GraphicsItem is flickering

[anafor2004]

Dear Friends,
I have a problem with setPos() function in QGraphicsItem class, I have created my own GraphicsItem class derived from QGraphicsItem. I loaded Iems in a Scene. Now I am locating Items, and trying to slide some pictures, but pictures are flickering.

I am using a QTimer and it's slot for moving pictures, setPos() function .

How can I prevend this problem.

[wysota]

Please provide a minimal compilable example reproducing the problem.

[anafor2004]

GraphicsItem.cpp

#include "GraphicItem.h"
 
GraphicItem::GraphicItem(QPixmap image)
{
	// TODO Auto-generated constructor stub
	myWidth = 150;
	myHeight =150;
	m_Selected = false;
	Org = image;
	makePhoto(Org);
	makeReflection();
}
 
GraphicItem::GraphicItem()
{
	myWidth = 150;
	myHeight =150;
	m_Selected = false;
	Org = NULL;
	makePhoto(Org);
	makeReflection();
}
GraphicItem::~GraphicItem() {
	// TODO Auto-generated destructor stub
}
 
 
QRectF GraphicItem::boundingRect() const
{
    return QRectF(0.0f,0.0f,myWidth,myHeight);
}
 
 
void GraphicItem::SelectedStatus(bool Selected)
{
	m_Selected = Selected;
	makePhoto(Org);
	makeReflection();
}
 
void GraphicItem::MoveLeft()
{
	SetRightPlace(pos().x()+200,pos().y());
}
 
void GraphicItem::MoveRight()
{
	SetRightPlace(pos().x()-200,pos().y());
}
 
void GraphicItem::SetRightPlace(int x,int y)
{
		RightX = x;
		RightY = y;
}
 
bool GraphicItem::IsRightPlace()
{
	return(RightX == pos().x()) && (RightY == pos().y());
}
 
void GraphicItem::Animate()
{
	int x = pos().x();
	int y = pos().y();
 
	int dx = 6;
	int dy = 6;
 
	if(pos().x() < RightX)
	{
	        if((pos().x() +  dx >= RightX))
	            x = RightX;
	        else
	            x = pos().x() + dx;
	}
	else if(pos().x() > RightX)
	{
	        if((pos().x() - dx <= RightX))
	            x = RightX;
	        else
	            x = pos().x() - dx;
	}
 
	    if(pos().y() < RightY)
	    {
	        if((pos().y() + dy >= RightY))
	            y = RightY;
	        else
	            y = pos().y() + dy;
	    }
	    else if(pos().y() > RightY)
	    {
	        if((pos().y() - dy <= RightY))
	            y = RightY;
	        else
	            y = pos().y() - dy;
	    }
	   setPos(x,y);
}
 
 
void GraphicItem::ChangePixmap(QPixmap pixmap)
{
	Org = pixmap;
	makePhoto(Org);
	makeReflection();
}
 
void GraphicItem::paint(QPainter* painter,const QStyleOptionGraphicsItem*,
                         QWidget*)
{
	printf("void GraphicItem::paint\n");
    painter->drawPixmap(0,0,item);
    painter->drawPixmap(0,static_cast<int>(myHeight*0.5f),itemMirror);
}
 
void GraphicItem::makePhoto(QPixmap image)
{
	  item =  QPixmap(myWidth,static_cast<int>(myHeight*0.5f));
	  if((image.width() > myWidth - 2) || (image.height() > myHeight*0.5f-2))
	        image = image.scaled(myWidth-2,static_cast<int>(myHeight*0.5f-2),
	                             Qt::KeepAspectRatio,Qt::SmoothTransformation);
	  QPainter* painter = new QPainter(&item);
	  QPen pen;
	  if(m_Selected)
		  pen.setBrush(Qt::red);
	  else
		  pen.setBrush(Qt::darkGray);
 
	    pen.setWidth(5);
	    painter->setPen(pen);
	    QLinearGradient gradient;
	    gradient = QLinearGradient(0,0,0,static_cast<int>(myHeight*0.5f));
	    gradient.setColorAt(0.0f,QColor(175,175,175));
	    gradient.setColorAt(0.5f,QColor(215,215,215));
	    gradient.setColorAt(1.0f,QColor(175,175,175));
	    painter->setBrush(QBrush(gradient));
	    painter->drawRect(0,0,myWidth,static_cast<int>(myHeight*0.5f));
	    painter->drawPixmap(static_cast<int>(myWidth*0.5f-(image.width()*0.5f)),
	                        static_cast<int>(myHeight*0.25f-(image.height()*0.5f)),
	                        image);
	    delete painter;
}
 
