[glibmm] Subprojects can use meson.add_dist_script() if meson.version() >= 0.58.0

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 983668cfd40f5eed4a555922586826ccdef560de
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed May 5 10:59:53 2021 +0200

    Subprojects can use meson.add_dist_script() if meson.version() >= 0.58.0
    
    * meson.build:
    * docs/reference/meson.build:
    * gio/giomm/meson.build:
    * glib/glibmm/meson.build:
    Call add_dist_script() in a subproject, if meson.version() >= 0.58.0.
    * tools/build_scripts/handle-built-files.py:
    Use MESON_PROJECT_DIST_ROOT if it exists, else MESON_DIST_ROOT.
    It exists if meson.version() >= 0.58.0.

 docs/reference/meson.build                |  5 ++---
 gio/giomm/meson.build                     |  5 ++---
 glib/glibmm/meson.build                   |  5 ++---
 meson.build                               | 12 +++++++-----
 tools/build_scripts/handle-built-files.py |  7 +++++--
 5 files changed, 18 insertions(+), 16 deletions(-)
---
diff --git a/docs/reference/meson.build b/docs/reference/meson.build
index 1c3e7579..8e866ec1 100644
--- a/docs/reference/meson.build
+++ b/docs/reference/meson.build
@@ -4,7 +4,7 @@
 #        glibmm_hg_ccg_basenames, giomm_hg_ccg_basenames, build_documentation,
 #        glibmm_extra_h_files, giomm_extra_h_files, glibmm_built_h_file_targets,
 #        giomm_built_h_file_targets, glibmm_h_m4_files, install_datadir,
-#        python3, doc_reference_py
+#        python3, doc_reference_py, can_add_dist_script
 # Output: install_docdir, install_devhelpdir, tag_file
 
 tag_file_modules = [
@@ -161,9 +161,8 @@ endforeach
 
 install_data(image_files, install_dir: install_image_docdir)
 
-if not meson.is_subproject()
+if can_add_dist_script
   # Distribute built files and files copied by mm-common-get.
-  # (add_dist_script() is not allowed in a subproject)
   meson.add_dist_script(
     python3.path(), doc_reference_py, 'dist_doc',
     doctool_dir,
diff --git a/gio/giomm/meson.build b/gio/giomm/meson.build
index fad7ce98..2f2193e3 100644
--- a/gio/giomm/meson.build
+++ b/gio/giomm/meson.build
@@ -4,7 +4,7 @@
 #        generate_binding_py, handle_built_files_py, m4_files, pm_files,
 #        glibmm_libversion, install_includedir, python3, giomm_rc, gmmproc_dir,
 #        is_host_windows, gmmproc, generate_wrap_init_pl, giomm_libname,
-#        macos_darwin_versions
+#        macos_darwin_versions, can_add_dist_script
 # Output: giomm_hg_ccg_basenames, giomm_extra_h_files, built_files_root,
 #         giomm_built_h_file_targets, giomm_own_dep
 
@@ -381,9 +381,8 @@ meson.add_install_script(
   giomm_used_hg_ccg_basenames
 )
 
-if not meson.is_subproject()
+if can_add_dist_script
   # Distribute built files.
-  # (add_dist_script() is not allowed in a subproject)
   meson.add_dist_script(
     python3.path(), generate_binding_py, 'dist_built_files',
     built_h_cc_dir,
diff --git a/glib/glibmm/meson.build b/glib/glibmm/meson.build
index 5ba85320..b736a3cf 100644
--- a/glib/glibmm/meson.build
+++ b/glib/glibmm/meson.build
@@ -4,7 +4,7 @@
 #        generate_binding_py, handle_built_files_py, m4_files, pm_files,
 #        glibmm_libversion, install_includedir, python3, glibmm_rc, gmmproc_dir,
 #        is_host_windows, gmmproc, generate_wrap_init_pl, glibmm_libname,
-#        macos_darwin_versions
+#        macos_darwin_versions, can_add_dist_script
 # Output: glibmm_hg_ccg_basenames, glibmm_extra_h_files, built_files_root,
 #         glibmm_built_h_file_targets, glibmm_h_m4_files, glibmm_own_dep
 
@@ -328,9 +328,8 @@ meson.add_install_script(
   glibmm_h_m4_files,
 )
 
-if not meson.is_subproject()
+if can_add_dist_script
   # Distribute built files.
-  # (add_dist_script() is not allowed in a subproject)
   meson.add_dist_script(
     python3.path(), generate_binding_py, 'dist_built_files',
     built_h_cc_dir,
diff --git a/meson.build b/meson.build
index fdc59966..2f7144a5 100644
--- a/meson.build
+++ b/meson.build
@@ -229,6 +229,9 @@ endif
 glibmm_libname = meson.project_name() + msvc14x_toolset_ver + '-' + glibmm_api_version
 giomm_libname = 'giomm' + msvc14x_toolset_ver + '-' + glibmm_api_version
 
+# add_dist_script() is not allowed in a subproject if meson.version() < 0.58.0.
+can_add_dist_script = not meson.is_subproject() or meson.version().version_compare('>= 0.58.0')
+
 subdir('tools')
 subdir('glib')
 subdir('MSVC_NMake/glibmm')
@@ -240,23 +243,22 @@ subdir('examples')
 subdir('tests')
 subdir('docs/reference')
 
-if not meson.is_subproject()
+if can_add_dist_script
   # Add a ChangeLog file to the distribution directory.
-  # (add_dist_script() is not allowed in a subproject)
   meson.add_dist_script(
     python3.path(), dist_changelog_py,
     project_source_root,
   )
   # Add build scripts to the distribution directory, and delete .gitignore
-  # files and an empty $MESON_DIST_ROOT/build/ directory.
+  # files and an empty $MESON_PROJECT_DIST_ROOT/build/ directory.
   meson.add_dist_script(
     python3.path(), dist_build_scripts_py,
     project_source_root,
     'untracked' / 'build_scripts',
   )
-else
-  # This is a subproject.
+endif
 
+if meson.is_subproject()
   # A version of gmmproc that can be executed uninstalled by a main project.
   conf_data_subproj = configuration_data()
   conf_data_subproj.merge_from(gmmproc_conf_data)
diff --git a/tools/build_scripts/handle-built-files.py b/tools/build_scripts/handle-built-files.py
index 862ab5f7..e22600b4 100755
--- a/tools/build_scripts/handle-built-files.py
+++ b/tools/build_scripts/handle-built-files.py
@@ -123,9 +123,12 @@ def dist_built_files(is_msvc_files=False):
   # <built_h_cc_dir> <dist_dir> <built_files>...
 
   # <built_h_cc_dir> is an absolute path in the build directory or source directory.
-  # <dist_dir> is a distribution directory, relative to MESON_DIST_ROOT.
+  # <dist_dir> is a distribution directory, relative to MESON_PROJECT_DIST_ROOT.
+
+  # MESON_PROJECT_DIST_ROOT is set only if meson.version() >= 0.58.0.
+  project_dist_root = os.getenv('MESON_PROJECT_DIST_ROOT', os.getenv('MESON_DIST_ROOT'))
   built_h_cc_dir = sys.argv[2]
-  dist_dir_root = os.path.join(os.getenv('MESON_DIST_ROOT'), sys.argv[3])
+  dist_dir_root = os.path.join(project_dist_root, sys.argv[3])
   dist_dir = dist_dir_root
 
   # Distribute .h and .cc files built from .m4 files, or generated MSVC files.