gst-plugin-scanner: Add support for Windows

Adding Win32 specific plugin loader implementation.

Fixes: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/11
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3512>

subprojects/gstreamer/gst/gst_private.h

@@ -154,7 +154,7 @@ gboolean _priv_gst_registry_remove_cache_plugins (GstRegistry *registry);
 G_GNUC_INTERNAL  void _priv_gst_registry_cleanup (void);
 
 GST_API
-gboolean _gst_plugin_loader_client_run (void);
+gboolean _gst_plugin_loader_client_run (const gchar * pipe_name);
 
 G_GNUC_INTERNAL  GstPlugin * _priv_gst_plugin_load_file_for_registry (const gchar *filename,
                                                                       GstRegistry * registry,

subprojects/gstreamer/gst/gstpluginloader.c

@@ -644,7 +644,7 @@ plugin_loader_cleanup_child (GstPluginLoader * l)
 }
 
 gboolean
-_gst_plugin_loader_client_run (void)
+_gst_plugin_loader_client_run (const gchar * pipe_name)
 {
   gboolean res = TRUE;
   GstPluginLoader *l;

subprojects/gstreamer/gst/gstregistry.c

@@ -1154,12 +1154,6 @@ gst_registry_scan_plugin_file (GstRegistryScanContext * context,
   gboolean changed = FALSE;
   GstPlugin *newplugin = NULL;
 
-#ifdef G_OS_WIN32
-  /* Disable external plugin loader on Windows until it is ported properly. */
-  context->helper_state = REGISTRY_SCAN_HELPER_DISABLED;
-#endif
-
-
   /* Have a plugin to load - see if the scan-helper needs starting */
   if (context->helper_state == REGISTRY_SCAN_HELPER_NOT_STARTED) {
     GST_DEBUG ("Starting plugin scanner for file %s", filename);

subprojects/gstreamer/gst/meson.build

@@ -40,7 +40,6 @@ gst_sources = files(
   'gstpipeline.c',
   'gstplugin.c',
   'gstpluginfeature.c',
-  'gstpluginloader.c',
   'gstpoll.c',
   'gstpreset.c',
   'gstprotection.c',
@@ -155,6 +154,13 @@ endif
 
 install_headers(gst_headers, subdir : 'gstreamer-1.0/gst')
 
+# Some Win32 APIs are not allowed for UWP
+if host_system == 'windows' and not building_for_uwp
+  gst_sources += files('gstpluginloader-win32.c')
+else
+  gst_sources += files('gstpluginloader.c')
+endif
+
 extra_deps = []
 if host_system == 'android'
   gst_sources += 'gstandroid.c'

subprojects/gstreamer/libs/gst/helpers/gst-plugin-scanner.c

@@ -37,11 +37,28 @@ main (int argc, char *argv[])
   gboolean res;
   char **my_argv;
   int my_argc;
+  char *pipe_name = NULL;
 
+#ifdef G_OS_WIN32
+  /* On Windows, we need pipe name
+   * arg0: exe path
+   * arg1: -l
+   * arg2: parent process exe path
+   * arg3: pipe name */
+  if (argc != 4)
+    return 1;
+
+  _gst_executable_path = g_strdup (argv[2]);
+  pipe_name = argv[3];
+#else
   /* We may or may not have an executable path */
   if (argc != 2 && argc != 3)
     return 1;
 
+  if (argc == 3)
+    _gst_executable_path = g_strdup (argv[2]);
+#endif
+
   if (strcmp (argv[1], "-l"))
     return 1;
 
@@ -54,9 +71,6 @@ main (int argc, char *argv[])
   _gst_disable_registry_cache = TRUE;
 #endif
 
-  if (argc == 3)
-    _gst_executable_path = g_strdup (argv[2]);
-
   res = gst_init_check (&my_argc, &my_argv, NULL);
 
   g_free (my_argv);
@@ -64,7 +78,7 @@ main (int argc, char *argv[])
     return 1;
 
   /* Create registry scanner listener and run */
-  if (!_gst_plugin_loader_client_run ())
+  if (!_gst_plugin_loader_client_run (pipe_name))
     return 1;
 
   return 0;