QGraphicsView coordinate system

[roband915]

Nothing really. The map(QGraphicsItem) is still centered and small.

I tried your zoom method and I still get the same result. After just a few movements with the wheel then the map disappears.

[totem]

After adding an item to the scene, the following code should have worked

ui->graphicsView->fitInView(scene->itemsBoundingRect());

ui->graphicsView->fitInView(scene->itemsBoundingRect());

To copy to clipboard, switch view to plain text mode 

Can you post your graphicsitem's code ? because I don't see were the problem comes from. Something must be wrong, like item's bounding rect or something

[roband915]

Hmm ok maybe like you said I´m doing something wrong in with the QGraphicsItem.
Here is the .h file

#ifndef ITEM_H
#define ITEM_H
 
#include <QGraphicsItem>
#include <QPointF>
#include <QRectF>
#include <QPolygonF>
#include <QPainter>
#include <QPainterPath>
#include <QWidget>
#include <QGraphicsSceneMouseEvent>
#include <QGraphicsSceneHoverEvent>
#include <QMessageBox>
#include <shapelib/shapefil.h>
 
#include <object.h>
 
class item : public QObject, public QGraphicsItem
{
	Q_OBJECT
public:
   item(QGraphicsItem *parent = 0);
 
   QRectF boundingRect() const;
   void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
   void OpenShapeFile(char *fileName);
 
   virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event);
   virtual void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
   virtual void mouseMoveEvent(QGraphicsSceneEvent *event);
 
   QVector<object*> vMap;
   object *map;
 
private:
   typedef struct MyPoint2D
   {
	   double x;
	   double y;
   }MyPoint2D;
 
   std::vector<MyPoint2D> vPoints;
 
   typedef struct MyLineString2D
   {
	   std::vector<MyPoint2D> vPointList;
   }MyLineString2D;
 
	//Holds coordinates of Line Shapefile
   std::vector<MyLineString2D> vLines;
 
   typedef struct MyPolygon2D
   {
	   std::vector<MyPoint2D> vPointList;
 
   }MyPolygon2D;
 
   //Holds coordinates of Polygon Shapefile
   std::vector<MyPolygon2D> vPolygons;
 
   typedef struct SBoundingBox
   {
	   qreal maxX;
	   qreal maxY;
	   qreal minX;
	   qreal minY;
   }SBoundingBox;
 
   qreal xMax,yMax,x2Min,y2Min;
   //BoundingBox of Shapefile
   SBoundingBox sBoundingBox;
};
 
#endif // ITEM_H

#ifndef ITEM_H
#define ITEM_H

#include <QGraphicsItem>
#include <QPointF>
#include <QRectF>
#include <QPolygonF>
#include <QPainter>
#include <QPainterPath>
#include <QWidget>
#include <QGraphicsSceneMouseEvent>
#include <QGraphicsSceneHoverEvent>
#include <QMessageBox>
#include <shapelib/shapefil.h>

#include <object.h>

class item : public QObject, public QGraphicsItem
{
	Q_OBJECT
public:
   item(QGraphicsItem *parent = 0);

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

   virtual void hoverEnterEvent(QGraphicsSceneHoverEvent *event);
   virtual void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
   virtual void mouseMoveEvent(QGraphicsSceneEvent *event);

   QVector<object*> vMap;
   object *map;

private:
   typedef struct MyPoint2D
   {
	   double x;
	   double y;
   }MyPoint2D;

   std::vector<MyPoint2D> vPoints;

   typedef struct MyLineString2D
   {
	   std::vector<MyPoint2D> vPointList;
   }MyLineString2D;

	//Holds coordinates of Line Shapefile
   std::vector<MyLineString2D> vLines;

   typedef struct MyPolygon2D
   {
	   std::vector<MyPoint2D> vPointList;

   }MyPolygon2D;

   //Holds coordinates of Polygon Shapefile
   std::vector<MyPolygon2D> vPolygons;

   typedef struct SBoundingBox
   {
	   qreal maxX;
	   qreal maxY;
	   qreal minX;
	   qreal minY;
   }SBoundingBox;

   qreal xMax,yMax,x2Min,y2Min;
   //BoundingBox of Shapefile
   SBoundingBox sBoundingBox;
};

