# SelectedGraphIDs

VTKExamples/Python/Infovis/SelectedGraphIDs

### Code

SelectedGraphIDs.py

    #!/usr/bin/env python

    # This is a variation on VTK/Examples/Infovis/Python/selection.py
    # which shows how to use a vtkAnnotationLink to view the contents
    # of a selection from a vtkGraphLayoutView

    from __future__ import print_function
    import vtk

    source = vtk.vtkRandomGraphSource()
    source.DirectedOff()
    source.SetNumberOfVertices(100)
    source.SetEdgeProbability(0)  # Basically generates a tree
    source.SetUseEdgeProbability(True)
    source.SetStartWithTree(True)
    source.IncludeEdgeWeightsOn()

    # Create force directed layout
    strategy = vtk.vtkSimple2DLayoutStrategy()
    strategy.SetInitialTemperature(5)

    # Create a graph layout view
    view = vtk.vtkGraphLayoutView()
    view.AddRepresentationFromInputConnection(source.GetOutputPort())
    view.SetVertexLabelArrayName("vertex id")
    view.SetVertexLabelVisibility(True)
    view.SetVertexColorArrayName("vertex id")
    view.SetColorVertices(True)
    view.SetEdgeColorArrayName("edge weight")
    view.SetColorEdges(True)
    view.SetLayoutStrategy(strategy)

    # Make sure the views are using a pedigree id selection
    view.GetRepresentation(0).SetSelectionType(2)

    # Create a selection link and set both view to use it
    annotationLink = vtk.vtkAnnotationLink()
    view.GetRepresentation(0).SetAnnotationLink(annotationLink)

    def select_callback(caller, event):
        # In this particular data representation the current selection in the
        # annotation link should always contain two nodes: one for the edges and
        # one for the vertices. Which is which is not consistent, so you need to
        # check the FieldType of each SelectionNode

        sel = caller.GetCurrentSelection()

        for nn in range(sel.GetNumberOfNodes()):
            sel_ids = sel.GetNode(nn).GetSelectionList()
            field_type = sel.GetNode(nn).GetFieldType()
            if field_type == 3:
                print("Vertex selection Pedigree IDs")
            if field_type == 4:
                print("Edge selection Pedigree IDs")
            if sel_ids.GetNumberOfTuples() > 0:
                for ii in range(sel_ids.GetNumberOfTuples()):
                    print(int(sel_ids.GetTuple1(ii)))
            else:
                print("-- empty")

        print("")

    # AnnotationChangedEvent will fire when the selection is changed
    annotationLink.AddObserver("AnnotationChangedEvent", select_callback)

    # Set the theme on the view
    theme = vtk.vtkViewTheme.CreateMellowTheme()
    theme.SetLineWidth(5)
    theme.SetPointSize(10)
    theme.SetCellOpacity(0.99)
    theme.SetOutlineColor(0.6, 0.6, 0.6)
    # Vertices
    theme.SetSelectedPointColor(0, 0.5, 1)
    theme.SetPointHueRange(1.0, 1.0)
    theme.SetPointSaturationRange(1.0, 1.0)
    theme.SetPointValueRange(0.0, 1.0)
    # theme.SetPointAlphaRange(0.2, 0.8)
    # Edges
    theme.SetSelectedCellColor(1.0, 0.95, 0.75)
    theme.SetCellHueRange(0.1, 0.1)
    theme.SetCellSaturationRange(0.2, 1.0)
    theme.SetCellValueRange(0.5, 1.0)
    # theme.SetPointAlphaRange(0.2, 0.8)
    view.ApplyViewTheme(theme)
    theme.FastDelete()

    view.GetRenderWindow().SetSize(600, 600)
    view.ResetCamera()
    view.Render()

    view.GetInteractor().Start()