/****************************************************************************
** $Id:  qt/qrangecontrol.cpp   3.0.3   edited Mar 8 16:39 $
**
** Implementation of QRangeControl class
**
** Created : 940427
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#include "qrangecontrol.h"
#ifndef QT_NO_RANGECONTROL
#include "qglobal.h"
#include <limits.h>

/*!
  \class QRangeControl qrangecontrol.h
  \brief The QRangeControl class provides an integer value within a range.

  \ingroup misc

  Although originally designed for the QScrollBar widget, the
  QRangeControl can also be used in conjunction with other widgets
  such as QSlider and QSpinBox. Here are the five main concepts in the
  class:

  \list 1

  \i Current value.  This is the bounded integer that
  QRangeControl maintains.  value() returns this and several
  functions, including setValue(), set it.

  \i Minimum.  This is the lowest value that value() can ever
  return. Returned by minValue() and set by setRange() or one of the
  constructors.

  \i Maximum.  This is the highest value that value() can ever
  return. Returned by maxValue() and set by setRange() or one of the
  constructors.

  \i Line step.  This is the smaller of two natural steps that
  QRangeControl provides and typically corresponds to the user
  pressing an arrow key.  The line step is returned by lineStep() and
  set using setSteps(). The functions addLine() and subtractLine()
  respectively increment and decrement the current value by lineStep().

  \i Page step.  This is the larger of two natural steps that
  QRangeControl provides and typically corresponds to the user
  pressing PageUp or PageDown.  The page step is
  returned by pageStep() and set using setSteps(). The functions
  addPage() and substractPage() respectively increment and decrement
  the current value by pageStep().

  \endlist

  Unity (1) may be viewed as a third step size.  setValue() lets you
  set the current value to any integer in the allowed range, not just
  minValue() + \e n * lineStep() for integer values of \e n.  Some
  widgets may allow the user to set any value at all; others may just
  provide multiples of lineStep() or pageStep().

  QRangeControl provides three virtual functions that are well suited
  for updating the on-screen representation of range controls and
  emitting signals, namely valueChange(), rangeChange() and
  stepChange().

  QRangeControl also provides a function called bound() which
  lets you force arbitrary integers to be within the allowed range of
  the range control.

  We recommend that all widgets that inherit QRangeControl provide at
  least a signal called valueChanged(); many widgets will want to
  provide addStep(), addPage(), substractStep() and substractPage() as
  slots.

  Note that you have to use multiple inheritance if you plan to implement
  a widget using QRangeControl because QRangeControl is not derived from
  QWidget.
*/


/*!
  Constructs a range control with min value 0, max value 99,
  line step 1, page step 10 and initial value 0.
*/

QRangeControl::QRangeControl()
{
    minVal  = 0;
    maxVal  = 99;
    line    = 1;
    page    = 10;
    val	    = 0;
    prevVal = -1;
    d	    = 0;
}

/*!
  Constructs a range control whose value can never be smaller than \a
  minValue or greater than \a maxValue, whose line step size is \a
  lineStep and page step size is \a pageStep and whose value is
  initially \a value (which is guaranteed to be in range using bound()).
*/

QRangeControl::QRangeControl( int minValue, int maxValue,
			      int lineStep, int pageStep,
			      int value )
{
    minVal  = minValue;
    maxVal  = maxValue;
    line    = QABS( lineStep );
    page    = QABS( pageStep );
    prevVal = minVal - 1;
    val	    = bound( value );
    d	    = 0;
}

/*!
  Destroys the range control
*/

QRangeControl::~QRangeControl()
{
}


/*!
  \fn int QRangeControl::value() const

  Returns the current range control value.  This is guaranteed to be
  within the range [minValue(), maxValue()].

  \sa setValue() prevValue()
*/

/*!
  \fn int QRangeControl::prevValue() const

  Returns the previous value of the range control. "Previous value"
  means the value before the last change occurred. Setting a new range
  may affect the value, too, because the value is forced to be inside
  the specified range. When the range control is initially created,
  this is the same as value().

  prevValue() can be outside the current legal range if a call to
  setRange() causes the current value to change.  For example, if the
  range was [0, 1000] and the current value is 500, setRange(0, 400)
  makes value() return 400 and prevValue() return 500.

