Problem with labeled edges

Question

Hi,

 

I'm working on a graph that have nodes and Labeled Edges. In the Viewer I have enabled the Layout Algorithm settings button. When I change the Layout Method to "MDS" or "Ranking" the graph is drawn without Labels. Then I try to drag some node I get an unhandled NullReferenceException. This only occurs if I try to drag a node linked to a edge labeled.

Next I paste the stacktrace:

 

System.NullReferenceException was unhandled
  Message="Object reference not set to an instance of an object."
  Source="Microsoft.Msagl.GraphViewerGdi"
  StackTrace:
       at Microsoft.Msagl.GraphViewerGdi.DGraph.RebuildBBHierarchyUnderObject(DObject dObj)
       at Microsoft.Msagl.GraphViewerGdi.DGraph.UpdateBBoxHierarchy(IEnumerable`1 movedObjects)
       at Microsoft.Msagl.GraphViewerGdi.GViewer.OnDragEnd(IEnumerable`1 changedObjects)
       at Microsoft.Msagl.Drawing.DrawingLayoutEditor.viewer_MouseUp(Object sender, MsaglMouseEventArgs args)
       at Microsoft.Msagl.GraphViewerGdi.GViewer.RaiseMouseUpEvent(MsaglMouseEventArgs iArgs)
       at Microsoft.Msagl.GraphViewerGdi.DrawingPanel.OnMouseUp(MouseEventArgs args)
       at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
       at System.Windows.Forms.Control.WndProc(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
       at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
       at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
       at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
       at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
       at System.Windows.Forms.Application.Run(Form mainForm)
       at TestMSAGL.Program.Main() in C:\Users\dcaicedo\Documents\Visual Studio 2008\Projects\TestMSAGL\TestMSAGL\Program.cs:line 18
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException:

 

Thanks in advance,

 

Daniel

Answer 1

Hi Daniel,

Thank you for reporting the bug.  The problem will be fixed and the sources of the viewer with the fix will be availabe but  not immediately.  Please for the time being,  as a workaround, remove the edge labels before using layout others than the Sugiyama scheme.

Lev

Answer 2

Hi Lev,

just purchased MSAGL and while I am quite impressed by the ease of graph handling over Glee, the above issue is still present.
I need to visualize RDF-based graph structures so both MDS and edge-labels (for predicates) combined are a necessity for whichever graph visualization is used.

MSAGL allowing edge labels was the major feature which made me go for your solution instead of some scenario involving Graphviz/Dot2Wpf after all.


Thank you for the otherwise very nice Library,
Hinnerk


edit:
Sorry if I am somehow blind here, but your post http://social.msdn.microsoft.com/Forums/en-US/automaticgraphlayout/thread/29d15b24-b1ae-4cf8-b60b-023880686c25 gave the impression sources for the viewer would be available in the package on Windows Store, but I see only /bin and /samples in the version I got.
Is there a difference in the European (which I used) and US download?

Answer 3

Hi Hinnerk,
It seems that only today the new version with the viewer sources and with your problem solved has appeared at the UK store. Sorry for the confusion. Can you try to download the MSI again?
Thanks,
Lev

---

Lev Nachmanson

Answer 4

Hi Lev,

thank you for your fast and helpful reply.
I ended up having to retour and reorder MSAGL to get the 2.1 version but now everything works fine as you described.

Again thanks a bunch,
Hinnerk

Answer 5

hi,

i have MSAGL 2.1 version only but still i have the problem with labeled edges

if i drag some node I get an unhandled NullReferenceException .

any one can help how to solve it ..............

 

Thanks in Advance,

Aravinda

 

 

 

 

 

Answer 6

hi LEV,


In  MSAGL 2.1 version, how to enable label display for edges  while using MDSLayoutSettings.


Plz reply as soon as possible.


Thanks In Advance

 

Answer 7

Hi Aravindabe,
The labels for MDS layouts are not supported, sorry.
Thanks,
Lev

---

Lev Nachmanson

Answer 8

Hi Lev,

     Thanks for ur immediate reply.

Answer 9

Hi again Lev,

Is there a reasonably easy/quick way to put edge labels for MDS in the code, just the same as with the mds layout problem with no viewer.  Could you just give us some input where to look in the code for it etc.  Thanks a lot.

