From b920b785f8193414fd66fe2a6d69c2e2ebf22023 Mon Sep 17 00:00:00 2001
From: Heiko Becker <heiko.becker@kde.org>
Date: Tue, 21 Sep 2021 16:56:02 +0200
Subject: [PATCH] Add FindERFA cmake module

ERFA doesn't seem to come with a cmake find module or a config file,
so I wrote one, which also provides an imported target.
---
 CMakeLists.txt                  |  5 +--
 Tests/skyobjects/CMakeLists.txt |  5 ++-
 cmake/modules/FindERFA.cmake    | 72 +++++++++++++++++++++++++++++++++
 3 files changed, 77 insertions(+), 5 deletions(-)
 create mode 100644 cmake/modules/FindERFA.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b7b02258a..052987438 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -229,10 +229,7 @@ if(BUILD_TESTING)
     # Find liberfa, which we check our computation against
     find_package(ERFA)
     MACRO_BOOL_TO_01(ERFA_FOUND HAVE_LIBERFA)
-    set_package_properties(ERFA PROPERTIES DESCRIPTION "Essential Routines for Fundamental Astronomy" URL "https://github.com/liberfa/erfa" TYPE OPTIONAL PURPOSE "BSD-compatible version of SOFA, used to test core computations of KStars (only needed by tests)")
-    if (ERFA_FOUND)
-    include_directories(${ERFA_INCLUDE_DIR})
-    endif()
+    set_package_properties(ERFA PROPERTIES TYPE OPTIONAL PURPOSE "BSD-compatible version of SOFA, used to test core computations of KStars (only needed by tests)")
 endif ()
 
 ## Libraw
diff --git a/Tests/skyobjects/CMakeLists.txt b/Tests/skyobjects/CMakeLists.txt
index 7dc9b918c..ca2d06209 100644
--- a/Tests/skyobjects/CMakeLists.txt
+++ b/Tests/skyobjects/CMakeLists.txt
@@ -5,5 +5,8 @@ ADD_TEST( NAME TestSkyPoint COMMAND test_skypoint )
 endif()
 
 ADD_EXECUTABLE( test_starobject test_starobject.cpp )
-TARGET_LINK_LIBRARIES( test_starobject ${TEST_LIBRARIES} ${ERFA_LIBRARIES})
+TARGET_LINK_LIBRARIES( test_starobject ${TEST_LIBRARIES} )
+if (TARGET ERFA::ERFA)
+    TARGET_LINK_LIBRARIES( test_starobject ERFA::ERFA )
+endif()
 ADD_TEST( NAME TestStarobject COMMAND test_starobject )
diff --git a/cmake/modules/FindERFA.cmake b/cmake/modules/FindERFA.cmake
new file mode 100644
index 000000000..ea6f3e7d8
--- /dev/null
+++ b/cmake/modules/FindERFA.cmake
@@ -0,0 +1,72 @@
+# SPDX-FileCopyrightText: 2021 Heiko Becker <heiko.becker@kde.org>
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+#[=======================================================================[.rst:
+FindERFA
+----------
+
+Try to find the ERFA (Essential Routines for Fundamental Astronomy) library.
+
+This will define the following variables:
+
+``ERFA_FOUND``
+      True if the system has the ERFA library of at least the minimum
+      version specified by the version parameter to find_package()
+``ERFA_INCLUDE_DIRS``
+      The ERFA include dirs for use with target_include_directories
+``ERFA_LIBRARIES``
+      The ERFA libraries for use with target_link_libraries()
+``ERFA_VERSION``
+      The version of ERFA that was found
+
+If ``ERFA_FOUND` is TRUE, it will also define the following imported
+target:
+
+``ERFA::ERFA``
+      The ERFA library
+
+#]=======================================================================]
+
+find_package(PkgConfig QUIET)
+
+pkg_check_modules(PC_ERFA QUIET erfa)
+
+find_path(ERFA_INCLUDE_DIRS
+    NAMES erfa.h
+    HINTS ${PC_ERFA_INCLUDEDIR}
+)
+
+find_library(ERFA_LIBRARIES
+    NAMES erfa
+    HINTS ${PC_ERFA_LIBDIR}
+)
+
+set(ERFA_VERSION ${PC_ERFA_VERSION})
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(ERFA
+    FOUND_VAR
+        ERFA_FOUND
+    REQUIRED_VARS
+        ERFA_LIBRARIES
+        ERFA_INCLUDE_DIRS
+    VERSION_VAR
+        ERFA_VERSION
+)
+
+if (ERFA_FOUND AND NOT TARGET ERFA::ERFA)
+    add_library(ERFA::ERFA UNKNOWN IMPORTED)
+    set_target_properties(ERFA::ERFA PROPERTIES
+        IMPORTED_LOCATION "${ERFA_LIBRARIES}"
+        INTERFACE_INCLUDE_DIRECTORIES "${ERFA_INCLUDE_DIRS}"
+    )
+endif()
+
+mark_as_advanced(ERFA_LIBRARIES ERFA_INCLUDE_DIRS)
+
+include(FeatureSummary)
+set_package_properties(ERFA PROPERTIES
+    URL "https://github.com/liberfa/erfa/"
+    DESCRIPTION "Essential Routines for Fundamental Astronomy"
+)
-- 
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