[gimp] app: in GimpThresholdTool, calculate histogram asynchronously

[N/A <ell src gnome org>]

commit 4af6fb5944dde908bcb858230973fc5873c517fa
Author: Ell <ell_se yahoo com>
Date:   Fri May 11 12:41:11 2018 -0400

    app: in GimpThresholdTool, calculate histogram asynchronously
    
    In GimpThresholdTool, calculate the histogram of the target
    drawable asynchronously, rather than synchronously, to avoid
    blocking the UI while the histogram is calculated.
    
    Additionally, fix the initial "low" threshold value for > 8bpc
    images (127/255 => 0.5).

 app/tools/gimpthresholdtool.c |   64 ++++++++++++++++++++++++++++------------
 app/tools/gimpthresholdtool.h |    1 +
 2 files changed, 46 insertions(+), 19 deletions(-)
---
diff --git a/app/tools/gimpthresholdtool.c b/app/tools/gimpthresholdtool.c
index a179c1c..2364fc2 100644
--- a/app/tools/gimpthresholdtool.c
+++ b/app/tools/gimpthresholdtool.c
@@ -25,6 +25,7 @@
 
 #include "tools-types.h"
 
+#include "core/gimpasync.h"
 #include "core/gimpdrawable.h"
 #include "core/gimpdrawable-histogram.h"
 #include "core/gimphistogram.h"
@@ -119,11 +120,8 @@ gimp_threshold_tool_finalize (GObject *object)
 {
   GimpThresholdTool *t_tool = GIMP_THRESHOLD_TOOL (object);
 
-  if (t_tool->histogram)
-    {
-      g_object_unref (t_tool->histogram);
-      t_tool->histogram = NULL;
-    }
+  g_clear_object (&t_tool->histogram);
+  g_clear_object (&t_tool->histogram_async);
 
   G_OBJECT_CLASS (parent_class)->finalize (object);
 }
@@ -133,19 +131,55 @@ gimp_threshold_tool_initialize (GimpTool     *tool,
                                 GimpDisplay  *display,
                                 GError      **error)
 {
-  GimpThresholdTool *t_tool   = GIMP_THRESHOLD_TOOL (tool);
-  GimpImage         *image    = gimp_display_get_image (display);
-  GimpDrawable      *drawable = gimp_image_get_active_drawable (image);
+  GimpThresholdTool *t_tool      = GIMP_THRESHOLD_TOOL (tool);
+  GimpFilterTool    *filter_tool = GIMP_FILTER_TOOL (tool);
+  GimpImage         *image       = gimp_display_get_image (display);
+  GimpDrawable      *drawable    = gimp_image_get_active_drawable (image);
+  gdouble            low;
+  gdouble            high;
+  gint               n_bins;
 
   if (! GIMP_TOOL_CLASS (parent_class)->initialize (tool, display, error))
     {
       return FALSE;
     }
 
-  gimp_drawable_calculate_histogram (drawable, t_tool->histogram, FALSE);
+  g_clear_object (&t_tool->histogram_async);
+
+  g_object_get (filter_tool->config,
+                "low",  &low,
+                "high", &high,
+                NULL);
+
+  /* this is a hack to make sure that
+   * 'gimp_histogram_n_bins (t_tool->histogram)' returns the correct value for
+   * 'drawable' before the asynchronous calculation of its histogram is
+   * finished.
+   */
+  {
+    GeglBuffer *temp;
+
+    temp = gegl_buffer_new (GEGL_RECTANGLE (0, 0, 1, 1),
+                            gimp_drawable_get_format (drawable));
+
+    gimp_histogram_calculate (t_tool->histogram,
+                              temp, GEGL_RECTANGLE (0, 0, 1, 1),
+                              NULL, NULL);
+
+    g_object_unref (temp);
+  }
+
+  n_bins = gimp_histogram_n_bins (t_tool->histogram);
+
+  t_tool->histogram_async = gimp_drawable_calculate_histogram_async (
+    drawable, t_tool->histogram, FALSE);
   gimp_histogram_view_set_histogram (t_tool->histogram_box->view,
                                      t_tool->histogram);
 
+  gimp_histogram_view_set_range (t_tool->histogram_box->view,
+                                 low  * (n_bins - 0.0001),
+                                 high * (n_bins - 0.0001));
+
   return TRUE;
 }
 
@@ -177,9 +211,6 @@ gimp_threshold_tool_dialog (GimpFilterTool *filter_tool)
   GtkWidget            *box;
   GtkWidget            *button;
   GimpHistogramChannel  channel;
-  gdouble               low;
-  gdouble               high;
-  gint                  n_bins;
 
   main_vbox = gimp_filter_tool_dialog_get_vbox (filter_tool);
 
@@ -230,16 +261,9 @@ gimp_threshold_tool_dialog (GimpFilterTool *filter_tool)
 
   g_object_get (filter_tool->config,
                 "channel", &channel,
-                "low",     &low,
-                "high",    &high,
                 NULL);
 
-  n_bins = gimp_histogram_n_bins (t_tool->histogram);
-
   gimp_histogram_view_set_channel (t_tool->histogram_box->view, channel);
-  gimp_histogram_view_set_range (t_tool->histogram_box->view,
-                                 low  * (n_bins - 0.0001),
-                                 high * (n_bins - 0.0001));
 
   g_signal_connect (t_tool->histogram_box->view, "range-changed",
                     G_CALLBACK (gimp_threshold_tool_histogram_range),
@@ -378,6 +402,8 @@ gimp_threshold_tool_auto_clicked (GtkWidget         *button,
   gint                  n_bins;
   gdouble               low;
 
+  gimp_async_wait (t_tool->histogram_async);
+
   g_object_get (GIMP_FILTER_TOOL (t_tool)->config,
                 "channel", &channel,
                 NULL);
diff --git a/app/tools/gimpthresholdtool.h b/app/tools/gimpthresholdtool.h
index 4eca23a..9966656 100644
--- a/app/tools/gimpthresholdtool.h
+++ b/app/tools/gimpthresholdtool.h
@@ -39,6 +39,7 @@ struct _GimpThresholdTool
 
   /*  dialog  */
   GimpHistogram    *histogram;
+  GimpAsync        *histogram_async;
   GtkWidget        *channel_menu;
   GimpHistogramBox *histogram_box;
 };