¿Cómo hacer QScrollBar con mango de tamaño fijo?

Question

Tengo que hacer la barra de desplazamiento con el mango de tamaño fijo ya que su imagen de fondo se pone fea cuando se escala. Yo uso la siguiente hoja de estilo:

QScrollBar::handle:vertical { 
    border-image:url(:/images/handle.png); 
    min-height: 47px; 
    max-height: 47px; 
    height: 47px; 
    width:10px; 
} 

pero parece que no es max-height propiedad válida. ¿Cómo prevenir la escala de manejo?

Answer 1

Uso este plugin de jQuery http://jscrollpane.kelvinluck.com/

Answer 2

pequeño truco, a partir del código fuente de Qt: myScrollbar.h

class myScrollBar : public QScrollBar 
{ 
public: 
    myScrollBar(Qt::Orientation orientation, QWidget *parent = 0); 
    void setSliderLength(int length); 
protected: 
    void paintEvent(QPaintEvent *); 

private: 
    QRect subControlRect(QStyle::ComplexControl cc, const QStyleOptionComplex *opt, QStyle::SubControl sc, /*const*/ QWidget *widget); 

    QRect visualRect(Qt::LayoutDirection direction, const QRect &boundingRect, const QRect &logicalRect); 

    int sliderPositionFromValue(int min, int max, int logicalValue, int span, bool upsideDown); 

private: 
    int _sliderLength; 
}; 

myScrollbar.cpp

myScrollBar::myScrollBar(Qt::Orientation orientation, QWidget *parent) 
    : QScrollBar(orientation, parent), 
     _sliderLength(100) 
{ 

} 
void myScrollBar::paintEvent(QPaintEvent *e) 
{ 
    qDebug() << "scrollbar paintevent"; 

    //Q_D(QScrollBar); 
    QScollBar::paintEvent(e); 
    QPainter painter(this); 
    QStyleOptionSlider opt; 
    initStyleOption(&opt); 
    opt.subControls = QStyle::SC_All; 
    QWidget *widget = this; 
    //  if (d->pressedControl) { 
    //   opt.activeSubControls = (QStyle::SubControl)d->pressedControl; 
    //   if (!d->pointerOutsidePressedControl) 
    //    opt.state |= QStyle::State_Sunken; 
    //  } else { 
    //   opt.activeSubControls = (QStyle::SubControl)d->hoverControl; 
    //  } 
    QPainter *p = &painter; 
    //style()->drawComplexControl(QStyle::CC_ScrollBar, &opt, &p, this); 
    if (const QStyleOptionSlider *scrollbar = &opt) { 
     // Make a copy here and reset it for each primitive. 
     QStyleOptionSlider newScrollbar = *scrollbar; 
     QStyle::State saveFlags = scrollbar->state; 

     if (scrollbar->subControls & QStyle::SC_ScrollBarSubLine) { 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarSubLine, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarSubLine)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarSubLine, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarAddLine) { 
      newScrollbar.rect = scrollbar->rect; 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarAddLine, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarAddLine)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarAddLine, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarSubPage) { 
      newScrollbar.rect = scrollbar->rect; 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarSubPage, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarSubPage)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarSubPage, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarAddPage) { 
      newScrollbar.rect = scrollbar->rect; 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarAddPage, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarAddPage)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarAddPage, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarFirst) { 
      newScrollbar.rect = scrollbar->rect; 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarFirst, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarFirst)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarFirst, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarLast) { 
      newScrollbar.rect = scrollbar->rect; 
      newScrollbar.state = saveFlags; 
      newScrollbar.rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarLast, widget); 
      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarLast)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 
       style()->drawControl(QStyle::CE_ScrollBarLast, &newScrollbar, p, widget); 
      } 
     } 
     if (scrollbar->subControls & QStyle::SC_ScrollBarSlider) { 

      newScrollbar.rect = scrollbar->rect; 

      newScrollbar.state = saveFlags; 
      QRect rect = subControlRect(QStyle::CC_ScrollBar, &newScrollbar, QStyle::SC_ScrollBarSlider, widget); 
      newScrollbar.rect = QRect(rect.topLeft(), QSize(rect.width(), 100)); 

      if (newScrollbar.rect.isValid()) { 
       if (!(scrollbar->activeSubControls & QStyle::SC_ScrollBarSlider)) 
        newScrollbar.state &= ~(QStyle::State_Sunken | QStyle::State_MouseOver); 

       style()->drawControl(QStyle::CE_ScrollBarSlider, &newScrollbar, p, widget); 

       if (scrollbar->state & QStyle::State_HasFocus) { 
        QStyleOptionFocusRect fropt; 
        fropt.QStyleOption::operator=(newScrollbar); 
        fropt.rect.setRect(newScrollbar.rect.x() + 2, newScrollbar.rect.y() + 2, 
             newScrollbar.rect.width() - 5, 
             newScrollbar.rect.height() - 5); 
        style()->drawPrimitive(QStyle::PE_FrameFocusRect, &fropt, p, widget); 
       } 
      } 
     } 
    } 

} 

void myScrollBar::setSliderLength(int length) 
{ 
    _sliderLength = length; 
} 

QRect myScrollBar::subControlRect(QStyle::ComplexControl cc, const QStyleOptionComplex *opt, QStyle::SubControl sc, /*const*/ QWidget *widget) 
{ 
    QRect ret; 
    switch (cc) { 
    case QStyle::CC_ScrollBar: 
     if (const QStyleOptionSlider *scrollbar = qstyleoption_cast<const QStyleOptionSlider *>(opt)) { 
      const QRect scrollBarRect = scrollbar->rect; 
      int sbextent = 0; 
      if (!style()->styleHint(QStyle::SH_ScrollBar_Transient, scrollbar, widget)) 
       sbextent = style()->pixelMetric(QStyle::PM_ScrollBarExtent, scrollbar, widget); 
      int maxlen = ((scrollbar->orientation == Qt::Horizontal) ? 
           scrollBarRect.width() : scrollBarRect.height()) - (sbextent * 2); 
      int sliderlen; 

