Add portal helpers

These are private helper functions that will be used in
the following commits to get information about whether
we are running in a flatpak sandbox, etc.

We allow the use of GTK_USE_PORTAL=1 in the environment
to force the use of portals. This can be useful for
testing and debugging portal interaction.

https://bugzilla.gnome.org/show_bug.cgi?id=768498

gio/Makefile.am

@@ -424,6 +424,8 @@ libgio_2_0_la_SOURCES =		\
 	gpollableutils.c	\
 	gpollfilemonitor.c 	\
 	gpollfilemonitor.h 	\
+	gportalsupport.c	\
+	gportalsupport.h	\
 	gproxy.c		\
 	gproxyaddress.c         \
 	gproxyaddressenumerator.c \

gio/gportalsupport.c

@@ -0,0 +1,84 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright 2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include "gportalsupport.h"
+
+static gboolean flatpak_info_read;
+static gboolean use_portal;
+static gboolean network_available;
+
+static void
+read_flatpak_info (void)
+{
+  char *path;
+
+  if (flatpak_info_read)
+    return;
+
+  flatpak_info_read = TRUE;
+
+  path = g_build_filename (g_get_user_runtime_dir (), "flatpak-info", NULL);
+  if (g_file_test (path, G_FILE_TEST_EXISTS))
+    {
+      GKeyFile *keyfile;
+
+      use_portal = TRUE;
+      network_available = FALSE;
+
+      keyfile = g_key_file_new ();
+      if (g_key_file_load_from_file (keyfile, path, G_KEY_FILE_NONE, NULL))
+        {
+          char **shared = NULL;
+
+          shared = g_key_file_get_string_list (keyfile, "Context", "shared", NULL, NULL);
+          if (shared)
+            {
+              network_available = g_strv_contains ((const char * const *)shared, "network");
+              g_strfreev (shared);
+            }
+        }
+    }
+  else
+    {
+      const char *var;
+
+      var = g_getenv ("GTK_USE_PORTAL");
+      if (var && var[0] == '1')
+        use_portal = TRUE;
+      network_available = TRUE;
+    }
+
+  g_free (path);
+}
+
+gboolean
+glib_should_use_portal (void)
+{
+  read_flatpak_info ();
+  return use_portal;
+}
+
+gboolean
+glib_network_available_in_sandbox (void)
+{
+  read_flatpak_info ();
+  return network_available;
+}
+

gio/gportalsupport.h

@@ -0,0 +1,30 @@
+/* GIO - GLib Input, Output and Streaming Library
+ *
+ * Copyright 2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __G_PORTAL_SUPPORT_H__
+
+#include <glib.h>
+
+G_BEGIN_DECLS
+
+gboolean glib_should_use_portal (void);
+gboolean glib_network_available_in_sandbox (void);
+
+G_END_DECLS
+
+#endif