hi friends,

Please help me to get the basic method of showing the panview of QGraphicsView

on following the the forum code .
http://qtcenter.org/wiki/index.php?t...ng_and_Zooming

Qt Code: 
  1. {
  2.     QBrush m_background_brush;
  3.     m_background_brush.setStyle(Qt::SolidPattern);
  4.     m_background_brush.setColor(QColor(3, 24, 39));
  5.     Scene->setBackgroundBrush(m_background_brush);
  6.  
  7.  
  8.     //Set-up the view
  9.     setSceneRect(-500, -500, 1000, 1000);
  10. }
  11.  
  12. void MyGraphicsView::SetCenter(const QPointF& centerPoint) {
  13.     //Get the rectangle of the visible area in scene coords
  14.     QRectF visibleArea = mapToScene(rect()).boundingRect();
  15.  
  16.     //Get the scene area
  17.     QRectF sceneBounds = sceneRect();
  18.     double boundX, boundY, boundWidth, boundHeight;
  19.  
  20.     if(centerPoint.x() >= 0)
  21.     {
  22.         boundX = visibleArea.width() / 2.0;
  23.         boundY = visibleArea.height() / 2.0;
  24.         boundWidth = (sceneBounds.width() - 2.0 * boundX);
  25.         boundHeight = (sceneBounds.height() - 2.0 * boundY);
  26.     } else
  27.     {
  28.         boundX = visibleArea.width() / 2.0;
  29.         boundY = visibleArea.height() / 2.0;
  30.         boundWidth = (sceneBounds.width() + 2.0 * boundX);
  31.         boundHeight = (sceneBounds.height() + 2.0 * boundY);
  32.     }
  33.  
  34.     //The max boundary that the centerPoint can be to
  35.     QRectF bounds(boundX, boundY, boundWidth, boundHeight);
  36.  
  37.     if(bounds.contains(centerPoint)) {
  38.  
  39.         CurrentCenterPoint = centerPoint;
  40.     } else {
  41.  
  42.         if(visibleArea.contains(sceneBounds)) {
  43.  
  44.             CurrentCenterPoint = sceneBounds.center();
  45.         } else {
  46.  
  47.             CurrentCenterPoint = centerPoint;
  48.  
  49.  
  50.             if(centerPoint.x() > bounds.x() + bounds.width()) {
  51.                 qDebug()<<"The Clamping on the min X"<<bounds <<" and the clamp:"<< centerPoint;
  52.                 CurrentCenterPoint.setX(bounds.x() + bounds.width());
  53.             } else if(centerPoint.x() < bounds.x()) {
  54.                 CurrentCenterPoint.setX(bounds.x() );
  55.             }
  56.  
  57.             if(centerPoint.y() > bounds.y() + bounds.height()) {
  58.                 qDebug()<<"The Clamping on the min Y";
  59.                 CurrentCenterPoint.setY(bounds.y() + bounds.height());
  60.             } else if(centerPoint.y() < bounds.y()) {
  61.                 CurrentCenterPoint.setY(bounds.y() );
  62.             }
  63.  
  64.         }
  65.     }
  66.  
  67.     qDebug() <<"Update the scrollbars:" << CurrentCenterPoint;
  68.     centerOn(CurrentCenterPoint);
  69. }
  70.  
  71.  
  72.   */
  73. void MyGraphicsView::mousePressEvent(QMouseEvent* event) {
  74.     //For panning the view
  75.     LastPanPoint = event->pos();
  76.     setCursor(Qt::ClosedHandCursor);
  77. }
  78.  
  79. /**
  80.   * Handles when the mouse button is released
  81.   */
  82. void MyGraphicsView::mouseReleaseEvent(QMouseEvent* event) {
  83.     setCursor(Qt::OpenHandCursor);
  84.     LastPanPoint = QPoint();
  85. }
  86.  
  87. /**
  88. *Handles the mouse move event
  89. */
  90. void MyGraphicsView::mouseMoveEvent(QMouseEvent* event) {
  91.     if(!LastPanPoint.isNull()) {
  92.         //Get how much we panned
  93.         QPointF delta = mapToScene(LastPanPoint) - mapToScene(event->pos());
  94.         qDebug()<<"The Wheel Delta value:"<< delta;
  95.         LastPanPoint = event->pos();
  96.  
  97.         //Update the center ie. do the pan
  98.         if(delta.x() < 0 )
  99.         {
  100.             SetCenter(GetCenter() - delta);
  101.         } else
  102.             SetCenter(GetCenter() + delta);
  103.     }
  104. }
  105.  
  106. /**
  107.   * Zoom the view in and out.
  108.   */
  109. void MyGraphicsView::wheelEvent(QWheelEvent* event) {
  110.  
  111.     //Get the position of the mouse before scaling, in scene coords
  112.     QPointF pointBeforeScale(mapToScene(event->pos()));
  113.  
  114.     //Get the original screen centerpoint
  115.     QPointF screenCenter = GetCenter(); //CurrentCenterPoint; //(visRect.center());
  116.  
  117.     //Scale the view ie. do the zoom
  118.     double scaleFactor = 1.15; //How fast we zoom
  119.     if(event->delta() > 0) {
  120.         //Zoom in
  121.         scale(scaleFactor, scaleFactor);
  122.     } else {
  123.         //Zooming out
  124.         scale(1.0 / scaleFactor, 1.0 / scaleFactor);
  125.     }
  126.  
  127.     //Get the position after scaling, in scene coords
  128.     QPointF pointAfterScale(mapToScene(event->pos()));
  129.  
  130.     //Get the offset of how the screen moved
  131.     QPointF offset = pointBeforeScale - pointAfterScale;
  132.  
  133.     //Adjust to the new center for correct zooming
  134.     QPointF newCenter = screenCenter + offset;
  135.     SetCenter(newCenter);
  136. }
  137.  
  138. void MyGraphicsView::resizeEvent(QResizeEvent* event) {
  139.     QRectF visibleArea = mapToScene(rect()).boundingRect();
  140.     SetCenter(visibleArea.center());
  141.  
  142.     //Call the subclass resize so the scrollbars are updated correctly
  143.     QGraphicsView::resizeEvent(event);
  144. }
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but this code pans only on the positive direction of the zoom area ..

.. if i set the sceneRect to (0, 0, 1000, 1000) panning view was clear and perfect ..
please help me to solve this problem ..

Thnks in advance ..