composition.h Example File
demos/composition/composition.h

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 #ifndef COMPOSITION_H
 #define COMPOSITION_H

 #include "arthurwidgets.h"

 #include <QPainter>
 #include <QEvent>

 QT_FORWARD_DECLARE_CLASS(QPushButton)
 QT_FORWARD_DECLARE_CLASS(QRadioButton)

 #ifdef QT_OPENGL_SUPPORT
 #include <QtOpenGL>
 #endif

 class CompositionWidget : public QWidget
 {
     Q_OBJECT

 public:
     CompositionWidget(QWidget *parent);

 public slots:
 void nextMode();

 private:
     bool m_cycle_enabled;

     QRadioButton *rbClear;
     QRadioButton *rbSource;
     QRadioButton *rbDest;
     QRadioButton *rbSourceOver;
     QRadioButton *rbDestOver;
     QRadioButton *rbSourceIn;
     QRadioButton *rbDestIn;
     QRadioButton *rbSourceOut;
     QRadioButton *rbDestOut;
     QRadioButton *rbSourceAtop;
     QRadioButton *rbDestAtop;
     QRadioButton *rbXor;

     QRadioButton *rbPlus;
     QRadioButton *rbMultiply;
     QRadioButton *rbScreen;
     QRadioButton *rbOverlay;
     QRadioButton *rbDarken;
     QRadioButton *rbLighten;
     QRadioButton *rbColorDodge;
     QRadioButton *rbColorBurn;
     QRadioButton *rbHardLight;
     QRadioButton *rbSoftLight;
     QRadioButton *rbDifference;
     QRadioButton *rbExclusion;
 };

 class CompositionRenderer : public ArthurFrame
 {
     Q_OBJECT

     enum ObjectType { NoObject, Circle, Rectangle, Image };

     Q_PROPERTY(int circleColor READ circleColor WRITE setCircleColor)
     Q_PROPERTY(int circleAlpha READ circleAlpha WRITE setCircleAlpha)
     Q_PROPERTY(bool animation READ animationEnabled WRITE setAnimationEnabled)

 public:
     CompositionRenderer(QWidget *parent);

     void paint(QPainter *);

     void setCirclePos(const QPointF &pos);

     QSize sizeHint() const { return QSize(500, 400); }

     bool animationEnabled() const { return m_animation_enabled; }
     int circleColor() const { return m_circle_hue; }
     int circleAlpha() const { return m_circle_alpha; }

 protected:
     void mousePressEvent(QMouseEvent *);
     void mouseMoveEvent(QMouseEvent *);
     void mouseReleaseEvent(QMouseEvent *);
     void timerEvent(QTimerEvent *);

 public slots:
     void setClearMode() { m_composition_mode = QPainter::CompositionMode_Clear; update(); }
     void setSourceMode() { m_composition_mode = QPainter::CompositionMode_Source; update(); }
     void setDestMode() { m_composition_mode = QPainter::CompositionMode_Destination; update(); }
     void setSourceOverMode() { m_composition_mode = QPainter::CompositionMode_SourceOver; update(); }
     void setDestOverMode() { m_composition_mode = QPainter::CompositionMode_DestinationOver; update(); }
     void setSourceInMode() { m_composition_mode = QPainter::CompositionMode_SourceIn; update(); }
     void setDestInMode() { m_composition_mode = QPainter::CompositionMode_DestinationIn; update(); }
     void setSourceOutMode() { m_composition_mode = QPainter::CompositionMode_SourceOut; update(); }
     void setDestOutMode() { m_composition_mode = QPainter::CompositionMode_DestinationOut; update(); }
     void setSourceAtopMode() { m_composition_mode = QPainter::CompositionMode_SourceAtop; update(); }
     void setDestAtopMode() { m_composition_mode = QPainter::CompositionMode_DestinationAtop; update(); }
     void setXorMode() { m_composition_mode = QPainter::CompositionMode_Xor; update(); }

     void setPlusMode() { m_composition_mode = QPainter::CompositionMode_Plus; update(); }
     void setMultiplyMode() { m_composition_mode = QPainter::CompositionMode_Multiply; update(); }
     void setScreenMode() { m_composition_mode = QPainter::CompositionMode_Screen; update(); }
     void setOverlayMode() { m_composition_mode = QPainter::CompositionMode_Overlay; update(); }
     void setDarkenMode() { m_composition_mode = QPainter::CompositionMode_Darken; update(); }
     void setLightenMode() { m_composition_mode = QPainter::CompositionMode_Lighten; update(); }
     void setColorDodgeMode() { m_composition_mode = QPainter::CompositionMode_ColorDodge; update(); }
     void setColorBurnMode() { m_composition_mode = QPainter::CompositionMode_ColorBurn; update(); }
     void setHardLightMode() { m_composition_mode = QPainter::CompositionMode_HardLight; update(); }
     void setSoftLightMode() { m_composition_mode = QPainter::CompositionMode_SoftLight; update(); }
     void setDifferenceMode() { m_composition_mode = QPainter::CompositionMode_Difference; update(); }
     void setExclusionMode() { m_composition_mode = QPainter::CompositionMode_Exclusion; update(); }

     void setCircleAlpha(int alpha) { m_circle_alpha = alpha; update(); }
     void setCircleColor(int hue) { m_circle_hue = hue; update(); }
     void setAnimationEnabled(bool enabled);

 private:
     void updateCirclePos();
     void drawBase(QPainter &p);
     void drawSource(QPainter &p);

     QPainter::CompositionMode m_composition_mode;

 #ifdef Q_WS_QWS
     QPixmap m_image;
     QPixmap m_buffer;
     QPixmap m_base_buffer;
 #else
     QImage m_image;
     QImage m_buffer;
     QImage m_base_buffer;
 #endif

     int m_circle_alpha;
     int m_circle_hue;

     QPointF m_circle_pos;
     QPointF m_offset;

     ObjectType m_current_object;
     bool m_animation_enabled;
     int m_animationTimer;

 #ifdef QT_OPENGL_SUPPORT
     QGLPixelBuffer *m_pbuffer;
     GLuint m_base_tex;
     GLuint m_compositing_tex;
     int m_pbuffer_size; // width==height==size of pbuffer
     QSize m_previous_size;
 #endif
 };

 #endif // COMPOSITION_H