[Qgis-developer] Re: creating a new vector layer supporting all line, point n polygon

[nitin quick]

Hello everybody,
As against my previous approach, i followed a newer one.
Let user put/mark on canvas as QgsMapCanvasItem  and mouse interactivity
using QgsMapCanvasTool.
But i have some issue which i couldn't sort out.
a. When i click on canvas ,after loading plugin , point symbol donot apears
until i refesh.
Header file look like this:-
/*----------vp.h-------------*/
class vP:public QgsMapCanvasItem, public QgsMapTool, public QgisPlugin
{
  Q_OBJECT;
  public:
  vP(QgisApp * theApplication, QgisIface * theInterface);
  //! Destructor
  virtual ~vP();
    //! Mouse move event for overriding
    virtual void canvasMoveEvent(QMouseEvent * e) { }

    //! Mouse press event for overriding
    virtual void canvasPressEvent(QMouseEvent * e) { }

    //! Mouse release event for overriding
    virtual void canvasReleaseEvent(QMouseEvent * e);

     void drawShape(QPainter & p);

     void updatePixmap();

public slots:
  //! init the gui
  virtual void initGui();
  //! Show the dialog box
  void run();
  //! unload the plugin
  void unload();
  //! show the help document
  void help();

  //!draw a raster layer in the qui
  void drawRasterLayer(QString);
  //! Add a vector layer given vectorLayerPath, baseName, providerKey ("ogr"
or "postgres");
  void drawVectorLayer(QString,QString,QString);
  //!will receive signal pbnOk clicked
    void recvOkClicked();
private:
  int mPluginType;
  //! Pointer to our toolbar
  QToolBar *mToolBarPointer;
  //! Pionter to QGIS main application object
  QgisApp *mQGisApp;
  //! Pointer to the QGIS interface object
  QgisIface *mQGisIface;
  //!pointer to the qaction for this plugin
  QAction * mQActionPointer;
    //! container for storing location of elements, later will be made of
appropriate struct
    QList<float > elementList;

};

here is code for drawShape()
    [CODE]
  //!This will draw the elements on to canvas
void vP::drawShape(QPainter &p)
{
    double temp_x, temp_y;
    QgsPoint qPoint(0.0,0.0);
    QPoint cPoint(0,0);
    //loading image to pixmap which will be displayed on points
    QString myFileNameQString= "/home1/qgis/images/vP/hit.png";
    QPixmap myQPixmap;
    myQPixmap.load(myFileNameQString);

    //displaying it at position where the points are marked
    //currently drwing all points which are is in list but only point which
is added latest should be drawn
    QListIterator<float> listIterator(elementList);
    cout<<"\n";
    while(listIterator.hasNext())
    {    temp_x=listIterator.next();
        //cout<<"\t"<<temp_x<<" ";
        if(listIterator.hasNext())
        {    temp_y=listIterator.next(); //cout<<temp_y;
            qPoint.setX(temp_x);
            qPoint.setY(temp_y);
            cPoint=QgsMapCanvasItem::toCanvasCoords(qPoint);
            p.drawPixmap(cPoint.x(),cPoint.y(),myQPixmap);
            show();

        }
        cout<<"vp.cpp-205\t";
    }
    updateCanvas();

    //update();
    cout<<"vp.cpp-210\n";
 }
[/CODE]

I had observer that this function drawShape() is continuously being called.
I myself has not made any connection to it.

Code for canvasReleaseEvent() is :-
void vP::canvasReleaseEvent(QMouseEvent * e)
{
  QgsPoint point =
mQGisIface->getMapCanvas()->getCoordinateTransform()->toMapCoordinates(e->x(),
e->y());
if (e->button() == Qt::LeftButton)
  {
    show();//why here-find out priority at 5
    //!make data available for storage
    cout<<"\nelement bein added "<<point.x()<<" "<<point.y()<<"vp.cpp -171";
    elementList.append(point.x());
    elementList.append(point.y());
  }
}

All advices are welcome. Also i keep stucking at such situations where i i
have to display on canvas through interactivity with user. Will anyone guide
me in improving here?
regards
quickNitin

On 8/21/06, nitin quick <quick.nitin at gmail.com> wrote:
>
> hello everybody,
> Currently i am trying to create a application which let me overlay(
> creation of some  objects using mouse like marking something on map) some
> shapes over current map.
> For this purpose i am thinking of few steps:
> 1. Creating a new vector layer:
>                   Issue: here issue is layer supports only either lineor
> point or polygon but usually i want to have all of these available to me.
> How i can sort out this issue?
> 2. Add projection information ( if this is independent of underlying map's
> projection information)
> 3. Displaying it and editing it.
>
> Any advices on how i can carry out this task more effectively is welcome.
>
> regards
> quickNitin
>
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