Add proj_get_suggested_operation()

Return the index of the operation that would be the most appropriate to
transform the specified coordinates.

This operation may use resources that are not locally available, depending
on the search criteria used by proj_create_operations().

This could be done by using proj_create_operations() with a punctual bounding
box, but this function is faster when one needs to evaluate on many points
with the same (source_crs, target_crs) tuple.

1 files changed, 29 insertions, 5 deletions

diff --git a/test/unit/test_c_api.cpp b/test/unit/test_c_api.cpp
index 0f1b906e..f274af57 100644
--- a/test/unit/test_c_api.cpp
+++ b/test/unit/test_c_api.cpp
@@ -1348,12 +1348,36 @@ TEST_F(CApi, proj_create_operations) {
 
     EXPECT_EQ(proj_list_get(m_ctxt, res, -1), nullptr);
     EXPECT_EQ(proj_list_get(m_ctxt, res, proj_list_get_count(res)), nullptr);
-    auto op = proj_list_get(m_ctxt, res, 0);
-    ASSERT_NE(op, nullptr);
-    ObjectKeeper keeper_op(op);
-    EXPECT_FALSE(proj_coordoperation_has_ballpark_transformation(m_ctxt, op));
+    {
+        auto op = proj_list_get(m_ctxt, res, 0);
+        ASSERT_NE(op, nullptr);
+        ObjectKeeper keeper_op(op);
+        EXPECT_FALSE(
+            proj_coordoperation_has_ballpark_transformation(m_ctxt, op));
+        EXPECT_EQ(proj_get_name(op), std::string("NAD27 to NAD83 (3)"));
+    }
+
+    {
+        PJ_COORD coord;
+        coord.xy.x = 40;
+        coord.xy.y = -100;
+        int idx = proj_get_suggested_operation(m_ctxt, res, PJ_FWD, coord);
+        ASSERT_GE(idx, 0);
+        ASSERT_LT(idx, proj_list_get_count(res));
+        auto op = proj_list_get(m_ctxt, res, idx);
+        ASSERT_NE(op, nullptr);
+        ObjectKeeper keeper_op(op);
+        // Transformation for USA
+        EXPECT_EQ(proj_get_name(op), std::string("NAD27 to NAD83 (1)"));
+    }
 
-    EXPECT_EQ(proj_get_name(op), std::string("NAD27 to NAD83 (3)"));
+    {
+        PJ_COORD coord;
+        coord.xy.x = 40;
+        coord.xy.y = 10;
+        int idx = proj_get_suggested_operation(m_ctxt, res, PJ_FWD, coord);
+        EXPECT_GE(idx, -1);
+    }
 }
 
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