Add message to request a state change

Add a GST_MESSAGE_REQUEST_STATE that can be posted by element when they would
like to have the application change the state of the pipeline. the primary use
case is to pause the pipeline when an audio mixer is mixing a higher priority
stream but it can also be used for other purposes.

Add some docs and a unit test.

Implement the REQUEST_STATE message in gst-launch.

API: gst_message_new_request_state()
API: gst_message_parse_request_state()
API: GST_MESSAGE_REQUEST_STATE

1 files changed, 32 insertions, 15 deletions

diff --git a/tools/gst-launch.c b/tools/gst-launch.c
index d23f1c7c1..3930eaee8 100644
--- a/tools/gst-launch.c
+++ b/tools/gst-launch.c
@@ -523,7 +523,7 @@ event_loop (GstElement * pipeline, gboolean blocking, GstState target_state)
         gint percent;
 
         gst_message_parse_buffering (message, &percent);
-        if(!quiet)
+        if (!quiet)
           fprintf (stderr, "%s %d%%  \r", _("buffering..."), percent);
 
         /* no state management needed for live pipelines */
@@ -535,7 +535,7 @@ event_loop (GstElement * pipeline, gboolean blocking, GstState target_state)
           buffering = FALSE;
           /* if the desired state is playing, go back */
           if (target_state == GST_STATE_PLAYING) {
-            if(!quiet)
+            if (!quiet)
               fprintf (stderr,
                   _("Done buffering, setting pipeline to PLAYING ...\n"));
             gst_element_set_state (pipeline, GST_STATE_PLAYING);
@@ -545,8 +545,9 @@ event_loop (GstElement * pipeline, gboolean blocking, GstState target_state)
           /* buffering busy */
           if (buffering == FALSE && target_state == GST_STATE_PLAYING) {
             /* we were not buffering but PLAYING, PAUSE  the pipeline. */
-            if(!quiet)
-              fprintf (stderr, _("Buffering, setting pipeline to PAUSED ...\n"));
+            if (!quiet)
+              fprintf (stderr,
+                  _("Buffering, setting pipeline to PAUSED ...\n"));
             gst_element_set_state (pipeline, GST_STATE_PAUSED);
           }
           buffering = TRUE;
@@ -559,6 +560,21 @@ event_loop (GstElement * pipeline, gboolean blocking, GstState target_state)
         gst_bin_recalculate_latency (GST_BIN (pipeline));
         break;
       }
+      case GST_MESSAGE_REQUEST_STATE:
+      {
+        GstState state;
+        gchar *name = gst_object_get_path_string (GST_MESSAGE_SRC (message));
+
+        gst_message_parse_request_state (message, &state);
+
+        fprintf (stderr, _("Setting state to %s as requested by %s...\n"),
+            gst_element_state_get_name (state), name);
+
+        gst_element_set_state (pipeline, state);
+
+        g_free (name);
+        break;
+      }
       case GST_MESSAGE_APPLICATION:{
         const GstStructure *s;
 
@@ -567,7 +583,7 @@ event_loop (GstElement * pipeline, gboolean blocking, GstState target_state)
         if (gst_structure_has_name (s, "GstLaunchInterrupt")) {
           /* this application message is posted when we caught an interrupt and
            * we need to stop the pipeline. */
-          if(!quiet)
+          if (!quiet)
             fprintf (stderr, _("Interrupt: Stopping pipeline ...\n"));
           /* return TRUE when we caught an interrupt */
           res = TRUE;
@@ -728,7 +744,7 @@ main (int argc, char *argv[])
       gst_bin_add (GST_BIN (real_pipeline), pipeline);
       pipeline = real_pipeline;
     }
-    if(!quiet)
+    if (!quiet)
       fprintf (stderr, _("Setting pipeline to PAUSED ...\n"));
     ret = gst_element_set_state (pipeline, GST_STATE_PAUSED);
 
@@ -739,12 +755,13 @@ main (int argc, char *argv[])
         event_loop (pipeline, FALSE, GST_STATE_VOID_PENDING);
         goto end;
       case GST_STATE_CHANGE_NO_PREROLL:
-        if(!quiet)
-          fprintf (stderr, _("Pipeline is live and does not need PREROLL ...\n"));
+        if (!quiet)
+          fprintf (stderr,
+              _("Pipeline is live and does not need PREROLL ...\n"));
         is_live = TRUE;
         break;
       case GST_STATE_CHANGE_ASYNC:
-        if(!quiet)
+        if (!quiet)
           fprintf (stderr, _("Pipeline is PREROLLING ...\n"));
         caught_error = event_loop (pipeline, TRUE, GST_STATE_PAUSED);
         if (caught_error) {
@@ -754,7 +771,7 @@ main (int argc, char *argv[])
         state = GST_STATE_PAUSED;
         /* fallthrough */
       case GST_STATE_CHANGE_SUCCESS:
-        if(!quiet)
+        if (!quiet)
           fprintf (stderr, _("Pipeline is PREROLLED ...\n"));
         break;
     }
@@ -767,7 +784,7 @@ main (int argc, char *argv[])
       GstClockTime tfthen, tfnow;
       GstClockTimeDiff diff;
 
-      if(!quiet)
+      if (!quiet)
         fprintf (stderr, _("Setting pipeline to PLAYING ...\n"));
 
       if (gst_element_set_state (pipeline,
@@ -804,24 +821,24 @@ main (int argc, char *argv[])
     /* iterate mainloop to process pending stuff */
     while (g_main_context_iteration (NULL, FALSE));
 
-    if(!quiet)
+    if (!quiet)
       fprintf (stderr, _("Setting pipeline to PAUSED ...\n"));
     gst_element_set_state (pipeline, GST_STATE_PAUSED);
     if (!caught_error)
       gst_element_get_state (pipeline, &state, &pending, GST_CLOCK_TIME_NONE);
-    if(!quiet)
+    if (!quiet)
       fprintf (stderr, _("Setting pipeline to READY ...\n"));
     gst_element_set_state (pipeline, GST_STATE_READY);
     gst_element_get_state (pipeline, &state, &pending, GST_CLOCK_TIME_NONE);
 
   end:
-    if(!quiet)
+    if (!quiet)
       fprintf (stderr, _("Setting pipeline to NULL ...\n"));
     gst_element_set_state (pipeline, GST_STATE_NULL);
     gst_element_get_state (pipeline, &state, &pending, GST_CLOCK_TIME_NONE);
   }
 
-  if(!quiet)
+  if (!quiet)
     fprintf (stderr, _("Freeing pipeline ...\n"));
   gst_object_unref (pipeline);