Merge topic 'tanglegram' into master

8bb5d5f8 various minor improvements to vtkTanglegram
2e85c7cd various minor improvements to tanglegrams
dda53180 update tests & baselines
bd266aab new class: vtkTanglegramItem
3ea80450 refactor vtkTreeHeatmapItem into three classes
ab999619 new function: ComputeFontSizeForBoundedString
8a4c60bb preserve FieldData when pruning a tree

Infovis/Core/vtkPruneTreeFilter.cxx

@@ -84,6 +84,9 @@ int vtkPruneTreeFilter::RequestData(
   builderVertexData->CopyAllocate(inputVertexData);
   builderEdgeData->CopyAllocate(inputEdgeData);
 
+  // Copy field data
+  builder->GetFieldData()->DeepCopy(inputTree->GetFieldData());
+
   // Build a copy of the tree, skipping the parent vertex to remove.
   vtksys_stl::vector< vtksys_stl::pair<vtkIdType, vtkIdType> > vertStack;
   if (inputTree->GetRoot() != this->ParentVertex)

Rendering/Context2D/vtkContext2D.cxx

@@ -654,6 +654,45 @@ void vtkContext2D::ComputeStringBounds(const char* string,
   this->ComputeStringBounds(vtkStdString(string), bounds);
 }
 
+//-----------------------------------------------------------------------------
+int vtkContext2D::ComputeFontSizeForBoundedString(const vtkStdString &string,
+                                                  float width, float height)
+{
+  int orientation = this->GetTextProp()->GetOrientation();
+  this->GetTextProp()->SetOrientation(0.0);
+
+  float stringBounds[4];
+  int currentFontSize = this->GetTextProp()->GetFontSize();
+  this->ComputeStringBounds(string, stringBounds);
+
+  // font size is too big
+  if (stringBounds[2] > width || stringBounds[3] > height)
+    {
+    while (stringBounds[2] > width || stringBounds[3] > height)
+      {
+      --currentFontSize;
+      this->GetTextProp()->SetFontSize(currentFontSize);
+      this->ComputeStringBounds(string, stringBounds);
+      }
+    }
+
+  // font size is too small
+  else
+    {
+      while (stringBounds[2] < width && stringBounds[3] < height)
+      {
+      ++currentFontSize;
+      this->GetTextProp()->SetFontSize(currentFontSize);
+      this->ComputeStringBounds(string, stringBounds);
+      }
+    --currentFontSize;
+    this->GetTextProp()->SetFontSize(currentFontSize);
+    }
+
+  this->GetTextProp()->SetOrientation(orientation);
+  return currentFontSize;
+}
+
 //-----------------------------------------------------------------------------
 void vtkContext2D::DrawMathTextString(vtkPoints2D *point,
                                       const vtkStdString &string)

Rendering/Context2D/vtkContext2D.h

@@ -299,7 +299,6 @@ public:
   // supplied bounds variable, the first two elements are the bottom corner of
   // the string, and the second two elements are the width and height of the
   // bounding box.
-  // NOTE: This function does not take account of the text rotation.
   void ComputeStringBounds(const vtkStdString &string, vtkPoints2D *bounds);
   void ComputeStringBounds(const vtkStdString &string, float bounds[4]);
   void ComputeStringBounds(const vtkUnicodeString &string, vtkPoints2D *bounds);
@@ -307,6 +306,14 @@ public:
   void ComputeStringBounds(const char* string, vtkPoints2D *bounds);
   void ComputeStringBounds(const char* string, float bounds[4]);
 
+  // Description:
+  // Calculate the largest possible font size where the supplied string will fit
+  // within the specified bounds.  In addition to being returned, this font size
+  // is also used to update the vtkTextProperty used by this object.
+  // NOTE: text rotation is ignored for the purposes of this function.
+  int ComputeFontSizeForBoundedString(const vtkStdString &string, float width,
+                                      float height);
+
   // Description:
   // Draw a MathText formatted equation to the screen. See
   // http://matplotlib.sourceforge.net/users/mathtext.html for more information.

