source: src/UIElements/Views/Qt4/Plotting/QScrollZoomer/ScrollBar.cpp

/*
 * QSeisScrollbar.cpp
 *
 *  taken from "realtime"-example
 *
 */

// include config.h
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <qstyle.h>
#if QT_VERSION >= 0x040000
#include <qstyleoption.h>
#endif
#include "ScrollBar.hpp"


// have this after(!) all Qt includes
//#include "CodePatterns/MemDebug.hpp"

ScrollBar::ScrollBar(QWidget * parent):
    QScrollBar(parent)
{
    init();
}

ScrollBar::ScrollBar(Qt::Orientation o, 
        QWidget *parent):
    QScrollBar(o, parent)
{
    init();
}

ScrollBar::ScrollBar(double minBase, double maxBase, 
        Qt::Orientation o, QWidget *parent):
    QScrollBar(o, parent)
{
    init();
    setBase(minBase, maxBase);
    moveSlider(minBase, maxBase);
}

void ScrollBar::init()
{
    d_inverted = orientation() == Qt::Vertical;
    d_baseTicks = 1000000;
    d_minBase = 0.0;
    d_maxBase = 1.0;
    moveSlider(d_minBase, d_maxBase);

    connect(this, SIGNAL(sliderMoved(int)), SLOT(catchSliderMoved(int)));
    connect(this, SIGNAL(valueChanged(int)), SLOT(catchValueChanged(int)));
}

void ScrollBar::setInverted(bool inverted)
{
    if ( d_inverted != inverted )
    {
        d_inverted = inverted;
        moveSlider(minSliderValue(), maxSliderValue());
    }
}

bool ScrollBar::isInverted() const
{
    return d_inverted;
}

void ScrollBar::setBase(double min, double max)
{
    if ( min != d_minBase || max != d_maxBase )
    {
        d_minBase = min;
        d_maxBase = max;

        moveSlider(minSliderValue(), maxSliderValue());
    }
}

void ScrollBar::moveSlider(double min, double max)
{
    const int sliderTicks = qRound((max - min) / 
        (d_maxBase - d_minBase) * d_baseTicks);

    // setRange initiates a valueChanged of the scrollbars
    // in some situations. So we block
    // and unblock the signals.

    blockSignals(true);

    setRange(sliderTicks / 2, d_baseTicks - sliderTicks / 2);
    int steps = sliderTicks / 200;
    if ( steps <= 0 )
        steps = 1;

#if QT_VERSION < 0x040000
    setSteps(steps, sliderTicks);
#else
    setSingleStep(steps);
    setPageStep(sliderTicks);
#endif

    int tick = mapToTick(min + (max - min) / 2);
    if ( isInverted() )
        tick = d_baseTicks - tick;

#if QT_VERSION < 0x040000
    directSetValue(tick);
    rangeChange();
#else
    setSliderPosition(tick);
#endif
    blockSignals(false);
}

double ScrollBar::minBaseValue() const
{
    return d_minBase;
}

double ScrollBar::maxBaseValue() const
{
    return d_maxBase;
}

void ScrollBar::sliderRange(int value, double &min, double &max) const
{
    if ( isInverted() )
        value = d_baseTicks - value;

    const int visibleTicks = pageStep();

    min = mapFromTick(value - visibleTicks / 2);
    max = mapFromTick(value + visibleTicks / 2);
}

double ScrollBar::minSliderValue() const
{
    double min, dummy;
    sliderRange(value(), min, dummy);

    return min;
}

double ScrollBar::maxSliderValue() const
{
    double max, dummy;
    sliderRange(value(), dummy, max);

    return max;
}

int ScrollBar::mapToTick(double v) const
{   
    return (int) ( ( v - d_minBase) / (d_maxBase - d_minBase ) * d_baseTicks );
}

double ScrollBar::mapFromTick(int tick) const
{   
    return d_minBase + ( d_maxBase - d_minBase ) * tick / d_baseTicks;
}

void ScrollBar::catchValueChanged(int value)
{
    double min, max;
    sliderRange(value, min, max);
    emit valueChanged(orientation(), min, max);
}

void ScrollBar::catchSliderMoved(int value)
{
    double min, max;
    sliderRange(value, min, max);
    emit sliderMoved(orientation(), min, max);
}

int ScrollBar::extent() const
{
#if QT_VERSION < 0x040000
    return style().pixelMetric(QStyle::PM_ScrollBarExtent, this);
#else
    QStyleOptionSlider opt;
    opt.init(this);
    opt.subControls = QStyle::SC_None;
    opt.activeSubControls = QStyle::SC_None;
    opt.orientation = orientation();
    opt.minimum = minimum();
    opt.maximum = maximum();
    opt.sliderPosition = sliderPosition();
    opt.sliderValue = value();
    opt.singleStep = singleStep();
    opt.pageStep = pageStep();
    opt.upsideDown = invertedAppearance();
    if (orientation() == Qt::Horizontal)
        opt.state |= QStyle::State_Horizontal;
    return style()->pixelMetric(QStyle::PM_ScrollBarExtent, &opt, this);
#endif
}