query: Add a new stream selection query

This new API allows querying whether elements can handle stream selection
themselves or not.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1905>

subprojects/gstreamer/gst/gstquark.c

@@ -80,7 +80,7 @@ static const gchar *_quark_strings[] = {
   "GstEventInstantRateChange",
   "GstEventInstantRateSyncTime", "GstMessageInstantRateRequest",
   "upstream-running-time", "base", "offset", "plugin-api", "plugin-api-flags",
-  "gap-flags"
+  "gap-flags", "GstQuerySelectable", "selectable"
 };
 
 GQuark _priv_gst_quark_table[GST_QUARK_MAX];

subprojects/gstreamer/gst/gstquark.h

@@ -231,7 +231,9 @@ typedef enum _GstQuarkId
   GST_QUARK_PLUGIN_API = 200,
   GST_QUARK_PLUGIN_API_FLAGS = 201,
   GST_QUARK_GAP_FLAGS = 202,
-  GST_QUARK_MAX = 203
+  GST_QUARK_QUERY_SELECTABLE = 203,
+  GST_QUARK_SELECTABLE = 204,
+  GST_QUARK_MAX = 205
 } GstQuarkId;
 
 extern GQuark _priv_gst_quark_table[GST_QUARK_MAX];

subprojects/gstreamer/gst/gstquery.c

@@ -2728,6 +2728,80 @@ gst_query_parse_bitrate (GstQuery * query, guint * nominal_bitrate)
   }
 }
 
+/**
+ * gst_query_new_selectable:
+ *
+ * Constructs a new query object for querying the stream selection capability.
+ *
+ * Free-function: gst_query_unref()
+ *
+ * Returns: (transfer full): a new #GstQuery
+ *
+ * Since: 1.22
+ */
+GstQuery *
+gst_query_new_selectable (void)
+{
+  GstQuery *query;
+  GstStructure *structure;
+
+  structure = gst_structure_new_id_empty (GST_QUARK (QUERY_SELECTABLE));
+  query = gst_query_new_custom (GST_QUERY_SELECTABLE, structure);
+
+  return query;
+}
+
+/**
+ * gst_query_set_selectable:
+ * @query: a GST_QUERY_SELECTABLE type #GstQuery
+ * @selectable: Whether the element can handle stream selection.
+ *
+ * Set the results of a selectable query. If the element answering the query can
+ * handle stream selection, @selectable should be set to %TRUE.
+ *
+ * Since: 1.22
+ */
+void
+gst_query_set_selectable (GstQuery * query, gboolean selectable)
+{
+  GstStructure *s;
+
+  g_return_if_fail (GST_QUERY_TYPE (query) == GST_QUERY_SELECTABLE);
+
+  s = GST_QUERY_STRUCTURE (query);
+
+  gst_structure_id_set (s,
+      GST_QUARK (SELECTABLE), G_TYPE_BOOLEAN, selectable, NULL);
+}
+
+/**
+ * gst_query_parse_selectable:
+ * @query: a GST_QUERY_SELECTABLE type #GstQuery
+ * @selectable: (out) (allow-none): The resulting stream selection capability
+ *
+ * Get the results of a selectable query. See also gst_query_set_selectable().
+ *
+ * Since: 1.22
+ */
+void
+gst_query_parse_selectable (GstQuery * query, gboolean * selectable)
+{
+  GstStructure *structure;
+
+  g_return_if_fail (GST_QUERY_TYPE (query) == GST_QUERY_SELECTABLE);
+
+  structure = GST_QUERY_STRUCTURE (query);
+
+  if (selectable) {
+    const GValue *value =
+        gst_structure_id_get_value (structure, GST_QUARK (SELECTABLE));
+    if (value)
+      *selectable = g_value_get_boolean (value);
+    else
+      *selectable = FALSE;
+  }
+}
+
 /**
  * gst_query_ref:
  * @q: a #GstQuery to increase the refcount of.

subprojects/gstreamer/gst/gstquery.h

@@ -100,6 +100,7 @@ typedef enum {
  * @GST_QUERY_CONTEXT: query the pipeline-local context from
  *     downstream or upstream (since 1.2)
  * @GST_QUERY_BITRATE: the bitrate query (since 1.16)
+ * @GST_QUERY_SELECTABLE: Query stream selection capability (Since: 1.22)
  *
  * Standard predefined Query types
  */
@@ -126,6 +127,15 @@ typedef enum {
   GST_QUERY_DRAIN        = GST_QUERY_MAKE_TYPE (180, _FLAG(DOWNSTREAM) | _FLAG(SERIALIZED)),
   GST_QUERY_CONTEXT      = GST_QUERY_MAKE_TYPE (190, _FLAG(BOTH)),
   GST_QUERY_BITRATE      = GST_QUERY_MAKE_TYPE (200, _FLAG(DOWNSTREAM)),
+
+  /**
+   * GST_QUERY_SELECTABLE:
+   *
+   * Query stream selection capability.
+   *
+   * Since: 1.22
+   */
+  GST_QUERY_SELECTABLE   = GST_QUERY_MAKE_TYPE (210, _FLAG(BOTH)),
 } GstQueryType;
 #undef _FLAG
 
@@ -653,6 +663,17 @@ void            gst_query_set_bitrate              (GstQuery * query, guint nomi
 GST_API
 void            gst_query_parse_bitrate            (GstQuery * query, guint * nominal_bitrate);
 
+/* selectable query */
+
+GST_API
+GstQuery *      gst_query_new_selectable           (void) G_GNUC_MALLOC;
+
+GST_API
+void            gst_query_set_selectable           (GstQuery *query, gboolean selectable);
+
+GST_API
+void            gst_query_parse_selectable         (GstQuery *query, gboolean * selectable);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GstQuery, gst_query_unref)
 
 G_END_DECLS