Provided by: libqwt-doc_6.1.4-2_all 
NAME
QwtScaleEngine - Base class for scale engines.
SYNOPSIS
#include <qwt_scale_engine.h>
Inherited by QwtLinearScaleEngine, and QwtLogScaleEngine.
Public Types
enum Attribute { NoAttribute = 0x00, IncludeReference = 0x01, Symmetric = 0x02, Floating = 0x04, Inverted
= 0x08 }
typedef QFlags< Attribute > Attributes
Layout attributes.
Public Member Functions
QwtScaleEngine (uint base=10)
virtual ~QwtScaleEngine ()
Destructor.
void setBase (uint base)
uint base () const
void setAttribute (Attribute, bool on=true)
bool testAttribute (Attribute) const
void setAttributes (Attributes)
Attributes attributes () const
void setReference (double)
Specify a reference point.
double reference () const
void setMargins (double lower, double upper)
Specify margins at the scale's endpoints.
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 maxMajorSteps, int maxMinorSteps, double
stepSize=0.0) const =0
Calculate a scale division.
void setTransformation (QwtTransform *)
QwtTransform * transformation () const
Protected Member Functions
bool contains (const QwtInterval &, double value) const
QList< double > strip (const QList< double > &, const QwtInterval &) const
double divideInterval (double intervalSize, int numSteps) const
QwtInterval buildInterval (double value) const
Build an interval around a value.
Detailed Description
Base class for scale engines.
A scale engine tries to find 'reasonable' ranges and step sizes for scales.
The layout of the scale can be varied with setAttribute().
Qwt offers implementations for logarithmic and linear scales.
Member Enumeration Documentation
enum QwtScaleEngine::Attribute
Layout attributes
See also:
setAttribute(), testAttribute(), reference(), lowerMargin(), upperMargin()
Enumerator
NoAttribute
No attributes.
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.
Constructor & Destructor Documentation
QwtScaleEngine::QwtScaleEngine (uint base = 10) [explicit]
Constructor
Parameters:
base Base of the scale engine
See also:
setBase()
Member Function Documentation
QwtScaleEngine::Attributes QwtScaleEngine::attributes () const
Returns:
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 QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.
uint QwtScaleEngine::base () const
Returns:
base Base of the scale engine
See also:
setBase()
QwtInterval QwtScaleEngine::buildInterval (double value) const [protected]
Build an interval around a value. In case of v == 0.0 the interval is [-0.5, 0.5], otherwide it is [0.5 *
v, 1.5 * v]
Parameters:
value Initial value
Returns:
Calculated interval
bool QwtScaleEngine::contains (const QwtInterval & interval, double value) const [protected]
Check if an interval 'contains' a value
Parameters:
interval Interval
value Value
Returns:
True, when the value is inside the interval
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 maxMajorSteps, int maxMinorSteps,
double stepSize = 0.0) const [pure virtual]
Calculate a scale division.
Parameters:
x1 First interval limit
x2 Second interval limit
maxMajorSteps Maximum for the number of major steps
maxMinorSteps Maximum number of minor steps
stepSize Step size. If stepSize == 0.0, the scaleEngine calculates one.
Returns:
Calculated scale division
Implemented in QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.
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 (Attributes attributes)
Change the scale attribute
Parameters:
attributes Set scale attributes
See also:
Attribute, attributes()
void QwtScaleEngine::setBase (uint base)
Set the base of the scale engine
While a base of 10 is what 99.9% of all applications need certain scales might need a different base: f.e
2
The default setting is 10
Parameters:
base Base of the engine
See also:
base()
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:
• QwtLogScaleEngine measures the margins in decades.
See also:
upperMargin(), lowerMargin()
void QwtScaleEngine::setReference (double reference)
Specify a reference point.
Parameters:
reference New reference value
The reference point is needed if options IncludeReference or Symmetric are active. Its default value is
0.0.
See also:
Attribute
void QwtScaleEngine::setTransformation (QwtTransform * transform)
Assign a transformation
Parameters:
transform Transformation
The transformation object is used as factory for clones that are returned by transformation()
The scale engine takes ownership of the transformation.
See also:
QwtTransform::copy(), transformation()
QList< double > QwtScaleEngine::strip (const QList< double > & ticks, const QwtInterval & 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
Returns:
True, if attribute is enabled.
Parameters:
attribute Attribute to be tested
See also:
Attribute, setAttribute()
QwtTransform * QwtScaleEngine::transformation () const
Create and return a clone of the transformation of the engine. When the engine has no special
transformation NULL is returned, indicating no transformation.
Returns:
A clone of the transfomation
See also:
setTransformation()
double QwtScaleEngine::upperMargin () const
Returns:
the margin at the upper end of the scale The default margin is 0.
See also:
setMargins()
Author
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Version 6.1.4 Wed Jan 2 2019 QwtScaleEngine(3)