 

Dino

 

Answer 10

Hi Dino,

Not rendering of labels in MDS layout is pretty much hard coded. You can try the following hack that seems working for me. It draws each label on the center of its edge.

edit: C:\dev\MSAGL_RTMJune2008\GraphViewerGDI\DGraph.cs
File: GraphViewerGDI\DGraph.cs
===================================================================
308a309,328
>             //hack for MDS label start - it is the very end of  DGraph.DrawEdge
>             if (dEdge.Label != null) {
>                 var geomEdge = drawingEdge.Attr.GeometryEdge;
>                 var center = 0.5 * (geomEdge.Source.Center + geomEdge.Target.Center);
>                 using (SolidBrush sb = new SolidBrush(Draw.MsaglColorToDrawingColor(dEdge.Label.DrawingLabel.FontColor)))
>                 {
>                     double w;
>                     double h;
>                     var font = dEdge.Label.Font;
>                     StringMeasure.MeasureWithFont(dEdge.Label.DrawingLabel.Text, font, out w, out h);
>
>                     Draw.DrawStringInRectCenter(graphics, sb,
>                     font, dEdge.Label.DrawingLabel.Text,
>                                                            new RectangleF((float)(center.X-w/2), (float)(center.Y-h/2),
>                                                                           (float)w, (float)h));
>                 }
>
>             }
>             //hack for MDS labels end
>
===================================================================
edit: C:\dev\MSAGL_RTMJune2008\GraphViewerGDI\Draw.cs
File: GraphViewerGDI\Draw.cs
===================================================================
570c570
<         static void DrawStringInRectCenter(Graphics g, Brush brush, Font f, string s, RectangleF r /*, double rectLineWidth*/) {
---
>         static internal void DrawStringInRectCenter(Graphics g, Brush brush, Font f, string s, RectangleF r /*, double rectLineWidth*/) {
===================================================================
edit: C:\dev\MSAGL_RTMJune2008\Samples\WindowsApplicationSample\Form1.cs
File: Samples\WindowsApplicationSample\Form1.cs
===================================================================
8a9,10
> using Microsoft.Msagl.GraphViewerGdi;
> using Microsoft.Msagl.Mds;
171c173,174
<
---
>             gViewer.CurrentLayoutMethod= LayoutMethod.UseSettingsOfTheGraph; //testing that the hack works
>             graph.LayoutAlgorithmSettings = new MdsLayoutSettings();
===================================================================

---

Lev Nachmanson

Answer 11

Hi,

that was quick... thanks a lot, I will try it out.

---

Dino

Answer 12

Hi again,

and thanks again Lev for your snippet, it works nice.  Here is only a little enhancement which introduces offset to the Label position:

            //hack for MDS label start - it is the very end of  DGraph.DrawEdge
            if (dEdge.Label != null)
            {
                var geomEdge = drawingEdge.Attr.GeometryEdge;
                var srcCenter = geomEdge.Source.Center;
                var trgCenter = geomEdge.Target.Center;
                var center = 0.5 * (srcCenter + trgCenter);
                
                //To control the offset for differently inclined edges
                double Xoffset =  Math.Abs(srcCenter.X - trgCenter.X);
                double gradient = Xoffset > 0.1 ?  Math.Abs(srcCenter.Y - trgCenter.Y) / Math.Abs(srcCenter.X - trgCenter.X) : 0;

                using (SolidBrush sb = new SolidBrush(Draw.MsaglColorToDrawingColor(dEdge.Label.DrawingLabel.FontColor)))
                {
                    double w;
                    double h;
                    var font = dEdge.Label.Font;
                    StringMeasure.MeasureWithFont(dEdge.Label.DrawingLabel.Text, font, out w, out h);

                    RectangleF rct;

                    //Specially handle small angle or incline
                    if (gradient < 0.2)
                    {
                        var y = center.Y;

                        if (srcCenter.X < trgCenter.X )
                           y += 3;
                        else
                          y -= h ;

                        rct = new RectangleF((float)(center.X - w / 2), (float)y, (float)w, (float)h);

                    }

                    else if ((srcCenter.X < trgCenter.X &&  srcCenter.Y < trgCenter.Y) ||
                             (srcCenter.X > trgCenter.X && srcCenter.Y > trgCenter.Y))
                        rct = new RectangleF((float)(center.X - w - 3), (float)(center.Y + 3), (float)w, (float)h);                      

                    else if ((srcCenter.X < trgCenter.X && srcCenter.Y > trgCenter.Y) ||
                            (srcCenter.X > trgCenter.X && srcCenter.Y < trgCenter.Y))
                        rct = new RectangleF((float)(center.X + 3), (float)(center.Y + 3), (float)w, (float)h);
                    else
                        rct = new RectangleF((float)(center.X - w / 2), (float)(center.Y - h/2), (float)w, (float)h);

                    Draw.DrawStringInRectCenter(graphics, sb, font, dEdge.Label.DrawingLabel.Text, rct);
                }

            }
            //hack for MDS labels end

---

Dino