How can I handle events in the titlebar and change

 

The titlebar belongs to the OS and we don't have control over that one. You can create your own titlebar, but note that this requires some work. In order to create your own titlebar then make a QWidget subclass that contains three toolbuttons that handle the close, minimize and maximize events in addition to the moving of the window. Then make a QFrame subclass which does not have a titlebar provided via the window system. This is done by setting the Qt::FramelessWindowHint window flag, however this will make it impossible to resize or move the window via the window system. What can be done is you can add your custom titlbar as a private member to the frame and add the it first to the frame's vertical layout. The frame also needs a content widget which allows widgets to be added to it. Finally the QFrame subclass needs to reimplement the mouse events to handle the resizing and moving of the window. The example below demonstrates how this can be achieved.

#include     
#include     
#include     
#include 
class ImTitleBar : public QWidget    
{   
 Q_OBJECT
public:
 ImTitleBar(QWidget *parent)
  :QWidget(parent)
 {    

 }
protected:
 void paintEvent(QPaintEvent *)
 {
  QStyleOption opt;
  opt.init(this);
  QPainter p(this);
  style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
};

class TitleBar : public QWidget    
{   
 Q_OBJECT

public: 
 TitleBar(QWidget *parent)        
 {    
  // Don't let this widget inherit the parent's backround color    
  setAutoFillBackground(true) ;  
  // Use a brush with a Highlight color role to render the background    
  setBackgroundRole(QPalette::Highlight) ;  
  //setPalette(QPalette(QColor(250, 0, 0)));
  minimize = new QToolButton(this) ;  
  maximize = new QToolButton(this) ;  
  close= new QToolButton(this) ;  
  setFixedHeight(35);
  // Use the style to set the button pixmaps    
  QPixmap pix = style()->standardPixmap(QStyle::SP_TitleBarCloseButton) ;  
  close->setIcon(pix) ; 
  close->setObjectName("Close");
  maxPix = style()->standardPixmap(QStyle::SP_TitleBarMaxButton) ;  
  maximize->setIcon(maxPix) ;  
  pix = style()->standardPixmap(QStyle::SP_TitleBarMinButton) ;  
  minimize->setIcon(pix) ;  
  restorePix = style()->standardPixmap(QStyle::SP_TitleBarNormalButton) ;  

  minimize->setMinimumHeight(20) ;  
  close->setMinimumHeight(20) ;  
  maximize->setMinimumHeight(20) ;  

  QLabel *label = new QLabel(this) ;  
  label->setObjectName("title");
  label->setText("Window Label") ;  
  parent->setWindowTitle("Window Title") ;  

  QHBoxLayout *hbox = new QHBoxLayout(this) ;  
  hbox->addWidget(label) ;  
  hbox->addWidget(minimize) ;  
  hbox->addWidget(maximize) ;  
  hbox->addWidget(close) ;  

  hbox->insertStretch(1, 500) ;  
  hbox->setSpacing(0) ;  
  setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed) ;  

  maxNormal = false ;  

  connect(close, SIGNAL( clicked() ), parent, SLOT(close() ) ) ;  
  connect(minimize, SIGNAL( clicked() ), this, SLOT(showSmall() ) ) ;  
  connect(maximize, SIGNAL( clicked() ), this, SLOT(showMaxRestore() ) ) ;  
 }

public slots:    
 void showSmall()        
 {    
  parentWidget()->showMinimized() ;  
 }

 void showMaxRestore()        
 {    
  if (maxNormal)     
  {    
   parentWidget()->showNormal() ;  
   maxNormal = !maxNormal ;  
   maximize->setIcon(maxPix) ;  
  }
  else     
  {    
   parentWidget()->showMaximized() ;  
   maxNormal = !maxNormal ;  
   maximize->setIcon(restorePix) ;  
  }
 }

protected:   
 void mousePressEvent(QMouseEvent *me)        
 {    
  startPos = me->globalPos() ;  
  clickPos = mapToParent(me->pos()) ;  
 }

 void mouseMoveEvent(QMouseEvent *me)        
 {    
  if (maxNormal)    
   return ;  
  parentWidget()->move(me->globalPos() - clickPos) ;  
 }
protected:
 void paintEvent(QPaintEvent *)
 {
  QStyleOption opt;
  opt.init(this);
  QPainter p(this);
  style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
private:    
 QToolButton *minimize ;  
 QToolButton *maximize ;  
 QToolButton *close ;  
 QPixmap restorePix, maxPix ;  
 bool maxNormal ;  
 QPoint startPos ;  
 QPoint clickPos ;  

};

class Frame : public QFrame    
{
public:  
 Frame()        
 {    
  m_mouse_down = false ;  
  setFrameShape(Panel) ;  

