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32a72cd9aa
added a field in the assistant to specify the symbol size when expression evaluates to NULL
89 lines
2.5 KiB
Plaintext
89 lines
2.5 KiB
Plaintext
/** \ingroup core
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* \class QgsScaleExpression
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* \brief Class storing parameters of a scale expression, which is a subclass of
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* QgsExpression for expressions which return a size or width.
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* \note Added in version 2.9
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*/
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class QgsScaleExpression : QgsExpression
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{
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%TypeHeaderCode
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#include <qgsscaleexpression.h>
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%End
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public:
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enum Type
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{
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Linear,
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Area,
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Flannery,
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Unknown
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};
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/** Constructor for QgsScaleExpression which parses an expression string
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* to determine whether it's a scale expression
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* @param expression expression string
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*/
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QgsScaleExpression( const QString &expression );
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/** Constructor for QgsScaleExpression which creates an expression from
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* specified parameters
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* @param type scale method
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* @param baseExpression expression (or field) used for value
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* @param minValue minimum value, corresponds to specified minimum size
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* @param maxValue maximum value, corresponds to specified maximum size
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* @param minSize minimum size
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* @param maxSize maximum size
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* @param nullSize size in case expression evaluates to NULL
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*/
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QgsScaleExpression( Type type, const QString& baseExpression, double minValue, double maxValue, double minSize, double maxSize, double nullSize = 0 );
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operator bool() const;
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/** Calculates the size corresponding to a specific value.
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* @param value
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* @returns calculated size using expression's parameters and type
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*/
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double size( double value ) const;
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/** Returns the minimum size calculated by the expression
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* @see maxSize
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*/
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double minSize() const;
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/** Returns the maximum size calculated by the expression
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* @see minSize
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*/
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double maxSize() const;
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/** Returns the minimum value expected by the expression. The minimum
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* value corresponds to the expression's minimum size.
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* @see maxValue
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*/
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double minValue() const;
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/** Returns the maximum value expected by the expression. The maximum
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* value corresponds to the expression's maximum size.
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* @see minValue
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*/
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double maxValue() const;
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/** Returns the size value when expression evaluates to NULL.
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* @see nullSize
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*/
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double nullSize() const;
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/** Returns the base expression string (or field reference) used for
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* calculating the values to be mapped to a size.
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*/
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QString baseExpression() const;
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/** Returns the scale expression's type (method used to calculate
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* the size from a value).
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*/
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Type type() const;
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};
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