  \sa value() setRange()
*/

/*!
  Sets the range control's value to \a value and forces it to be within
  the legal range.

  Calls the virtual valueChange() function if the new value is
  different from the previous value. The old value can still be
  retrieved using prevValue().

   \sa value()
*/

void QRangeControl::setValue( int value )
{
    directSetValue( value );
    if ( prevVal != val )
	valueChange();
}

/*!
  Sets the range control \a value directly without calling valueChange().

  Forces the new \a value to be within the legal range.

  You will rarely have to call this function. However, if you want to
  change the range control's value inside the overloaded method
  valueChange(), setValue() would call the function valueChange()
  again. To avoid this recursion you must use directSetValue()
  instead.

  \sa setValue()
*/

void QRangeControl::directSetValue(int value)
{
    prevVal = val;
    val = bound( value );
}

/*!
  Equivalent to \c{setValue( value() + pageStep() )}.

  If the value is changed, then valueChange() is called.

  \sa subtractPage() addLine() setValue()
*/

void QRangeControl::addPage()
{
    setValue( value() + pageStep() );
}

/*!
  Equivalent to \c{setValue( value() - pageStep() )}.

  If the value is changed, then valueChange() is called.

  \sa addPage() subtractLine() setValue()
*/

void QRangeControl::subtractPage()
{
    setValue( value() - pageStep() );
}

/*!
  Equivalent to \c{setValue( value() + lineStep() )}.

  If the value is changed, then valueChange() is called.

  \sa subtractLine() addPage() setValue()
*/

void QRangeControl::addLine()
{
    setValue( value() + lineStep() );
}

/*!
  Equivalent to \c{setValue( value() - lineStep() )}.

  If the value is changed, then valueChange() is called.

  \sa addLine() subtractPage() setValue()
*/

void QRangeControl::subtractLine()
{
    setValue( value() - lineStep() );
}


/*!
  \fn int QRangeControl::minValue() const

  Returns the current minimum value of the range.

  \sa setMinValue() setRange() maxValue()
*/

/*!
  \fn int QRangeControl::maxValue() const

  Returns the current maximum value of the range.

  \sa setMaxValue() setRange() minValue()
*/

/*!
  Sets the current minimum value of the range to \a minVal.

  If necessary, the maxValue() is adjusted so that the range remains
  valid.

  \sa minValue() setMaxValue()
*/
void QRangeControl::setMinValue( int minVal )
{
    int maxVal = maxValue();
    if ( maxVal < minVal )
	maxVal = minVal;
    setRange( minVal, maxVal );
}

/*!
  Sets the current minimum value of the range to \a maxVal.

  If necessary, the minValue() is adjusted so that the range remains
  valid.

  \sa maxValue() setMinValue()
*/
void QRangeControl::setMaxValue( int maxVal )
{
    int minVal = minValue();
    if ( minVal > maxVal )
	minVal = maxVal;
    setRange( minVal, maxVal );
}

/*!
  Sets the range control's min value to \a minValue and its max value
  to \a maxValue.

  Calls the virtual rangeChange() function if one or both of the new
  min and max values are different from the previous setting.  Calls
  the virtual valueChange() function if the current value is adjusted
  because it was outside the new range.

  If \a maxValue is smaller than \a minValue, \a minValue becomes the
  only legal value.

  \sa minValue() maxValue()
*/

void QRangeControl::setRange( int minValue, int maxValue )
{
    if ( minValue > maxValue ) {
#if defined(QT_CHECK_RANGE)
	qWarning( "QRangeControl::setRange: minValue %d > maxValue %d",
		  minValue, maxValue );
#endif
	maxValue = minValue;
    }
    if ( minValue == minVal && maxValue == maxVal )
	return;
    minVal = minValue;
    maxVal = maxValue;
    int tmp = bound( val );
    rangeChange();
    if ( tmp != val ) {
	prevVal = val;
	val = tmp;
	valueChange();
    }
}


/*!
  \fn int QRangeControl::lineStep() const

  Returns the current line step.

