[gimp] app: limit color-history palette size

[Ell <ell src gnome org>]

commit 07b7d63a7d623a5d984dd5f7bbad6c725c51d9e7
Author: Ell <ell_se yahoo com>
Date:   Wed Aug 7 19:05:13 2019 +0300

    app: limit color-history palette size
    
    Limit the color-history palette size (currently, to 256 colors), to
    avoid slowdowns, especially during loading.

 app/core/gimppalettemru.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)
---
diff --git a/app/core/gimppalettemru.c b/app/core/gimppalettemru.c
index 7ca33ff991..f68c4695a6 100644
--- a/app/core/gimppalettemru.c
+++ b/app/core/gimppalettemru.c
@@ -34,6 +34,7 @@
 #include "gimp-intl.h"
 
 
+#define MAX_N_COLORS 256
 #define RGBA_EPSILON 1e-4
 
 enum
@@ -116,10 +117,13 @@ gimp_palette_mru_load (GimpPaletteMru *mru,
                   GimpRGB color;
 
                   if (! gimp_scanner_parse_color (scanner, &color))
-                    goto error;
+                    goto end;
 
                   gimp_palette_add_entry (palette, -1,
                                           _("History Color"), &color);
+
+                  if (gimp_palette_get_n_colors (palette) == MAX_N_COLORS)
+                    goto end;
                 }
             }
           token = G_TOKEN_RIGHT_PAREN;
@@ -134,7 +138,7 @@ gimp_palette_mru_load (GimpPaletteMru *mru,
         }
     }
 
- error:
+ end:
   gimp_scanner_destroy (scanner);
 }
 
@@ -215,5 +219,12 @@ gimp_palette_mru_add (GimpPaletteMru *mru,
         }
     }
 
+  if (gimp_palette_get_n_colors (palette) == MAX_N_COLORS)
+    {
+      gimp_palette_delete_entry (palette,
+                                 gimp_palette_get_entry (palette,
+                                                         MAX_N_COLORS - 1));
+    }
+
   gimp_palette_add_entry (palette, 0, _("History Color"), color);
 }