Hi,

I have a requirement of Zoom-In and Zoom-Out functionality in my application on MouseScroll event. For the pupose I have used the following code :

private void OnDiagramMouseWheel(object sender, MouseWheelEventArgs e)
{
e.Handled = true;
Point p = e.GetPosition(Parent as ScrollViewer);
Point oldcurpos = diagram.ClientToDoc(p);

diagram.ZoomFactor += e.Delta / 60;

Point newcurpos = diagram.ClientToDoc(e.GetPosition(Parent as ScrollViewer));// diagram.ClientToDoc(e.GetPosition(diagram));
double diffx = (oldcurpos.X - newcurpos.X);
double diffy = (oldcurpos.Y - newcurpos.Y);

diagram.ScrollTo(new Point(
diagram.ScrollX + diffx < 0 ? 0 : diagram.ScrollX + diffx,
diagram.ScrollY + diffy < 0 ? 0 : diagram.ScrollY + diffy));
}

The issues faced by me are as follows :

1. In my diagram I have a node placed at coordinates (200,-80). Now when I Zoom-In the diagram this node disappears even with the slightest of zoom.

2. I require the diagram should always fit to the container i.e when I Zoom-In and Zoom-Out the diagram should not get resized only the items within that diagram should get zoomed in and zoomed-out. The diagram should always fit to the container.

3. The zoom-in and zoom-out should be respective to the mouse position while moving the mouse wheel.

Any suggestion how can I accomplish these requirements.

Thanks and Regards,
Anant Shukla.

2. Set the ScrollViewer's Background to have the same value as the diagram's BackBrush and the effect should be pretty much the same.

Hi Stoyan,

Thanks for the sample code.

The code is working fine.

Whereas I do have another requirement which is I require the diagram to resize itself accordingly to fit all the items present on the diagram at moment of initialization of the diagram. The code used by me to initialize the diagram is as follows :

private void InitDiagram(Diagram diagram)
{
diagram.AllowSelfLoops = false;
diagram.AllowUnconnectedLinks = false;
diagram.AllowLinksRepeat = false;
diagram.Behavior = Behavior.Modify;
diagram.BackBrush = Brushes.LightBlue;
diagram.AutoResize = AutoResize.AllDirections;
double newScrollX = diagram.ScrollX;
double newScrollY = diagram.ScrollY;
Rect newBounds = diagram.ClientToDoc(
new Rect(0,0,scrollViewer.ActualWidth, scrollViewer.ActualHeight));
newBounds.X = newScrollX;
newBounds.Y = newScrollY;
newBounds.Union(diagram.GetContentBounds(false, false));
newBounds.Inflate(50, 50);
diagram.Bounds = newBounds;

diagram.ScrollTo(new Point(newScrollX, newScrollY));

}

Can you please tell me what I am missing here.

Thanks and Regards,
Anant Shukla.

Hi Stoyan,

There are few issues in the same Zoom-In and Zoom-Out functionality.

1. I needed the diagram should occupy the complete container area no matter I Zoom-In or Zoom-Out. You suggested to match the ScrollViewers background property with the diagram's backbrush property. But this do not resolve the issue because the diagram area still resizes when I Zoom-In or Zoom-Out. I do not want the diagram to resize it should always fit to the container.

2. I want my diagram should zoom to fit all the items present on the diagram when the diagram is initialized. I tried the ZoomToFit method but its not working and I also need the diagram to zoom only when required i.e if there is only one node in the diagram then it should get zoomed. The code used by me is as follows :

private void InitDiagram(Diagram diagram)
{
diagram.Behavior = Behavior.Modify;
diagram.BackBrush = Brushes.LightBlue;
diagram.AutoResize = AutoResize.AllDirections;
diagram.AutoScroll = false;
diagram.AllowSelfLoops = false;
diagram.AllowUnconnectedLinks = false;
diagram.AllowLinksRepeat = false;
diagram.LinkCrossings = LinkCrossings.Arcs;
diagram.ZoomToFit();

}

3. In Your suggestion which is as follows :

" The code above should do that when the diagram.Bounds is larger than the ScrollViewer's visible area. However if it's smaller, it won't work because it would require setting a new scroll position, and the ScrollViewer doesn't allow that when its content is smaller than the visible area. A solution is to always set diagram.Bounds to a value that would make the zoomed content larger than the scrollviewer, e.g. this seems to work

Code:

private void OnDiagramMouseWheel(object sender, MouseWheelEventArgs e)
{

e.Handled = true;

Point p = e.GetPosition(Parent as ScrollViewer);

Point oldcurpos = diagram.ClientToDoc(p);


double newScrollX = diagram.ScrollX;

double newScrollY = diagram.ScrollY;

diagram.ZoomFactor += e.Delta / 60;


Rect newBounds = diagram.ClientToDoc(


new Rect(0, 0, scrollViewer.ActualWidth, scrollViewer.ActualHeight));


Point newcurpos = diagram.ClientToDoc(e.GetPosition(Parent as ScrollViewer));

double diffx = (oldcurpos.X - newcurpos.X);

double diffy = (oldcurpos.Y - newcurpos.Y);

newScrollX += diffx;

newScrollY += diffy;


newBounds.X = newScrollX;

newBounds.Y = newScrollY;

newBounds.Union(diagram.GetContentBounds(false, false));

newBounds.Inflate(200, 200);

diagram.Bounds = newBounds;


diagram.ScrollTo(new Point(newScrollX, newScrollY));
}

"
What is the "scrollViewer" variable can you describe in detail. How to declare that. Also after a particular value of zooming out it stops working.

Any suggestion how can I resolve above issues.

Thanks and Regards,
Anant Shukla.

This happens if the diagram is initially smaller than the scrollviewer, right?

1. You could add this to the Window_Loaded handler:

diagram.Bounds = diagram.ClientToDoc(
	new Rect(0, 0, scrollViewer.ActualWidth, scrollViewer.ActualHeight));
 

2. Should be possible if you subtract the offset of the diagram's top-left corner from the scrollviers's top-left corner from ths point in the MouseWheel code:
...
Point p = e.GetPosition(Parent as ScrollViewer); 
p.X -= ???;
p.Y -= ???;
...
I don't know how you can find that offset though.

Stoyan

http://mindfusion.eu/Forum/YaBB.pl?board=wpfdg_disc;action=display;num=123755029...

I hope that helps.
Stoyan