  // Make this a borderless window which can't    
  // be resized or moved via the window system    
  setWindowFlags(Qt::FramelessWindowHint) ;  
  setMouseTracking(true) ;  

  m_titleBar = new TitleBar(this) ;  
  m_content = new QWidget(this) ;  
  QVBoxLayout *vbox = new QVBoxLayout(this) ;  
  vbox->addWidget(m_titleBar) ;  
  vbox->setMargin(0) ;  
  vbox->setSpacing(0) ;  

  QVBoxLayout *layout = new QVBoxLayout(this) ;  
  layout->addWidget(m_content) ;  
  layout->setMargin(5) ;  
  layout->setSpacing(0) ;  
  vbox->addLayout(layout) ;  
 }

 // Allows you to access the content area of the frame   
 // where widgets and layouts can be added   
 QWidget *contentWidget() const     
 { 
  return m_content ;  
 }

 TitleBar *titleBar() const     
 { 
  return m_titleBar ;  
 }

 void mousePressEvent(QMouseEvent *e)        
 {    
  m_old_pos = e->pos() ;  
  m_mouse_down = e->button() == Qt::LeftButton ;  
 }

 void mouseMoveEvent(QMouseEvent *e)        
 {    
  int x = e->x() ;  
  int y = e->y() ;  
  if (m_mouse_down)     
  {    
   int dx = x - m_old_pos.x() ;  
   int dy = y - m_old_pos.y() ;  
   QRect g = geometry() ;  
   if (left)    
    g.setLeft(g.left() + dx) ;  

   if (right)    
    g.setRight(g.right() + dx) ;  

   if (bottom)    
    g.setBottom(g.bottom() + dy) ;  
   setGeometry(g) ;  
   m_old_pos = QPoint(!left ? e->x() : m_old_pos.x(), e->y()) ;  
  }
  else     
  {    
   QRect r = rect() ;  
   left = qAbs(x - r.left()) <= 5 ;  
   right = qAbs(x - r.right()) <= 5 ;  
   bottom = qAbs(y - r.bottom()) <= 5 ;  
   bool hor = left | right ;  
   if (hor && bottom)     
   {    
    if (left)    
     setCursor(Qt::SizeBDiagCursor) ;  
    else    
     setCursor(Qt::SizeFDiagCursor) ;  
   }
   else if (hor)     
   {    
    setCursor(Qt::SizeHorCursor) ;  
   }
   else if (bottom)     
   {    
    setCursor(Qt::SizeVerCursor) ;  
   }
   else     
   {    
    setCursor(Qt::ArrowCursor) ;  
   }
  }
 }

 void mouseReleaseEvent(QMouseEvent *e)        
 {    
  Q_UNUSED(e)
  m_mouse_down = false ;  
 }

private:   
 TitleBar *m_titleBar ;  
 QWidget *m_content ;  
 QPoint m_old_pos ;  
 bool m_mouse_down ;  
 bool left, right, bottom ;  

};  

#include "main.moc"
int main(int argc, char **argv)    
{ 
 QApplication app(argc, argv) ;  

 Frame box ;  
 box.move(0,0) ;  

 QVBoxLayout *l = new QVBoxLayout(box.contentWidget()) ;  
 l->setMargin(0) ;  
 QTextEdit *edit = new QTextEdit(box.contentWidget()) ;  
 l->addWidget(edit) ;  
 l->addWidget(new QPushButton("Start")) ;  
 ImTitleBar *line = new ImTitleBar(NULL);
 //QWidget *line = new QWidget;
 //line->setPalette(QPalette(QColor(250, 250, 0)));
 line->setObjectName("Line");
 //line->setWindowTitle("Line Title");
 line->setAutoFillBackground(true);
 line->setBackgroundRole(QPalette::Highlight) ;  
 //line->setPalette(QPalette(QColor(250, 250, 0)));
 line->setFixedHeight(25);
 QLabel *label = new QLabel(line) ;  
 label->setText("Window Label") ;
 l->addWidget(line) ;  

 box.show() ;  
 //QLabel{ background-color: blue; color: red;}
 QString sStyle = "QPushButton{ background-color:red; }\
      TitleBar { background: #FF6699; color: red; background-image: url(:/images/woodbackground.png);}\
      TitleBar#title { color: red;}\
      TitleBar::title { color: red;}\
      TitleBar QLabel { color: red;}\
      Line { background: green;}\
      ImTitleBar { background: green;}\
      TitleBar QToolButton#Close{ background-color:red; }";
 app.setStyleSheet(sStyle);
 return app.exec() ;  
}

Note that some strange behavior may be seen when resizing the window really small horizonally to the right on Windows (the window will start moving instead of resizing). This is due to limitations on Windows and there is nothing we can do about this unfortunately.

