一、可按比例拖拽窗体大小的无边框窗口

前几天接到一个需求，就是视频广播的窗体画面要可以拖拽，修改成了可以拖拽全屏的窗口之后，又有一个问题：视频画面也被拉伸了。

由于视频画面是有比例的，所以我们最好也能保证窗口画面也保持一定的比例，所以这里我就改了一下之前的无边框窗口方案如下：

优点：改造过的无边框方案，可以让无边框的窗体变换大小的时候保持一定比例，保证窗体中的画面不变形

缺点：1.不够自由，不能自由拖动

2.如果拖动的是左边，因为拖动事件实际上是先变换大小后修改坐标，那么右边就会有明显抖动

3.因为要检测当前的鼠标状态，所以是挺浪费系统资源的，较差的机型上可能会有一些意想不到的问题。

.h文件下：

enum {

    TOPLEFT = 11,

    TOP = 12,

    TOPRIGHT = 13,

    LEFT = 21,

    CENTER = 22,

    RIGHT = 23,

    BUTTOMLEFT = 31,

    BUTTOM = 32,

    BUTTOMRIGHT = 33

  };

#define FRAMESHAPE 15

const double default_rate = 4.00 / 3.00; //画面比例参数

public:

  int CalCursorCol(QPoint pt);    //计算鼠标X的位置

  int CalCursorPos(QPoint pt, int colPos);    //计算鼠标的位置

  void setCursorShape(int CalPos);    //设置鼠标对应位置的形状

protected:

  void mouseMoveEvent(QMouseEvent *event);

  void mousePressEvent(QMouseEvent *event);

  void mouseReleaseEvent(QMouseEvent *event);

private:

  int     m_iCalCursorPos;

  bool    m_bLeftPress;

  QRect   m_rtPreGeometry;

  QPoint  m_ptViewMousePos;

.cpp文件：

//注，要在构造函数写上setMouseTracking(true)，要从表面的控件->控件的父控件 ->...->this都要写上

void Mengban::mouseMoveEvent(QMouseEvent * event)

{

  //窗体不是最大的话就改变鼠标的形状

  if (Qt::WindowMaximized != windowState())

  {

    setCursorShape(CalCursorPos(event->pos(), CalCursorCol(event->pos())));

  }

  //获取当前的点，这个点是全局的

  QPoint ptCurrentPos = QCursor::pos();

  //计算出移动的位置，当前点 - 鼠标左键按下的点

  QPoint ptMoveSize = ptCurrentPos - m_ptViewMousePos;

  QRect rtTempGeometry = m_rtPreGeometry;

  if (m_bLeftPress)

  {

    switch (m_iCalCursorPos)

    {

    //case TOPLEFT:

    //	rtTempGeometry.setTopLeft(m_rtPreGeometry.topLeft() + ptMoveSize);

    //	break;

    case TOP:

      rtTempGeometry.setTop(m_rtPreGeometry.top() + ptMoveSize.y());

      rtTempGeometry.setRight(this->x() + this->height() * default_rate);

      break;

    //case TOPRIGHT:

    //	rtTempGeometry.setTopRight(m_rtPreGeometry.topRight() + ptMoveSize);

    //	break;

    case LEFT:

      rtTempGeometry.setLeft(m_rtPreGeometry.left() + ptMoveSize.x());

      rtTempGeometry.setTop(this->y() - this->width() / default_rate + this->height());

      break;

    case RIGHT:

      rtTempGeometry.setRight(m_rtPreGeometry.right() + ptMoveSize.x());

      rtTempGeometry.setBottom(this->y() + this->width() / default_rate);

      break;

    //case BUTTOMLEFT:

    //	rtTempGeometry.setBottomLeft(m_rtPreGeometry.bottomLeft() + ptMoveSize);

    //	break;

    case BUTTOM:

      rtTempGeometry.setBottom(m_rtPreGeometry.bottom() + ptMoveSize.y());

      rtTempGeometry.setLeft(this->x() - this->height() * default_rate+this->width());

      break;

    //case BUTTOMRIGHT:

    //	rtTempGeometry.setBottomRight(m_rtPreGeometry.bottomRight() + ptMoveSize);

    //	break;

    case CENTER:

      rtTempGeometry.moveTo(rtTempGeometry.x() + ptMoveSize.x(), rtTempGeometry.y() + ptMoveSize.y());

    default:

      break;