      // calculate slider length 
      if (scrollbar->maximum != scrollbar->minimum) { 
       uint range = scrollbar->maximum - scrollbar->minimum; 
       sliderlen = (qint64(scrollbar->pageStep) * maxlen)/(range + scrollbar->pageStep); 

       int slidermin = style()->pixelMetric(QStyle::PM_ScrollBarSliderMin, scrollbar, widget); 
       if (_sliderLength < slidermin || range > INT_MAX/2) 
        _sliderLength = slidermin; 
       if (_sliderLength > maxlen) 
        _sliderLength = maxlen; 
       //length of the slider 
       sliderlen = _sliderLength; 
      } else { 
       sliderlen = maxlen; 
      } 

      int sliderstart = sbextent + this->sliderPositionFromValue(scrollbar->minimum, 
                     scrollbar->maximum, 
                     scrollbar->sliderPosition, 
                     maxlen - sliderlen, 
                     scrollbar->upsideDown); 

      switch (sc) { 
      case QStyle::SC_ScrollBarSubLine:   // top/left button 
       if (scrollbar->orientation == Qt::Horizontal) { 
        int buttonWidth = qMin(scrollBarRect.width()/2, sbextent); 
        ret.setRect(0, 0, buttonWidth, scrollBarRect.height()); 
       } else { 
        int buttonHeight = qMin(scrollBarRect.height()/2, sbextent); 
        ret.setRect(0, 0, scrollBarRect.width(), buttonHeight); 
       } 
       break; 
      case QStyle::SC_ScrollBarAddLine:   // bottom/right button 
       if (scrollbar->orientation == Qt::Horizontal) { 
        int buttonWidth = qMin(scrollBarRect.width()/2, sbextent); 
        ret.setRect(scrollBarRect.width() - buttonWidth, 0, buttonWidth, scrollBarRect.height()); 
       } else { 
        int buttonHeight = qMin(scrollBarRect.height()/2, sbextent); 
        ret.setRect(0, scrollBarRect.height() - buttonHeight, scrollBarRect.width(), buttonHeight); 
       } 
       break; 
      case QStyle::SC_ScrollBarSubPage:   // between top/left button and slider 
       if (scrollbar->orientation == Qt::Horizontal) 
        ret.setRect(sbextent, 0, sliderstart - sbextent, scrollBarRect.height()); 
       else 
        ret.setRect(0, sbextent, scrollBarRect.width(), sliderstart - sbextent); 
       break; 
      case QStyle::SC_ScrollBarAddPage:   // between bottom/right button and slider 
       if (scrollbar->orientation == Qt::Horizontal) 
        ret.setRect(sliderstart + sliderlen, 0, 
           maxlen - sliderstart - sliderlen + sbextent, scrollBarRect.height()); 
       else 
        ret.setRect(0, sliderstart + sliderlen, scrollBarRect.width(), 
           maxlen - sliderstart - sliderlen + sbextent); 
       break; 
      case QStyle::SC_ScrollBarGroove: 
       if (scrollbar->orientation == Qt::Horizontal) 
        ret.setRect(sbextent, 0, scrollBarRect.width() - sbextent * 2, 
           scrollBarRect.height()); 
       else 
        ret.setRect(0, sbextent, scrollBarRect.width(), 
           scrollBarRect.height() - sbextent * 2); 
       break; 
      case QStyle::SC_ScrollBarSlider: 
       if (scrollbar->orientation == Qt::Horizontal) 
        ret.setRect(sliderstart, 0, sliderlen, scrollBarRect.height()); 
       else 
        ret.setRect(0, sliderstart, scrollBarRect.width(), sliderlen); 

       break; 
      default: 
       break; 
      } 
      ret = visualRect(scrollbar->direction, scrollBarRect, ret); 
     } 
     return ret; 
    } 
} 

QRect myScrollBar::visualRect(Qt::LayoutDirection direction, const QRect &boundingRect, const QRect &logicalRect) 
{ 
    if (direction == Qt::LeftToRight) 
     return logicalRect; 
    QRect rect = logicalRect; 
    rect.translate(2 * (boundingRect.right() - logicalRect.right()) + 
        logicalRect.width() - boundingRect.width(), 0); 
    return rect; 
} 

int myScrollBar::sliderPositionFromValue(int min, int max, int logicalValue, int span, bool upsideDown) 
{ 
    if (span <= 0 || logicalValue < min || max <= min) 
     return 0; 
    if (logicalValue > max) 
     return upsideDown ? span : min; 

    uint range = max - min; 
    uint p = upsideDown ? max - logicalValue : logicalValue - min; 

    if (range > (uint)INT_MAX/4096) { 
     double dpos = (double(p))/(double(range)/span); 
     return int(dpos); 
    } else if (range > (uint)span) { 
     return (2 * p * span + range)/(2*range); 
    } else { 
     uint div = span/range; 
     uint mod = span % range; 
     return p * div + (2 * p * mod + range)/(2 * range); 
    } 
    // equiv. to (p * span)/range + 0.5 
    // no overflow because of this implicit assumption: 
    // span <= 4096 
} 

por ejemplo:

myScrollBar *bar = new myScrollBar(Qt::Vertical, ui->treeWidget); 
ui->treeWidget->setVerticalScrollBar(bar);