Add pkg-config export to CMake script

Author: OPNA2608

src/CMakeLists.txt

@@ -1,12 +1,15 @@
 cmake_minimum_required(VERSION 3.3)
 project(QZXing)
 
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
 option(BUILD_SHARED "Build as shared library" OFF)
 
 if(BUILD_SHARED)
     SET(SOVERSION_MAJOR 3)
     SET(SOVERSION_MINOR 3)
     SET(SOVERSION_PATCH 0)
+    SET(SOVERSION_FULL "${SOVERSION_MAJOR}.${SOVERSION_MINOR}.${SOVERSION_PATCH}")
 
     OPTION(QZXING_MULTIMEDIA "" OFF)
     OPTION(QZXING_USE_QML "" OFF)
@@ -39,6 +42,8 @@ set(PUBLIC_HEADERS
     QZXing_global.h
 )
 
+set(PUBLIC_DEFINES "")
+
 set(SOURCES
 
     CameraImageWrapper.cpp
@@ -53,7 +58,7 @@ if(QZXING_MULTIMEDIA)
 
     LIST(APPEND SOURCES QZXingFilter.cpp QZXingFilter.h)
     LIST(APPEND PUBLIC_HEADERS QZXingFilter.h)
-    add_definitions(-DQZXING_MULTIMEDIA)
+    LIST(APPEND PUBLIC_DEFINES QZXING_MULTIMEDIA)
 
     SET(QZXING_USE_QML ON)
 
@@ -62,24 +67,27 @@ endif(QZXING_MULTIMEDIA)
 if(QZXING_USE_QML)
     LIST(APPEND SOURCES QZXingImageProvider.cpp QZXingImageProvider.h)
     LIST(APPEND PUBLIC_HEADERS QZXingImageProvider.h)
-    add_definitions(-DQZXING_QML)
+    LIST(APPEND PUBLIC_DEFINES QZXING_QML)
 endif(QZXING_USE_QML)
 
 if(QZXING_USE_ENCODER)
-    add_definitions(-DENABLE_ENCODER_GENERIC -DENABLE_ENCODER_QR_CODE)
+    LIST(APPEND PUBLIC_DEFINES ENABLE_ENCODER_GENERIC ENABLE_ENCODER_QR_CODE)
 endif(QZXING_USE_ENCODER)
 
 if(BUILD_SHARED)
     add_library(qzxing SHARED ${SOURCES})
     set_target_properties(qzxing
         PROPERTIES
-        VERSION ${SOVERSION_MAJOR}.${SOVERSION_MINOR}.${SOVERSION_PATCH}
+        VERSION ${SOVERSION_FULL}
         SOVERSION ${SOVERSION_MAJOR}
 )
 else()
     add_library(qzxing "" ${SOURCES})
 endif()
 
+# Change Global Definitions depending on how you want to use the library
+list(APPEND PUBLIC_DEFINES DISABLE_LIBRARY_FEATURES)
+
 if(WIN32)
     add_subdirectory(zxing/win32)
     if(MSVC)
@@ -105,20 +113,16 @@ target_link_libraries(qzxing Qt5::Core Qt5::Gui)
 
 if(QZXING_MULTIMEDIA)
     target_link_libraries(qzxing Qt5::Multimedia)
-    target_compile_definitions(qzxing PUBLIC -DQZXING_MULTIMEDIA)
 endif(QZXING_MULTIMEDIA)
 
 if(QZXING_USE_QML)
     target_link_libraries(qzxing
         Qt5::Svg
         Qt5::Quick
         Qt5::QuickControls2)
-    target_compile_definitions(qzxing PUBLIC -DQZXING_QML)
 endif(QZXING_USE_QML)
 
-if(QZXING_USE_ENCODER)
-    target_compile_definitions(qzxing PUBLIC -DENABLE_ENCODER_GENERIC -DENABLE_ENCODER_QR_CODE)
-endif(QZXING_USE_ENCODER)
+target_compile_definitions(qzxing PUBLIC ${PUBLIC_DEFINES})
 
 if(QZXING_USE_DECODER_QR_CODE)
     target_compile_definitions(qzxing PRIVATE -DENABLE_DECODER_QR_CODE)
@@ -144,11 +148,6 @@ if(QZXING_USE_DECODER_1D_BARCODES)
     target_compile_definitions(qzxing PRIVATE -DENABLE_DECODER_1D_BARCODES)
 endif()
 
-if(!BUILD_SHARED)
-    # Change Global Definitions depending on how you want to use the library
-    target_compile_definitions(qzxing PUBLIC DISABLE_LIBRARY_FEATURES)
-endif()
-
 # Target includes
 target_include_directories(qzxing
   PRIVATE
@@ -163,6 +162,7 @@ target_include_directories(qzxing
 
 if(BUILD_SHARED)
     include (GNUInstallDirs)
+    include (JoinPaths)
 
     set(QZXING_INSTALL_TARGETS qzxing)
 
@@ -176,4 +176,15 @@ if(BUILD_SHARED)
     install (
         FILES ${PUBLIC_HEADERS} DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/qzxing"
     )
+
+    join_paths(PC_LIBDIR "\${prefix}" "${CMAKE_INSTALL_LIBDIR}")
+    join_paths(PC_INCLUDEDIR "\${prefix}" "${CMAKE_INSTALL_INCLUDEDIR}" "qzxing")
+
+    string(REPLACE ";" " -D" PC_DEFINES "${PUBLIC_DEFINES}")
+    if(PC_DEFINES)
+        set(PC_DEFINES "-D${PC_DEFINES}")
+    endif()
+
+    configure_file(QZXing.pc.in ${CMAKE_CURRENT_BINARY_DIR}/QZXing.pc @ONLY)
+    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/QZXing.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 endif()

src/QZXing.pc.in

@@ -0,0 +1,10 @@
+prefix=@CMAKE_INSTALL_PREFIX@
+exec_prefix=${prefix}
+libdir=@PC_LIBDIR@
+includedir=@PC_INCLUDEDIR@
+
+Name: Qzxing
+Description: Qzxing Library
+Version: @SOVERSION_FULL@
+Cflags: @PC_DEFINES@ -I${includedir}
+Libs: -L${libdir} -lqzxing

src/cmake/JoinPaths.cmake

@@ -0,0 +1,23 @@
+# This module provides function for joining paths
+# known from most languages
+#
+# SPDX-License-Identifier: (MIT OR CC0-1.0)
+# Copyright 2020 Jan Tojnar
+# https://github.com/jtojnar/cmake-snips
+#
+# Modelled after Python’s os.path.join
+# https://docs.python.org/3.7/library/os.path.html#os.path.join
+# Windows not supported
+function(join_paths joined_path first_path_segment)
+    set(temp_path "${first_path_segment}")
+    foreach(current_segment IN LISTS ARGN)
+        if(NOT ("${current_segment}" STREQUAL ""))
+            if(IS_ABSOLUTE "${current_segment}")
+                set(temp_path "${current_segment}")
+            else()
+                set(temp_path "${temp_path}/${current_segment}")
+            endif()
+        endif()
+    endforeach()
+    set(${joined_path} "${temp_path}" PARENT_SCOPE)
+endfunction()