Views/Infovis/CMakeLists.txt

 SET(Module_SRCS
   vtkApplyColors.cxx
   vtkApplyIcons.cxx
+  vtkDendrogramItem.cxx
   vtkGraphItem.cxx
   vtkGraphLayoutView.cxx
+  vtkHeatmapItem.cxx
   vtkHierarchicalGraphPipeline.cxx
   vtkHierarchicalGraphView.cxx
   vtkIcicleView.cxx
@@ -17,6 +19,7 @@ SET(Module_SRCS
   vtkRenderedSurfaceRepresentation.cxx
   vtkRenderedTreeAreaRepresentation.cxx
   vtkRenderView.cxx
+  vtkTanglegramItem.cxx
   vtkTreeAreaView.cxx
   vtkTreeHeatmapItem.cxx
   vtkTreeMapView.cxx

Views/Infovis/Testing/Cxx/CMakeLists.txt

 vtk_add_test_cxx(
   TestCoincidentGraphLayoutView.cxx
   TestConeLayoutStrategy.cxx
-  TestDendrogramOnly.cxx
+  TestDendrogramItem.cxx
   TestGraphLayoutView.cxx
-  TestHeatmapOnly.cxx
+  TestHeatmapItem.cxx
   TestHierarchicalGraphView.cxx
   TestIcicleView.cxx
   TestInteractorStyleTreeMapHover.cxx
   TestNetworkViews.cxx
   TestRenderView.cxx
   TestSpanTreeLayoutStrategy.cxx
+  TestTanglegramItem.cxx
   TestTreeHeatmapAutoCollapse.cxx
   TestTreeHeatmapItem.cxx
   TestTreeMapView.cxx

Views/Infovis/Testing/Cxx/TestDendrogramOnly.cxx → Views/Infovis/Testing/Cxx/TestDendrogramItem.cxx

 /*=========================================================================
 
   Program:   Visualization Toolkit
-  Module:    TestDendrogramOnly.cxx
+  Module:    TestDendrogramItem.cxx
 
   Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
   All rights reserved.
@@ -13,7 +13,7 @@
 
 =========================================================================*/
 
-#include "vtkTreeHeatmapItem.h"
+#include "vtkDendrogramItem.h"
 #include "vtkDataSetAttributes.h"
 #include "vtkDoubleArray.h"
 #include "vtkMutableDirectedGraph.h"
@@ -33,7 +33,7 @@
 #include "vtkRegressionTestImage.h"
 
 //----------------------------------------------------------------------------
-int TestDendrogramOnly(int argc, char* argv[])
+int TestDendrogramItem(int argc, char* argv[])
 {
   vtkNew<vtkMutableDirectedGraph> graph;
   vtkIdType root = graph->AddVertex();
@@ -79,12 +79,14 @@ int TestDendrogramOnly(int argc, char* argv[])
   vtkNew<vtkTree> tree;
   tree->ShallowCopy(graph.GetPointer());
 
-  vtkNew<vtkTreeHeatmapItem> treeItem;
-  treeItem->SetTree(tree.GetPointer());
+  vtkNew<vtkDendrogramItem> dendrogram;
+  dendrogram->SetTree(tree.GetPointer());
+  dendrogram->SetPosition(40, 15);
 
   vtkNew<vtkContextTransform> trans;
   trans->SetInteractive(true);
-  trans->AddItem(treeItem.GetPointer());
+  trans->AddItem(dendrogram.GetPointer());
+  trans->Scale(3, 3);
   actor->GetScene()->AddItem(trans.GetPointer());
 
   vtkNew<vtkRenderer> renderer;

Views/Infovis/Testing/Cxx/TestHeatmapOnly.cxx → Views/Infovis/Testing/Cxx/TestHeatmapItem.cxx

 /*=========================================================================
 
   Program:   Visualization Toolkit
-  Module:    TestHeatmapOnly.cxx
+  Module:    TestHeatmapItem.cxx
 
   Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
   All rights reserved.
@@ -13,7 +13,7 @@
 
 =========================================================================*/
 
-#include "vtkTreeHeatmapItem.h"
+#include "vtkHeatmapItem.h"
 #include "vtkDoubleArray.h"
 #include "vtkNew.h"
 #include "vtkStringArray.h"
@@ -31,7 +31,7 @@
 #include "vtkRegressionTestImage.h"
 
 //----------------------------------------------------------------------------
-int TestHeatmapOnly(int argc, char* argv[])
+int TestHeatmapItem(int argc, char* argv[])
 {
   vtkNew<vtkTable> table;
   vtkNew<vtkStringArray> tableNames;
@@ -80,12 +80,14 @@ int TestHeatmapOnly(int argc, char* argv[])
 
   vtkNew<vtkContextActor> actor;
 
