NAME
QwtScaleEngine - Base class for scale engines.
SYNOPSIS
#include <qwt_scale_engine.h>
Inherited by QwtLinearScaleEngine, and QwtLog10ScaleEngine.
Public Types
enum Attribute { NoAttribute = 0, IncludeReference = 1, Symmetric =
2, Floating = 4, Inverted = 8 }
Public Member Functions
QwtScaleEngine ()
virtual ~QwtScaleEngine ()
void setAttribute (Attribute, bool on=true)
bool testAttribute (Attribute) const
void setAttributes (int)
int attributes () const
void setReference (double reference)
double reference () const
void setMargins (double lower, double upper)
double lowerMargin () const
double upperMargin () const
virtual void autoScale (int maxNumSteps, double &x1, double &x2, double
&stepSize) const =0
virtual QwtScaleDiv divideScale (double x1, double x2, int maxMajSteps,
int maxMinSteps, double stepSize=0.0) const =0
virtual QwtScaleTransformation * transformation () const =0
Protected Member Functions
bool contains (const QwtDoubleInterval &, double val) const
QwtValueList strip (const QwtValueList &, const QwtDoubleInterval &)
const
double divideInterval (double interval, int numSteps) const
QwtDoubleInterval buildInterval (double v) const
Detailed Description
Base class for scale engines.
A scale engine trys to find ’reasonable’ ranges and step sizes for
scales.
The layout of the scale can be varied with setAttribute().
Qwt offers implementations for logarithmic (log10) and linear scales.
Contributions for other types of scale engines (date/time, log2 ... )
are welcome.
Member Enumeration Documentation
enum QwtScaleEngine::Attribute
· IncludeReference
Build a scale which includes the reference() value.
· Symmetric
Build a scale which is symmetric to the reference() value.
· Floating
The endpoints of the scale are supposed to be equal the outmost
included values plus the specified margins (see setMargins()). If
this attribute is *not* set, the endpoints of the scale will be
integer multiples of the step size.
· Inverted
Turn the scale upside down.
See also:
setAttribute(), testAttribute(), reference(), lowerMargin(),
upperMargin()
Constructor & Destructor Documentation
QwtScaleEngine::QwtScaleEngine () [explicit]
Constructor.
QwtScaleEngine::~QwtScaleEngine () [virtual]
Destructor.
Member Function Documentation
int QwtScaleEngine::attributes () const
Return the scale attributes
See also:
Attribute, setAttributes(), testAttribute()
virtual void QwtScaleEngine::autoScale (int maxNumSteps, double & x1,
double & x2, double & stepSize) const [pure virtual]
Align and divide an interval
Parameters:
maxNumSteps Max. number of steps
x1 First limit of the interval (In/Out)
x2 Second limit of the interval (In/Out)
stepSize Step size (Return value)
Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.
QwtDoubleInterval QwtScaleEngine::buildInterval (double v) const
[protected]
Build an interval for a value.
In case of v == 0.0 the interval is [-0.5, 0.5], otherwide it is [0.5 *
v, 1.5 * v]
bool QwtScaleEngine::contains (const QwtDoubleInterval & interval, double
value) const [protected]
Check if an interval ’contains’ a value
Parameters:
interval Interval
value Value
See also:
QwtScaleArithmetic::compareEps()
double QwtScaleEngine::divideInterval (double intervalSize, int numSteps)
const [protected]
Calculate a step size for an interval size
Parameters:
intervalSize Interval size
numSteps Number of steps
Returns:
Step size
virtual QwtScaleDiv QwtScaleEngine::divideScale (double x1, double x2, int
maxMajSteps, int maxMinSteps, double stepSize = 0.0) const [pure
virtual]
Calculate a scale division.
Parameters:
x1 First interval limit
x2 Second interval limit
maxMajSteps Maximum for the number of major steps
maxMinSteps Maximum number of minor steps
stepSize Step size. If stepSize == 0.0, the scaleEngine calculates
one.
Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.
double QwtScaleEngine::lowerMargin () const
Returns:
the margin at the lower end of the scale The default margin is 0.
See also:
setMargins()
double QwtScaleEngine::reference () const
Returns:
the reference value
See also:
setReference(), setAttribute()
void QwtScaleEngine::setAttribute (Attribute attribute, bool on = true)
Change a scale attribute
Parameters:
attribute Attribute to change
on On/Off
See also:
Attribute, testAttribute()
void QwtScaleEngine::setAttributes (int attributes)
Change the scale attribute
Parameters:
attributes Set scale attributes
See also:
Attribute, attributes()
void QwtScaleEngine::setMargins (double lower, double upper)
Specify margins at the scale’s endpoints.
Parameters:
lower minimum distance between the scale’s lower boundary and the
smallest enclosed value
upper minimum distance between the scale’s upper boundary and the
greatest enclosed value
Margins can be used to leave a minimum amount of space between the
enclosed intervals and the boundaries of the scale.
Warning:
· QwtLog10ScaleEngine measures the margins in decades.
See also:
upperMargin(), lowerMargin()
void QwtScaleEngine::setReference (double r)
Specify a reference point.
Parameters:
r new reference value
The reference point is needed if options IncludeReference or Symmetric
are active. Its default value is 0.0.
See also:
Attribute
QwtValueList QwtScaleEngine::strip (const QwtValueList & ticks, const
QwtDoubleInterval & interval) const [protected]
Remove ticks from a list, that are not inside an interval
Parameters:
ticks Tick list
interval Interval
Returns:
Stripped tick list
bool QwtScaleEngine::testAttribute (Attribute attribute) const
Check if a attribute is set.
Parameters:
attribute Attribute to be tested
See also:
Attribute, setAttribute()
virtual QwtScaleTransformation* QwtScaleEngine::transformation () const
[pure virtual]
Returns:
a transformation
Implemented in QwtLinearScaleEngine, and QwtLog10ScaleEngine.
double QwtScaleEngine::upperMargin () const
Returns:
the margin at the upper end of the scale The default margin is 0.
See also:
setMargins()
Author
Generated automatically by Doxygen for Qwt User’s Guide from the source
code.