[pangomm/pangomm-2-42] Meson build: Fix versioning on macOS

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 603d9a7e089a0f1cbaeb78d2bbc9dc05801924ea
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Thu Oct 1 10:18:07 2020 +0200

    Meson build: Fix versioning on macOS
    
    See libsigcplusplus, pull request 65

 meson.build               | 7 ++++++-
 pango/pangomm/meson.build | 4 +++-
 2 files changed, 9 insertions(+), 2 deletions(-)
---
diff --git a/meson.build b/meson.build
index 337988e..efd0a35 100644
--- a/meson.build
+++ b/meson.build
@@ -29,7 +29,12 @@ libtool_soversion = [1, 30, 0]
 pangomm_libversion = '@0@.@1@.@2@'.format(
   libtool_soversion[0] - libtool_soversion[2],
   libtool_soversion[2],
-  libtool_soversion[1])
+  libtool_soversion[1]
+)
+macos_darwin_versions = [
+  libtool_soversion[0] + 1,
+  '@0@.@1@'.format(libtool_soversion[0] + 1, libtool_soversion[1])
+]
 
 # Use these instead of meson.source_root() and meson.build_root() in subdirectories.
 # source_root() and build_root() are not useful, if this is a subproject.
diff --git a/pango/pangomm/meson.build b/pango/pangomm/meson.build
index 045225e..edbbf01 100644
--- a/pango/pangomm/meson.build
+++ b/pango/pangomm/meson.build
@@ -3,7 +3,7 @@
 # Input: pangomm_build_dep, pangomm_pcname, maintainer_mode, project_source_root,
 #        generate_binding_py, m4_files, pangomm_libversion, install_includedir,
 #        python3, pangomm_rc, dummy_header_py, gmmproc_dir, build_shared_libs_directly,
-#        msvc14x_toolset_ver
+#        msvc14x_toolset_ver, macos_darwin_versions
 # Output: hg_ccg_basenames, extra_h_files, built_h_file_targets, built_files_root,
 #         pangomm_dep
 
@@ -207,6 +207,7 @@ if build_shared_libs_directly
     include_directories: extra_include_dirs,
     cpp_args: pangomm_cpp_args,
     version: pangomm_libversion,
+    darwin_versions: macos_darwin_versions,
     dependencies: pangomm_build_dep,
     install: true,
   )
@@ -239,6 +240,7 @@ else
   pangomm_library = library(pangomm_libname, extra_pangomm_objects,
     objects: pango_int_lib.extract_all_objects(),
     version: pangomm_libversion,
+    darwin_versions: macos_darwin_versions,
     dependencies: pangomm_build_dep,
     link_depends: pangomm_def,
     link_args: pangomm_extra_link_args,