void GraphicItem::makeReflection()
{
	itemMirror = QPixmap(myWidth,static_cast<int>(myHeight*0.5f));
	QPainter* painter = new QPainter(&itemMirror);
    painter->drawPixmap(0,0,QPixmap::fromImage(item.toImage()
	                                               .mirrored(false,true)));
    painter->resetTransform();
	QPen pen(Qt::transparent);
	painter->setPen(pen);
	QLinearGradient gradient;
	gradient = QLinearGradient(0,0,0,static_cast<int>(myHeight*0.375f));
	gradient.setColorAt(0.0f,QColor(0,15,15,155));
	gradient.setColorAt(1.0f,QColor(0,15,15,255));
	painter->setBrush(QBrush(gradient));
	painter->drawRect(0,0,myWidth,static_cast<int>(myHeight*0.5f));
	delete painter;
}

#include "GraphicItem.h"

GraphicItem::GraphicItem(QPixmap image)
{
	// TODO Auto-generated constructor stub
	myWidth = 150;
	myHeight =150;
	m_Selected = false;
	Org = image;
	makePhoto(Org);
	makeReflection();
}

GraphicItem::GraphicItem()
{
	myWidth = 150;
	myHeight =150;
	m_Selected = false;
	Org = NULL;
	makePhoto(Org);
	makeReflection();
}
GraphicItem::~GraphicItem() {
	// TODO Auto-generated destructor stub
}


QRectF GraphicItem::boundingRect() const
{
    return QRectF(0.0f,0.0f,myWidth,myHeight);
}


void GraphicItem::SelectedStatus(bool Selected)
{
	m_Selected = Selected;
	makePhoto(Org);
	makeReflection();
}

void GraphicItem::MoveLeft()
{
	SetRightPlace(pos().x()+200,pos().y());
}

void GraphicItem::MoveRight()
{
	SetRightPlace(pos().x()-200,pos().y());
}

void GraphicItem::SetRightPlace(int x,int y)
{
		RightX = x;
		RightY = y;
}

bool GraphicItem::IsRightPlace()
{
	return(RightX == pos().x()) && (RightY == pos().y());
}

void GraphicItem::Animate()
{
	int x = pos().x();
	int y = pos().y();

	int dx = 6;
	int dy = 6;

	if(pos().x() < RightX)
	{
	        if((pos().x() +  dx >= RightX))
	            x = RightX;
	        else
	            x = pos().x() + dx;
	}
	else if(pos().x() > RightX)
	{
	        if((pos().x() - dx <= RightX))
	            x = RightX;
	        else
	            x = pos().x() - dx;
	}

	    if(pos().y() < RightY)
	    {
	        if((pos().y() + dy >= RightY))
	            y = RightY;
	        else
	            y = pos().y() + dy;
	    }
	    else if(pos().y() > RightY)
	    {
	        if((pos().y() - dy <= RightY))
	            y = RightY;
	        else
	            y = pos().y() - dy;
	    }
	   setPos(x,y);
}


void GraphicItem::ChangePixmap(QPixmap pixmap)
{
	Org = pixmap;
	makePhoto(Org);
	makeReflection();
}

void GraphicItem::paint(QPainter* painter,const QStyleOptionGraphicsItem*,
                         QWidget*)
{
	printf("void GraphicItem::paint\n");
    painter->drawPixmap(0,0,item);
    painter->drawPixmap(0,static_cast<int>(myHeight*0.5f),itemMirror);
}

void GraphicItem::makePhoto(QPixmap image)
{
	  item =  QPixmap(myWidth,static_cast<int>(myHeight*0.5f));
	  if((image.width() > myWidth - 2) || (image.height() > myHeight*0.5f-2))
	        image = image.scaled(myWidth-2,static_cast<int>(myHeight*0.5f-2),
	                             Qt::KeepAspectRatio,Qt::SmoothTransformation);
	  QPainter* painter = new QPainter(&item);
	  QPen pen;
	  if(m_Selected)
		  pen.setBrush(Qt::red);
	  else
		  pen.setBrush(Qt::darkGray);