    }

    //移动窗体，如果比最小窗体大，就移动

    if (rtTempGeometry.width() >= 360 && rtTempGeometry.height() >= 270)

      setGeometry(rtTempGeometry);

  }

}

void Mengban::mousePressEvent(QMouseEvent * event)

{

  m_iCalCursorPos = CalCursorPos(event->pos(), CalCursorCol(event->pos()));

  if (event->button() == Qt::LeftButton /*&& Qt::WindowMaximized != windowState()*/)

  {

    //if (m_iCalCursorPos != CENTER)

    //{

      m_bLeftPress = true;

    //}

  }

  m_rtPreGeometry = geometry();

  m_ptViewMousePos = event->globalPos();

}

void Mengban::mouseReleaseEvent(QMouseEvent * event)

{

  m_bLeftPress = false;

  QApplication::restoreOverrideCursor();

}

int Mengban::CalCursorCol(QPoint pt)

{

  return (pt.x() < FRAMESHAPE ? 1 : ((pt.x() > this->width() - FRAMESHAPE) ? 3 : 2));

}

int Mengban::CalCursorPos(QPoint pt, int colPos)

{

  return ((pt.y() < FRAMESHAPE ? 10 : ((pt.y() > this->height() - FRAMESHAPE) ? 30 : 20)) + colPos);

}

void Mengban::setCursorShape(int CalPos)

{

  Qt::CursorShape cursor;

  switch (CalPos)

  {

  //case TOPLEFT:

  //case BUTTOMRIGHT:

  //	cursor = Qt::SizeFDiagCursor;

  //	break;

  //case TOPRIGHT:

  //case BUTTOMLEFT:

  //	cursor = Qt::SizeBDiagCursor;

  //	break;

  case TOP:

  case BUTTOM:

    cursor = Qt::SizeVerCursor;

    break;

  case LEFT:

  case RIGHT:

    cursor = Qt::SizeHorCursor;

    break;

  default:

    cursor = Qt::ArrowCursor;

    break;

  }

  //qDebug() << "fresh!!";

  //qDebug() << "current cursor" << cursor;

  this->setCursor(cursor);

}

二、可拖拽大小的windows系统方案：

这个方案拖拽窗体大小是通过系统api实现的，具体怎么实现的我也不是很清楚，之后有时间系统看一下windows高级编程再回来聊聊这个技术点。这里只谈优缺点

优点:

1.windows自带api，效率更高，消耗资源更少

2.没有限制，自由拖拽大小（当然了，窗体会受到最大最小窗口大小的限制）

3.代码简单，分析方便

缺点：

1.不可修改，这部分就像个黑盒，native只是告诉你现在修改的时候那个地方是锚点，仅此而已，基本上没法修改，当然了，我什么都不知道 :<

2.因为是windows的api，所以该功能仅限windows平台

  #ifndef MBASEWIDGET_H

  #define MBASEWIDGET_H

  #include <QtWidgets/QWidget>

  #include "windows.h"

  class MBaseWidget : public QWidget

  {

      Q_OBJECT

  public:

      MBaseWidget(QWidget *parent);

      ~MBaseWidget();

      void setMarginWidth(const int &);           //设置鼠标可以在界面边缘多大范围内拖动改变界面大小

      void serResizable(bool);                    //设置是否可以拖动改变大小

  protected:

      bool nativeEvent(const QByteArray & eventType, void * message, long * result);

  private:

      int m_iMarginWidth;

      bool m_bCanResize;

  };

  #endif // MBASEWIDGET_H

  #include "MBaseWidget.h"

  #include "windowsx.h"

  MBaseWidget::MBaseWidget(QWidget *parent)

      : QWidget(parent)

  {

      m_iMarginWidth = 3;

      m_bCanResize = true;

      setWindowFlags(Qt::FramelessWindowHint);

  }

  MBaseWidget::~MBaseWidget()

  {

  }

  void MBaseWidget::setMarginWidth(const int &iWidth)

  {

      m_iMarginWidth = iWidth;

  }

  void MBaseWidget::serResizable(bool bCanResize)

  {

      m_bCanResize = bCanResize;

  }

  bool MBaseWidget::nativeEvent(const QByteArray &eventType, void *message, long *result)

