hi friends,

I just implement the pan zooming of QGraphicsView by following this example in this forum

http://qtcenter.org/wiki/index.php?t...ng_and_Zooming


but this pan zooming was behaving different when i change the coordinates of the scene from (0, 0, 1000, 1000) to ( -500, -500, 1000, 1000)
i tried to identify where to correct but failed

Qt Code: 
  1. QRectF visibleArea = mapToScene(rect()).boundingRect();
  2.  
  3.     //Get the scene area
  4.     QRectF sceneBounds = sceneRect();
  5.  
  6.     double boundX = visibleArea.width() / 2.0;
  7.     double boundY = visibleArea.height() / 2.0;
  8.     double boundWidth = sceneBounds.width() - 2.0 * boundX;
  9.     double boundHeight = sceneBounds.height() - 2.0 * boundY;
  10.  
  11.     //The max boundary that the centerPoint can be to
  12.     QRectF bounds(boundX, boundY, boundWidth, boundHeight);
  13.  
  14.     if(bounds.contains(centerPoint)) {
  15.         //We are within the bounds
  16.         CurrentCenterPoint = centerPoint;
  17.     } else {
  18.         //We need to clamp or use the center of the screen
  19.         if(visibleArea.contains(sceneBounds)) {
  20.             //Use the center of scene ie. we can see the whole scene
  21.             CurrentCenterPoint = sceneBounds.center();
  22.         } else {
  23.  
  24.             CurrentCenterPoint = centerPoint;
  25.  
  26.             //We need to clamp the center. The centerPoint is too large
  27.             if(centerPoint.x() > bounds.x() + bounds.width()) {
  28.                 CurrentCenterPoint.setX(bounds.x() + bounds.width());
  29.             } else if(centerPoint.x() < bounds.x()) {
  30.                 CurrentCenterPoint.setX(bounds.x());
  31.             }
  32.  
  33.             if(centerPoint.y() > bounds.y() + bounds.height()) {
  34.                 CurrentCenterPoint.setY(bounds.y() + bounds.height());
  35.             } else if(centerPoint.y() < bounds.y()) {
  36.                 CurrentCenterPoint.setY(bounds.y());
  37.             }
  38.  
  39.         }
  40.     }
  41.  
  42.     //Update the scrollbars
  43.     centerOn(CurrentCenterPoint);
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is where they are centering the viewport but while zooming only positive half was visible and pan is not working

please help me