else
        {
            m_pWidget->setGeometry(newRect);
        }
    }
}

void WidgetData::moveWidget(const QPoint& gMousePos)
{
    if (d->m_bRubberBandOnMove)
    {
        m_pRubberBand->move(gMousePos - m_ptDragPos);
    }
    else
    {
        m_pWidget->move(gMousePos - m_ptDragPos);
    }
}

void WidgetData::handleMousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton)
    {
        m_bLeftButtonPressed = true;
        m_bLeftButtonTitlePressed = event->pos().y() < m_moveMousePos.m_nTitleHeight;

        QRect frameRect = m_pWidget->frameGeometry();
        m_pressedMousePos.recalculate(event->globalPos(), frameRect);

        m_ptDragPos = event->globalPos() - frameRect.topLeft();

        if (m_pressedMousePos.m_bOnEdges)
        {
            if (d->m_bRubberBandOnResize)
            {
                m_pRubberBand->setGeometry(frameRect);
                m_pRubberBand->show();
            }
        }
        else if (d->m_bRubberBandOnMove)
        {
            m_pRubberBand->setGeometry(frameRect);
            m_pRubberBand->show();
        }
    }
}

void WidgetData::handleMouseReleaseEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton)
    {
        m_bLeftButtonPressed = false;
        m_bLeftButtonTitlePressed = false;
        m_pressedMousePos.reset();
        if (m_pRubberBand && m_pRubberBand->isVisible())
        {
            m_pRubberBand->hide();
            m_pWidget->setGeometry(m_pRubberBand->geometry());
        }
    }
}

void WidgetData::handleMouseMoveEvent(QMouseEvent *event)
{
    if (m_bLeftButtonPressed)
    {
        if (d->m_bWidgetResizable && m_pressedMousePos.m_bOnEdges)
        {
            resizeWidget(event->globalPos());
        }
        else if (d->m_bWidgetMovable && m_bLeftButtonTitlePressed)
        {
            moveWidget(event->globalPos());
        }
    }
    else if (d->m_bWidgetResizable)
    {
        updateCursorShape(event->globalPos());
    }
}

void WidgetData::handleLeaveEvent(QEvent *event)
{
    Q_UNUSED(event)
    if (!m_bLeftButtonPressed)
    {
        m_pWidget->unsetCursor();
    }
}

void WidgetData::handleHoverMoveEvent(QHoverEvent *event)
{
    if (d->m_bWidgetResizable)
    {
        updateCursorShape(m_pWidget->mapToGlobal(event->pos()));
    }
}

FramelessHelper类

#include <QRect>
#include <QRubberBand>
#include <QMouseEvent>
#include <QHoverEvent>
#include <QApplication>
#include "frameless_helper.h"

class WidgetData;

/*****FramelessHelper*****/
FramelessHelper::FramelessHelper(QObject *parent)
    : QObject(parent),
      d(new FramelessHelperPrivate())
{
    d->m_bWidgetMovable = true;
    d->m_bWidgetResizable = true;
    d->m_bRubberBandOnResize = false;
    d->m_bRubberBandOnMove = false;
}

FramelessHelper::~FramelessHelper()
{
    QList<QWidget*> keys = d->m_widgetDataHash.keys();
    int size = keys.size();
    for (int i = 0; i < size; ++i)
    {
        delete d->m_widgetDataHash.take(keys[i]);
    }

    delete d;
}

bool FramelessHelper::eventFilter(QObject *obj, QEvent *event)
{
    switch (event->type())
    {
    case QEvent::MouseMove:
    case QEvent::HoverMove:
    case QEvent::MouseButtonPress:
    case QEvent::MouseButtonRelease:
    case QEvent::Leave:
    {
        WidgetData *data = d->m_widgetDataHash.value(static_cast<QWidget*>(obj));
        if (data)
        {
            data->handleWidgetEvent(event);
            return true;
        }
    }
    }
    return QObject::eventFilter(obj, event);
}

void FramelessHelper::activateOn(QWidget *topLevelWidget)
{
    if (!d->m_widgetDataHash.contains(topLevelWidget))
    {
        WidgetData *data = new WidgetData(d, topLevelWidget);
        d->m_widgetDataHash.insert(topLevelWidget, data);

        topLevelWidget->installEventFilter(this);
    }
}

void FramelessHelper::removeFrom(QWidget *topLevelWidget)
{
    WidgetData *data = d->m_widgetDataHash.take(topLevelWidget);
    if (data)
    {
        topLevelWidget->removeEventFilter(this);
        delete data;
    }
}

void FramelessHelper::setRubberBandOnMove(bool movable)
{
    d->m_bRubberBandOnMove = movable;
    QList<WidgetData*> list = d->m_widgetDataHash.values();
    foreach (WidgetData *data, list)
    {
        data->updateRubberBandStatus();
    }
}

void FramelessHelper::setWidgetMovable(bool movable)
{
    d->m_bWidgetMovable = movable;
}

void FramelessHelper::setWidgetResizable(bool resizable)
{
    d->m_bWidgetResizable = resizable;
}

void FramelessHelper::setRubberBandOnResize(bool resizable)
{
    d->m_bRubberBandOnResize = resizable;
    QList<WidgetData*> list = d->m_widgetDataHash.values();
    foreach (WidgetData *data, list)
    {
        data->updateRubberBandStatus();
    }
}

void FramelessHelper::setBorderWidth(uint width)
{
    if (width > 0)
    {
        CursorPosCalculator::m_nBorderWidth = width;
    }
}

void FramelessHelper::setTitleHeight(uint height)
{
    if (height > 0)
    {
        CursorPosCalculator::m_nTitleHeight = height;
    }
}

bool FramelessHelper::widgetMovable()
{
    return d->m_bWidgetMovable;
}

bool FramelessHelper::widgetResizable()
{
    return d->m_bWidgetResizable;
}

bool FramelessHelper::rubberBandOnMove()
{
    return d->m_bRubberBandOnMove;
}

bool FramelessHelper::rubberBandOnResisze()
{
    return d->m_bRubberBandOnResize;
}

uint FramelessHelper::borderWidth()
{
    return CursorPosCalculator::m_nBorderWidth;
}

uint FramelessHelper::titleHeight()
{
    return CursorPosCalculator::m_nTitleHeight;
}

接口说明

• FramelessHelperPrivate

  存储界面对应的数据集合，以及是否可移动、可缩放属性

• CursorPosCalculator

  计算鼠标是否位于左、上、右、下、左上角、左下角、右上角、右下角

• WidgetData

  更新鼠标样式、移动窗体、缩放窗体

• FramelessHelper

  激活窗体、移除窗体、设置窗体移动、窗体缩放、橡皮筋移动、橡皮筋缩放、边框的宽度、标题栏高度等

代码很多，我就不详细解答了，里面主要的接口我都添加了注释。其它接口的命名也是比较规范的-见名知义。

使用方式

这里的this指的是要处理的窗体。

FramelessHelper *pHelper = new FramelessHelper(this);
pHelper->activateOn(this);  //激活当前窗体
pHelper->setTitleHeight(m_pTitleBar->height());  //设置窗体的标题栏高度
pHelper->setWidgetMovable(true);  //设置窗体可移动
pHelper->setWidgetResizable(true);  //设置窗体可缩放
pHelper->setRubberBandOnMove(true);  //设置橡皮筋效果-可移动
pHelper->setRubberBandOnResize(true);  //设置橡皮筋效果-可缩放

平台支持

因为使用的是纯Qt实现，所以支持跨平台！Win7、Win10、Redhat7.0已测试通过，其它平台尚未测试，有需要的童鞋可自行实验。