[gimp] app: set the number of threads on GeglConfig again, it needs testing

[Michael Natterer <mitch src gnome org>]

commit 1f5739de57de85780fd2b8f74049e4c1d6b519fa
Author: Michael Natterer <mitch gimp org>
Date:   Wed Jun 28 19:05:58 2017 +0200

    app: set the number of threads on GeglConfig again, it needs testing
    
    - enable the setting code in gimp-gegl.c again
    - but set the default to one thread in GimpGeglConfig, with a CPP warning
    - rename "processors" to "threads" in the GUI
    - add a warning box about unexpected results when increasing #threads

 app/config/gimpgeglconfig.c      |    7 ++++++-
 app/config/gimprc-blurbs.h       |    2 +-
 app/dialogs/preferences-dialog.c |   12 +++++++++++-
 app/gegl/gimp-gegl.c             |    8 --------
 4 files changed, 18 insertions(+), 11 deletions(-)
---
diff --git a/app/config/gimpgeglconfig.c b/app/config/gimpgeglconfig.c
index 05569ef..e17d2cc 100644
--- a/app/config/gimpgeglconfig.c
+++ b/app/config/gimpgeglconfig.c
@@ -139,9 +139,14 @@ gimp_gegl_config_class_init (GimpGeglConfigClass *klass)
 
   num_processors = MIN (num_processors, GIMP_MAX_NUM_THREADS);
 
+#ifdef __GNUC__
+#warning Defaulting # of threads to 1
+#endif
+  num_processors = 1;
+
   GIMP_CONFIG_PROP_UINT (object_class, PROP_NUM_PROCESSORS,
                          "num-processors",
-                         "Number of processors to use",
+                         "Number of threads to use",
                          NUM_PROCESSORS_BLURB,
                          1, GIMP_MAX_NUM_THREADS, num_processors,
                          GIMP_PARAM_STATIC_STRINGS);
diff --git a/app/config/gimprc-blurbs.h b/app/config/gimprc-blurbs.h
index 7d3ddf8..b9a97b3 100644
--- a/app/config/gimprc-blurbs.h
+++ b/app/config/gimprc-blurbs.h
@@ -253,7 +253,7 @@ _("Sets the size of the navigation preview available in the lower right " \
   "corner of the image window.")
 
 #define NUM_PROCESSORS_BLURB \
-_("Sets how many processors GIMP should try to use simultaneously.")
+_("Sets how many threads GIMP should use for operations that support it.")
 
 #define PALETTE_PATH_BLURB \
 "Sets the palette search path."
diff --git a/app/dialogs/preferences-dialog.c b/app/dialogs/preferences-dialog.c
index 82de4f4..e1339a3 100644
--- a/app/dialogs/preferences-dialog.c
+++ b/app/dialogs/preferences-dialog.c
@@ -1080,8 +1080,18 @@ prefs_dialog_new (Gimp       *gimp,
 
 #ifdef ENABLE_MP
   prefs_spin_button_add (object, "num-processors", 1.0, 4.0, 0,
-                         _("Number of _processors to use:"),
+                         _("Number of _threads to use:"),
                          GTK_TABLE (table), 4, size_group);
+
+  vbox2 = g_object_new (GIMP_TYPE_HINT_BOX,
+                        "icon-name", GIMP_ICON_DIALOG_WARNING,
+                        "hint",      _("Threading support is not yet stable.\n"
+                                       "Setting this to greater than one might\n"
+                                       "result in image errors or crashes."),
+                        NULL);
+  gtk_table_attach (GTK_TABLE (table), vbox2, 1, 2, 5, 6,
+                    GTK_FILL | GTK_EXPAND, GTK_FILL, 0, 0);
+  gtk_widget_show (vbox2);
 #endif /* ENABLE_MP */
 
   /*  Hardware Acceleration  */
diff --git a/app/gegl/gimp-gegl.c b/app/gegl/gimp-gegl.c
index db6a3c1..143bb0b 100644
--- a/app/gegl/gimp-gegl.c
+++ b/app/gegl/gimp-gegl.c
@@ -49,15 +49,9 @@ gimp_gegl_init (Gimp *gimp)
 
   config = GIMP_GEGL_CONFIG (gimp->config);
 
-#ifdef __GNUC__
-#warning not setting GeglConfig:threads
-#endif
-
   g_object_set (gegl_config (),
                 "tile-cache-size", (guint64) config->tile_cache_size,
-#if 0
                 "threads",         config->num_processors,
-#endif
                 "use-opencl",      config->use_opencl,
                 NULL);
 
@@ -87,11 +81,9 @@ gimp_gegl_notify_tile_cache_size (GimpGeglConfig *config)
 static void
 gimp_gegl_notify_num_processors (GimpGeglConfig *config)
 {
-#if 0
   g_object_set (gegl_config (),
                 "threads", config->num_processors,
                 NULL);
-#endif
 }
 
 static void