	    pen.setWidth(5);
	    painter->setPen(pen);
	    QLinearGradient gradient;
	    gradient = QLinearGradient(0,0,0,static_cast<int>(myHeight*0.5f));
	    gradient.setColorAt(0.0f,QColor(175,175,175));
	    gradient.setColorAt(0.5f,QColor(215,215,215));
	    gradient.setColorAt(1.0f,QColor(175,175,175));
	    painter->setBrush(QBrush(gradient));
	    painter->drawRect(0,0,myWidth,static_cast<int>(myHeight*0.5f));
	    painter->drawPixmap(static_cast<int>(myWidth*0.5f-(image.width()*0.5f)),
	                        static_cast<int>(myHeight*0.25f-(image.height()*0.5f)),
	                        image);
	    delete painter;
}

void GraphicItem::makeReflection()
{
	itemMirror = QPixmap(myWidth,static_cast<int>(myHeight*0.5f));
	QPainter* painter = new QPainter(&itemMirror);
    painter->drawPixmap(0,0,QPixmap::fromImage(item.toImage()
	                                               .mirrored(false,true)));
    painter->resetTransform();
	QPen pen(Qt::transparent);
	painter->setPen(pen);
	QLinearGradient gradient;
	gradient = QLinearGradient(0,0,0,static_cast<int>(myHeight*0.375f));
	gradient.setColorAt(0.0f,QColor(0,15,15,155));
	gradient.setColorAt(1.0f,QColor(0,15,15,255));
	painter->setBrush(QBrush(gradient));
	painter->drawRect(0,0,myWidth,static_cast<int>(myHeight*0.5f));
	delete painter;
}

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GraphicsItem.h

/*
 * GraphicItem.h
 *
 *  Created on: Sep 29, 2009
 *      Author: root
 */
 
#ifndef GRAPHICITEM_H_
#define GRAPHICITEM_H_
 
#include <QGraphicsItem>
#include <QGraphicsScene>
#include <QPixmap>
#include <QImage>
#include <QLinearGradient>
#include <QPainter>
 
class GraphicItem : public QGraphicsItem
{
public:
	GraphicItem(QPixmap image);
	GraphicItem();
	virtual ~GraphicItem();
 
	 QRectF boundingRect() const;
	 void paint(QPainter* painter,const QStyleOptionGraphicsItem* option,
	               QWidget* widget);
 
	 void SelectedStatus(bool Selected);
	 void ChangePixmap(QPixmap pixmap);
 
	 void MoveRight();
	 void MoveLeft();
 
	 void SetRightPlace(int x,int y);
	 bool IsRightPlace();
	 void Animate();
 
public:
	 bool m_Selected;
	 int RightX;
	 int RightY;
	 int myWidth;
	 int myHeight;
	 //Pixmap's for drawing methods
	 QPixmap Org; // Original Pixmap
	 QPixmap item; // Scaled and Framed
	 QPixmap itemMirror; // Mirrored
 
 
	 void  makePhoto(QPixmap Image);
	 void  makeReflection();
};
 
#endif /* GRAPHICITEM_H_ */

/*
 * GraphicItem.h
 *
 *  Created on: Sep 29, 2009
 *      Author: root
 */

#ifndef GRAPHICITEM_H_
#define GRAPHICITEM_H_

#include <QGraphicsItem>
#include <QGraphicsScene>
#include <QPixmap>
#include <QImage>
#include <QLinearGradient>
#include <QPainter>

class GraphicItem : public QGraphicsItem
{
public:
	GraphicItem(QPixmap image);
	GraphicItem();
	virtual ~GraphicItem();

	 QRectF boundingRect() const;
	 void paint(QPainter* painter,const QStyleOptionGraphicsItem* option,
	               QWidget* widget);

	 void SelectedStatus(bool Selected);
	 void ChangePixmap(QPixmap pixmap);

	 void MoveRight();
	 void MoveLeft();

	 void SetRightPlace(int x,int y);
	 bool IsRightPlace();
	 void Animate();

public:
	 bool m_Selected;
	 int RightX;
	 int RightY;
	 int myWidth;
	 int myHeight;
	 //Pixmap's for drawing methods
	 QPixmap Org; // Original Pixmap
	 QPixmap item; // Scaled and Framed
	 QPixmap itemMirror; // Mirrored


	 void  makePhoto(QPixmap Image);
	 void  makeReflection();
};

