Difference between revisions of "A sample highlighting QGraphicsEffect"

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'''English''' | [[A sample highlighting QGraphicsEffect Persian|فارسی]]
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[[Category:HowTo]]
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__NOEDITSECTION__
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__NOTOC__
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== Introduction ==
  
While learning Qt, I wrote this sample highlighting graphics effect to be used with rectangular QGraphicsPixmapItem.<br /> ..and I use this post just to learn how to publish a wiki page here too.. <span class="smiley">;-)</span>
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While learning Qt, I wrote this sample highlighting graphics effect to be used with rectangular {{DocLink|QGraphicsPixmapItem}}... and I use this post just to learn how to publish a wiki page here too.. ;-)
  
highlight.h
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'''highlight.h'''
  
highlight.cpp
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<code>
 +
#ifndef HIGHLIGHT_H
 +
#define HIGHLIGHT_H
  
The strange thing in the implementation is that the sourceIsPixmap() function returns always false, even if the documentation states that “Returns true if the source effectively is a pixmap, e.g., a QGraphicsPixmapItem.”<br /> I ask to Qt gurus what can be going on here…
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#include <QtGui>
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class HighlightEffect : public QGraphicsEffect
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{
 +
Q_OBJECT
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Q_PROPERTY( QColor color READ color WRITE setColor )
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Q_PROPERTY( QPointF offset READ offset WRITE setOffset )
 +
 
 +
public:
 +
  HighlightEffect( qreal offset = 1.5 );
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  virtual QRectF boundingRectFor( const QRectF& sourceRect; ) const;
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  QColor color() const { return mColor;}
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  void setColor( QColor& color; ) { mColor = color;}
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  QPointF offset() const { return mOffset;}
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  void setOffset( QPointF offset ) { mOffset = offset;}
 +
 
 +
protected:
 +
  virtual void draw( QPainter *painter ); // , QGraphicsEffectSource *source );
 +
 
 +
private:
 +
  QColor mColor;
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  QPointF mOffset;
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};
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#endif // HIGHLIGHT_H
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</code>
 +
 
 +
'''highlight.cpp'''
 +
 
 +
<code>
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#include "highlight.h"
 +
 
 +
HighlightEffect::HighlightEffect( qreal offset ) :
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QGraphicsEffect(),
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mColor( 255, 255, 0, 128 ), // yellow, semi-transparent
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mOffset( offset, offset ) {}
 +
 
 +
QRectF HighlightEffect::boundingRectFor( const QRectF& sourceRect; ) const
 +
{
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return sourceRect.adjusted( -mOffset.x(), -mOffset.y(), mOffset.x(), mOffset.y() );
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}
 +
 
 +
void HighlightEffect::draw( QPainter* painter )
 +
{
 +
QPoint offset;
 +
QPixmap pixmap;
 +
 
 +
// if ( sourceIsPixmap() ) // doesn't seems to work, return false
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// {
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// No point in drawing in device coordinates (pixmap will be scaled anyways).
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pixmap = sourcePixmap( Qt::LogicalCoordinates, &offset; );
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//}
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QRectF bound = boundingRectFor( pixmap.rect() );
 +
 
 +
painter->save();
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painter->setPen( Qt::NoPen );
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painter->setBrush( mColor );
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QPointF p( offset.x()-mOffset.x(), offset.y()-mOffset.y() );
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bound.moveTopLeft( p );
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painter->drawRoundedRect( bound, 5, 5, Qt::RelativeSize );
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painter->drawPixmap( offset, pixmap );
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painter->restore();
 +
}
 +
</code>
 +
 
 +
The strange thing in the implementation is that the {{DocLink|QGraphicsEffect|sourceIsPixmap}} function returns always false, even if the documentation states that ''Returns true if the source effectively is a pixmap, e.g., a QGraphicsPixmapItem.''
 +
I asked the Qt gurus what can be going on here...
  
