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

Rename XCF property PROP_SAMPLE_POINT to PROP_OLD_SAMPLE_POINT and add
new PROP_SAMPLE_POINT.

The new property saves the sample point's pick mode plus some padding
for whatever else we might want to add. Always save the old property
too so nothing changes for older GIMP versions, and avoid loading the
old property if the new one was loaded before.

app/xcf/xcf-load.c

@@ -801,17 +801,56 @@ xcf_load_image_props (XcfInfo   *info,
           break;
 
         case PROP_SAMPLE_POINTS:
+          {
+            gint n_sample_points, i;
+
+            n_sample_points = prop_size / (5 * 4);
+            for (i = 0; i < n_sample_points; i++)
+              {
+                GimpSamplePoint   *sample_point;
+                gint32             x, y;
+                GimpColorPickMode  pick_mode;
+                guint32            padding[2] = { 0, };
+
+                xcf_read_int32 (info, (guint32 *) &x,         1);
+                xcf_read_int32 (info, (guint32 *) &y,         1);
+                xcf_read_int32 (info, (guint32 *) &pick_mode, 1);
+                xcf_read_int32 (info, (guint32 *) padding,    2);
+
+                GIMP_LOG (XCF, "prop sample point x=%d y=%d mode=%d",
+                          x, y, pick_mode);
+
+                sample_point = gimp_image_add_sample_point_at_pos (image,
+                                                                   x, y, FALSE);
+                gimp_image_set_sample_point_pick_mode (image, sample_point,
+                                                       pick_mode, FALSE);
+              }
+          }
+          break;
+
+        case PROP_OLD_SAMPLE_POINTS:
           {
             gint32 x, y;
             gint   i, n_sample_points;
 
+            /* if there are already sample points, we loaded the new
+             * prop before
+             */
+            if (gimp_image_get_sample_points (image))
+              {
+                if (! xcf_skip_unknown_prop (info, prop_size))
+                  return FALSE;
+
+                break;
+              }
+
             n_sample_points = prop_size / (4 + 4);
             for (i = 0; i < n_sample_points; i++)
               {
                 xcf_read_int32 (info, (guint32 *) &x, 1);
                 xcf_read_int32 (info, (guint32 *) &y, 1);
 
-                GIMP_LOG (XCF, "prop sample point x=%d y=%d", x, y);
+                GIMP_LOG (XCF, "prop old sample point x=%d y=%d", x, y);
 
                 gimp_image_add_sample_point_at_pos (image, x, y, FALSE);
               }

app/xcf/xcf-private.h

@@ -52,7 +52,7 @@ typedef enum
   PROP_USER_UNIT          = 24,
   PROP_VECTORS            = 25,
   PROP_TEXT_LAYER_FLAGS   = 26,
-  PROP_SAMPLE_POINTS      = 27,
+  PROP_OLD_SAMPLE_POINTS  = 27,
   PROP_LOCK_CONTENT       = 28,
   PROP_GROUP_ITEM         = 29,
   PROP_ITEM_PATH          = 30,
@@ -63,7 +63,8 @@ typedef enum
   PROP_COMPOSITE_MODE     = 35,
   PROP_COMPOSITE_SPACE    = 36,
   PROP_BLEND_SPACE        = 37,
-  PROP_FLOAT_COLOR        = 38
+  PROP_FLOAT_COLOR        = 38,
+  PROP_SAMPLE_POINTS      = 39,
 } PropType;
 
 typedef enum

app/xcf/xcf-save.c

@@ -383,8 +383,15 @@ xcf_save_image_props (XcfInfo    *info,
                                     gimp_image_get_guides (image)));
 
   if (gimp_image_get_sample_points (image))
-    xcf_check_error (xcf_save_prop (info, image, PROP_SAMPLE_POINTS, error,
+    {
-                                    gimp_image_get_sample_points (image)));
+      /* save the new property before the old one, so loading can skip
+       * the latter
+       */
+      xcf_check_error (xcf_save_prop (info, image, PROP_SAMPLE_POINTS, error,
+                                      gimp_image_get_sample_points (image)));
+      xcf_check_error (xcf_save_prop (info, image, PROP_OLD_SAMPLE_POINTS, error,
+                                      gimp_image_get_sample_points (image)));
+    }
 
   xcf_check_error (xcf_save_prop (info, image, PROP_RESOLUTION, error,
                                   xres, yres));
@@ -1074,6 +1081,34 @@ xcf_save_prop (XcfInfo    *info,
       break;
 
     case PROP_SAMPLE_POINTS:
+      {
+        GList *sample_points   = va_arg (args, GList *);
+        gint   n_sample_points = g_list_length (sample_points);
+
+        size = n_sample_points * (5 * 4);
+
+        xcf_write_prop_type_check_error (info, prop_type);
+        xcf_write_int32_check_error (info, &size, 1);
+
+        for (; sample_points; sample_points = g_list_next (sample_points))
+          {
+            GimpSamplePoint   *sample_point = sample_points->data;
+            gint32             x, y;
+            GimpColorPickMode  pick_mode;
+            guint32            padding[2] = { 0, };
+
+            gimp_sample_point_get_position (sample_point, &x, &y);
+            pick_mode = gimp_sample_point_get_pick_mode (sample_point);
+
+            xcf_write_int32_check_error (info, (guint32 *) &x,         1);
+            xcf_write_int32_check_error (info, (guint32 *) &y,         1);
+            xcf_write_int32_check_error (info, (guint32 *) &pick_mode, 1);
+            xcf_write_int32_check_error (info, (guint32 *) padding,    2);
+          }
+      }
+      break;
+
+    case PROP_OLD_SAMPLE_POINTS:
       {
         GList *sample_points   = va_arg (args, GList *);
         gint   n_sample_points = g_list_length (sample_points);