#endif /* GRAPHICITEM_H_ */

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TestView derived from QGraphicsView

#pragma once
 
#include "GenericView.h"
#include "ITestView.h"
#include "ITestCallBack.h"
#include "GraphicItem.h"
#include <QTimer>
 
class TestView : public GenericView , public ITestView
{
	Q_OBJECT
    public:
      TestView();
      virtual~TestView();
      void SetCallBack(ITestCallBack *CallBack);
      void SetIndex(int Indx);
      int GetIndex();
      void SetList(std::list <Media> Liste);
      void ShowView();
 
    private:
      std::vector <GraphicItem*> Items;
      std::vector <GraphicItem*>::iterator Itr;
 
      int SelectIndx;
      void Key_Right();
      void Key_Left();
      void LoadData(std::list <Media> Liste);
      void LoadMenuItems(int Indx);
      void GetXYData(int Indx);
      QPoint *points;
      QTimer* timer;
      QTimer* timer2;
 
      ITestCallBack *callback;
      std::list <Media> _Liste;
 
public slots:
	void Animate();
 
 
protected:
	void showEvent(QShowEvent* event);
};

#pragma once

#include "GenericView.h"
#include "ITestView.h"
#include "ITestCallBack.h"
#include "GraphicItem.h"
#include <QTimer>

class TestView : public GenericView , public ITestView
{
	Q_OBJECT
    public:
      TestView();
      virtual~TestView();
      void SetCallBack(ITestCallBack *CallBack);
      void SetIndex(int Indx);
      int GetIndex();
      void SetList(std::list <Media> Liste);
      void ShowView();

    private:
      std::vector <GraphicItem*> Items;
      std::vector <GraphicItem*>::iterator Itr;

      int SelectIndx;
      void Key_Right();
      void Key_Left();
      void LoadData(std::list <Media> Liste);
      void LoadMenuItems(int Indx);
      void GetXYData(int Indx);
      QPoint *points;
      QTimer* timer;
      QTimer* timer2;

      ITestCallBack *callback;
      std::list <Media> _Liste;

public slots:
	void Animate();


protected:
	void showEvent(QShowEvent* event);
};

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#include "TestView.h"
#include <QPixmap>
 
TestView::TestView()
{
	timer = new QTimer(this);
	timer->setInterval(15);
	connect(timer,SIGNAL(timeout()),this,SLOT(Animate()));
 
}
 
TestView::~TestView()
{
   delete callback;
}
 
 
 
void TestView::Key_Right()
{
   callback->Key_RightPressed();
}   
 
void TestView::Key_Left()
{
	callback->Key_LeftPressed();
}
 
void TestView::SetCallBack(ITestCallBack *CallBack)
{
    callback = CallBack;
}
 
void TestView::SetIndex(int Indx)
{
	if(Indx < Items.size() && Indx >= 0)
	{
		if(!timer->isActive())
		{
			if(Indx > SelectIndx)
			{
				for(int i=0;i<Items.size();i++)
					Items[i]->MoveRight();
 
			}
			else if(Indx < SelectIndx)
			{
				for(int i=0;i<Items.size();i++)
					Items[i]->MoveLeft();
			}
 
			SelectIndx = Indx;
			timer->start();
		}
	}
}
int TestView::GetIndex()
{
    return SelectIndx;
}
 
void TestView::SetList(std::list <Media> Liste)
{
    _Liste = Liste;
    LoadData(_Liste);
}
void TestView::ShowView()
{
    show();
}
 
void TestView::showEvent(QShowEvent* event)
{
	if(!timer->isActive())
		timer->start();
}
 
void TestView::LoadData(std::list <Media> Liste)
{
	int i = 0;
	for(std::list<Media>::iterator itr=Liste.begin();itr != Liste.end();itr++)
	{
		QPixmap pixmap(QString().fromStdString(itr->_PicUrl));
		GraphicItem *item = new GraphicItem(pixmap);
		Items.push_back(item);
		m_GraphicsScene->addItem(item);
		item->setPos(25+i,150);
		i+=200;
	}
 
	SelectIndx = 0;
	LoadMenuItems(SelectIndx);
	Items[SelectIndx]->SelectedStatus(true);
 
