reorganize cmake in small scripts with some fix from https://github.com/cnjinhao/nana/pull/278

build/cmake/OS.cmake

@@ -0,0 +1,70 @@
+########### OS
+# https://blog.kowalczyk.info/article/j/guide-to-predefined-macros-in-c-compilers-gcc-clang-msvc-etc..html
+# http://nadeausoftware.com/articles/2012/01/c_c_tip_how_use_compiler_predefined_macros_detect_operating_system
+
+if(WIN32)
+    target_compile_definitions(nana PUBLIC WIN32)    # todo: why not simple test for _WIN32 in code??
+    set(CMAKE_DEBUG_POSTFIX "_d")    # ??
+    # Global MSVC definitions. You may prefer the hand-tuned sln and projects from the nana repository.
+    if(MSVC)
+        option(MSVC_USE_MP "Set to ON to build nana with the /MP option (Visual Studio 2005 and above)." ON)
+        option(MSVC_USE_STATIC_RUNTIME "Set to ON to build nana with the /MT(d) option." ON)
+
+        # Change the MSVC Compiler flags
+        if(MSVC_USE_MP)
+            target_compile_options(nana PUBLIC "/MP" )
+        endif()
+
+        if(MSVC_USE_STATIC_RUNTIME)
+            foreach(flag
+                    CMAKE_C_FLAGS              CMAKE_C_FLAGS_DEBUG             CMAKE_C_FLAGS_RELEASE
+                    CMAKE_C_FLAGS_MINSIZEREL   CMAKE_C_FLAGS_RELWITHDEBINFO
+                    CMAKE_CXX_FLAGS            CMAKE_CXX_FLAGS_DEBUG           CMAKE_CXX_FLAGS_RELEASE
+                    CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
+                if(${flag} MATCHES "/MD")
+                    string(REGEX REPLACE "/MD" "/MT" ${flag} "${${flag}}")
+                endif()
+            endforeach()
+        endif()
+    endif()
+
+    if(MINGW)
+        if(NANA_CMAKE_ENABLE_MINGW_STD_THREADS_WITH_MEGANZ)      # deprecated ?????
+            target_compile_definitions(nana PUBLIC STD_THREAD_NOT_SUPPORTED
+                                            PUBLIC NANA_ENABLE_MINGW_STD_THREADS_WITH_MEGANZ  )
+        endif()
+    endif()
+endif()
+
+if(APPLE)
+    target_compile_definitions(nana PUBLIC APPLE)      # ??? not added by compilers? use  __APPLE__  ?
+    target_include_directories(nana PUBLIC /opt/X11/include/)
+    target_link_libraries(nana PRIVATE iconv)
+    set(ENABLE_AUDIO OFF)
+endif()
+
+if(UNIX)
+
+    find_package(X11 REQUIRED)            # X11  - todo test PRIVATE
+    target_link_libraries(nana
+            PUBLIC ${X11_LIBRARIES}
+            PUBLIC ${X11_Xft_LIB}
+            )
+    target_include_directories(nana SYSTEM
+            PUBLIC ${X11_Xft_INCLUDE_PATH}
+            PUBLIC ${X11_INCLUDE_DIR}
+            )
+
+    find_package(Freetype)                # Freetype - todo test PRIVATE
+    if (FREETYPE_FOUND)
+        find_package(Fontconfig REQUIRED)
+        target_include_directories(nana SYSTEM
+                PUBLIC ${FREETYPE_INCLUDE_DIRS}
+                PUBLIC ${FONTCONFIG_INCLUDE_DIR}
+                )
+        target_link_libraries(nana
+                PUBLIC ${FREETYPE_LIBRARIES}
+                PUBLIC ${FONTCONFIG_LIBRARIES}
+                )
+    endif(FREETYPE_FOUND)
+endif(UNIX)