#endif // ITEM_H

To copy to clipboard, switch view to plain text mode 

And the .cpp file

#include "item.h"
 
item::item(QGraphicsItem *parent)
    : QObject(), QGraphicsItem(parent)
{
	setAcceptHoverEvents(true);
	setFlags(ItemIsMovable | ItemIsFocusable | QGraphicsItem::ItemIsSelectable);
}
 
QRectF item::boundingRect() const
{
	QRectF recWindow;
	recWindow.setBottomLeft(QPointF(sBoundingBox.minX,sBoundingBox.minY));
	recWindow.setBottomRight(QPointF(sBoundingBox.maxX, sBoundingBox.minY));
	recWindow.setTopLeft(QPointF(sBoundingBox.minX,sBoundingBox.maxY));
	recWindow.setTopRight(QPointF(sBoundingBox.maxX,sBoundingBox.maxY));
	return recWindow;
}
 
void item::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
	OpenShapeFile("./Maps/Norden_wgs84.shp");
	painter->setRenderHint(QPainter::Antialiasing);
	painter->setBrush(Qt::red);
 
	for(int i = 0;i< vMap.size(); i++)
	{
		painter->drawPolyline(vMap.at(i)->p.data() ,vMap.at(i)->p.size());
	}
}
 
void item::hoverEnterEvent(QGraphicsSceneHoverEvent* event)
{
}
 
void item::mousePressEvent(QGraphicsSceneMouseEvent* event)
{
}
 
void item::mouseMoveEvent(QGraphicsSceneEvent *event)
{
}
 
void item::OpenShapeFile(char *fileName)
{
    SHPHandle hSHP = SHPOpen(fileName, "rb");
 
    if(hSHP == NULL)
    {
        QMessageBox m;
        m.setText("Could not open shape.");
        m.exec();
    }
    else
    {
        //Read boundingbox of shapefile.
        sBoundingBox.maxX = hSHP->adBoundsMax[0];
        sBoundingBox.maxY = hSHP->adBoundsMax[1];
 
        sBoundingBox.minX = hSHP->adBoundsMin[0];
        sBoundingBox.minY = hSHP->adBoundsMin[1];
 
        //Point shape-file
        if(hSHP->nShapeType == SHPT_POINT)
        {
                SHPObject *psShape;
                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        double fX = psShape->padfX[0];
                        double fY = -psShape->padfY[0];
 
                        //Plot these points
                        MyPoint2D pt;
                        pt.x = fX;
                        pt.y = fY;
 
                        vPoints.push_back(pt);
                }
        }
 
        //Line Shapefile
        else if(hSHP->nShapeType == SHPT_ARC)
        {
                SHPObject *psShape;
 
                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        std::vector<MyPoint2D> tempPointArray;
                        QVector<QPointF> tempQPointArray;
                        map = new object();
 
                        for(int j=0;j<psShape->nVertices;j++)
                        {
                                double fX = psShape->padfX[j];
                                double fY = psShape->padfY[j];
                                MyPoint2D pt;
                                pt.x = fX;
                                pt.y= fY;
 
                                //QT Point
                                QPointF test = QPointF(fX,fY);
 
                                map->addVertices(test);
                                tempPointArray.push_back(pt);
                        }
 
                        vMap.push_back(map);
 
                        MyLineString2D linestring;
                        linestring.vPointList=tempPointArray;
                        vLines.push_back(linestring);
                }
        }
 
        //Polygon Shapefile
        if(hSHP->nShapeType == SHPT_POLYGON)
        {
                SHPObject *psShape;
                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        std::vector<MyPoint2D> tempPointArray;
 
                        for(int j=0;j<psShape->nVertices;j++)
                        {
                                double fX = psShape->padfX[j];
                                double fY = psShape->padfY[j];
                                MyPoint2D pt;
                                pt.x = fX;
                                pt.y= fY;
 
                                tempPointArray.push_back(pt);
                        }
 
                        MyPolygon2D polygon;
                        polygon.vPointList = tempPointArray;
                        vPolygons.push_back(polygon);
                }
        }
    }
}

#include "item.h"

item::item(QGraphicsItem *parent)
    : QObject(), QGraphicsItem(parent)
{
	setAcceptHoverEvents(true);
	setFlags(ItemIsMovable | ItemIsFocusable | QGraphicsItem::ItemIsSelectable);
}

