[Qt-interest] QGraphicsEffect drawing

[Malyushytsky, Alex]

QGraphicsEffect is base class for the for graphics effects.

This probably means that when you set effect you do not create instance of QGraphicsEffect, but
QGraphicsBlurEffect, QGraphicsColorizeEffect, QGraphicsDropShadowEffect, or QGraphicsOpacityEffect.

So what you are trying to do below is illegal, cause none of the above classes are derived from
BadEffectAccessor.

I can't give you direct answer on your question, but I don't think you need id.

void QGraphicsScene::render calls
   virtual void drawItems(...) to draw items.

All you need to make standard render work the way you want is override so it skips items you don't want to draw ( set flag before calling it for example ).


Regards,
  Alex


-----Original Message-----
From: qt-interest-bounces+alex=wai.com at qt.nokia.com [mailto:qt-interest-bounces+alex=wai.com at qt.nokia.com] On Behalf Of Anton Chernov
Sent: Friday, July 15, 2011 12:47 AM
To: qt-interest at trolltech.com
Subject: [Qt-interest] QGraphicsEffect drawing

Hi,

I have a problem drawing QGraphicsEffects - a have a scene with lots
of items, but when rendering for print only particular items should be
drawn.
If i would call

QGraphicsScene::render( ... )

all will be drawn, so I use a custom renderer. Everything draws good
except the graphics effects - their

draw( QPainter* painter )

is protected.

class BadEffectAccessor : public QGraphicsEffect
{
   public:
      void publicDraw( QPainter* painter ) { draw( painter ); }
};

[...]
if( text->graphicsEffect() ) {
   BadEffectAccessor* accessor = static_cast< BadEffectAccessor* >(
text->graphicsEffect() );
   accessor->publicDraw( painter );
}
[...]

Does not help, nothing is drawn! How do I draw the effects?
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