introspection: Re-add platform specific APIs to GLib-2.0.gir and Gio-2.0.gir

To avoid a big introspection API break.

These APIs are now listed in the new `{GLib,Gio}{Unix,Win32}-2.0.gir`
files, but for backwards compatibility they need to continue to be
listed in `Gio-2.0.gir` and `GLib-2.0.gir` as well, until the next major
introspection API break (and none is planned).

No new platform specific APIs should be added to these GIR files, but
these existing ones must remain.

See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/3892#note_2001361

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

girepository/introspection/meson.build

@@ -15,20 +15,33 @@ if get_option('b_sanitize') != ''
 endif
 
 # GLib
+glib_gir_sources = [
+  gi_gen_shared_sources,
+  glibconfig_h,
+  gversionmacros_h,
+  glib_visibility_h,
+  glib_headers,
+  glib_deprecated_headers,
+  glib_sub_headers,
+  glib_enumtypes_h,
+  glib_types_h,
+  glib_deprecated_sources,
+  glib_sources,
+]
+
+# For API compatibility reasons, GLib-2.0.gir needs to contain the platform
+# specific APIs which are also present in the (newer) GLibUnix-2.0.gir and
+# GLibWin32-2.0.gir repositories.
+# See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/3892#note_2001361
+# These can be dropped when GLib next breaks API (i.e. with GLib-3.0.gir).
+if host_system == 'windows'
+  glib_gir_sources += files('../../glib/gwin32.h')
+else
+  glib_gir_sources += files('../../glib/glib-unix.h')
+endif
+
 glib_gir = gnome.generate_gir(libglib,
-  sources: [
+  sources: glib_gir_sources,
-    gi_gen_shared_sources,
-    glibconfig_h,
-    gversionmacros_h,
-    glib_visibility_h,
-    glib_headers,
-    glib_deprecated_headers,
-    glib_sub_headers,
-    glib_enumtypes_h,
-    glib_types_h,
-    glib_deprecated_sources,
-    glib_sources,
-  ],
   namespace: 'GLib',
   nsversion: '2.0',
   identifier_prefix: gi_identifier_prefix,
@@ -173,19 +186,41 @@ gio_gir_sources = [
   contenttype_sources,
   settings_sources,
 ]
+gio_gir_packages = [ 'gio-2.0' ]
 gio_gir_args = [
   '-DGIO_COMPILATION',
   '-DG_SETTINGS_ENABLE_BACKEND',
   '--symbol-prefix=gio',
 ]
 
+# For API compatibility reasons, Gio-2.0.gir needs to contain the platform
+# specific APIs which are also present in the (newer) GioUnix-2.0.gir and
+# GioWin32-2.0.gir repositories.
+# See https://gitlab.gnome.org/GNOME/glib/-/merge_requests/3892#note_2001361
+# These can be dropped when GIO next breaks API (i.e. with Gio-3.0.gir).
+if host_system == 'windows'
+  gio_gir_sources += [ gio_win32_include_headers, win32_sources ]
+  foreach h: gio_win32_include_headers
+    gio_gir_args += '--c-include=@0@'.format(h)
+  endforeach
+  gio_gir_packages += 'gio-win32-2.0'
+  gio_gir_args += '--pkg=gio-win32-2.0'
+else
+  gio_gir_sources += [ gio_unix_include_headers, unix_sources ]
+  foreach h: gio_unix_include_headers
+    gio_gir_args += '--c-include=@0@'.format(h)
+  endforeach
+  gio_gir_packages += 'gio-unix-2.0'
+  gio_gir_args += '--pkg=gio-unix-2.0'
+endif
+
 gio_gir = gnome.generate_gir(libgio,
   sources: gio_gir_sources,
   namespace: 'Gio',
   nsversion: '2.0',
   identifier_prefix: gi_identifier_prefix,
   symbol_prefix: gi_symbol_prefix,
-  export_packages: [ 'gio-2.0' ],
+  export_packages: gio_gir_packages,
   header: 'gio/gio.h',
   includes: [ glib_gir[0], gmodule_gir[0], gobject_gir[0] ],
   install: true,