  {

      if (!m_bCanResize)

      {

          return QWidget::nativeEvent(eventType,message,result);

      }

      MSG* msg = (MSG*)message;

      switch(msg->message)

          {

          case WM_NCHITTEST:

              int xPos = GET_X_LPARAM(msg->lParam) - this->frameGeometry().x();

              int yPos = GET_Y_LPARAM(msg->lParam) - this->frameGeometry().y();

              if(xPos < m_iMarginWidth && yPos<m_iMarginWidth)                    //左上角

                  *result = HTTOPLEFT;

              else if(xPos>=width()-m_iMarginWidth&&yPos<m_iMarginWidth)          //右上角

                  *result = HTTOPRIGHT;

              else if(xPos<m_iMarginWidth&&yPos>=height()-m_iMarginWidth)         //左下角

                  *result = HTBOTTOMLEFT;

              else if(xPos>=width()-m_iMarginWidth&&yPos>=height()-m_iMarginWidth)//右下角

                  *result = HTBOTTOMRIGHT;

              else if(xPos < m_iMarginWidth)                                     //左边

                  *result =  HTLEFT;

              else if(xPos>=width()-m_iMarginWidth)                              //右边

                  *result = HTRIGHT;

              else if(yPos<m_iMarginWidth)                                       //上边

                  *result = HTTOP;

              else if(yPos>=height()-m_iMarginWidth)                             //下边

                  *result = HTBOTTOM;

              else              //其他部分不做处理，返回false，留给其他事件处理器处理

                 return false;

              return true;

          }

          return false;         //此处返回false，留给其他事件处理器处理

  }

三、之前用的老的frameless方案：

最开始在网上找的frameless的方案，没什么好说的，详情见一个关于如何将widget变成一个像商用软件那样不可拖拽大小、没有开启、关闭等按钮的固定窗口

讲道理，我发现莫名其妙的其实在这里就包含了前两种写法，但是我莫名其妙地一点都没用过。所以说抄代码也要看源码啊

内容如下：

在程序中定义Padding 为2，并同时定义枚举类型。

    #define PADDING 2

    enum Direction { UP=0, DOWN=1, LEFT, RIGHT, LEFTTOP, LEFTBOTTOM, RIGHTBOTTOM, RIGHTTOP, NONE };

在.cpp中设置当前窗口

    this->setWindowFlags(Qt::FramelessWindowHint);                //取消标题栏

    // 去掉标题栏,去掉工具栏，窗口置顶

    setWindowFlags(Qt::FramelessWindowHint | Qt::Tool | Qt::WindowStaysOnTopHint);

    setWindowOpacity(0.7); //设置窗体透明度

    重写mouseMoveEvent,mousePressEvent,mouseReleaseEvent

MainWindow.h

    public:

        void region(const QPoint &currentGlobalPoint);  //鼠标的位置,改变光标

    protected:

        //鼠标按下移动及释放事件

        void mousePressEvent(QMouseEvent *event);

        void mouseMoveEvent(QMouseEvent *event);

        void mouseReleaseEvent(QMouseEvent *event);

    private:

        QPoint m_movePoint;  //鼠标的位置

        bool isLeftPressDown;  // 判断左键是否按下

        Direction dir;        // 窗口大小改变时，记录改变方向

MainWindow.cpp

void MainWindow::region(const QPoint &currentGlobalPoint)

{

  // 获取窗体在屏幕上的位置区域，topLeft为坐上角点，rightButton为右下角点

  QRect rect = this->rect();

  QPoint topLeft = this->mapToGlobal(rect.topLeft()); //将左上角的(0,0)转化为全局坐标

  QPoint rightButton = this->mapToGlobal(rect.bottomRight());

  int x = currentGlobalPoint.x(); //当前鼠标的坐标

  int y = currentGlobalPoint.y();

  if(((topLeft.x() + PADDING >= x) && (topLeft.x() <= x))

          && ((topLeft.y() + PADDING >= y) && (topLeft.y() <= y)))

  {

      // 左上角

      dir = LEFTTOP;

      this->setCursor(QCursor(Qt::SizeFDiagCursor));  // 设置光标形状

  }else if(((x >= rightButton.x() - PADDING) && (x <= rightButton.x()))

