Using find_package to import custom HAL library

CMakeLists.txt

@@ -603,29 +603,25 @@ endif()
 include(cmake/OpenCVDetectVTK.cmake)
 
 # -- Custom HAL replacement --
-set(_includes "")
-# assuming OPENCV_HAL_HEADERS and OPENCV_HAL_LIBS are lists of files:
-# option example: -DOPENCV_HAL_HEADERS="<some-path>/header1.h;<some-path>/header2.h"
-if (OPENCV_HAL_HEADERS AND OPENCV_HAL_LIBS)
-  foreach (h ${OPENCV_HAL_HEADERS})
-    get_filename_component(h "${h}" ABSOLUTE)
-    set(_includes "${_includes}\n#include \"${h}\"")
-  endforeach()
-  foreach (l ${OPENCV_HAL_LIBS})
+# Package config in: OpenCV_HALConfig.cmake or opencv_hal-config.cmake
+# Use variables: OpenCV_HAL_LIBRARIES, OpenCV_HAL_HEADERS and OpenCV_HAL_INCLUDE_DIRS variables
+find_package(OpenCV_HAL CONFIG QUIET)
+if (OpenCV_HAL_FOUND)
+  # 1. libraries
+  foreach (l ${OpenCV_HAL_LIBRARIES})
     get_filename_component(l "${l}" ABSOLUTE)
     set(OPENCV_LINKER_LIBS ${OPENCV_LINKER_LIBS} ${l})
-    # TODO: install?
-    # ocv_install_target(${l} EXPORT OpenCVModules ARCHIVE DESTINATION ${OPENCV_3P_LIB_INSTALL_PATH} COMPONENT dev)
   endforeach()
-else()
-  set(_includes "// using default HAL")
-  unset(OPENCV_HAL_HEADERS CACHE)
-  unset(OPENCV_HAL_LIBS CACHE)
+  # 2. headers
+  set(_includes "")
+  foreach (h ${OpenCV_HAL_HEADERS})
+    set(_includes "${_includes}\n#include \"${h}\"")
+  endforeach()
+  configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/custom_hal.hpp.in" "${CMAKE_BINARY_DIR}/custom_hal.hpp" @ONLY)
+  unset(_includes)
+  # 3. include paths
+  ocv_include_directories(${OpenCV_HAL_INCLUDE_DIRS})
 endif()
-set(OPENCV_HAL_HEADERS "${OPENCV_HAL_HEADERS}" CACHE STRING "Headers with custom HAL implementation")
-set(OPENCV_HAL_LIBS "${OPENCV_HAL_LIBS}" CACHE STRING "Libraries with custom HAL implementation")
-configure_file("${OpenCV_SOURCE_DIR}/cmake/templates/custom_hal.hpp.in" "${CMAKE_BINARY_DIR}/custom_hal.hpp" @ONLY)
-unset(_includes)
 
 # ----------------------------------------------------------------------------
 # Add CUDA libraries (needed for apps/tools, samples)
@@ -1164,7 +1160,7 @@ endif(DEFINED WITH_VA_INTEL)
 status("    Use Eigen:"      HAVE_EIGEN       THEN "YES (ver ${EIGEN_WORLD_VERSION}.${EIGEN_MAJOR_VERSION}.${EIGEN_MINOR_VERSION})" ELSE NO)
 status("    Use Cuda:"       HAVE_CUDA        THEN "YES (ver ${CUDA_VERSION_STRING})" ELSE NO)
 status("    Use OpenCL:"     HAVE_OPENCL      THEN YES ELSE NO)
-status("    Use custom HAL:" OPENCV_HAL_HEADERS AND OPENCV_HAL_LIBS THEN "YES (${OPENCV_HAL_HEADERS}; ${OPENCV_HAL_LIBS})" ELSE "NO")
+status("    Use custom HAL:" OpenCV_HAL_FOUND THEN "YES (ver ${OpenCV_HAL_VERSION}, ${OpenCV_HAL_CONFIG})" ELSE "NO")
 
 if(HAVE_CUDA)
   status("")

samples/hal/README.md

@@ -23,8 +23,7 @@ Build OpenCV with HAL replacement
 2. Go to the created folder and run cmake:
     ```
     cmake \
-        -DOPENCV_HAL_HEADERS="<opencv-src>/samples/hal/slow_hal/impl.hpp" \
-        -DOPENCV_HAL_LIBS="<home-dir>/my-hal-build/libslow_hal.a" \
+        -DOpenCV_HAL_DIR="<home-dir>/my-hal-build/" \
         <opencv-src>
     ```
 3. Run make (or `make opencv_perf_core` to build the demonstration test executable only)

samples/hal/c_hal/CMakeLists.txt

 cmake_minimum_required(VERSION 2.8.8 FATAL_ERROR)
 
-if(UNIX)
-  if(CMAKE_COMPILER_IS_GNUC OR CV_ICC)
-    set(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
-  endif()
-endif()
-
 add_library(c_hal impl.c)
+set_target_properties(c_hal PROPERTIES POSITION_INDEPENDENT_CODE TRUE)
 set(OPENCV_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../..")
 target_include_directories(c_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)
+
+configure_file("impl.h" "${CMAKE_BINARY_DIR}/impl.h" COPYONLY)
+configure_file("config.cmake" "${CMAKE_BINARY_DIR}/OpenCV_HALConfig.cmake" COPYONLY)

samples/hal/c_hal/config.cmake

+set(OpenCV_HAL_FOUND TRUE)
+set(OpenCV_HAL_VERSION "0.0.1")
+set(OpenCV_HAL_LIBRARIES "${CMAKE_CURRENT_LIST_DIR}/libc_hal.a")
+set(OpenCV_HAL_HEADERS "impl.h")
+set(OpenCV_HAL_INCLUDE_DIRS "${CMAKE_CURRENT_LIST_DIR}")

samples/hal/slow_hal/CMakeLists.txt

 cmake_minimum_required(VERSION 2.8.8 FATAL_ERROR)
 
-if(UNIX)
-  if(CMAKE_COMPILER_IS_GNUCXX OR CV_ICC)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
-  endif()
-endif()
-
 add_library(slow_hal impl.cpp)
+set_target_properties(slow_hal PROPERTIES POSITION_INDEPENDENT_CODE TRUE)
 set(OPENCV_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../../..")
 target_include_directories(slow_hal PUBLIC ${CMAKE_CURRENT_SOURCE_DIR} ${OPENCV_SRC_DIR}/modules/core/include)
+
+configure_file("impl.hpp" "${CMAKE_BINARY_DIR}/impl.hpp" COPYONLY)
+configure_file("config.cmake" "${CMAKE_BINARY_DIR}/OpenCV_HALConfig.cmake" COPYONLY)

samples/hal/slow_hal/config.cmake

+set(OpenCV_HAL_FOUND TRUE)
+set(OpenCV_HAL_VERSION "0.0.1")
+set(OpenCV_HAL_LIBRARIES "${CMAKE_CURRENT_LIST_DIR}/libslow_hal.a")
+set(OpenCV_HAL_HEADERS "impl.hpp")
+set(OpenCV_HAL_INCLUDE_DIRS "${CMAKE_CURRENT_LIST_DIR}")