How to make QScrollBar with fixed size handle? - css

Question

I have to make scrollbar with handle of fixed size since its background image becomes ugly when being scaled. I use the following style sheet:
QScrollBar::handle:vertical {
border-image:url(:/images/handle.png);
min-height: 47px;
max-height: 47px;
height: 47px;
width:10px;
}
but it seems like max-height isn't valid property. How to prevent handle scaling?

Answer 1

Little trick, from Qt source code:
myScrollbar.h
class myScrollBar : public QScrollBar
{
Q_OBJECT
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);
QScrollBar::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
}
eg:
myScrollBar *bar = new myScrollBar(Qt::Vertical, ui->treeWidget);
ui->treeWidget->setVerticalScrollBar(bar);

Answer 2

Use
this jquery plugin http://jscrollpane.kelvinluck.com/