core: pipeline: add gst_pipeline_is_live()

Convenient API for applications wanting to check if a pipeline is live
or not. Save them from checking the change_state return value or sending
latency queries.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/4472>

girs/Gst-1.0.gir

@@ -32902,6 +32902,22 @@ clock, even if the pipeline is not in the PLAYING state.</doc>
           </instance-parameter>
         </parameters>
       </method>
+      <method name="is_live" c:identifier="gst_pipeline_is_live" version="1.24">
+        <doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpipeline.c">Check if @pipeline is live.</doc>
+        <source-position filename="../subprojects/gstreamer/gst/gstpipeline.h"/>
+        <return-value transfer-ownership="none">
+          <doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpipeline.c">%TRUE if @pipeline is live, %FALSE if not or if it did not reach the PAUSED state yet.
+
+MT safe.</doc>
+          <type name="gboolean" c:type="gboolean"/>
+        </return-value>
+        <parameters>
+          <instance-parameter name="pipeline" transfer-ownership="none">
+            <doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpipeline.c">a #GstPipeline</doc>
+            <type name="Pipeline" c:type="GstPipeline*"/>
+          </instance-parameter>
+        </parameters>
+      </method>
       <method name="set_auto_flush_bus" c:identifier="gst_pipeline_set_auto_flush_bus">
         <doc xml:space="preserve" filename="../subprojects/gstreamer/gst/gstpipeline.c">Usually, when a pipeline goes from READY to NULL state, it automatically
 flushes all pending messages on the bus, which is done for refcounting

subprojects/gstreamer/gst/gstpipeline.c

@@ -1176,3 +1176,27 @@ gst_pipeline_handle_instant_rate (GstPipeline * pipeline, gdouble rate,
 
   return gst_element_send_event (GST_ELEMENT_CAST (pipeline), event);
 }
+
+/**
+ * gst_pipeline_is_live:
+ * @pipeline: a #GstPipeline
+ *
+ * Check if @pipeline is live.
+ *
+ * Returns: %TRUE if @pipeline is live, %FALSE if not or if it did not reach the PAUSED state yet.
+ *
+ * MT safe.
+ *
+ * Since: 1.24
+ */
+gboolean
+gst_pipeline_is_live (GstPipeline * pipeline)
+{
+  gboolean is_live;
+
+  GST_OBJECT_LOCK (pipeline);
+  is_live = pipeline->priv->is_live;
+  GST_OBJECT_UNLOCK (pipeline);
+
+  return is_live;
+}

subprojects/gstreamer/gst/gstpipeline.h

@@ -130,6 +130,9 @@ void            gst_pipeline_set_auto_flush_bus (GstPipeline *pipeline, gboolean
 GST_API
 gboolean        gst_pipeline_get_auto_flush_bus (GstPipeline *pipeline);
 
+GST_API
+gboolean        gst_pipeline_is_live            (GstPipeline *pipeline);
+
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GstPipeline, gst_object_unref)
 
 G_END_DECLS