[gimp/gimp-2-10] app: avoid updating image bounding box multiple times when reordering layer

[Ell <ell src gnome org>]

commit a93d410916544b86121c037ad4acaa035ffe4f9f
Author: Ell <ell_se yahoo com>
Date:   Sat Sep 28 11:08:22 2019 +0300

    app: avoid updating image bounding box multiple times when reordering layer
    
    Add internal gimp_image_{freeze,thaw}_bounding_box() functions, and
    use them in gimp_image_reorder_item() to avoid updating the
    bounding box multiple times while moving a layer across group
    boundary, to prevent flickering.
    
    (cherry picked from commit a6ebbfe3170d80fbac42745ed1fbbbe477c4ee05)

 app/core/gimpimage.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
---
diff --git a/app/core/gimpimage.c b/app/core/gimpimage.c
index 8b51f3ab56..abb6b36875 100644
--- a/app/core/gimpimage.c
+++ b/app/core/gimpimage.c
@@ -264,6 +264,8 @@ static void     gimp_image_active_vectors_notify (GimpItemTree      *tree,
                                                   const GParamSpec  *pspec,
                                                   GimpImage         *image);
 
+static void     gimp_image_freeze_bounding_box   (GimpImage         *image);
+static void     gimp_image_thaw_bounding_box     (GimpImage         *image);
 static void     gimp_image_update_bounding_box   (GimpImage         *image);
 
 
@@ -1792,12 +1794,43 @@ gimp_image_active_vectors_notify (GimpItemTree     *tree,
   g_signal_emit (image, gimp_image_signals[ACTIVE_VECTORS_CHANGED], 0);
 }
 
+static void
+gimp_image_freeze_bounding_box (GimpImage *image)
+{
+  GimpImagePrivate *private = GIMP_IMAGE_GET_PRIVATE (image);
+
+  private->bounding_box_freeze_count++;
+}
+
+static void
+gimp_image_thaw_bounding_box (GimpImage *image)
+{
+  GimpImagePrivate *private = GIMP_IMAGE_GET_PRIVATE (image);
+
+  private->bounding_box_freeze_count--;
+
+  if (private->bounding_box_freeze_count == 0 &&
+      private->bounding_box_update_pending)
+    {
+      private->bounding_box_update_pending = FALSE;
+
+      gimp_image_update_bounding_box (image);
+    }
+}
+
 static void
 gimp_image_update_bounding_box (GimpImage *image)
 {
   GimpImagePrivate *private = GIMP_IMAGE_GET_PRIVATE (image);
   GeglRectangle     bounding_box;
 
+  if (private->bounding_box_freeze_count > 0)
+    {
+      private->bounding_box_update_pending = TRUE;
+
+      return;
+    }
+
   bounding_box.x      = 0;
   bounding_box.y      = 0;
   bounding_box.width  = gimp_image_get_width  (image);
@@ -4444,6 +4477,8 @@ gimp_image_reorder_item (GimpImage   *image,
                                    undo_desc);
     }
 
+  gimp_image_freeze_bounding_box (image);
+
   gimp_item_start_move (item, push_undo);
 
   /*  item and new_parent are type-checked in GimpItemTree
@@ -4454,6 +4489,8 @@ gimp_image_reorder_item (GimpImage   *image,
 
   gimp_item_end_move (item, push_undo);
 
+  gimp_image_thaw_bounding_box (image);
+
   if (push_undo)
     gimp_image_undo_group_end (image);