PDT: Add user-requested Tangent Functions (new feature)

This Branch is WIP, still in development and not yet suitable for a release.

This process will add the ability to draw tangents from a point to an arc, or circle.
It will also add the ability to draw tangents, both inner and outer, between two arcs.
Arc centres and radii can be manually input into the UI, or set from three vertices that
lie on an imaginary arc. Tangent functions have their own PDT Sub-menu.

This commit only works in Front view, to get the maths right, later commits will expand
this into any view orientation, using existing PDT code.

This commit does not contain DocStrings for the new pdt_tangent.py file, these will
also follow in a later commit.

It is recommended that this commit is not used in a production environment. Once
complete, a new version Branch will be added, at this point the code will reach Alpha
status and be appropriate for extensive user testing.

1 files changed, 6 insertions, 0 deletions

diff --git a/precision_drawing_tools/pdt_msg_strings.py b/precision_drawing_tools/pdt_msg_strings.py
index 8c7b9db2..9eeb08f1 100644
--- a/precision_drawing_tools/pdt_msg_strings.py
+++ b/precision_drawing_tools/pdt_msg_strings.py
@@ -192,3 +192,9 @@ PDT_DES_FILLETSEG = "Number of Fillet Segments"
 PDT_DES_FILLETPROF = "Fillet Profile"
 PDT_DES_FILLETVERTS = "Use Vertices, or Edges, Set to False for Extruded Geometry"
 PDT_DES_FILLINT = "Intersect & Fillet Two Selected Edges"
+PDT_DES_TANCEN1 = "Centre of First Tangent Arc"
+PDT_DES_TANCEN2 = "Centre of Second Tangent Arc"
+PDT_DES_TANCEN3 = "Tangents From a Point"
+PDT_DES_RADIUS1 = "Radius of First Tangent Arc"
+PDT_DES_RADIUS2 = "Radius of Second Tangent Arc"
+PDT_DES_TPOINT = "Calculate Tangents From Point"