-  vtkNew<vtkTreeHeatmapItem> treeItem;
-  treeItem->SetTable(table.GetPointer());
+  vtkNew<vtkHeatmapItem> heatmap;
+  heatmap->SetTable(table.GetPointer());
+  heatmap->SetPosition(20, 5);
 
   vtkNew<vtkContextTransform> trans;
   trans->SetInteractive(true);
-  trans->AddItem(treeItem.GetPointer());
+  trans->AddItem(heatmap.GetPointer());
+  trans->Scale(2, 2);
   actor->GetScene()->AddItem(trans.GetPointer());
 
   vtkNew<vtkRenderer> renderer;

Views/Infovis/Testing/Cxx/TestTanglegramItem.cxx

+/*=========================================================================
+
+  Program:   Visualization Toolkit
+  Module:    TestTanglegramItem.cxx
+
+  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+  All rights reserved.
+  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notice for more information.
+
+=========================================================================*/
+
+#include "vtkTanglegramItem.h"
+#include "vtkDataSetAttributes.h"
+#include "vtkDoubleArray.h"
+#include "vtkMutableDirectedGraph.h"
+#include "vtkNew.h"
+#include "vtkStringArray.h"
+#include "vtkTable.h"
+#include "vtkTree.h"
+
+#include "vtkRenderer.h"
+#include "vtkRenderWindow.h"
+#include "vtkRenderWindowInteractor.h"
+#include "vtkContextInteractorStyle.h"
+#include "vtkContextActor.h"
+#include "vtkContextMouseEvent.h"
+#include "vtkContextScene.h"
+#include "vtkContextTransform.h"
+#include "vtkNew.h"
+
+#include "vtkRegressionTestImage.h"
+
+//----------------------------------------------------------------------------
+int TestTanglegramItem(int argc, char* argv[])
+{
+  //tree #1
+  vtkNew<vtkMutableDirectedGraph> graph1;
+  vtkIdType root = graph1->AddVertex();
+  vtkIdType internalOne = graph1->AddChild(root);
+  vtkIdType internalTwo = graph1->AddChild(internalOne);
+  vtkIdType a = graph1->AddChild(internalTwo);
+  vtkIdType b = graph1->AddChild(internalTwo);
+  vtkIdType c = graph1->AddChild(internalOne);
+
+  vtkNew<vtkDoubleArray> weights;
+  weights->SetNumberOfTuples(5);
+  weights->SetValue(graph1->GetEdgeId(root, internalOne), 1.0f);
+  weights->SetValue(graph1->GetEdgeId(internalOne, internalTwo), 2.0f);
+  weights->SetValue(graph1->GetEdgeId(internalTwo, a), 1.0f);
+  weights->SetValue(graph1->GetEdgeId(internalTwo, b), 1.0f);
+  weights->SetValue(graph1->GetEdgeId(internalOne, c), 3.0f);
+
+  weights->SetName("weight");
+  graph1->GetEdgeData()->AddArray(weights.GetPointer());
+
+  vtkNew<vtkStringArray> names1;
+  names1->SetNumberOfTuples(6);
+  names1->SetValue(a, "cat");
+  names1->SetValue(b, "dog");
+  names1->SetValue(c, "human");
+
+  names1->SetName("node name");
+  graph1->GetVertexData()->AddArray(names1.GetPointer());
+
+  vtkNew<vtkDoubleArray> nodeWeights;
+  nodeWeights->SetNumberOfTuples(6);
+  nodeWeights->SetValue(root, 0.0f);
+  nodeWeights->SetValue(internalOne, 1.0f);
+  nodeWeights->SetValue(internalTwo, 3.0f);
+  nodeWeights->SetValue(a, 4.0f);
+  nodeWeights->SetValue(b, 4.0f);
+  nodeWeights->SetValue(c, 4.0f);
+  nodeWeights->SetName("node weight");
+  graph1->GetVertexData()->AddArray(nodeWeights.GetPointer());
+
+  //tree #2
+  vtkNew<vtkMutableDirectedGraph> graph2;
+  root = graph2->AddVertex();
+  internalOne = graph2->AddChild(root);
+  internalTwo = graph2->AddChild(internalOne);
+  a = graph2->AddChild(internalTwo);
