[gimp] Issue #1805 - Sample Points keep resetting themselves to "Pixel"

[Michael Natterer <mitch src gnome org>]

commit 370680f9bc81227b45c3abbdb9a632cb444bb71d
Author: Michael Natterer <mitch gimp org>
Date:   Sat Jul 7 19:17:58 2018 +0200

    Issue #1805 - Sample Points keep resetting themselves to "Pixel"
    
    Don't destroy the color frames when the number of points changes.
    Instead, simply hide them so they keep their color model, but add an
    upper limit of an arbitrary number of 16 frames to keep around.

 app/widgets/gimpsamplepointeditor.c | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)
---
diff --git a/app/widgets/gimpsamplepointeditor.c b/app/widgets/gimpsamplepointeditor.c
index 3f41da1730..5f646762d6 100644
--- a/app/widgets/gimpsamplepointeditor.c
+++ b/app/widgets/gimpsamplepointeditor.c
@@ -422,15 +422,25 @@ gimp_sample_point_editor_points_changed (GimpSamplePointEditor *editor)
   gtk_widget_set_visible (editor->empty_label,
                           image_editor->image && n_points == 0);
 
-  if (n_points < editor->n_color_frames)
+  /*  Keep that many color frames around so they remember their color
+   *  model. Let's hope nobody uses more and notices they get reset to
+   *  "pixel". See https://gitlab.gnome.org/GNOME/gimp/issues/1805
+   */
+#define RANDOM_MAGIC 16
+
+  if (n_points < editor->n_color_frames &&
+      n_points < RANDOM_MAGIC           &&
+      editor->n_color_frames > RANDOM_MAGIC)
     {
-      for (i = n_points; i < editor->n_color_frames; i++)
+      for (i = RANDOM_MAGIC; i < editor->n_color_frames; i++)
         {
           gtk_widget_destroy (editor->color_frames[i]);
         }
 
       editor->color_frames = g_renew (GtkWidget *, editor->color_frames,
-                                      n_points);
+                                      RANDOM_MAGIC);
+
+      editor->n_color_frames = RANDOM_MAGIC;
     }
   else if (n_points > editor->n_color_frames)
     {
@@ -461,14 +471,18 @@ gimp_sample_point_editor_points_changed (GimpSamplePointEditor *editor)
 
           gtk_grid_attach (GTK_GRID (editor->grid), editor->color_frames[i],
                            column, row, 1, 1);
-          gtk_widget_show (editor->color_frames[i]);
 
           g_object_set_data (G_OBJECT (editor->color_frames[i]),
                              "dirty", GINT_TO_POINTER (TRUE));
         }
+
+      editor->n_color_frames = n_points;
     }
 
-  editor->n_color_frames = n_points;
+  for (i = 0; i < editor->n_color_frames; i++)
+    {
+      gtk_widget_set_visible (editor->color_frames[i], i < n_points);
+    }
 
   if (n_points > 0)
     gimp_sample_point_editor_dirty (editor, -1);