Come rendere QScrollBar con handle di dimensioni fisse?

Question

Devo eseguire la barra di scorrimento con la maniglia di dimensione fissa poiché l'immagine di sfondo diventa brutta quando viene ridimensionata. Io uso il seguente foglio di stile:

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

ma sembra max-height non è proprietà valida. Come prevenire il ridimensionamento della maniglia?

Answer 1

Usa questo plugin jQuery http://jscrollpane.kelvinluck.com/

Answer 2

piccolo trucco, dal codice sorgente di 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 
} 

esempio:

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