+  b = graph2->AddChild(internalTwo);
+  c = graph2->AddChild(internalOne);
+
+  weights->SetName("weight");
+  graph2->GetEdgeData()->AddArray(weights.GetPointer());
+
+  vtkNew<vtkStringArray> names2;
+  names2->SetNumberOfTuples(6);
+  names2->SetValue(a, "dog food");
+  names2->SetValue(b, "cat food");
+  names2->SetValue(c, "steak");
+
+  names2->SetName("node name");
+  graph2->GetVertexData()->AddArray(names2.GetPointer());
+
+  graph2->GetVertexData()->AddArray(nodeWeights.GetPointer());
+
+  // set up correspondence table: who eats what
+  vtkNew<vtkTable> table;
+  vtkNew<vtkStringArray> eaters;
+  vtkNew<vtkDoubleArray> hungerForSteak;
+  hungerForSteak->SetName("steak");
+  vtkNew<vtkDoubleArray> hungerForDogFood;
+  hungerForDogFood->SetName("dog food");
+  vtkNew<vtkDoubleArray> hungerForCatFood;
+  hungerForCatFood->SetName("cat food");
+
+  eaters->SetNumberOfTuples(3);
+  hungerForSteak->SetNumberOfTuples(3);
+  hungerForDogFood->SetNumberOfTuples(3);
+  hungerForCatFood->SetNumberOfTuples(3);
+
+  eaters->SetValue(0, "human");
+  eaters->SetValue(1, "dog");
+  eaters->SetValue(2, "cat");
+
+  hungerForSteak->SetValue(0, 2.0);
+  hungerForSteak->SetValue(1, 1.0);
+  hungerForSteak->SetValue(2, 1.0);
+
+  hungerForDogFood->SetValue(0, 0.0);
+  hungerForDogFood->SetValue(1, 2.0);
+  hungerForDogFood->SetValue(2, 0.0);
+
+  hungerForCatFood->SetValue(0, 0.0);
+  hungerForCatFood->SetValue(1, 1.0);
+  hungerForCatFood->SetValue(2, 2.0);
+
+  table->AddColumn(eaters.GetPointer());
+  table->AddColumn(hungerForSteak.GetPointer());
+  table->AddColumn(hungerForDogFood.GetPointer());
+  table->AddColumn(hungerForCatFood.GetPointer());
+
+  vtkNew<vtkContextActor> actor;
+
+  vtkNew<vtkTree> tree1;
+  tree1->ShallowCopy(graph1.GetPointer());
+
+  vtkNew<vtkTree> tree2;
+  tree2->ShallowCopy(graph2.GetPointer());
+
+  vtkNew<vtkTanglegramItem> tanglegram;
+  tanglegram->SetTree1(tree1.GetPointer());
+  tanglegram->SetTree2(tree2.GetPointer());
+  tanglegram->SetTable(table.GetPointer());
+  tanglegram->SetTree1Label("Diners");
+  tanglegram->SetTree2Label("Meals");
+
+  vtkNew<vtkContextTransform> trans;
+  trans->SetInteractive(true);
+  trans->AddItem(tanglegram.GetPointer());
+  // center the item within the render window
+  trans->Translate(10, 75);
+  trans->Scale(1.375, 1.375);
+  actor->GetScene()->AddItem(trans.GetPointer());
+
+  vtkNew<vtkRenderer> renderer;
+  renderer->SetBackground(1.0, 1.0, 1.0);
+
+  vtkNew<vtkRenderWindow> renderWindow;
+  renderWindow->SetSize(400, 200);
+  renderWindow->AddRenderer(renderer.GetPointer());
+  renderer->AddActor(actor.GetPointer());
+  actor->GetScene()->SetRenderer(renderer.GetPointer());
+
+  vtkNew<vtkContextInteractorStyle> interactorStyle;
+  interactorStyle->SetScene(actor->GetScene());
+
+  vtkNew<vtkRenderWindowInteractor> interactor;
+  interactor->SetInteractorStyle(interactorStyle.GetPointer());
+  interactor->SetRenderWindow(renderWindow.GetPointer());
+  renderWindow->SetMultiSamples(0);
+  renderWindow->Render();
+
+  int retVal = vtkRegressionTestImageThreshold(renderWindow.GetPointer(), 100);
+  if (retVal == vtkRegressionTester::DO_INTERACTOR)
+    {
+    renderWindow->Render();
+    interactor->Start();
+    retVal = vtkRegressionTester::PASSED;
+    }
+  return !retVal;
+}