#include    
#include    
#include    
#include
class ImTitleBar : public QWidget   
{  
 Q_OBJECT
public:
 ImTitleBar(QWidget *parent)  :QWidget(parent)
 {   
  frame = new QFrame(this);
  frame->resize(size());
  frame->setObjectName("TitleBar");
 }
protected:
 void paintEvent(QPaintEvent *)
 {
  frame->resize(size());
  QStyleOption opt;  
  opt.init(this);  
  QPainter p(this);  
  style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
private:
 QFrame *frame;
};

class TitleBar : public QWidget   
{  
 Q_OBJECT
public: 
 TitleBar(QWidget *parent)
 {
  frame = new QFrame(this);
  frame->resize(size());
  frame->setObjectName("TitleBarBg");
  // Don't let this widget inherit the parent's backround color
  setAutoFillBackground(true) ;  

  // Use a brush with a Highlight color role to render the background
  setBackgroundRole(QPalette::Highlight) ;  
  //setPalette(QPalette(QColor(250, 0, 0)));  
  minimize = new QToolButton(this) ;  
  maximize = new QToolButton(this) ;  
  close= new QToolButton(this) ;  
  setFixedHeight(35);  
  // Use the style to set the button pixmaps
  QPixmap pix = style()->standardPixmap(QStyle::SP_TitleBarCloseButton) ;  
  close->setIcon(pix) ;  
  close->setObjectName("Close");  
  maxPix = style()->standardPixmap(QStyle::SP_TitleBarMaxButton) ;  
  maximize->setIcon(maxPix) ;  
  pix = style()->standardPixmap(QStyle::SP_TitleBarMinButton) ;  
  minimize->setIcon(pix) ;  
  restorePix = style()->standardPixmap(QStyle::SP_TitleBarNormalButton) ;  

  minimize->setMinimumHeight(20) ;  
  close->setMinimumHeight(20) ;  
  maximize->setMinimumHeight(20) ;  

  QLabel *label = new QLabel(this) ;  
  label->setObjectName("title");  
  label->setText("Window Label") ;  
  parent->setWindowTitle("Window Title") ;  

  QHBoxLayout *hbox = new QHBoxLayout(this) ;  
  hbox->addWidget(label) ;  
  hbox->addWidget(minimize) ;  
  hbox->addWidget(maximize) ;  
  hbox->addWidget(close) ;  

  hbox->insertStretch(1, 500) ;  
  hbox->setSpacing(0) ;  
  setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Fixed) ;  

  maxNormal = false ;  

  connect(close, SIGNAL( clicked() ), parent, SLOT(close() ) ) ;  
  connect(minimize, SIGNAL( clicked() ), this, SLOT(showSmall() ) ) ;  
  connect(maximize, SIGNAL( clicked() ), this, SLOT(showMaxRestore() ) ) ;  
 }
 public slots:
  void showSmall()
  {
   parentWidget()->showMinimized() ;  
  }
  void showMaxRestore()
  {
   if (maxNormal)
   {
    parentWidget()->showNormal() ;  
    maxNormal = !maxNormal ;  
    maximize->setIcon(maxPix) ;  
   } 
   else
   {
    parentWidget()->showMaximized() ;  
    maxNormal = !maxNormal ;  
    maximize->setIcon(restorePix) ;  
   }
  }
protected:  
 void mousePressEvent(QMouseEvent *me)
 {
  startPos = me->globalPos() ;  
  clickPos = mapToParent(me->pos()) ;  
 }
 void mouseMoveEvent(QMouseEvent *me)
 {
  if (maxNormal)
   return ;  
  parentWidget()->move(me->globalPos() - clickPos) ;  
 }
protected:
 void paintEvent(QPaintEvent *)
 {
  frame->resize(size());
  QStyleOption opt;  
  opt.init(this);  
  QPainter p(this);  
  style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
 }
private:
 QFrame *frame;
 QToolButton *minimize ;  
 QToolButton *maximize ;  
 QToolButton *close ;  
 QPixmap restorePix, maxPix ;  
 bool maxNormal ;  
 QPoint startPos ;  
 QPoint clickPos ;  
};

class Frame : public QFrame   
{
public:  
 Frame()
 {
  m_mouse_down = false ;  
  setFrameShape(Panel) ;  
  // Make this a borderless window which can't
  // be resized or moved via the window system
  setWindowFlags(Qt::FramelessWindowHint) ;  
  setMouseTracking(true) ;  

  m_titleBar = new TitleBar(this) ;  
  m_content = new QWidget(this) ;  
  QVBoxLayout *vbox = new QVBoxLayout(this) ;  
  vbox->addWidget(m_titleBar) ;  
  vbox->setMargin(0) ;  
  vbox->setSpacing(0) ;  

