From 85534c7014b65ec92ad388338c784b2e2e847a78 Mon Sep 17 00:00:00 2001
From: Yorik van Havre <yorik@uncreated.net>
Date: Fri, 28 Oct 2016 18:08:13 -0200
Subject: [PATCH] Draft: Allow to override system unit in dimensions

---
 src/Mod/Draft/Draft.py    |  8 ++++++--
 src/Mod/Draft/DraftGui.py | 17 +++++++++++------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/Mod/Draft/Draft.py b/src/Mod/Draft/Draft.py
index 8953e88ba2..955e308832 100644
--- a/src/Mod/Draft/Draft.py
+++ b/src/Mod/Draft/Draft.py
@@ -3566,6 +3566,7 @@ class _ViewProviderDimension(_ViewProviderDraft):
         obj.addProperty("App::PropertyBool","ShowUnit","Draft",QT_TRANSLATE_NOOP("App::Property","Show the unit suffix"))
         obj.addProperty("App::PropertyVectorDistance","TextPosition","Draft",QT_TRANSLATE_NOOP("App::Property","The position of the text. Leave (0,0,0) for automatic position"))
         obj.addProperty("App::PropertyString","Override","Draft",QT_TRANSLATE_NOOP("App::Property","Text override. Use $dim to insert the dimension length"))
+        obj.addProperty("App::PropertyString","UnitOverride","Draft",QT_TRANSLATE_NOOP("App::Property","A unit to express the measurement. Leave blank for system default"))
         obj.FontSize = getParam("textheight",0.20)
         obj.TextSpacing = getParam("dimspacing",0.05)
         obj.FontName = getParam("textfont","")
@@ -3749,15 +3750,18 @@ class _ViewProviderDimension(_ViewProviderDraft):
                 su = obj.ViewObject.ShowUnit
             # set text value
             l = self.p3.sub(self.p2).Length
+            unit = None
+            if hasattr(obj.ViewObject,"UnitOverride"):
+                unit = obj.ViewObject.UnitOverride
             # special representation if "Building US" scheme
             if FreeCAD.ParamGet("User parameter:BaseApp/Preferences/Units").GetInt("UserSchema",0) == 5:
                 s = FreeCAD.Units.Quantity(l,FreeCAD.Units.Length).UserString
                 self.string = s.replace("' ","'- ")
                 self.string = s.replace("+"," ")
             elif hasattr(obj.ViewObject,"Decimals"):
-                self.string = DraftGui.displayExternal(l,obj.ViewObject.Decimals,'Length',su)
+                self.string = DraftGui.displayExternal(l,obj.ViewObject.Decimals,'Length',su,unit)
             else:
-                self.string = DraftGui.displayExternal(l,None,'Length',su)
+                self.string = DraftGui.displayExternal(l,None,'Length',su,unit)
             if hasattr(obj.ViewObject,"Override"):
                 if obj.ViewObject.Override:
                     self.string = obj.ViewObject.Override.replace("$dim",\
diff --git a/src/Mod/Draft/DraftGui.py b/src/Mod/Draft/DraftGui.py
index cd0fba7e56..0470330251 100644
--- a/src/Mod/Draft/DraftGui.py
+++ b/src/Mod/Draft/DraftGui.py
@@ -134,16 +134,21 @@ def makeFormatSpec(decimals=4,dim='Length'):
         fmtSpec = "%." + str(decimals) + "f " + "??"
     return fmtSpec
 
-def displayExternal(internValue,decimals=None,dim='Length',showUnit=True):
+def displayExternal(internValue,decimals=None,dim='Length',showUnit=True,unit=None):
     '''return an internal value (ie mm) Length or Angle converted for display according 
-    to Units Schema in use.'''
+    to Units Schema in use. Unit can be used to force the value to express in a certain unit'''
     from FreeCAD import Units
     if dim == 'Length':
         q = FreeCAD.Units.Quantity(internValue,FreeCAD.Units.Length)
-        if (decimals == None) and showUnit:
-            return q.UserString
-        conversion = q.getUserPreferred()[1]
-        uom = q.getUserPreferred()[2]
+        if not unit:
+            if (decimals == None) and showUnit:
+                return q.UserString
+            conversion = q.getUserPreferred()[1]
+            uom = q.getUserPreferred()[2]
+        else:
+            uom = unit
+            internValue = q.getValueAs(unit)
+            conversion = 1
     elif dim == 'Angle':
         return FreeCAD.Units.Quantity(internValue,FreeCAD.Units.Angle).UserString
     else: