QRangeControl(3qt)QRangeControl(3qt)NAMEQRangeControl - Integer value within a range
#include <qrangecontrol.h>
Inherited by QDial, QScrollBar, QSlider and QSpinBox.
Public Members
QRangeControl ()
QRangeControl ( int minValue, int maxValue, int lineStep,
int pageStep, int value )
int value () const
void setValue ( int )
void addPage ()
void subtractPage ()
void addLine ()
void subtractLine ()
int minValue () const
int maxValue () const
void setRange ( int minValue, int maxValue )
int lineStep () const
int pageStep () const
void setSteps ( int line, int page )
int bound ( int ) const
Protected Members
int positionFromValue ( int val, int space ) const
int valueFromPosition ( int pos, int space ) const
void directSetValue ( int val )
int prevValue () const
virtual void valueChange ()
virtual void rangeChange ()
virtual void stepChange ()
DESCRIPTION
The QRangeControl class provides an integer value within a
range.
It was originally designed for the QScrollBar widget, but
it can also be practical for other purposes such as
QSlider and QSpinBox. Here are the five main concepts in
the class:
The current value. This is the bounded integer that
QRangeControl maintains. value() returns this, and several
functions including setValue() set it.
The minimum. This is the lowest value value() can ever
return. Returned by minValue(), set by setRange() or one
of the constructors.
The maximum. This is the highest value value() can ever
return. Returned by maxValue(), set by setRange() or one
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of the constructors.
The line step. This is the smaller of two natural steps
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() allow easy movement of the
current value by lineStep().
The page step. This is the larger of two natural steps
QRangeControl provides, and typically corresponds to the
user pressing one of the PageUp and PageDown keys. The
page step is returned by pageStep() and set using
setSteps(). The functions addPage() and substractPage()
allow easy movement of the current value by pageStep().
Note that 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()/pageStep().
QRangeControl provides three virtual functions that are
well-suited e.g. for updating the on-screen representation
of range controls and emitting signals, namely
valueChange(), rangeChange() and stepChange().
Finally, QRangeControl 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, which inherit
QRangeControl, provide at least a signal called
valueChanged(), and 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, since
QRangeControl is not derived from QWidget.
MEMBER FUNCTION DOCUMENTATIONQRangeControl::QRangeControl ()
Constructs a range control with min value 0, max value 99,
line step 1, page step 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.
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value is forced to be within the legal range using the
bound() method.
void QRangeControl::addLine ()
Equivalent to
setValue( value()+lineStep() )
plus a test for numerical overflow
If the value is changed, then valueChange() is called.
See also subtractLine(), addPage() and setValue().
void QRangeControl::addPage ()
Equivalent to
setValue( value()+pageStep() )
plus a test for numerical overflow.
If the value is changed, then valueChange() is called.
See also subtractPage(), addLine() and setValue().
int QRangeControl::bound ( int v ) const
Forces 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 find few cases only where you have to call this
function. However, if you want to change the range
controls value inside the overloaded method valueChange()
then 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 current line step.
See also setSteps() and pageStep().
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QRangeControl(3qt)QRangeControl(3qt)int QRangeControl::maxValue () const
Returns the current maximum value of the range.
See also setRange() and minValue().
int QRangeControl::minValue () const
Returns the current minimum value of the range.
See also setRange() and maxValue().
int QRangeControl::pageStep () const
Returns the current 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.
Callings this method is useful when actually drawing a
range control like a QScrollBar on the 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, since the
value is forced to be inside the specified range. When the
range control is initially created, this is the same as
value().
Note that 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 500, setRange( 0, 400 ) makes value() return
400 and prevValue() 500)
See also value() and setRange().
void QRangeControl::rangeChange () [virtual protected]
This virtual function is called whenever the range
controls 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.
See also setRange(), valueChange() and stepChange().
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Reimplemented in QSlider, QDial and QScrollBar.
void QRangeControl::setRange ( int minValue, int maxValue )
Sets the range min value to minValue and the max value to
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 maxValue is smaller than minValue, minValue becomes the
only legal value.
See also minValue() and maxValue().
Examples: xform/xform.cpp
void QRangeControl::setSteps ( int lineStep,int pageStep )
Sets the range line step to lineStep and page step to
pageStep.
Calls the virtual stepChange() function if the new line
step and/or page step are different from the previous
settings.
See also lineStep(), pageStep() and setRange().
void QRangeControl::setValue ( int value )
Sets the range controls 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
controls line/page step settings changes. 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
changed.
See also setSteps(), rangeChange() and valueChange().
Reimplemented in QScrollBar.
void QRangeControl::subtractLine ()
Equivalent to
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setValue( value()-lineStep() )
plus a test for numerical underflow
If the value is changed, then valueChange() is called.
See also addLine(), subtractPage() and setValue().
void QRangeControl::subtractPage ()
Equivalent to
setValue( value()-pageStep() )
plus a test for numerical underflow
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 changed.
The previous value can be retrieved using prevValue().
See also setValue(), addPage(), subtractPage(), addLine(),
subtractLine(), rangeChange() and stepChange().
Reimplemented in QDial, QScrollBar and QSlider.
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 like QScrollBar and want to handle
mouse press events. This function maps then screen
coordinates to the logical values.
See also positionFromValue().
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QRangeControl(3qt)QRangeControl(3qt)SEE ALSO
http://doc.trolltech.com/qrangecontrol.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
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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http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page
(qrangecontrol.3qt) and the Qt version (2.3.1).
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