[gimp] app: replace GimpHistogramEditor's "valid" by "recompute" flag.

[Jehan Pagès <jehanp src gnome org>]

commit 1a8edbed51db2ef60ee8b8118f89c781d9ad9eb3
Author: Jehan <jehan girinstud io>
Date:   Wed Feb 21 17:02:07 2018 +0100

    app: replace GimpHistogramEditor's "valid" by "recompute" flag.
    
    Having to sync the "valid" flag with the presence of a histogram is
    error-prone (cf. previous commit).
    Instead gimp_histogram_editor_validate() return value will just depend
    on the presence of the histogram. And "valid" becomes "recompute", i.e.
    a flag to request for "recomputation" of the histogram.

 app/widgets/gimphistogrameditor.c |   23 ++++++++---------------
 app/widgets/gimphistogrameditor.h |    2 +-
 2 files changed, 9 insertions(+), 16 deletions(-)
---
diff --git a/app/widgets/gimphistogrameditor.c b/app/widgets/gimphistogrameditor.c
index d771189..685f1f9 100644
--- a/app/widgets/gimphistogrameditor.c
+++ b/app/widgets/gimphistogrameditor.c
@@ -252,7 +252,6 @@ gimp_histogram_editor_set_property (GObject      *object,
       if (editor->histogram)
         {
           g_clear_object (&editor->histogram);
-          editor->valid = FALSE;
           gimp_histogram_view_set_histogram (view, NULL);
         }
 
@@ -350,7 +349,6 @@ gimp_histogram_editor_set_image (GimpImageEditor *image_editor,
       if (editor->histogram)
         {
           g_clear_object (&editor->histogram);
-          editor->valid = FALSE;
           gimp_histogram_view_set_histogram (view, NULL);
         }
 
@@ -396,7 +394,6 @@ gimp_histogram_editor_layer_changed (GimpImage           *image,
       if (editor->histogram)
         {
           g_clear_object (&editor->histogram);
-          editor->valid = FALSE;
           gimp_histogram_view_set_histogram (view, NULL);
         }
 
@@ -451,7 +448,7 @@ gimp_histogram_editor_layer_changed (GimpImage           *image,
     }
   else if (editor->histogram)
     {
-      editor->valid = FALSE;
+      editor->recompute = TRUE;
       gtk_widget_queue_draw (GTK_WIDGET (editor->box));
     }
 
@@ -462,7 +459,7 @@ gimp_histogram_editor_layer_changed (GimpImage           *image,
 static gboolean
 gimp_histogram_editor_validate (GimpHistogramEditor *editor)
 {
-  if (! editor->valid)
+  if (editor->recompute || ! editor->histogram)
     {
       if (editor->drawable)
         {
@@ -479,19 +476,16 @@ gimp_histogram_editor_validate (GimpHistogramEditor *editor)
                                              editor->histogram,
                                              TRUE);
         }
-      else
+      else if (editor->histogram)
         {
-          if (editor->histogram)
-            gimp_histogram_clear_values (editor->histogram);
+          gimp_histogram_clear_values (editor->histogram);
         }
 
       gimp_histogram_editor_info_update (editor);
-
-      if (editor->histogram)
-        editor->valid = TRUE;
+      editor->recompute = FALSE;
     }
 
-  return editor->valid;
+  return (editor->histogram != NULL);
 }
 
 static void
@@ -552,11 +546,10 @@ gimp_histogram_editor_idle_update (GimpHistogramEditor *editor)
 {
   editor->idle_id = 0;
 
-  /* Mark the histogram as invalid and queue a redraw.
+  /* Mark the histogram for recomputation and queue a redraw.
    * We will then recalculate the histogram when the view is exposed.
    */
-
-  editor->valid = FALSE;
+  editor->recompute = TRUE;
   gtk_widget_queue_draw (GTK_WIDGET (editor->box));
 
   return FALSE;
diff --git a/app/widgets/gimphistogrameditor.h b/app/widgets/gimphistogrameditor.h
index 33bf399..f92562e 100644
--- a/app/widgets/gimphistogrameditor.h
+++ b/app/widgets/gimphistogrameditor.h
@@ -43,7 +43,7 @@ struct _GimpHistogramEditor
   GimpHistogram        *bg_histogram;
 
   guint                 idle_id;
-  gboolean              valid;
+  gboolean              recompute;
 
   GtkWidget            *menu;
   GtkWidget            *box;