Add a display-coordinate offset to billboard text.

Rendering/Core/vtkBillboardTextActor3D.cxx

@@ -210,7 +210,9 @@ void vtkBillboardTextActor3D::PrintSelf(std::ostream &os, vtkIndent indent)
      << indent << "InputMTime: " << this->InputMTime << "\n"
      << indent << "TextRenderer: " << this->TextRenderer.Get() << "\n"
      << indent << "AnchorDC: " << this->AnchorDC[0] << " " << this->AnchorDC[1]
-     << " " << this->AnchorDC[2] << "\n";
+     << " " << this->AnchorDC[2] << "\n"
+     << indent << "DisplayOffset: " << this->DisplayOffset[0] << " "
+     << this->DisplayOffset[1] << "\n";
 
   os << indent << "Image:\n";
   this->Image->PrintSelf(os, indent.GetNextIndent());
@@ -337,6 +339,7 @@ vtkBillboardTextActor3D::vtkBillboardTextActor3D()
     RenderedDPI(-1)
 {
   std::fill(this->AnchorDC, this->AnchorDC + 3, 0.);
+  std::fill(this->DisplayOffset, this->DisplayOffset + 2, 0);
 
   // Connect internal rendering pipeline:
   this->Texture->InterpolateOff();
@@ -481,6 +484,10 @@ void vtkBillboardTextActor3D::GenerateQuad(vtkRenderer *ren)
   anchorDC[0] = std::floor(anchorDC[0]);
   anchorDC[1] = std::floor(anchorDC[1]);
 
+  // Apply the requested offset:
+  anchorDC[0] += static_cast<double>(this->DisplayOffset[0]);
+  anchorDC[1] += static_cast<double>(this->DisplayOffset[1]);
+
   // Cached for OpenGL2 GL2PS exports:
   this->AnchorDC[0] = anchorDC[0];
   this->AnchorDC[1] = anchorDC[1];

Rendering/Core/vtkBillboardTextActor3D.h

@@ -48,6 +48,15 @@ public:
   vtkGetStringMacro(Input)
   /** @} */
 
+  /**
+   * Can be used to set a fixed offset from the anchor point.
+   * Use display coordinates.
+   * @{
+   */
+  vtkGetVector2Macro(DisplayOffset, int)
+  vtkSetVector2Macro(DisplayOffset, int)
+  /** @} */
+
   /**
    * The vtkTextProperty object that controls the rendered text.
    * @{
@@ -105,6 +114,9 @@ protected:
   char *Input;
   vtkTextProperty *TextProperty;
 
+  // Offset in display coordinates.
+  int DisplayOffset[2];
+
   // Cached metadata to determine if things need rebuildin'
   int RenderedDPI;
   vtkTimeStamp InputMTime;