  QVBoxLayout *layout = new QVBoxLayout(this) ;  
  layout->addWidget(m_content) ;  
  layout->setMargin(5) ;  
  layout->setSpacing(0) ;  
  vbox->addLayout(layout) ;  
 }
 // Allows you to access the content area of the frame  
 // where widgets and layouts can be added   
 QWidget *contentWidget() const
 {  
  return m_content ;  
 }
 TitleBar *titleBar() const
 {  
  return m_titleBar ;  
 }
 void mousePressEvent(QMouseEvent *e)
 {
  m_old_pos = e->pos() ;  
  m_mouse_down = e->button() == Qt::LeftButton ;  
 }

 void mouseMoveEvent(QMouseEvent *e)
 {
  int x = e->x() ;  
  int y = e->y() ;  
  if (m_mouse_down)

  {
   int dx = x - m_old_pos.x() ;  
   int dy = y - m_old_pos.y() ;  
   QRect g = geometry() ;  
   if (left)
    g.setLeft(g.left() + dx) ;  

   if (right)
    g.setRight(g.right() + dx) ;  

   if (bottom)
    g.setBottom(g.bottom() + dy) ;  
   setGeometry(g) ;  
   m_old_pos = QPoint(!left ? e->x() : m_old_pos.x(), e->y()) ;  
  } 
  else
  {
   QRect r = rect() ;  
   left = qAbs(x - r.left()) <= 5 ;  
   right = qAbs(x - r.right()) <= 5 ;  
   bottom = qAbs(y - r.bottom()) <= 5 ;  
   bool hor = left | right ;  
   if (hor && bottom)

   {
    if (left)
     setCursor(Qt::SizeBDiagCursor) ;  
    else
     setCursor(Qt::SizeFDiagCursor) ;  
   } 
   else if (hor)
   {
    setCursor(Qt::SizeHorCursor) ;  
   }  
   else if (bottom)
   {
    setCursor(Qt::SizeVerCursor) ;  
   } 
   else
   {
    setCursor(Qt::ArrowCursor) ;  
   }
  }
 }

 void mouseReleaseEvent(QMouseEvent *e)
 {
  Q_UNUSED(e)  m_mouse_down = false ;  
 }
private:
 TitleBar *m_titleBar ;  
 QWidget *m_content ;  
 QPoint m_old_pos ;  
 bool m_mouse_down ;  
 bool left, right, bottom ;  

};  

#include "main.moc"
int main(int argc, char **argv)   
{ 
 Q_INIT_RESOURCE(styles);
 QApplication app(argc, argv) ;  

 Frame box ;  
 box.move(0,0) ;  

 QVBoxLayout *l = new QVBoxLayout(box.contentWidget()) ;  
 l->setMargin(0) ;  
 QTextEdit *edit = new QTextEdit(box.contentWidget()) ;  
 l->addWidget(edit) ;  
 l->addWidget(new QPushButton("Start")) ;  
 ImTitleBar *line = new ImTitleBar(NULL);
 //QWidget *line = new QWidget;
 //line->setPalette(QPalette(QColor(250, 250, 0)));
 line->setObjectName("Line");
 //line->setWindowTitle("Line Title");
 line->setAutoFillBackground(true);
 line->setBackgroundRole(QPalette::Highlight) ;  
 //line->setPalette(QPalette(QColor(250, 250, 0)));
 line->setFixedHeight(105);
 QLabel *label = new QLabel(line) ;  
 label->setText("Window Label") ;
 l->addWidget(line) ;  

 box.show() ;  

 QString sStyle ="QPushButton{ background-color:red; } \
     TitleBar { color: red; } \
     TitleBar#title  { color: red;}\
     TitleBar::title { color: red;}\
     TitleBar QLabel { color: red;}\
     QFrame#titleFrame {border: 20; border-image: url(:/images/titlebar_c.png) 20 20 20 20;}\
     ImTitleBar QFrame#TitleBar {background: red;border-width: 30 30 5 30; border-image: url(:/images/titlebar_c.png) 30 30 5 30;}\
     TitleBar QFrame#TitleBarBg {background: white;border-width: 30 30 5 30; border-image: url(:/images/titlebar_c.png) 30 30 5 30;}\
     TitleBar QToolButton#Close{ background-color:red; }";
 app.setStyleSheet(sStyle);
 return app.exec() ;  
}

附：图片及效果图