QwtScaleEngine(3) | Qwt User's Guide | QwtScaleEngine(3) |
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 reference)
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 val) const
QList< double > strip (const QList< double > &, const QwtInterval &) const
double divideInterval (double interval, int numSteps) const
QwtInterval buildInterval (double v) 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 attributesSee Also:
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 (uintbase = 10) [explicit]¶
ConstructorParameters:
See Also:
Member Function Documentation¶
QwtScaleEngine::Attributes QwtScaleEngine::attributes () const¶
Returns:See Also:
virtual void QwtScaleEngine::autoScale (intmaxNumSteps, double &x1, double &x2, double &stepSize) const [pure virtual]¶
Align and divide an intervalParameters:
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:See Also:
QwtInterval QwtScaleEngine::buildInterval (doublevalue) 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:
Returns:
bool QwtScaleEngine::contains (const QwtInterval &interval, doublevalue) const [protected]¶
Check if an interval 'contains' a valueParameters:
value Value
Returns:
double QwtScaleEngine::divideInterval (doubleintervalSize, intnumSteps) const [protected]¶
Calculate a step size for an interval sizeParameters:
numSteps Number of steps
Returns:
virtual QwtScaleDiv QwtScaleEngine::divideScale (doublex1, doublex2, intmaxMajorSteps, intmaxMinorSteps, doublestepSize = 0.0) const [pure virtual]¶
Calculate a scale division.Parameters:
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:
Implemented in QwtLogScaleEngine, QwtLinearScaleEngine, and QwtDateScaleEngine.
double QwtScaleEngine::lowerMargin () const¶
Returns:See Also:
double QwtScaleEngine::reference () const¶
Returns:See Also:
void QwtScaleEngine::setAttribute (Attributeattribute, boolon = true)¶
Change a scale attributeParameters:
on On/Off
See Also:
void QwtScaleEngine::setAttributes (Attributesattributes)¶
Change the scale attributeParameters:
See Also:
void QwtScaleEngine::setBase (uintbase)¶
Set the base of the scale engineWhile 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:
See Also:
void QwtScaleEngine::setMargins (doublelower, doubleupper)¶
Specify margins at the scale's endpoints.Parameters:
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:
void QwtScaleEngine::setReference (doubler)¶
Specify a reference point.Parameters:
The reference point is needed if options IncludeReference or Symmetric are active. Its default value is 0.0.
See Also:
void QwtScaleEngine::setTransformation (QwtTransform *transform)¶
Assign a transformationParameters:
The transformation object is used as factory for clones that are returned by transformation()
The scale engine takes ownership of the transformation.
See Also:
QList< double > QwtScaleEngine::strip (const QList< double > &ticks, const QwtInterval &interval) const [protected]¶
Remove ticks from a list, that are not inside an intervalParameters:
interval Interval
Returns:
bool QwtScaleEngine::testAttribute (Attributeattribute) const¶
Returns:Parameters:
See Also:
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:
See Also:
double QwtScaleEngine::upperMargin () const¶
Returns:See Also:
Author¶
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