add comment about threading for time/pitch dialog

diff --git a/gtk2_ardour/time_fx_dialog.cc b/gtk2_ardour/time_fx_dialog.cc
index 829ffd6504f372129383e80be2a96431b818a046..caf1191835c52654d3b331fc74472f494b97c2ed 100644 (file)
--- a/gtk2_ardour/time_fx_dialog.cc
+++ b/gtk2_ardour/time_fx_dialog.cc
@@ -224,6 +224,11 @@ TimeFXDialog::start_updates ()
 void
 TimeFXDialog::update_progress_gui (float p)
 {
+       /* time/pitch FX are applied in a dedicated thread, so we cannot just
+          update the GUI when notified about progress. That is deferred to a
+          timer-driven callback which will ensure that the visual progress
+          indicator is updated.
+       */
        progress = p;
 }