  \sa setSteps() pageStep()
*/

/*!
  \fn int QRangeControl::pageStep() const

  Returns the current page step.

  \sa setSteps() lineStep()
*/

/*!
  Sets the range line step to \a lineStep and page step to \a pageStep.

  Calls the virtual stepChange() function if the new line step and/or
  page step are different from the previous settings.

  \sa lineStep() pageStep() setRange()
*/

void QRangeControl::setSteps( int lineStep, int pageStep )
{
    if ( lineStep != line || pageStep != page ) {
	line = QABS( lineStep );
	page = QABS( pageStep );
	stepChange();
    }
}


/*!
  This virtual function is called whenever the range control value
  changes.  You can reimplement it if you want to be notified when the
  value changes.  The default implementation does nothing.

  Note that this method is called after the value changed. The previous
  value can be retrieved using prevValue().

  \sa setValue(), addPage(), subtractPage(), addLine(), subtractLine()
  rangeChange(), stepChange()
*/

void QRangeControl::valueChange()
{
}


/*!
  This virtual function is called whenever the range control's range
  changes.  You can reimplement it if you want to be notified when the range
  changes.  The default implementation does nothing.

  Note that this method is called after the range changed.

  \sa setRange(), valueChange(), stepChange()
*/

void QRangeControl::rangeChange()
{
}


/*!
  This virtual function is called whenever the range control's
  line/page step settings change.  You can reimplement it if you want
  to be notified when the step changes.  The default implementation
  does nothing.

  Note that this method is called after the step settings change.

  \sa setSteps(), rangeChange(), valueChange()
*/

void QRangeControl::stepChange()
{
}


/*!  Forces the value \a v to be within the range from minValue() to
    maxValue() inclusive, and returns the result.

  This function is provided so that you can easily force other numbers
  than value() into the allowed range.  You do not need to call it in
  order to use QRangeControl itself.

  \sa setValue() value() minValue() maxValue()
*/

int QRangeControl::bound( int v ) const
{
    if ( v < minVal )
	return minVal;
    if ( v > maxVal )
	return maxVal;
    return v;
}


/*!
  Converts \a logical_val to a pixel position.  minValue() maps to 0,
  maxValue() maps to \a span and other values are distributed evenly
  in-between.

  This function can handle the entire integer range without overflow.

  Calling this method is useful when actually drawing a range control
  such as a QScrollBar on-screen.

  \sa valueFromPosition()
*/

int QRangeControl::positionFromValue( int logical_val, int span ) const
{
    if ( span <= 0 || logical_val < minValue() || maxValue() <= minValue() )
	return 0;
    if ( logical_val > maxValue() )
	return span;

    uint range = maxValue() - minValue();
    uint p = logical_val - minValue();

    if ( range > (uint)INT_MAX/4096 ) {
	const int scale = 4096*2;
	return ( (p/scale) * span ) / (range/scale);
	// ### the above line is probably not 100% correct
	// ### but fixing it isn't worth the extreme pain...
    } 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
}


/*!
  Converts the pixel position \a pos to a value.  0 maps to minValue(),
  \a span maps to maxValue() and other values are distributed evenly
  in-between.

  This function can handle the entire integer range without overflow.

  Calling this method is useful if you actually implemented a range
  control widget such as QScrollBar and want to handle mouse press
  events.  This function then maps screen coordinates to the logical
  values.

  \sa positionFromValue()
*/

int QRangeControl::valueFromPosition( int pos, int span ) const
{
    if ( span <= 0 || pos <= 0 )
	return minValue();
    if ( pos >= span )
	return maxValue();

    uint range = maxValue() - minValue();

    if ( (uint)span > range )
	return  minValue() + (2*pos*range + span) / (2*span);
    else {
	uint div = range / span;
	uint mod = range % span;
	return  minValue() + pos*div + (2*pos*mod + span) / (2*span);
    }
    // equiv. to minValue() + (pos*range)/span + 0.5
    // no overflow because of this implicit assumption:
    // pos <= span < sqrt(INT_MAX+0.0625)+0.25 ~ sqrt(INT_MAX)
}
#endif
