PD: Enhance InvoluteGear's Task Panel with Tool Tips

In order to not maintain the same information in two places, the property
docs are reused as tool tips for their input fields. And for user
convenience, the same tool tip is assigned to the respective label as
well.

src/Mod/PartDesign/InvoluteGearFeature.py

@@ -166,6 +166,7 @@ class _InvoluteGearTaskPanel:
 
         self.form=FreeCADGui.PySideUic.loadUi(str(pathlib.Path(__file__).with_suffix(".ui")))
         self.form.setWindowIcon(QtGui.QIcon(":/icons/PartDesign_InternalExternalGear.svg"))
+        self.assignToolTipsFromPropertyDocs()
 
         def assignValue(property_name, fitView=False):
             """Returns a function that takes a single value and assigns it to the given property"""
@@ -198,6 +199,22 @@ class _InvoluteGearTaskPanel:
             self.obj.Proxy.execute(self.obj)  # calculate once
             FreeCAD.Gui.SendMsgToActiveView("ViewFit")
 
+    def assignToolTipsFromPropertyDocs(self):
+        def assign(property_name, *widgets):
+            doc = self.obj.getDocumentationOfProperty(property_name)
+            for w in widgets:
+                w.setToolTip(doc)
+
+        # we assign the tool tip to both, the label and the input field, for user convenience
+        assign("Modules", self.form.Quantity_Modules, self.form.label_Modules)
+        assign("PressureAngle", self.form.Quantity_PressureAngle, self.form.label_PressureAngle)
+        assign("NumberOfTeeth", self.form.spinBox_NumberOfTeeth, self.form.label_NumberOfTeeth)
+        assign("HighPrecision", self.form.comboBox_HighPrecision, self.form.label_HighPrecision)
+        assign("ExternalGear", self.form.comboBox_ExternalGear, self.form.label_ExternalGear)
+        assign("AddendumCoefficient", self.form.doubleSpinBox_Addendum, self.form.label_Addendum)
+        assign("DedendumCoefficient", self.form.doubleSpinBox_Dedendum, self.form.label_Dedendum)
+        assign("RootFilletCoefficient", self.form.doubleSpinBox_RootFillet, self.form.label_RootFillet)
+
     def transferTo(self):
         "Transfer from the dialog to the object"
         self.obj.NumberOfTeeth  = self.form.spinBox_NumberOfTeeth.value()