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# ViewportBorders

### Description

Draw the borders of a vtkRenderer's viewports.

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### Declaration Section

    #include <vtkRenderer.h>
    #include <vtkPoints.h>
    #include <vtkCellArray.h>
    #include <vtkPolyLines.h>
    #include <vtkPolyData.h>
    #include <vtkCoordinate.h>
    #include <vtkPolyDataMapper2D.h>
    #include <vtkActor2D.h>
    #include <vtkProperty.h>
    #include <vtkProperty2D.h>

    namespace
    {
    void ViewportBorders(vtkSmartPointer<vtkRenderer> &renderer,
                         double *color,
                         bool last = false);
    }

### Implementation Section

    namespace
    {
    // Draw the borders of a renderer's viewport
    void ViewportBorders(vtkSmartPointer<vtkRenderer> &renderer,
                         double *color,
                         bool last)
    {
      // points start at upper right and proceed anti-clockwise
      auto points = vtkSmartPointer<vtkPoints>::New();
      points->SetNumberOfPoints(4);
      points->InsertPoint(0, 1, 1, 0);
      points->InsertPoint(1, 0, 1, 0);
      points->InsertPoint(2, 0, 0, 0);
      points->InsertPoint(3, 1, 0, 0);

      // create cells, and lines
      auto cells =  vtkSmartPointer<vtkCellArray>::New();
      cells->Initialize();

      auto lines = vtkSmartPointer<vtkPolyLine>::New();

      // only draw last line if this is the last viewport
      // this prevents double vertical lines at right border
      // if different colors are used for each border, then do
      // not specify last
      if (last)
      {
        lines->GetPointIds()->SetNumberOfIds(5);
      }
      else
      {
      lines->GetPointIds()->SetNumberOfIds(4);
      }
      for(unsigned int i = 0; i < 4; ++i)
      {
        lines->GetPointIds()->SetId(i,i);
      }
      if (last)
      {
        lines->GetPointIds()->SetId(4, 0);
      }
      cells->InsertNextCell(lines);

      // now make tge polydata and display it
      auto poly = vtkSmartPointer<vtkPolyData>::New();
      poly->Initialize();
      poly->SetPoints(points);
      poly->SetLines(cells);

      // use normalized viewport coordinates since
      // they are independent of window size
      auto coordinate = vtkSmartPointer<vtkCoordinate>::New();
      coordinate->SetCoordinateSystemToNormalizedViewport();

      auto mapper = vtkSmartPointer<vtkPolyDataMapper2D>::New();
      mapper->SetInputData(poly);
      mapper->SetTransformCoordinate(coordinate);

      auto actor = vtkSmartPointer<vtkActor2D>::New();
      actor->SetMapper(mapper);
      actor->GetProperty()->SetColor(color);
      // line width should be at least 2 to be visible at extremes

      actor->GetProperty()->SetLineWidth(4.0); // Line Width

      renderer->AddViewProp(actor);
    }
    } // namespace