restore jack backend for portaudio

CMakeLists.txt

@@ -1,8 +1,23 @@
 cmake_minimum_required(VERSION 3.1) # we use target_sources()
 project(Extempore VERSION 0.8.9)
 
-# for backwards compatibility with CMake older than 3.19
-cmake_policy(SET CMP0114 OLD)
+if(POLICY CMP0114)
+  # for backwards compatibility with CMake older than 3.19
+  cmake_policy(SET CMP0114 OLD)
+endif()
+
+if(POLICY CMP0051)
+  cmake_policy(SET CMP0051 NEW)
+endif()
+
+if(POLICY CMP0075)
+  cmake_policy(SET CMP0075 NEW)
+endif()
+
+if(POLICY CMP0135)
+  # to suppress warning about DOWNLOAD_EXTRACT_TIMESTAMP using cmake 3.24+
+  cmake_policy(SET CMP0135 NEW)
+endif()
 
 option(ASSETS "download multimedia assets (approx 500MB)" OFF)
 option(BUILD_TESTS "build test targets (including examples)" ON)
@@ -15,7 +30,7 @@ set(EXTERNAL_SHLIBS (EXTERNAL_SHLIBS_AUDIO OR EXTERNAL_SHLIBS_GRAPHICS))
 option(EXT_DYLIB "build extempore as a dynamic library" OFF)
 
 ## see note about the status of the Jack backend in BUILDING.md
-option(JACK "use the Jack Portaudio backend" OFF)
+option(JACK "use the Jack Portaudio backend" ON)
 
 ## this is useful because we can group targets together (e.g. all the AOT libs)
 set_property(GLOBAL PROPERTY USE_FOLDERS ON)
@@ -175,12 +190,49 @@ if(PACKAGE)
     PRIVATE -mtune=generic)
 endif()
 
+########
+# JACK #
+########
+
+if(JACK)
+  #[[
+  jack is actually cross-platform.
+  according to this comment
+  https://github.com/PortAudio/portaudio/blob/2dc8b6eb17ac5fda1f89722cfa0889bfc6e73434/cmake/modules/FindJACK.cmake#L17
+  pipewire's jack implementation is only found by pkg-config
+  I don't feel like this is required anymore, since I am testing with:
+  $ pkg-config --modversion jack
+  1.9.17
+  $ pkg-config --list-all | grep jack
+  jack                           jack - PipeWire JACK API
+  and by commenting out the pkgconfig here it is found by find_library
+  so keeping mostly for backward compatibilty
+  ]]
+  find_package(PkgConfig QUIET)
+  if(PkgConfig_FOUND)
+    pkg_check_modules(JackCheck jack)
+    if(NOT JackCheck_FOUND)
+      message(NOTICE "JACK disabled because not found")
+      set(JACK OFF)
+    endif()
+  else()
+    find_library(JackCheck
+      NAMES jack
+      DOC "JACK library"
+    )
+    if(NOT JackCheck)
+      message(NOTICE "JACK disabled because not found")
+      set(JACK OFF)
+    endif()
+  endif()
+endif()
+
+
 #############
 # portaudio #
 #############
 
 include(ExternalProject)
-
 ExternalProject_Add(portaudio_static
   PREFIX portaudio
   URL https://github.com/PortAudio/portaudio/archive/3f7bee79a65327d2e0965e8a74299723ed6f072d.zip
@@ -350,6 +402,10 @@ target_include_directories(extempore
   ${CMAKE_BINARY_DIR}/portaudio/include # installed by ExternalProject
   ${EXT_LLVM_DIR}/include)
 
+if(JACK)
+  target_link_libraries(extempore PRIVATE jack)
+endif()
+
 target_link_directories(extempore PRIVATE ${CMAKE_BINARY_DIR}/portaudio/lib)
 target_link_libraries(extempore PRIVATE pcre portaudio${CMAKE_STATIC_LIBRARY_SUFFIX} ${LLVM_LIBRARIES})
 if(UNIX AND NOT APPLE)