Use vtkMRMLBoneNode GetLength instead of recomputed it ourselves.

In the meantime, changing the name from distance to length which
 makes more sense.

See Issue #13636

Modules/Loadable/Armatures/MRML/Core/vtkMRMLBoneNode.cxx

@@ -184,6 +184,14 @@ void vtkMRMLBoneNode::CreateBoneDisplayNode()
   this->AddAndObserveDisplayNodeID(boneDisplayNode->GetID());
 }
 
+//-- Length -----------------------------------------------------------------
+//---------------------------------------------------------------------------
+double vtkMRMLBoneNode::GetLength()
+{
+  std::cout<<"this->BoneProperties->GetLength() "<<this->BoneProperties->GetLength()<<std::endl;
+  return this->BoneProperties->GetLength();
+}
+
 //-- Name -------------------------------------------------------------------
 //---------------------------------------------------------------------------
 void vtkMRMLBoneNode::SetBoneName(vtkStdString name)

Modules/Loadable/Armatures/MRML/Core/vtkMRMLBoneNode.h

@@ -99,6 +99,10 @@ class VTK_BENDER_ARMATURES_MRML_CORE_EXPORT vtkMRMLBoneNode
   /// \sa CreateDefaultStorageNode()
   void CreateBoneDisplayNode();
 
+  // -- Length ----------------------------------------------------------------
+  /// Get the bone length.
+  double GetLength();
+
   // -- Name ----------------------------------------------------------------
   /// Set/Get the bone roll.
   void SetBoneName(vtkStdString name);

Modules/Loadable/Armatures/Resources/UI/qSlicerArmaturesModule.ui

@@ -208,7 +208,7 @@
              </widget>
             </item>
             <item row="1" column="0">
-             <widget class="QLabel" name="DirectionLabel">
+             <widget class="QLabel" name="LengthLabel">
               <property name="text">
                <string>Direction:</string>
               </property>
@@ -227,12 +227,12 @@
          <item row="2" column="0">
           <widget class="QLabel" name="DistanceDisplayLabel">
            <property name="text">
-            <string>Distance:</string>
+            <string>Length:</string>
            </property>
           </widget>
          </item>
          <item row="2" column="2">
-          <widget class="QDoubleSpinBox" name="DistanceSpinBox">
+          <widget class="QDoubleSpinBox" name="LengthSpinBox">
            <property name="maximum">
             <double>999999999.000000000000000</double>
            </property>

Modules/Loadable/Armatures/qSlicerArmaturesModuleWidget.cxx

@@ -119,7 +119,7 @@ ::setupUi(qSlicerWidget* armatureModuleWidget)
   QObject::connect(this->BonePositionTypeComboBox,
     SIGNAL(currentIndexChanged(QString)),
     this, SLOT(onPositionTypeChanged()));
-  QObject::connect(this->DistanceSpinBox,
+  QObject::connect(this->LengthSpinBox,
     SIGNAL(valueChanged(double)),
     this, SLOT(onDistanceChanged(double)));
   QObject::connect(this->DirectionCoordinatesWidget,
@@ -149,20 +149,6 @@ void qSlicerArmaturesModuleWidgetPrivate::onPositionTypeChanged()
   this->setCoordinatesFromBoneNode(this->BoneNode);
 }
 
-//-----------------------------------------------------------------------------
-double qSlicerArmaturesModuleWidgetPrivate::distance()
-{
-  QVector3D head(this->HeadCoordinatesWidget->coordinates()[0],
-    this->HeadCoordinatesWidget->coordinates()[1],
-    this->HeadCoordinatesWidget->coordinates()[2]);
-
-  QVector3D tail(this->TailCoordinatesWidget->coordinates()[0],
-    this->TailCoordinatesWidget->coordinates()[1],
-    this->TailCoordinatesWidget->coordinates()[2]);
-
-  return QVector3D(tail - head).length();
-}
-
 //-----------------------------------------------------------------------------
 void qSlicerArmaturesModuleWidgetPrivate::onDistanceChanged(double newDistance)
 {
@@ -197,7 +183,7 @@ void qSlicerArmaturesModuleWidgetPrivate::blockPositionsSignals(bool block)
 {
   this->HeadCoordinatesWidget->blockSignals(block);
   this->TailCoordinatesWidget->blockSignals(block);
-  this->DistanceSpinBox->blockSignals(block);
+  this->LengthSpinBox->blockSignals(block);
   this->DirectionCoordinatesWidget->blockSignals(block);
 }
 
@@ -219,7 +205,7 @@ ::onDirectionChanged(double* newDirection)
     this->HeadCoordinatesWidget->coordinates()[2]);
   QVector3D direction(newDirection[0], newDirection[1], newDirection[2]);
 
-  QVector3D newTail = head + direction * this->DistanceSpinBox->value();
+  QVector3D newTail = head + direction * this->LengthSpinBox->value();
 
   this->TailCoordinatesWidget->setCoordinates(
     newTail.x(), newTail.y(), newTail.z());
@@ -251,7 +237,6 @@ ::updatePositions(vtkMRMLBoneNode* boneNode)
   bool enableTailWidget = false;
 
   this->setCoordinatesFromBoneNode(boneNode);
-  this->DistanceSpinBox->setValue(this->distance());
 
   QVector3D direction(this->direction());
   this->DirectionCoordinatesWidget->setCoordinates(
@@ -271,10 +256,14 @@ ::updatePositions(vtkMRMLBoneNode* boneNode)
       enableTailWidget = true;
       }
     }
+  else
+    {
+    this->LengthSpinBox->setValue(0.0);
+    }
 
   this->HeadCoordinatesWidget->setEnabled(enableHeadWidget);
   this->TailCoordinatesWidget->setEnabled(enableTailWidget);
-  this->DistanceSpinBox->setEnabled(enableTailWidget);
+  this->LengthSpinBox->setEnabled(enableTailWidget);
   this->DirectionCoordinatesWidget->setEnabled(enableTailWidget);
 
   this->updateAdvancedPositions(boneNode);

Modules/Loadable/Armatures/qSlicerArmaturesModuleWidget_p.h

@@ -52,7 +52,6 @@ class qSlicerArmaturesModuleWidgetPrivate
   vtkSlicerArmaturesLogic* logic() const;
   virtual void setupUi(qSlicerWidget* armatureModuleWidget);
 
-  double distance();
   QVector3D direction();
 
   void blockPositionsSignals(bool block);