cmake: improve the FindONNXRuntime script and install the ONNX dll

* Add ONNXRuntime_DIR variable
* Change target name to onnxruntime::onnxruntime following naming
  conventions for imported libs
* Look for the DLL on windows and store it in a variable for later
* Correctly define the properties of the import library
* Change names and logic for global variables to follow standard conventions
* Change import library type from UNKNOWN to SHARED in order to make msvc
  link against the .lib file, not the dll.

1 files changed, 55 insertions, 16 deletions

diff --git a/cmake/FindONNXRuntime.cmake b/cmake/FindONNXRuntime.cmake
index 7350ec0d..44bc46c1 100644
--- a/cmake/FindONNXRuntime.cmake
+++ b/cmake/FindONNXRuntime.cmake
@@ -8,7 +8,9 @@
 # Input variables
 # ---------------
 # 
-#   ONNXRuntime_ROOT            Set root installation.
+#   ONNXRuntime_ROOT            Set root installation. This is an environment
+#                               variable
+#   ONNXRuntime_DIR             CMake variable to set the installation root.
 #
 # Output variable
 # ---------------
@@ -17,26 +19,63 @@
 #   ONNXRuntime_LIBRARIES       Component libraries to be linked.
 #   ONNXRuntime_INCLUDE_DIRS    Include directories.
 
-find_library(ORT_LIB onnxruntime
+set(ONNXRuntime_DIR CACHE PATH "Root directory of the ONNX Runtime installation")
+
+# This script is mostly inspired by the guide there:
+# https://gitlab.kitware.com/cmake/community/-/wikis/doc/tutorials/How-To-Find-Libraries
+# Finding of the DLLs was added so we can install them with the application.
+# We adhere to modern CMake standards and also define an import library.
+
+find_library(ONNXRuntime_LIBRARY onnxruntime
+    HINTS
+        ${ONNXRuntime_DIR}
+    PATHS
+        ${CMAKE_INSTALL_PREFIX}
+    PATH_SUFFIXES lib lib64 bin
     CMAKE_FIND_ROOT_PATH_BOTH)
 
-find_path(ORT_INCLUDE onnxruntime_cxx_api.h
+if(WIN32)
+    SET(CMAKE_FIND_LIBRARY_SUFFIXES ".dll" ".DLL")
+    find_library(ONNXRuntime_RUNTIME onnxruntime
+        HINTS
+            ${ONNXRuntime_DIR}
+        PATHS
+            ${CMAKE_INSTALL_PREFIX}
+        PATH_SUFFIXES lib lib64 bin
+        CMAKE_FIND_ROOT_PATH_BOTH)
+else()
+    SET(ONNXRuntime_RUNTIME ${ONNXRuntime_LIBRARY})
+endif()
+
+find_path(ONNXRuntime_INCLUDE_DIR onnxruntime_cxx_api.h
+    HINTS
+        ${ONNXRuntime_DIR}/include
+        ${ONNXRuntime_DIR}
+    PATHS
+        ${CMAKE_INSTALL_PREFIX}/include
     PATH_SUFFIXES onnxruntime/core/session
     CMAKE_FIND_ROOT_PATH_BOTH)
 
-if(ORT_LIB AND ORT_INCLUDE)
-    set(ONNXRuntime_FOUND TRUE)
-    set(ONNXRuntime_INCLUDE_DIRS "${ORT_INCLUDE}")
-
-    if(NOT TARGET onnxruntime)
-        add_library(onnxruntime UNKNOWN IMPORTED)
-        set_target_properties(onnxruntime PROPERTIES
-            IMPORTED_LOCATION "${ORT_LIB}"
-            INTERFACE_INCLUDE_DIRECTORIES "${ORT_INCLUDE}"
-            INTERFACE_LINK_LIBRARIES "onnxruntime")
-        list(APPEND ONNXRuntime_LIBRARIES onnxruntime)
+
+include(FindPackageHandleStandardArgs)
+# handle the QUIETLY and REQUIRED arguments and set ONNXRuntime_FOUND to TRUE
+# if all listed variables are TRUE
+find_package_handle_standard_args(ONNXRuntime  DEFAULT_MSG
+                                  ONNXRuntime_LIBRARY ONNXRuntime_INCLUDE_DIR ONNXRuntime_RUNTIME)
+
+if(ONNXRuntime_FOUND)
+    if(NOT TARGET onnxruntime::onnxruntime)
+        # Following this quide:
+        # https://cmake.org/cmake/help/git-stage/guide/importing-exporting/index.html#importing-libraries
+        add_library(onnxruntime::onnxruntime SHARED IMPORTED)
+        set_target_properties(onnxruntime::onnxruntime PROPERTIES
+            IMPORTED_LOCATION "${ONNXRuntime_RUNTIME}"
+            INTERFACE_INCLUDE_DIRECTORIES "${ONNXRuntime_INCLUDE_DIR}"
+            IMPORTED_IMPLIB "${ONNXRuntime_LIBRARY}")
     endif()
 endif()
 
-unset(ORT_LIB CACHE)
-unset(ORT_INCLUDE CACHE)
+mark_as_advanced(ONNXRuntime_INCLUDE_DIR ONNXRuntime_LIBRARY ONNXRuntime_RUNTIME)
+
+set(ONNXRuntime_INCLUDE_DIRS ${ONNXRuntime_INCLUDE_DIR})
+set(ONNXRuntime_LIBRARIES ${ONNXRuntime_LIBRARY})
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