            && ((y >= rightButton.y() - PADDING) && (y <= rightButton.y())))

  {

      // 右下角

      dir = RIGHTBOTTOM;

      this->setCursor(QCursor(Qt::SizeFDiagCursor));

  }else if(((x <= topLeft.x() + PADDING) && (x >= topLeft.x()))

            && ((y >= rightButton.y() - PADDING) && (y <= rightButton.y())))

  {

      //左下角

      dir = LEFTBOTTOM;

      this->setCursor(QCursor(Qt::SizeBDiagCursor));

  }else if(((x <= rightButton.x()) && (x >= rightButton.x() - PADDING))

            && ((y >= topLeft.y()) && (y <= topLeft.y() + PADDING)))

  {

      // 右上角

      dir = RIGHTTOP;

      this->setCursor(QCursor(Qt::SizeBDiagCursor));

  }else if((x <= topLeft.x() + PADDING) && (x >= topLeft.x()))

  {

      // 左边

      dir = LEFT;

      this->setCursor(QCursor(Qt::SizeHorCursor));

  }else if((x <= rightButton.x()) && (x >= rightButton.x() - PADDING))

  {

      // 右边

      dir = RIGHT;

      this->setCursor(QCursor(Qt::SizeHorCursor));

  }else if((y >= topLeft.y()) && (y <= topLeft.y() + PADDING))

  {

      // 上边

      dir = UP;

      this->setCursor(QCursor(Qt::SizeVerCursor));

  }else if((y <= rightButton.y()) && (y >= rightButton.y() - PADDING))

  {

      // 下边

      dir = DOWN;

      this->setCursor(QCursor(Qt::SizeVerCursor));

  }else

  {

      // 默认

      dir = NONE;

      this->setCursor(QCursor(Qt::ArrowCursor));

  }   }

//三个鼠标事件的重写 //鼠标按下事件

  void MainWindow::mousePressEvent(QMouseEvent *event)

  {

  switch(event->button())

  {

      case Qt::LeftButton:

          isLeftPressDown = true;

          if(dir != NONE)

          {

              this->mouseGrabber(); //返回当前抓取鼠标输入的窗口

          }

          else

          {

              m_movePoint = event->globalPos() - this->frameGeometry().topLeft();

              //globalPos()鼠标位置，topLeft()窗口左上角的位置

          }

          break;

      case Qt::RightButton:

          this->setWindowState(Qt::WindowMinimized);

          break;

      default:

          MainWindow::mousePressEvent(event);

  }   }

//鼠标移动事件 void MainWindow::mouseMoveEvent(QMouseEvent *event) { QPoint globalPoint = event->globalPos(); //鼠标全局坐标

  QRect rect = this->rect();  //rect == QRect(0,0 1280x720)

  QPoint topLeft = mapToGlobal(rect.topLeft());

  QPoint bottomRight = mapToGlobal(rect.bottomRight());

  if (this->windowState() != Qt::WindowMaximized)

  {

      if(!isLeftPressDown)  //没有按下左键时

      {

          this->region(globalPoint); //窗口大小的改变——判断鼠标位置，改变光标形状

      }

      else

      {

          if(dir != NONE)

          {

              QRect newRect(topLeft, bottomRight); //定义一个矩形  拖动后最大1000*1618

              switch(dir)

              {

                  case LEFT:

                      if(bottomRight.x() - globalPoint.x() <= this->minimumWidth())

                      {

                          newRect.setLeft(topLeft.x());  //小于界面的最小宽度时，设置为左上角横坐标为窗口x

                          //只改变左边界

                      }

                      else

                      {

                          newRect.setLeft(globalPoint.x());

                      }

                      break;

                  case RIGHT:

                      newRect.setWidth(globalPoint.x() - topLeft.x());  //只能改变右边界

                      break;

                  case UP:

                      if(bottomRight.y() - globalPoint.y() <= this->minimumHeight())

                      {

                          newRect.setY(topLeft.y());

                      }

                      else

                      {

                          newRect.setY(globalPoint.y());

                      }

                      break;

                  case DOWN:

                      newRect.setHeight(globalPoint.y() - topLeft.y());

                      break;

                  case LEFTTOP:

                      if(bottomRight.x() - globalPoint.x() <= this->minimumWidth())

