Added ConstructTree, CreateTree

src/PythonicAPI.md

@@ -308,6 +308,8 @@ This section includes ?vtkUnstructuredGrid?.
 
 | Example Name | Description | Image |
 | -------------- | ------------- | ------- |
+[ConstructTree](/PythonicAPI/Graphs/ConstructTree) | Construct a tree.
+[CreateTree](/PythonicAPI/Graphs/CreateTree) | Create a tree and label the vertices and edges.
 [GraphToPolyData](/PythonicAPI/Graphs/GraphToPolyData) | Convert a graph to a PolyData.
 [LabelVerticesAndEdges](/PythonicAPI/Graphs/LabelVerticesAndEdges) | Label vertices and edges.
 [SideBySideGraphs](/PythonicAPI/Graphs/SideBySideGraphs) | Display two graphs side by side.

src/PythonicAPI/Graphs/ConstructTree.py

+#!/usr/bin/env python3
+
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkInteractionStyle
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkRenderingOpenGL2
+from vtkmodules.vtkCommonDataModel import (
+    vtkMutableDirectedGraph,
+    vtkTree
+)
+from vtkmodules.vtkViewsInfovis import vtkGraphLayoutView
+
+
+def main():
+    graph = vtkMutableDirectedGraph()
+
+    v1 = graph.AddVertex()
+    v2 = graph.AddChild(v1)
+    graph.AddChild(v1)
+    graph.AddChild(v2)
+
+    # equivalent to:
+    # V1 = g.AddVertex()
+    # V2 = g.AddVertex()
+    # V3 = g.AddVertex()
+    # V4 = g.AddVertex()
+
+    # g.AddEdge ( V1, V2 )
+    # g.AddEdge ( V1, V3 )
+    # g.AddEdge ( V2, V4 )
+
+    tree = vtkTree()
+    success = tree.CheckedShallowCopy(graph)
+    print('Success?', success)
+
+    tree_layout_view = vtkGraphLayoutView(layout_strategy='Tree')
+    tree_layout_view.AddRepresentationFromInput(tree)
+    tree_layout_view.ResetCamera()
+    tree_layout_view.Render()
+    tree_layout_view.interactor.Start()
+
+
+if __name__ == '__main__':
+    main()

src/PythonicAPI/Graphs/CreateTree.md

+### Description
+
+We create the tree, and label the vertices and edges.
+
+!!! info
+  This is an update of the original example found in `vtk/Examples/Infovis/Cxx/CreateTree.cxx`.

src/PythonicAPI/Graphs/CreateTree.py

+#!/usr/bin/env python3
+
+# This example creates a tree and labels the vertices and edges.
+
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkInteractionStyle
+# noinspection PyUnresolvedReferences
+import vtkmodules.vtkRenderingOpenGL2
+from vtkmodules.vtkCommonCore import vtkStringArray
+from vtkmodules.vtkCommonDataModel import (
+    vtkMutableDirectedGraph,
+    vtkTree
+)
+from vtkmodules.vtkViewsCore import vtkViewTheme
+from vtkmodules.vtkViewsInfovis import vtkGraphLayoutView
+
+
+def main():
+    graph = vtkMutableDirectedGraph()
+
+    a = graph.AddVertex()
+    b = graph.AddChild(a)
+    c = graph.AddChild(a)
+    d = graph.AddChild(b)
+    e = graph.AddChild(c)
+    f = graph.AddChild(c)
+
+    vertex_labels = vtkStringArray()
+    vertex_labels.name = 'VertexLabel'
+    vertex_labels.InsertValue(a, 'a')
+    vertex_labels.InsertValue(b, 'b')
+    vertex_labels.InsertValue(c, 'c')
+    vertex_labels.InsertValue(d, 'd')
+    vertex_labels.InsertValue(e, 'e')
+    vertex_labels.InsertValue(f, 'f')
+    graph.vertex_data.AddArray(vertex_labels)
+
+    edge_labels = vtkStringArray()
+    edge_labels.name = 'EdgeLabel'
+    edge_labels.InsertValue(graph.GetEdgeId(a, b), 'a -> b')
+    edge_labels.InsertValue(graph.GetEdgeId(a, c), 'a -> c')
+    edge_labels.InsertValue(graph.GetEdgeId(b, d), 'b -> d')
+    edge_labels.InsertValue(graph.GetEdgeId(c, e), 'c -> e')
+    edge_labels.InsertValue(graph.GetEdgeId(c, f), 'c -> f')
+    graph.edge_data.AddArray(edge_labels)
+
+    tree = vtkTree()
+    valid_tree = tree.CheckedShallowCopy(graph)
+    if not valid_tree:
+        print('Invalid tree')
+        return
+
+    view = vtkGraphLayoutView(vertex_color_array_name='VertexDegree', color_vertices=True,
+                              vertex_label_array_name='VertexLabel', vertex_label_visibility=True,
+                              edge_label_array_name='EdgeLabel', edge_label_visibility=True,
+                              layout_strategy='Tree')
+    view.SetRepresentationFromInput(tree)
+    # Apply a theme to the views
+    theme = vtkViewTheme()
+    view.ApplyViewTheme(theme.CreateMellowTheme())
+
+    view.ResetCamera()
+    view.render_window.size = (600, 600)
+    view.render_window.window_name = 'CreateTree'
+    view.render_window.Render()
+    view.interactor.Initialize()
+    view.interactor.Start()
+
+
+if __name__ == '__main__':
+    main()