QRangeControl(3qt)QRangeControl(3qt)NAMEQRangeControl - Integer value within a range
SYNOPSIS
#include <qrangecontrol.h>
Inherited by QDial, QScrollBar, QSlider, and QSpinBox.
Public Members
QRangeControl ()
QRangeControl ( int minValue, int maxValue, int lineStep, int pageStep,
int value )
virtual ~QRangeControl ()
int value () const
void setValue ( int value )
void addPage ()
void subtractPage ()
void addLine ()
void subtractLine ()
int minValue () const
int maxValue () const
void setRange ( int minValue, int maxValue )
void setMinValue ( int minVal )
void setMaxValue ( int maxVal )
int lineStep () const
int pageStep () const
void setSteps ( int lineStep, int pageStep )
int bound ( int v ) const
Protected Members
int positionFromValue ( int logical_val, int span ) const
int valueFromPosition ( int pos, int span ) const
void directSetValue ( int value )
int prevValue () const
virtual void valueChange ()
virtual void rangeChange ()
virtual void stepChange ()
DESCRIPTION
The QRangeControl class provides an integer value within a range.
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:
<ol type=1>
1 Current value The bounded integer that QRangeControl maintains.
value() returns it, and several functions, including setValue(),
set it.
2 Minimum The lowest value that value() can ever return. Returned
by minValue() and set by setRange() or one of the constructors.
3 Maximum The highest value that value() can ever return. Returned
by maxValue() and set by setRange() or one of the constructors.
4 Line step 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().
5 Page step 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().
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() + n * lineStep() for integer values of 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: 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 must use multiple inheritance if you plan to implement a
widget using QRangeControl because QRangeControl is not derived from
QWidget.
See also Miscellaneous Classes.
MEMBER FUNCTION DOCUMENTATIONQRangeControl::QRangeControl ()
Constructs a range control with a minimum value of 0, maximum value of
99, line step of 1, page step of 10 and initial value 0.
QRangeControl::QRangeControl ( int minValue, int maxValue, int lineStep, int
pageStep, int value )
Constructs a range control whose value can never be smaller than
minValue or greater than maxValue, whose line step size is lineStep and
page step size is pageStep and whose value is initially value (which is
guaranteed to be in range using bound()).
QRangeControl::~QRangeControl () [virtual]
Destroys the range control
void QRangeControl::addLine ()
Equivalent to setValue( value() + lineStep() ).
If the value is changed, then valueChange() is called.
See also subtractLine(), addPage(), and setValue().
void QRangeControl::addPage ()
Equivalent to setValue( value() + pageStep() ).
If the value is changed, then valueChange() is called.
See also subtractPage(), addLine(), and setValue().
int QRangeControl::bound ( int v ) const
Forces the value 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.
See also setValue(), value(), minValue(), and maxValue().
void QRangeControl::directSetValue ( int value ) [protected]
Sets the range control value directly without calling valueChange().
Forces the new 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.
See also setValue().
int QRangeControl::lineStep () const
Returns the line step.
See also setSteps() and pageStep().
int QRangeControl::maxValue () const
Returns the maximum value of the range.
See also setMaxValue(), setRange(), and minValue().
int QRangeControl::minValue () const
Returns the minimum value of the range.
See also setMinValue(), setRange(), and maxValue().
int QRangeControl::pageStep () const
Returns the page step.
See also setSteps() and lineStep().
int QRangeControl::positionFromValue ( int logical_val, int span ) const
[protected]
Converts logical_val to a pixel position. minValue() maps to 0,
maxValue() maps to span and other values are distributed evenly in-
between.
This function can handle the entire integer range without overflow,
providing span is <= 4096.
Calling this method is useful when actually drawing a range control
such as a QScrollBar on-screen.
See also valueFromPosition().
int QRangeControl::prevValue () const [protected]
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.
See also value() and setRange().
void QRangeControl::rangeChange () [virtual protected]
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 has changed.
See also setRange(), valueChange(), and stepChange().
Reimplemented in QDial, QSlider, and QSpinBox.
void QRangeControl::setMaxValue ( int maxVal )
Sets the minimum value of the range to maxVal.
If necessary, the minValue() is adjusted so that the range remains
valid.
See also maxValue() and setMinValue().
void QRangeControl::setMinValue ( int minVal )
Sets the minimum value of the range to minVal.
If necessary, the maxValue() is adjusted so that the range remains
valid.
See also minValue() and setMaxValue().
void QRangeControl::setRange ( int minValue, int maxValue )
Sets the range control's minimum value to minValue and its maximum
value to maxValue.
Calls the virtual rangeChange() function if one or both of the new
minimum and maximum 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 maxValue is smaller than minValue, minValue becomes the only legal
value.
See also minValue() and maxValue().
Examples:
void QRangeControl::setSteps ( int lineStep, int pageStep )
Sets the range's line step to lineStep and page step to pageStep.
Calls the virtual stepChange() function if the new line step or page
step are different from the previous settings.
See also lineStep(), pageStep(), and setRange().
void QRangeControl::setValue ( int value )
Sets the range control's value to 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().
See also value().
void QRangeControl::stepChange () [virtual protected]
This virtual function is called whenever the range control's line or
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 a step setting has changed.
See also setSteps(), rangeChange(), and valueChange().
void QRangeControl::subtractLine ()
Equivalent to setValue( value() - lineStep() ).
If the value is changed, then valueChange() is called.
See also addLine(), subtractPage(), and setValue().
void QRangeControl::subtractPage ()
Equivalent to setValue( value() - pageStep() ).
If the value is changed, then valueChange() is called.
See also addPage(), subtractLine(), and setValue().
int QRangeControl::value () const
Returns the current range control value. This is guaranteed to be
within the range [minValue(), maxValue()].
See also setValue() and prevValue().
void QRangeControl::valueChange () [virtual protected]
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 has changed. The
previous value can be retrieved using prevValue().
See also setValue(), addPage(), subtractPage(), addLine(),
subtractLine(), rangeChange(), and stepChange().
Reimplemented in QDial, QSlider, and QSpinBox.
int QRangeControl::valueFromPosition ( int pos, int span ) const [protected]
Converts the pixel position pos to a value. 0 maps to minValue(), 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.
See also positionFromValue().
SEE ALSO
http://doc.trolltech.com/qrangecontrol.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
BUGS
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bugs@trolltech.com. Please include the name of the manual page
(qrangecontrol.3qt) and the Qt version (3.3.8).
Trolltech AS 2 February 2007 QRangeControl(3qt)