Add shell_write_string_to_stream()

Add a helper function to write a string as UTF-8 to a GOutputStream.
The signature of GOutputStream:

 gboolean g_output_stream_write_all (GOutputStream *stream,
                                     const void *buffer,
                                     gsize count,
                                     gsize *bytes_written,
                                     GCancellable *cancellable,
                                     GError **error);

Can't currently be handled by GJS.

https://bugzilla.gnome.org/show_bug.cgi?id=618189

src/shell-global.c

@@ -1303,6 +1303,26 @@ shell_popup_menu (GtkMenu *menu, int button, guint32 time,
                   button, time);
 }
 
+/**
+ * shell_write_string_to_stream:
+ * @stream: a #GOutputStream
+ * @str: a UTF-8 string to write to @stream
+ * @error: location to store GError
+ *
+ * Write a string to a GOutputStream as UTF-8. This is a workaround
+ * for not having binary buffers in GJS.
+ *
+ * Return value: %TRUE if write succeeded
+ */
+gboolean
+shell_write_string_to_stream (GOutputStream *stream,
+                              const char    *str,
+                              GError       **error)
+{
+  return g_output_stream_write_all (stream, str, strlen (str),
+                                    NULL, NULL, error);
+}
+
 /**
  * shell_global_get_current_time:
  * @global: A #ShellGlobal

src/shell-global.h

@@ -92,6 +92,10 @@ ClutterModifierType shell_get_event_state (ClutterEvent *event);
 void shell_popup_menu (GtkMenu *menu, int button, guint32 time,
                        int menu_x, int menu_y);
 
+gboolean shell_write_string_to_stream (GOutputStream *stream,
+                                       const char    *str,
+                                       GError       **error);
+
 guint32 shell_global_get_current_time (ShellGlobal *global);
 
 GAppLaunchContext *shell_global_create_app_launch_context (ShellGlobal *global);