QRectF item::boundingRect() const
{
	QRectF recWindow;
	recWindow.setBottomLeft(QPointF(sBoundingBox.minX,sBoundingBox.minY));
	recWindow.setBottomRight(QPointF(sBoundingBox.maxX, sBoundingBox.minY));
	recWindow.setTopLeft(QPointF(sBoundingBox.minX,sBoundingBox.maxY));
	recWindow.setTopRight(QPointF(sBoundingBox.maxX,sBoundingBox.maxY));
	return recWindow;
}

void item::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
	OpenShapeFile("./Maps/Norden_wgs84.shp");
	painter->setRenderHint(QPainter::Antialiasing);
	painter->setBrush(Qt::red);

	for(int i = 0;i< vMap.size(); i++)
	{
		painter->drawPolyline(vMap.at(i)->p.data() ,vMap.at(i)->p.size());
	}
}

void item::hoverEnterEvent(QGraphicsSceneHoverEvent* event)
{
}

void item::mousePressEvent(QGraphicsSceneMouseEvent* event)
{
}

void item::mouseMoveEvent(QGraphicsSceneEvent *event)
{
}

void item::OpenShapeFile(char *fileName)
{
    SHPHandle hSHP = SHPOpen(fileName, "rb");

    if(hSHP == NULL)
    {
        QMessageBox m;
        m.setText("Could not open shape.");
        m.exec();
    }
    else
    {
        //Read boundingbox of shapefile.
        sBoundingBox.maxX = hSHP->adBoundsMax[0];
        sBoundingBox.maxY = hSHP->adBoundsMax[1];

        sBoundingBox.minX = hSHP->adBoundsMin[0];
        sBoundingBox.minY = hSHP->adBoundsMin[1];

        //Point shape-file
        if(hSHP->nShapeType == SHPT_POINT)
        {
                SHPObject *psShape;
                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        double fX = psShape->padfX[0];
                        double fY = -psShape->padfY[0];

                        //Plot these points
                        MyPoint2D pt;
                        pt.x = fX;
                        pt.y = fY;

                        vPoints.push_back(pt);
                }
        }

        //Line Shapefile
        else if(hSHP->nShapeType == SHPT_ARC)
        {
                SHPObject *psShape;

                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        std::vector<MyPoint2D> tempPointArray;
                        QVector<QPointF> tempQPointArray;
                        map = new object();

                        for(int j=0;j<psShape->nVertices;j++)
                        {
                                double fX = psShape->padfX[j];
                                double fY = psShape->padfY[j];
                                MyPoint2D pt;
                                pt.x = fX;
                                pt.y= fY;

                                //QT Point
                                QPointF test = QPointF(fX,fY);

                                map->addVertices(test);
                                tempPointArray.push_back(pt);
                        }

                        vMap.push_back(map);

                        MyLineString2D linestring;
                        linestring.vPointList=tempPointArray;
                        vLines.push_back(linestring);
                }
        }

        //Polygon Shapefile
        if(hSHP->nShapeType == SHPT_POLYGON)
        {
                SHPObject *psShape;
                for(int i=0;i<hSHP->nRecords;i++)
                {
                        psShape = SHPReadObject(hSHP, i);
                        std::vector<MyPoint2D> tempPointArray;

                        for(int j=0;j<psShape->nVertices;j++)
                        {
                                double fX = psShape->padfX[j];
                                double fY = psShape->padfY[j];
                                MyPoint2D pt;
                                pt.x = fX;
                                pt.y= fY;

                                tempPointArray.push_back(pt);
                        }

                        MyPolygon2D polygon;
                        polygon.vPointList = tempPointArray;
                        vPolygons.push_back(polygon);
                }
        }
    }
}

To copy to clipboard, switch view to plain text mode 

[totem]

Looking your ::boundingRect() method, did you scale view's Y to -1 or not ?
In QGraphicsScene nominal coordinate system, the bottom of a valid QRectF has a greater value than its top, which is not the case in your code (bottom<top).

Try to define your boundingrect as follow : a point in space (x,y) and 2D dimensions (width,height)

Otherwise I don't see what can be wrong for now..

Beside, you define custom structs where using Qt would just be fine : I'm thinking of

MyPolygon2D => QPolygonF
MyPoint2D => QPointF
MyLineString2D => QPainterPath
SBoundingBox => QRectF

Another thing : you read your file and initialize your structs each time you paint your item, which is not good. You could read your file once in constructor, initialize some member and use these members in your paint method. Plus, it seems your OpenShapeFile() contains memory leaks (1 new == 1 delete somewhere in your code)