Add proj_degree_input() and proj_degree_output()

Equivalent to proj_angular_input() and proj_angular_output() but
checking for degree units instead. proj_create_crs_to_crs() rarely, if
ever, returns pipelines that has radians as input or output so using
proj_angular_*() is not a useful check for io units of pipelines.

These two new functions should make life a bit easier for users that
generally store there angular coordinates in radians.

Closes #2027

6 files changed, 44 insertions, 5 deletions

diff --git a/src/4D_api.cpp b/src/4D_api.cpp
index 6e494793..069093f2 100644
--- a/src/4D_api.cpp
+++ b/src/4D_api.cpp
@@ -93,6 +93,27 @@ int proj_angular_output (PJ *P, enum PJ_DIRECTION dir) {
     return proj_angular_input (P, opposite_direction(dir));
 }
 
+/*****************************************************************************/
+int proj_degree_input (PJ *P, enum PJ_DIRECTION dir) {
+/******************************************************************************
+    Returns 1 if the operator P expects degree input coordinates when
+    operating in direction dir, 0 otherwise.
+    dir: {PJ_FWD, PJ_INV}
+******************************************************************************/
+    if (PJ_FWD==dir)
+        return pj_left (P)==PJ_IO_UNITS_DEGREES;
+    return pj_right (P)==PJ_IO_UNITS_DEGREES;
+}
+
+/*****************************************************************************/
+int proj_degree_output (PJ *P, enum PJ_DIRECTION dir) {
+/******************************************************************************
+    Returns 1 if the operator P provides degree output coordinates when
+    operating in direction dir, 0 otherwise.
+    dir: {PJ_FWD, PJ_INV}
+******************************************************************************/
+    return proj_degree_input (P, opposite_direction(dir));
+}
 
 /* Geodesic distance (in meter) + fwd and rev azimuth between two points on the ellipsoid */
 PJ_COORD proj_geod (const PJ *P, PJ_COORD a, PJ_COORD b) {
diff --git a/src/conversions/unitconvert.cpp b/src/conversions/unitconvert.cpp
index 609b30e0..172e2c48 100644
--- a/src/conversions/unitconvert.cpp
+++ b/src/conversions/unitconvert.cpp
@@ -476,8 +476,12 @@ PJ *CONVERSION(unitconvert,0) {
                 return pj_default_destructor(P, PJD_ERR_UNKNOWN_UNIT_ID);
         }
         Q->xy_factor = f;
-        if (normalized_name != nullptr && strcmp(normalized_name, "Radian") == 0)
-            P->left = PJ_IO_UNITS_RADIANS;
+        if (normalized_name != nullptr) {
+            if (strcmp(normalized_name, "Radian") == 0)
+                P->left = PJ_IO_UNITS_RADIANS;
+            if (strcmp(normalized_name, "Degree") == 0)
+                P->left = PJ_IO_UNITS_DEGREES;
+        }
     }
 
     if ((name = pj_param (P->ctx, P->params, "sxy_out").s) != nullptr) {
@@ -491,8 +495,12 @@ PJ *CONVERSION(unitconvert,0) {
                 return pj_default_destructor(P, PJD_ERR_UNKNOWN_UNIT_ID);
         }
         Q->xy_factor /= f;
-        if (normalized_name != nullptr && strcmp(normalized_name, "Radian") == 0)
-            P->right= PJ_IO_UNITS_RADIANS;
+        if (normalized_name != nullptr) {
+            if (strcmp(normalized_name, "Radian") == 0)
+                P->right= PJ_IO_UNITS_RADIANS;
+            if (strcmp(normalized_name, "Degree") == 0)
+                P->right= PJ_IO_UNITS_DEGREES;
+        }
     }
 
     if( xy_in_is_linear >= 0 && xy_out_is_linear >= 0 &&
diff --git a/src/fwd.cpp b/src/fwd.cpp
index 3eb03582..962a5051 100644
--- a/src/fwd.cpp
+++ b/src/fwd.cpp
@@ -134,6 +134,9 @@ static PJ_COORD fwd_finalize (PJ *P, PJ_COORD coo) {
     case PJ_IO_UNITS_WHATEVER:
         break;
 
+    case PJ_IO_UNITS_DEGREES:
+        break;
+
     case PJ_IO_UNITS_RADIANS:
         coo.lpz.z = P->vfr_meter * (coo.lpz.z + P->z0);
 
diff --git a/src/inv.cpp b/src/inv.cpp
index 17eb15b4..626c9ee5 100644
--- a/src/inv.cpp
+++ b/src/inv.cpp
@@ -54,6 +54,9 @@ static PJ_COORD inv_prepare (PJ *P, PJ_COORD coo) {
     case PJ_IO_UNITS_WHATEVER:
         return coo;
 
+    case PJ_IO_UNITS_DEGREES:
+        return coo;
+
     /* de-scale and de-offset */
     case PJ_IO_UNITS_CARTESIAN:
         coo.xyz.x *= P->to_meter;
diff --git a/src/proj.h b/src/proj.h
index d2464d69..857fb862 100644
--- a/src/proj.h
+++ b/src/proj.h
@@ -567,6 +567,8 @@ typedef enum PJ_DIRECTION PJ_DIRECTION;
 int PROJ_DLL proj_angular_input (PJ *P, enum PJ_DIRECTION dir);
 int PROJ_DLL proj_angular_output (PJ *P, enum PJ_DIRECTION dir);
 
+int PROJ_DLL proj_degree_input (PJ *P, enum PJ_DIRECTION dir);
+int PROJ_DLL proj_degree_output (PJ *P, enum PJ_DIRECTION dir);
 
 PJ_COORD PROJ_DLL proj_trans (PJ *P, PJ_DIRECTION direction, PJ_COORD coord);
 int PROJ_DLL proj_trans_array (PJ *P, PJ_DIRECTION direction, size_t n, PJ_COORD *coord);
diff --git a/src/proj_internal.h b/src/proj_internal.h
index c4af479f..c102d910 100644
--- a/src/proj_internal.h
+++ b/src/proj_internal.h
@@ -174,7 +174,9 @@ enum pj_io_units {
     PJ_IO_UNITS_CLASSIC   = 1,  /* Scaled meters (right), projected system */
     PJ_IO_UNITS_PROJECTED = 2,  /* Meters, projected system */
     PJ_IO_UNITS_CARTESIAN = 3,  /* Meters, 3D cartesian system */
-    PJ_IO_UNITS_RADIANS   = 4   /* Radians */
+    PJ_IO_UNITS_RADIANS   = 4,  /* Radians */
+    PJ_IO_UNITS_DEGREES   = 5,  /* Degrees */
+
 };
 enum pj_io_units pj_left (PJ *P);
 enum pj_io_units pj_right (PJ *P);