Fem: Rename property SurfaceChargeDensity to ElectricFluxDensity

src/Mod/Fem/Gui/Resources/ui/ElectrostaticPotential.ui

@@ -416,14 +416,14 @@ Note: has no effect if a solid was selected</string>
       <item row="0" column="0">
        <widget class="QLabel" name="surfacechargedensityLbl">
         <property name="text">
-         <string>Surface Charge Density:</string>
+         <string>Electric Flux Density:</string>
         </property>
        </widget>
       </item>
       <item row="0" column="1">
-       <widget class="Gui::QuantitySpinBox" name="qsb_surface_charge_density">
+       <widget class="Gui::QuantitySpinBox" name="qsb_electric_flux_density">
         <property name="toolTip">
-         <string>Surface charge density</string>
+         <string>Normal component of electric displacement field</string>
         </property>
         <property name="unit" stdset="0">
          <string notr="true">C/m^2</string>

src/Mod/Fem/femobjects/constraint_electrostaticpotential.py

@@ -145,9 +145,11 @@ class ConstraintElectrostaticPotential(base_fempythonobject.BaseFemPythonObject)
         prop.append(
             _PropHelper(
                 type="App::PropertySurfaceChargeDensity",
-                name="SurfaceChargeDensity",
+                name="ElectricFluxDensity",
                 group="Parameter",
-                doc="Free surface charge density",
+                doc="Electric displacement field D.\n"
+                + "For interfaces, it represents the difference\n"
+                + "between the normal component in the two media",
                 value="0 C/m^2",
             )
         )
@@ -299,3 +301,12 @@ class ConstraintElectrostaticPotential(base_fempythonobject.BaseFemPythonObject)
 
         except Base.PropertyError:
             pass
+
+        # set electric flux density from old surface charge density
+        try:
+            obj.ElectricFluxDensity = obj.getPropertyByName("SurfaceChargeDensity")
+            obj.setPropertyStatus("SurfaceChargeDensity", "-LockDynamic")
+            obj.removeProperty("SurfaceChargeDensity")
+
+        except Base.PropertyError:
+            pass

src/Mod/Fem/femtaskpanels/task_constraint_electrostaticpotential.py

@@ -171,9 +171,9 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
             self.electric_infinity_changed,
         )
         QtCore.QObject.connect(
-            self.parameter_widget.qsb_surface_charge_density,
+            self.parameter_widget.qsb_electric_flux_density,
             QtCore.SIGNAL("valueChanged(Base::Quantity)"),
-            self.surface_charge_density_changed,
+            self.electric_flux_density_changed,
         )
 
         self.init_parameter_widget()
@@ -232,7 +232,7 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.electric_infinity = self.obj.ElectricInfinity
         self.capacitance_body_enabled = self.obj.CapacitanceBodyEnabled
         self.capacitance_body = self.obj.CapacitanceBody
-        self.surface_charge_density = self.obj.SurfaceChargeDensity
+        self.electric_flux_density = self.obj.ElectricFluxDensity
 
     def _set_params(self):
         self.obj.Potential = self.potential
@@ -258,7 +258,7 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.obj.CapacitanceBodyEnabled = self.capacitance_body_enabled
         self.obj.CapacitanceBody = self.capacitance_body
 
-        self.obj.SurfaceChargeDensity = self.surface_charge_density
+        self.obj.ElectricFluxDensity = self.electric_flux_density
 
     def init_parameter_widget(self):
         self._get_params()
@@ -313,11 +313,11 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
             self.obj, "CapacitanceBody"
         )
 
-        self.parameter_widget.qsb_surface_charge_density.setProperty(
-            "value", self.surface_charge_density
+        self.parameter_widget.qsb_electric_flux_density.setProperty(
+            "value", self.electric_flux_density
         )
-        FreeCADGui.ExpressionBinding(self.parameter_widget.qsb_surface_charge_density).bind(
-            self.obj, "SurfaceChargeDensity"
+        FreeCADGui.ExpressionBinding(self.parameter_widget.qsb_electric_flux_density).bind(
+            self.obj, "ElectricFluxDensity"
         )
 
         self.bc_enum = self.obj.getEnumerationsOfProperty("BoundaryCondition")
@@ -397,8 +397,8 @@ class _TaskPanel(base_femtaskpanel._BaseTaskPanel):
         self.capacitance_body = value
         self.parameter_widget.spb_capacitance_body.setValue(value)
 
-    def surface_charge_density_changed(self, value):
-        self.surface_charge_density = value
+    def electric_flux_density_changed(self, value):
+        self.electric_flux_density = value
 
     def boundary_condition_changed(self, index):
         self.boundary_condition = self.bc_enum[index]