Views/Infovis/Testing/Cxx/TestTreeHeatmapAutoCollapse.cxx

@@ -15,6 +15,7 @@
 
 #include "vtkTreeHeatmapItem.h"
 #include "vtkDataSetAttributes.h"
+#include "vtkDendrogramItem.h"
 #include "vtkDoubleArray.h"
 #include "vtkMutableDirectedGraph.h"
 #include "vtkNew.h"
@@ -123,6 +124,9 @@ int TestTreeHeatmapAutoCollapse(int argc, char* argv[])
 
   vtkNew<vtkContextTransform> trans;
   trans->SetInteractive(true);
+  // center the item within the render window
+  trans->Translate(20, 30);
+  trans->Scale(2.5, 2.5);
   trans->AddItem(treeItem.GetPointer());
   actor->GetScene()->AddItem(trans.GetPointer());
 

Views/Infovis/Testing/Cxx/TestTreeHeatmapItem.cxx

@@ -126,6 +126,9 @@ int TestTreeHeatmapItem(int argc, char* argv[])
   vtkNew<vtkContextTransform> trans;
   trans->SetInteractive(true);
   trans->AddItem(treeItem.GetPointer());
+  // center the item within the render window
+  trans->Translate(40, 30);
+  trans->Scale(2, 2);
   actor->GetScene()->AddItem(trans.GetPointer());
 
   vtkNew<vtkRenderer> renderer;

