[gimp] app: in GimpEditSelectionTool, freeze moved items' previews

[Ell <ell src gnome org>]

commit 915bdffb5a5ff38a42038be2e7380951df904e30
Author: Ell <ell_se yahoo com>
Date:   Wed Sep 4 18:49:54 2019 +0300

    app: in GimpEditSelectionTool, freeze moved items' previews
    
    ... to avoid unnecessarily updating their previews while dragging,
    and, in particular, to avoid updating the image's GimpImageViewable
    size in show-all mode.

 app/tools/gimpeditselectiontool.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
---
diff --git a/app/tools/gimpeditselectiontool.c b/app/tools/gimpeditselectiontool.c
index 43d430428f..8f931f6137 100644
--- a/app/tools/gimpeditselectiontool.c
+++ b/app/tools/gimpeditselectiontool.c
@@ -417,7 +417,13 @@ gimp_edit_selection_tool_start (GimpTool          *parent_tool,
     }
 
   for (list = edit_select->live_items; list; list = g_list_next (list))
-    gimp_item_start_transform (GIMP_ITEM (list->data), TRUE);
+    {
+      GimpItem *item = list->data;
+
+      gimp_viewable_preview_freeze (GIMP_VIEWABLE (item));
+
+      gimp_item_start_transform (item, TRUE);
+    }
 
   tool_manager_push_tool (display->gimp, tool);
 
@@ -471,7 +477,13 @@ gimp_edit_selection_tool_button_release (GimpTool              *tool,
                                   TRUE);
 
   for (list = edit_select->live_items; list; list = g_list_next (list))
-    gimp_item_end_transform (GIMP_ITEM (list->data), TRUE);
+    {
+      GimpItem *item = list->data;
+
+      gimp_item_end_transform (item, TRUE);
+
+      gimp_viewable_preview_thaw (GIMP_VIEWABLE (item));
+    }
 
   gimp_image_undo_group_end (image);