}
 
void TestView::Animate()
{
	for(int i = 0; i < Items.size(); ++i)
	        Items[i]->Animate();
 
	    bool stop = true;
	    for(int i = 0; i < Items.size(); ++i)
	    {
	        if(!Items.at(i)->IsRightPlace())
	        {
	            stop = false;
	            break;
	        }
	    }
	    if(stop)
	        timer->stop();
}
 
 
void TestView::LoadMenuItems(int Indx)
{
	GetXYData(Indx);
	for(int i = 0; i < Items.size(); ++i)
		 Items[i]->SetRightPlace(points[i].x(),points[i].y());
 
}
 
void TestView::GetXYData(int Indx)
{
 
	    points = new QPoint[Items.size()];
 
		points[Indx].setX(225);
		points[Indx].setY(150);
 
		for(int i=Indx-1;i>=0;i--)
		{
			points[i].setX(points[i+1].x()-200);
			points[i].setY(150);
		}
 
		for(int i=Indx+1;i<Items.size();i++)
		{
			points[i].setX(points[i-1].x()+200);
			points[i].setY(150);
		}
		for(int i=0;i<Items.size();i++)
				printf("%d = x=%d,y=%d*\n",i,points[i].x(),points[i].y());
 
}

#include "TestView.h"
#include <QPixmap>

TestView::TestView()
{
	timer = new QTimer(this);
	timer->setInterval(15);
	connect(timer,SIGNAL(timeout()),this,SLOT(Animate()));

}

TestView::~TestView()
{
   delete callback;
}



void TestView::Key_Right()
{
   callback->Key_RightPressed();
}   

void TestView::Key_Left()
{
	callback->Key_LeftPressed();
}

void TestView::SetCallBack(ITestCallBack *CallBack)
{
    callback = CallBack;
}

void TestView::SetIndex(int Indx)
{
	if(Indx < Items.size() && Indx >= 0)
	{
		if(!timer->isActive())
		{
			if(Indx > SelectIndx)
			{
				for(int i=0;i<Items.size();i++)
					Items[i]->MoveRight();

			}
			else if(Indx < SelectIndx)
			{
				for(int i=0;i<Items.size();i++)
					Items[i]->MoveLeft();
			}

			SelectIndx = Indx;
			timer->start();
		}
	}
}
int TestView::GetIndex()
{
    return SelectIndx;
}

void TestView::SetList(std::list <Media> Liste)
{
    _Liste = Liste;
    LoadData(_Liste);
}
void TestView::ShowView()
{
    show();
}

void TestView::showEvent(QShowEvent* event)
{
	if(!timer->isActive())
		timer->start();
}

void TestView::LoadData(std::list <Media> Liste)
{
	int i = 0;
	for(std::list<Media>::iterator itr=Liste.begin();itr != Liste.end();itr++)
	{
		QPixmap pixmap(QString().fromStdString(itr->_PicUrl));
		GraphicItem *item = new GraphicItem(pixmap);
		Items.push_back(item);
		m_GraphicsScene->addItem(item);
		item->setPos(25+i,150);
		i+=200;
	}

	SelectIndx = 0;
	LoadMenuItems(SelectIndx);
	Items[SelectIndx]->SelectedStatus(true);

}

void TestView::Animate()
{
	for(int i = 0; i < Items.size(); ++i)
	        Items[i]->Animate();

	    bool stop = true;
	    for(int i = 0; i < Items.size(); ++i)
	    {
	        if(!Items.at(i)->IsRightPlace())
	        {
	            stop = false;
	            break;
	        }
	    }
	    if(stop)
	        timer->stop();
}


void TestView::LoadMenuItems(int Indx)
{
	GetXYData(Indx);
	for(int i = 0; i < Items.size(); ++i)
		 Items[i]->SetRightPlace(points[i].x(),points[i].y());

}

void TestView::GetXYData(int Indx)
{

	    points = new QPoint[Items.size()];

		points[Indx].setX(225);
		points[Indx].setY(150);

		for(int i=Indx-1;i>=0;i--)
		{
			points[i].setX(points[i+1].x()-200);
			points[i].setY(150);
		}

		for(int i=Indx+1;i<Items.size();i++)
		{
			points[i].setX(points[i-1].x()+200);
			points[i].setY(150);
		}
		for(int i=0;i<Items.size();i++)
				printf("%d = x=%d,y=%d*\n",i,points[i].x(),points[i].y());

}

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[wysota]

I think we have a different understanding of the word "minimal". Please strip it to the absolute minimum (not more than 30 lines in total) and post it as an attachment.