KChartTextLabelCache.h

/*
 * SPDX-FileCopyrightText: 2001-2015 Klaralvdalens Datakonsult AB. All rights reserved.
 *
 * This file is part of the KD Chart library.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */
 
#ifndef KCHARTTEXTLABELCACHE_H
#define KCHARTTEXTLABELCACHE_H
 
#include <QPixmap>
#include <QFont>
#include <QBrush>
#include <QPen>
 
#include "KChartEnums.h"
 
/**
  * @brief  base class for prerendered elements like labels, pixmaps, markers, etc.
  */
class PrerenderedElement {
public:
    PrerenderedElement();
    virtual ~PrerenderedElement() {}
 
    /** Returns the rendered element.
        If any of the properties have change, the element will be
        regenerated. */
    virtual const QPixmap& pixmap() const = 0;
 
    /** Return the location of the reference point relatively to the
        pixmap's origin. */
    virtual QPointF referencePointLocation( KChartEnums::PositionValue ) const = 0;
 
    /** Set the position of the element. */
    void setPosition( const QPointF& position );
    /** Get the position of the element. */
    const QPointF& position() const;
 
    /** Set the reference point of the element.
        Every element has nine possible reference points (all compass
        directions, plus the center.
     */
    void setReferencePoint( KChartEnums::PositionValue );
    /** Get the reference point of the element. */
    KChartEnums::PositionValue referencePoint() const;
 
protected:
    /** invalidate() needs to be called if any of the properties that
        determine the visual appearance of the prerendered element
        change.
        It can be called for a const object, as objects may need to
        force recalculation of the pixmap.
    */
    virtual void invalidate() const = 0;
 
private:
    QPointF m_position;
    KChartEnums::PositionValue m_referencePoint;
};
 
/**
    @brief PrerenderedLabel is an internal KChart class that simplifies creation
    and caching of cached text labels.
 
    It provides referenze points to anchor the text to other
    elements. Reference points use the positions defined in
    KChartEnums.
 
    Usage:
    <pre>
    qreal angle = 90.0;
    CachedLabel label;
    label.paint( font, tr("Label"), angle );
    </pre>
*/
 
// FIXME this is merely a prototype
// FIXME caching could be done by a second layer that can be used to,
// e.g., query for a prerendered element by id or name, or by changing
// the pixmap() method to do lazy evaluation.
class PrerenderedLabel : public PrerenderedElement
{
public:
    PrerenderedLabel();
    ~PrerenderedLabel() override;
 
 
    /**
      * Sets the label's font to \a font.
      */
    void setFont( const QFont& font );
 
    /**
      * @return the label's font.
      */
    const QFont& font() const;
 
 
    /**
      * Sets the label's text to \a text
      */
    void setText( const QString& text );
 
    /**
      * @return the label's text
      */
    const QString& text() const;
 
 
    /**
      * Sets the label's brush to \a brush
      */
    void setBrush( const QBrush& brush );
 
    /**
      * @return the label's brush
      */
    const QBrush& brush() const;
 
    void setPen( const QPen& );
    const QPen& pen() const;
 
 
    /**
      * Sets the angle of the label to \a angle degrees
      */
    void setAngle( qreal angle );
 
    /**
      * @return the label's angle in degrees
      */
    qreal angle() const;
 
    // reimpl PrerenderedElement:
    const QPixmap& pixmap() const override;
    QPointF referencePointLocation( KChartEnums::PositionValue position ) const override;
    // overload: return location of referencePoint():
    QPointF referencePointLocation() const;
 
protected:
 
    /**
      * Invalidates the preredendered data, forces re-rendering.
      */
    void invalidate() const override;
 
private:
    /** Create a label with the given text and the given rotation
        angle. Needs to be const, otherwise the pixmap() method cannot
        update when needed. */
    void paint() const;
 
    // store the settings (these are used for the painting):
    mutable bool m_dirty;
    QFont m_font;
    QString m_text;
    QBrush m_brush;
    QPen m_pen;
    qreal m_angle;
 
    // these are valid once the label has been rendered:
    mutable QPixmap m_pixmap;
    mutable QPointF m_referenceBottomLeft;
    mutable QPointF m_textBaseLineVector;
    mutable QPointF m_textAscendVector;
};
 
#endif