Draft: Fix angular dimension issue caused by FreeCAD#10556

Forum topic:
https://forum.freecad.org/viewtopic.php?t=81956

This PR basically reverts PR FreeCAD#10556.

The angular offset required for the Draft_Arc command is handled in the gui_arc.py file instead. Also removed the unused `urotated` variable from that file.

src/Mod/Draft/draftguitools/gui_arcs.py

@@ -284,10 +284,11 @@ def action(self, arg):
                     elif self.step == 2:  # choose first angle
                         self.ui.labelRadius.setText(translate("draft", "Aperture angle"))
                         self.ui.radiusValue.setToolTip(translate("draft", "Aperture angle"))
+                        ang_offset = DraftVecUtils.angle(self.wp.u,
+                                                         self.arctrack.getDeviation(),
+                                                         self.wp.axis)
+                        self.arctrack.setStartAngle(self.firstangle - ang_offset)
                         self.step = 3
-                        # scale center->point vector for proper display
-                        # u = DraftVecUtils.scaleTo(self.point.sub(self.center), self.rad) obsolete?
-                        self.arctrack.setStartAngle(self.firstangle)
                         _msg(translate("draft", "Pick aperture"))
                     else:  # choose second angle
                         self.step = 4
@@ -449,12 +450,10 @@ def numericRadius(self, rad):
             self.ui.labelRadius.setText(translate("draft", "Aperture angle"))
             self.ui.radiusValue.setToolTip(translate("draft", "Aperture angle"))
             self.firstangle = math.radians(rad)
-            if DraftVecUtils.equals(self.wp.axis, App.Vector(1, 0, 0)):
-                u = App.Vector(0, self.rad, 0)
-            else:
-                u = DraftVecUtils.scaleTo(App.Vector(1, 0, 0).cross(self.wp.axis), self.rad)
-            urotated = DraftVecUtils.rotate(u, math.radians(rad), self.wp.axis)
-            self.arctrack.setStartAngle(self.firstangle)
+            ang_offset = DraftVecUtils.angle(self.wp.u,
+                                             self.arctrack.getDeviation(),
+                                             self.wp.axis)
+            self.arctrack.setStartAngle(self.firstangle - ang_offset)
             self.step = 3
             self.ui.radiusValue.setText("")
             self.ui.radiusValue.setFocus()

src/Mod/Draft/draftguitools/gui_trackers.py

@@ -528,7 +528,7 @@ def recompute(self):
 
 class arcTracker(Tracker):
     """An arc tracker."""
-
+    # Note: used by the Arc command but also for angular dimensions.
     def __init__(self, dotted=False, scolor=None, swidth=None,
                  start=0, end=math.pi*2):
         self.circle = None
@@ -539,10 +539,6 @@ def __init__(self, dotted=False, scolor=None, swidth=None,
         self.sep = coin.SoSeparator()
         self.autoinvert = True
         self.normal = FreeCAD.DraftWorkingPlane.axis
-        ang = DraftVecUtils.angle(self.getDeviation(),
-                                  FreeCAD.DraftWorkingPlane.u,
-                                  self.normal)
-        self.ang_offset = math.degrees(ang)
         self.recompute()
         super().__init__(dotted, scolor, swidth,
                          [self.trans, self.sep], name="arcTracker")
@@ -579,19 +575,19 @@ def getAngle(self, pt):
         """Return the angle of a given vector in radians."""
         c = self.trans.translation.getValue()
         center = Vector(c[0], c[1], c[2])
-        return DraftVecUtils.angle(self.getDeviation(), pt.sub(center), self.normal)
+        return DraftVecUtils.angle(pt.sub(center), self.getDeviation(), self.normal)
 
     def getAngles(self):
         """Return the start and end angles in degrees."""
         return(self.startangle, self.endangle)
 
     def setStartPoint(self, pt):
         """Set the start angle from a point."""
-        self.setStartAngle(self.getAngle(pt))
+        self.setStartAngle(-self.getAngle(pt))
 
     def setEndPoint(self, pt):
         """Set the end angle from a point."""
-        self.setEndAngle(self.getAngle(pt))
+        self.setEndAngle(-self.getAngle(pt))
 
     def setApertureAngle(self, ang):
         """Set the end angle by giving the aperture angle."""
@@ -620,16 +616,12 @@ def recompute(self):
         if self.circle:
             self.sep.removeChild(self.circle)
         self.circle = None
-        if self.autoinvert is False:
-            ang_sta = self.endangle
-            ang_end = self.startangle
-        elif self.endangle < self.startangle:
-            ang_sta = self.endangle + self.ang_offset
-            ang_end = self.startangle + self.ang_offset
+        if (self.endangle < self.startangle) or not self.autoinvert:
+            c = Part.makeCircle(1, Vector(0, 0, 0),
+                                self.normal, self.endangle, self.startangle)
         else:
-            ang_sta = self.startangle + self.ang_offset
-            ang_end = self.endangle + self.ang_offset
-        c = Part.makeCircle(1, Vector(0, 0, 0), self.normal, ang_sta, ang_end)
+            c = Part.makeCircle(1, Vector(0, 0, 0),
+                                self.normal, self.startangle, self.endangle)
         buf = c.writeInventor(2, 0.01)
         try:
             ivin = coin.SoInput()