screen-cast: Add textual context hint

data/org.freedesktop.impl.portal.ScreenCast.xml

@@ -138,6 +138,16 @@
         Start the screen cast session. This will typically result the portal presenting
         a dialog letting the user do the selection set up by SelectSources.
 
+        Supported keys in the @options vardict include:
+
+        * ``context_hint`` (``s``)
+
+          Textual hint that can be shown on the presented dialog. This allow the user to
+          know the context behind the selection dialog if the application happens use
+          multiple sessions.
+
+          The string is localized by the application.
+
         The following results get returned in the @results vardict:
 
         * ``streams`` (``a(ua{sv})``)

data/org.freedesktop.portal.ScreenCast.xml

@@ -168,6 +168,14 @@
           object path element. See the :ref:`org.freedesktop.portal.Request` documentation for
           more information about the @handle.
 
+        * ``context_hint`` (``s``)
+
+          Textual hint that can be shown on the presented dialog. This allow the user to
+          know the context behind the selection dialog if the application happens use
+          multiple sessions.
+
+          The string is localized by the application.
+
         The following results get returned via the
         :ref:`org.freedesktop.portal.Request::Response` signal:
 

src/screen-cast.c

@@ -831,6 +831,10 @@ start_done (GObject *source_object,
     }
 }
 
+static XdpOptionKey start_options[] = {
+  { "context_hint", G_VARIANT_TYPE_STRING, NULL },
+};
+
 static gboolean
 handle_start (XdpDbusScreenCast *object,
               GDBusMethodInvocation *invocation,
@@ -906,6 +910,9 @@ handle_start (XdpDbusScreenCast *object,
   request_export (request, g_dbus_method_invocation_get_connection (invocation));
 
   g_variant_builder_init (&options_builder, G_VARIANT_TYPE_VARDICT);
+  xdp_filter_options (arg_options, &options_builder,
+                      start_options, G_N_ELEMENTS (start_options),
+                      NULL);
   options = g_variant_builder_end (&options_builder);
 
   g_object_set_qdata_full (G_OBJECT (request),