 
The default color is pale yellow, semi-transparent and the border size is set to 1.5. To add the effect simply add this:
 
The default color is pale yellow, semi-transparent and the border size is set to 1.5. To add the effect simply add this:
 +
 +
<code>
 +
Pixmap *item = new Pixmap(kineticPix);
 +
.
 +
.
 +
HighlightEffect *effect = new HighlightEffect();
 +
 +
item->setGraphicsEffect( effect );
 +
</code>
  
 
Here the modified animated tiles example with the effect turned on:
 
Here the modified animated tiles example with the effect turned on:
  
[[Image:highlight.png|Animated tiles example with QGraphicsPixmapItem highlighting]]
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[[File:Highlight.png]]
 
 
Hope someone found this useful.
 
  
===Categories:===
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Animated tiles example with QGraphicsPixmapItem highlighting
  
* [[:Category:HowTo|HowTo]]
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Hope someone finds this useful.
* [[:Category:Learning|Learning]]
 

Latest revision as of 12:38, 21 October 2015


Introduction

While learning Qt, I wrote this sample highlighting graphics effect to be used with rectangular QGraphicsPixmapItem... and I use this post just to learn how to publish a wiki page here too.. ;-)

highlight.h

  1. ifndef HIGHLIGHT_H
  2. define HIGHLIGHT_H
  1. include <QtGui>

class HighlightEffect : public QGraphicsEffect {

Q_OBJECT
Q_PROPERTY( QColor color READ color WRITE setColor )
Q_PROPERTY( QPointF offset READ offset WRITE setOffset )
public:
 HighlightEffect( qreal offset = 1.5 );
 virtual QRectF boundingRectFor( const QRectF& sourceRect; ) const;
 QColor color() const { return mColor;}
 void setColor( QColor& color; ) { mColor = color;}
 QPointF offset() const { return mOffset;}
 void setOffset( QPointF offset ) { mOffset = offset;}
protected:
 virtual void draw( QPainter *painter ); // , QGraphicsEffectSource *source );
private:
 QColor mColor;
 QPointF mOffset;

};

  1. endif // HIGHLIGHT_H

highlight.cpp

  1. include "highlight.h"

HighlightEffect::HighlightEffect( qreal offset ) :

QGraphicsEffect(),
mColor( 255, 255, 0, 128 ), // yellow, semi-transparent
mOffset( offset, offset ) {}

QRectF HighlightEffect::boundingRectFor( const QRectF& sourceRect; ) const {

return sourceRect.adjusted( -mOffset.x(), -mOffset.y(), mOffset.x(), mOffset.y() );

}

void HighlightEffect::draw( QPainter* painter ) {

QPoint offset;
QPixmap pixmap;
// if ( sourceIsPixmap() ) // doesn't seems to work, return false
// {
// No point in drawing in device coordinates (pixmap will be scaled anyways).
pixmap = sourcePixmap( Qt::LogicalCoordinates, &offset; );
//} 
QRectF bound = boundingRectFor( pixmap.rect() );
painter->save();
painter->setPen( Qt::NoPen );
painter->setBrush( mColor );
QPointF p( offset.x()-mOffset.x(), offset.y()-mOffset.y() );
bound.moveTopLeft( p );
painter->drawRoundedRect( bound, 5, 5, Qt::RelativeSize );
painter->drawPixmap( offset, pixmap );
painter->restore();

}

The strange thing in the implementation is that the sourceIsPixmap function returns always false, even if the documentation states that Returns true if the source effectively is a pixmap, e.g., a QGraphicsPixmapItem. I asked the Qt gurus what can be going on here...

The default color is pale yellow, semi-transparent and the border size is set to 1.5. To add the effect simply add this:

Pixmap *item = new Pixmap(kineticPix);
.
.
HighlightEffect *effect = new HighlightEffect();
item->setGraphicsEffect( effect );

Here the modified animated tiles example with the effect turned on:

Highlight.png

Animated tiles example with QGraphicsPixmapItem highlighting

Hope someone finds this useful.