Views/Infovis/Testing/Data/Baseline/TestDendrogramItem.png.md5

+142adb34c8192d5c184cb04eca3b59da

Views/Infovis/Testing/Data/Baseline/TestHeatmapItem.png.md5

+cadc41b117b96aa790814a3f2f565835

Views/Infovis/Testing/Data/Baseline/TestTanglegramItem.png.md5

+815d766a2d6d7419df3976ee11bfea0c

Views/Infovis/Testing/Data/Baseline/TestTreeHeatmapAutoCollapse.png.md5

-ca3b7a7d5728458c046390d055a87776
+d1ffa41cd988a64cfccf48f4daa4cb0a

Views/Infovis/Testing/Data/Baseline/TestTreeHeatmapItem.png.md5

-005ad73f6a5959a65a360a0acf696859
+c7dd8c6992c367f078617aa914750897

Views/Infovis/vtkDendrogramItem.h

+/*=========================================================================
+
+  Program:   Visualization Toolkit
+  Module:    vtkDendrogramItem.h
+
+  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
+  All rights reserved.
+  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
+
+     This software is distributed WITHOUT ANY WARRANTY; without even
+     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+     PURPOSE.  See the above copyright notice for more information.
+
+=========================================================================*/
+// .NAME vtkDendrogramItem - A 2D graphics item for rendering a tree as
+// a dendrogram
+//
+// .SECTION Description
+// Draw a tree as a dendrogram
+// The input tree's vertex data must contain at least two arrays.
+// The first required array is a vtkStringArray called "node name".
+// This array is used to label the leaf nodes of the tree.
+// The second required array is a scalar array called "node weight".
+// This array is used by vtkTreeLayoutStrategy to set any particular
+// node's distance from the root of the tree.
+//
+// The vtkNewickTreeReader automatically initializes both of these
+// required arrays in its output tree.
+//
+// .SEE ALSO
+// vtkTree vtkNewickTreeReader
+
+#ifndef __vtkDendrogramItem_h
+#define __vtkDendrogramItem_h
+
+#include "vtkViewsInfovisModule.h" // For export macro
+#include "vtkContextItem.h"
+
+#include "vtkNew.h"               // For vtkNew ivars
+#include "vtkSmartPointer.h"      // For vtkSmartPointer ivars
+#include "vtkVector.h"            // For vtkVector2f ivar
+
+class vtkDoubleArray;
+class vtkGraphLayout;
+class vtkLookupTable;
+class vtkTree;
+class vtkPruneTreeFilter;
+
+class VTKVIEWSINFOVIS_EXPORT vtkDendrogramItem : public vtkContextItem
+{
+public:
+  static vtkDendrogramItem *New();
+  vtkTypeMacro(vtkDendrogramItem, vtkContextItem);
+  virtual void PrintSelf(ostream &os, vtkIndent indent);
+
+  // Description:
+  // Set the tree that this item draws.  Note that this tree's vertex data
+  // must contain a vtkStringArray called "node name".  The vtkNewickTreeReader
+  // automatically creates this required array for you.
+  virtual void SetTree(vtkTree *tree);
+
+  // Description:
+  // Get the tree that this item draws.
+  vtkTree * GetTree();
+
+  // Description:
+  // Collapse subtrees until there are only n leaf nodes left in the tree.
+  // The leaf nodes that remain are those that are closest to the root.
+  // Any subtrees that were collapsed prior to this function being called
+  // may be re-expanded.
+  void CollapseToNumberOfLeafNodes(unsigned int n);
+
+  // Description:
+  // Get the collapsed tree
+  vtkTree * GetPrunedTree();
+
+  // Description:
+  // Indicate which array within the Tree's VertexData should be used to
+  // color the tree.  The specified array must be a vtkDoubleArray.
+  // By default, the tree will be drawn in black.
+  void SetColorArray(const char *arrayName);
+
+  // Description:
+  // Get/set whether or not leaf nodes should be extended so that they all line
+  // up vertically.  The default is to NOT extend leaf nodes.  When extending
+  // leaf nodes, the extra length is drawn in grey so as to distinguish it from
+  // the actual length of the leaf node.
+  vtkSetMacro(ExtendLeafNodes, bool);
+  vtkGetMacro(ExtendLeafNodes, bool);
+  vtkBooleanMacro(ExtendLeafNodes, bool);
+
+  // Description:
+  // Set which way the tree should face within the visualization.  The default
+  // is for the tree to be drawn left to right.
+  void SetOrientation(int orientation);
+
+  // Description:
+  // Get the current tree orientation.
+  int GetOrientation();
+
+  // Description:
+  // Get the rotation angle (in degrees) that corresponds to the given
+  // tree orientation.  For the default orientation (LEFT_TO_RIGHT), this
+  // is 90 degrees.
+  double GetAngleForOrientation(int orientation);
+
+  // Description:
+  // Get the angle that vertex labels should be rotated for the correponding
+  // tree orientation.  For the default orientation (LEFT_TO_RIGHT), this
+  // is 0 degrees.
+  double GetTextAngleForOrientation(int orientation);
+
+  // Description:
+  // Get/Set whether or not leaf nodes should be labeled by this class.
+  // Default is true.
+  vtkSetMacro(DrawLabels, bool);
+  vtkGetMacro(DrawLabels, bool);
+  vtkBooleanMacro(DrawLabels, bool);
+
+  // Description:
+  // Set the position of the dendrogram.
+  vtkSetVector2Macro(Position, float);
+  void SetPosition(const vtkVector2f &pos);
+
+  // Description:
+  // Get position of the dendrogram.
+  vtkGetVector2Macro(Position, float);
+  vtkVector2f GetPositionVector();
+
+  // Description:
+  // Get/Set the spacing between the leaf nodes in our dendrogram.
+  // Default is 18 pixels.
+  vtkGetMacro(LeafSpacing, double);
+  vtkSetMacro(LeafSpacing, double);
+
+  // Description:
+  // This function calls RebuildBuffers() if necessary.
+  // Once PrepareToPaint() has been called, GetBounds() is guaranteed
+  // to provide useful information.
+  void PrepareToPaint();
+
+  // Description:
+  // Get the bounds for this item as (Xmin,Xmax,Ymin,Ymax).
+  // These bounds are only guaranteed to be accurate after Paint() or
+  // PrepareToPaint() has been called.
+  virtual void GetBounds(double bounds[4]);
+
+  // Description:
+  // Get the width of the longest leaf node label.
+  float GetLabelWidth(vtkContext2D *painter);
+
+  // Description:
+  // Find the position of the vertex with the specified name.  Store
+  // this information in the passed array.  Returns true if the vertex
+  // was found, false otherwise.
+  bool GetPositionOfVertex(std::string vertexName, double position[2]);
+
+  // this struct & class allow us to generate a priority queue of vertices.