                      {

                          newRect.setX(topLeft.x());

                      }

                      else

                      {

                          newRect.setX(globalPoint.x());

                      }

                      if(bottomRight.y() - globalPoint.y() <= this->minimumHeight())

                      {

                          newRect.setY(topLeft.y());

                      }

                      else

                      {

                          newRect.setY(globalPoint.y());

                      }

                      break;

                   case RIGHTTOP:

                        if (globalPoint.x() - topLeft.x() >= this->minimumWidth())

                        {

                            newRect.setWidth(globalPoint.x() - topLeft.x());

                        }

                        else

                        {

                            newRect.setWidth(bottomRight.x() - topLeft.x());

                        }

                        if (bottomRight.y() - globalPoint.y() >= this->minimumHeight())

                        {

                            newRect.setY(globalPoint.y());

                        }

                        else

                        {

                            newRect.setY(topLeft.y());

                        }

                        break;

                   case LEFTBOTTOM:

                        if (bottomRight.x() - globalPoint.x() >= this->minimumWidth())

                        {

                            newRect.setX(globalPoint.x());

                        }

                        else

                        {

                            newRect.setX(topLeft.x());

                        }

                        if (globalPoint.y() - topLeft.y() >= this->minimumHeight())

                        {

                            newRect.setHeight(globalPoint.y() - topLeft.y());

                        }

                        else

                        {

                            newRect.setHeight(bottomRight.y() - topLeft.y());

                        }

                        break;

                    case RIGHTBOTTOM:

                        newRect.setWidth(globalPoint.x() - topLeft.x());

                        newRect.setHeight(globalPoint.y() - topLeft.y());

                        break;

                    default:

                        break;

              }

              this->setGeometry(newRect);

          }

          else

          {

              move(event->globalPos() - m_movePoint); //移动窗口

              event->accept();

          }

      }

  }   }

//鼠标释放事件

void MainWindow::mouseReleaseEvent(QMouseEvent *event)

{

  if (event->button() == Qt::LeftButton)

  {

      isLeftPressDown = false;

      if (dir != NONE)

      {

          this->releaseMouse(); //释放鼠标抓取

          this->setCursor(QCursor(Qt::ArrowCursor));

          dir = NONE; //热心网友指正

      }

  }   }

法2：重写nativeEvent事件： MainWindow.h

    protected:

        bool nativeEvent(const QByteArray &eventType, void *message, long *result);

MainWindow.cpp

    bool MainWindow::nativeEvent(const QByteArray &eventType, void *message, long *result)

    {

        MSG* msg = (MSG*)message;

        switch(msg->message)

        {

        case WM_NCHITTEST:

            int xPos = GET_X_LPARAM(msg->lParam) - this->frameGeometry().x();

            int yPos = GET_Y_LPARAM(msg->lParam) - this->frameGeometry().y();

            if(this->childAt(xPos,yPos) == 0)

            {

                *result = HTCAPTION;

            }else{

                return false;

            }

            if(xPos > 0 && xPos < 8)

                *result = HTLEFT;

            if(xPos > (this->width() - 8) && xPos < (this->width() - 0))

                *result = HTRIGHT;

            if(yPos > 0 && yPos < 8)

                *result = HTTOP;

            if(yPos > (this->height() - 8) && yPos < (this->height() - 0))

                *result = HTBOTTOM;

            if(xPos > 18 && xPos < 22 && yPos > 18 && yPos < 22)

                *result = HTTOPLEFT;

            if(xPos > (this->width() - 22) && xPos < (this->width() - 18) && yPos > 18 && yPos < 22)

                *result = HTTOPRIGHT;

            if(xPos > 18 && xPos < 22 && yPos > (this->height() - 22) && yPos < (this->height() - 18))

                *result = HTBOTTOMLEFT;

            if(xPos > (this->width() - 22) && xPos < (this->width() - 18) && yPos > (this->height() - 22) && yPos < (this->height() - 18))

                *result = HTBOTTOMRIGHT;

            return true;

        }

        return false;

    }

巴特西

Qt的三套无边框窗体的方案：可按比例拖拽窗体大小的无边框窗口和几个常见的无边框实例

一、可按比例拖拽窗体大小的无边框窗口

二、可拖拽大小的windows系统方案：

三、之前用的老的frameless方案：

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