QGraphicsView Problem !!

[Gamalof]

i'm making a project, one of its parts in to control the size and place of any shape using sliders.

what i have got till now is, The shape's size is increasing when the slider's value increases,
the Problem is when decreasing the value of the slider, Nothing happen to the shape.

here is wt i did

// MYSlot.h
 public:
	 int GVar;
	  QGraphicsScene  scene;
          QGraphicsView * view;
 
public slots:
	 void  Slider_ValueChanged();
 
 private:
     Ui_MyForm ui;

// MYSlot.h
 public:
	 int GVar;
	  QGraphicsScene  scene;
          QGraphicsView * view;

public slots:
	 void  Slider_ValueChanged();

 private:
     Ui_MyForm ui;

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--------------------------------------------

// MySlot.cpp
 
// The Constructor
 
MySlot::MySlot(QWidget *parent)
     : QWidget(parent)
 {
     Ui_MyForm d;
	 MySlot::GVar=1;
	  //scene = new QGraphicsScene;
	 view = new QGraphicsView(&(MySlot::scene));
     ui.setupUi(this);
 }

// MySlot.cpp

// The Constructor

MySlot::MySlot(QWidget *parent)
     : QWidget(parent)
 {
     Ui_MyForm d;
	 MySlot::GVar=1;
	  //scene = new QGraphicsScene;
	 view = new QGraphicsView(&(MySlot::scene));
     ui.setupUi(this);
 }

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----------------------------------------

Slider Value Changed Slot.

void  MySlot::Slider_ValueChanged()
{
	    GVar= (int)(ui.horizontalSlider->value());
	    MySlot::scene.addEllipse (10, 10, GVar, 10,
			 QPen(Qt::black, 15, Qt::SolidLine, Qt::RoundCap,
					Qt::MiterJoin),
			 QBrush(Qt::blue, Qt::DiagCrossPattern)); 
 
             MySlot::scene.setBackgroundBrush(Qt::red);
	    MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
           CustomSlot::view ->show();
 
}

void  MySlot::Slider_ValueChanged()
{
	    GVar= (int)(ui.horizontalSlider->value());
	    MySlot::scene.addEllipse (10, 10, GVar, 10,
			 QPen(Qt::black, 15, Qt::SolidLine, Qt::RoundCap,
					Qt::MiterJoin),
			 QBrush(Qt::blue, Qt::DiagCrossPattern)); 

             MySlot::scene.setBackgroundBrush(Qt::red);
	    MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
           CustomSlot::view ->show();
		
}

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Again, The Problem is .. When the slider's value increases, the shape's size increases, when the slider's value decreases, Nothing happen to the shape.

Thanks

[Brandybuck]

Each time your slot is called, you're creating a new ellipse. Instead, you will want to change the size of an existing item, then call update() to repaint it.

[Gamalof]

Actually i used update function, but nothing happened !!

here is the Slot with updated function.

GVar= (int)(ui.horizontalSlider->value());
 
	        MySlot::scene.addEllipse (10, 10, GVar, GVar,
			 QPen(Qt::black, 15, Qt::SolidLine, Qt::RoundCap,
					Qt::MiterJoin),
			 QBrush(Qt::blue, Qt::DiagCrossPattern)); 
 
             MySlot::scene.setBackgroundBrush(Qt::red);
 
	     MySlot::view->update();
 
	     MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
             MySlot::view ->show();	
}

GVar= (int)(ui.horizontalSlider->value());

	        MySlot::scene.addEllipse (10, 10, GVar, GVar,
			 QPen(Qt::black, 15, Qt::SolidLine, Qt::RoundCap,
					Qt::MiterJoin),
			 QBrush(Qt::blue, Qt::DiagCrossPattern)); 

             MySlot::scene.setBackgroundBrush(Qt::red);

	     MySlot::view->update();

	     MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
             MySlot::view ->show();	
}

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[Gamalof]

I Got My incredible error :| , i was drawing circle"s" is the QSlider's value changed slot.

which gave me this bad result - many objects in the memory plus something like shadow appears - i solved it simply by drawing only one circle by this check :-

if (MySlot::MyE == NULL)
	 {
		MySlot::MyE = MySlot::scene.addEllipse (10, 10, 10, 10,
                QPen(Qt::red),
	    QBrush(Qt::white)); 
	    MySlot::scene.setBackgroundBrush(Qt::red);
	 }

if (MySlot::MyE == NULL)
	 {
		MySlot::MyE = MySlot::scene.addEllipse (10, 10, 10, 10,
                QPen(Qt::red),
	    QBrush(Qt::white)); 
	    MySlot::scene.setBackgroundBrush(Qt::red);
	 }

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then added the code which controls the size and location of the circle

MySlot::MyE->setRect(GVar3, GVar2, GVar, GVar );
MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
MySlot::view ->show(); 
MySlot::view->update();

MySlot::MyE->setRect(GVar3, GVar2, GVar, GVar );
MySlot::view->setAttribute(Qt::WA_DeleteOnClose);
MySlot::view ->show(); 
MySlot::view->update();

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Thanks