From 35683883cbd2def30aed25864ed0cbe59ae0d96b Mon Sep 17 00:00:00 2001
From: Uwe <donovaly@users.noreply.github.com>
Date: Mon, 29 Nov 2021 00:53:19 +0100
Subject: [PATCH] [PD] allow negative helix growth

Helices that become smaller with every turn are geometrically perfectly valid. Therefore we cannot forbid this.

(For example when creating a helix from a face you often cannot move it so that you can apply a positive growth.)
---
 src/Mod/PartDesign/App/FeatureHelix.cpp      | 12 +++++++++---
 src/Mod/PartDesign/App/FeatureHelix.h        |  2 +-
 src/Mod/PartDesign/Gui/TaskHelixParameters.h |  2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/Mod/PartDesign/App/FeatureHelix.cpp b/src/Mod/PartDesign/App/FeatureHelix.cpp
index d10c1bd01c..11de1bf859 100644
--- a/src/Mod/PartDesign/App/FeatureHelix.cpp
+++ b/src/Mod/PartDesign/App/FeatureHelix.cpp
@@ -134,14 +134,13 @@ App::DocumentObjectExecReturn *Helix::execute(void)
         if (Turns.getValue() < Precision::Confusion())
             return new App::DocumentObjectExecReturn("Error: turns too small!");
         if ((Height.getValue() < Precision::Confusion())
-            && (Growth.getValue() < Precision::Confusion()))
+            && (abs(Growth.getValue()) < Precision::Confusion()))
             return new App::DocumentObjectExecReturn("Error: either height or growth must not be zero!");
         Pitch.setValue(Height.getValue()/Turns.getValue());
     } else {
         return new App::DocumentObjectExecReturn("Error: unsupported mode");
     }
 
-
     TopoDS_Shape sketchshape;
     try {
         sketchshape = getVerifiedFace();
@@ -407,7 +406,7 @@ TopoDS_Shape Helix::generateHelixPath(void)
     bool growthMode = std::string(Mode.getValueAsString()).find("growth") != std::string::npos;
     double radiusTop;
     if (growthMode)
-        radiusTop = radius + turns*growth;
+        radiusTop = radius + turns * growth;
     else
         radiusTop = radius + height * tan(Base::toRadians(angle));
 
@@ -534,6 +533,13 @@ void Helix::handleChangedPropertyType(Base::XMLReader& reader, const char* TypeN
         TurnsProperty.Restore(reader);
         Turns.setValue(TurnsProperty.getValue());
     }
+    // property Growth had the App::PropertyLength and was changed to App::PropertyDistance
+    else if (prop == &Growth && strcmp(TypeName, "App::PropertyLength") == 0) {
+        App::PropertyLength GrowthProperty;
+        // restore the PropertyLength to be able to set its value
+        GrowthProperty.Restore(reader);
+        Growth.setValue(GrowthProperty.getValue());
+    }
     else {
         ProfileBased::handleChangedPropertyType(reader, TypeName, prop);
     }
diff --git a/src/Mod/PartDesign/App/FeatureHelix.h b/src/Mod/PartDesign/App/FeatureHelix.h
index 7e9823a0ef..f834f08be0 100644
--- a/src/Mod/PartDesign/App/FeatureHelix.h
+++ b/src/Mod/PartDesign/App/FeatureHelix.h
@@ -52,7 +52,7 @@ public:
     App::PropertyFloatConstraint   Turns;
     App::PropertyBool        LeftHanded;
     App::PropertyAngle       Angle;
-    App::PropertyLength      Growth;
+    App::PropertyDistance    Growth;
     App::PropertyEnumeration Mode;
     App::PropertyBool        Outside;
     App::PropertyBool        HasBeenEdited;
diff --git a/src/Mod/PartDesign/Gui/TaskHelixParameters.h b/src/Mod/PartDesign/Gui/TaskHelixParameters.h
index 8b9b017299..110cad5444 100644
--- a/src/Mod/PartDesign/Gui/TaskHelixParameters.h
+++ b/src/Mod/PartDesign/Gui/TaskHelixParameters.h
@@ -95,7 +95,7 @@ protected:
     App::PropertyBool*        propReversed;
     App::PropertyLinkSub*     propReferenceAxis;
     App::PropertyAngle*       propAngle;
-    App::PropertyLength*      propGrowth;
+    App::PropertyDistance*    propGrowth;
     App::PropertyEnumeration* propMode;
     App::PropertyBool*        propOutside;