[gegl] gegl-node: only emit the progress signal from the main thread

[N/A <ell src gnome org>]

commit e3787440917255b6936a8d55428aa9402fdfba08
Author: Ell <ell_se yahoo com>
Date:   Fri Aug 11 08:44:27 2017 -0400

    gegl-node: only emit the progress signal from the main thread
    
    Only emit the progress signal when gegl_node_progress() is called
    from the main thread -- don't queue a signal emission from other
    threads.  Otherwise, the queued signal may be emitted after the
    operation is complete, and, in particular, after the node is
    destroyed (we could keep a the node alive while the signal is
    queued, but that's not really useful.)
    
    Regardless, for auto-threaded ops, each thread would track its
    progress independently, so emitting interleaving progress signals
    from different threads is not too meaningful anyway, while only
    reporting the main thread's progress should give a good-enough
    indication of the overall progress.

 gegl/graph/gegl-node.c |   13 ++++++++++++-
 1 files changed, 12 insertions(+), 1 deletions(-)
---
diff --git a/gegl/graph/gegl-node.c b/gegl/graph/gegl-node.c
index 4f2488a..4d88065 100644
--- a/gegl/graph/gegl-node.c
+++ b/gegl/graph/gegl-node.c
@@ -2198,7 +2198,8 @@ static gboolean delayed_emission (void *data)
 
 /* this causes dispatch of the signal on the main thread - if we
  * are in the main thread the callback will be directly executed now
- * instead of queued
+ * instead of queued (XXX: and if we're on a different thread, this function is
+ * a nop -- see comment below.)
  */
 void gegl_node_progress (GeglNode *node,
                          gdouble   progress,
@@ -2208,10 +2209,20 @@ void gegl_node_progress (GeglNode *node,
     g_signal_emit (node, gegl_node_signals[PROGRESS], 0, progress, message, NULL);
   else
   {
+    /* XXX:  only emit the progress signal from the main thread; otherwise, the
+     * delayed signal may be emitted after the operation is finished, or,
+     * indeed, after the node is destroyed.  for auto-threaded operations, each
+     * thread tracks its progress independently, so reporting the progress of
+     * the main thread should be a reasonable estimate of the overall progress.
+     */
+#if 0
     Closure *closure = g_new0 (Closure, 1);
     closure->node = node;
     closure->progress = progress;
     g_idle_add (delayed_emission, closure);
+#else
+    (void) delayed_emission;
+#endif
   }
 }