[gimp/gimp-2-10] libgimp: in GimpTileBackendPlugin, don't read tile data upon TILE_SET

[Ell <ell src gnome org>]

commit 535fd3a04100dd9afecd8bca7b6d6b099d6f9e1e
Author: Ell <ell_se yahoo com>
Date:   Tue Jan 15 02:28:42 2019 -0500

    libgimp: in GimpTileBackendPlugin, don't read tile data upon TILE_SET
    
    Add an internal _gimp_tile_ref_noinit() function, which increases
    the ref-count of a tile *without* initializing its data (in
    particular, without reading its data from GIMP, or zeroing it.)
    Use this function, instead of gimp_tile_ref(), when storing a tile
    in GimpTileBackendPlugin, to avoid unnecessarily reading the tile
    data from GIMP.
    
    (cherry picked from commit 5ffdb9aa415c90b97c1ece736977717c50c1da1c)

 libgimp/gimptile.c              | 13 +++++++++++++
 libgimp/gimptile.h              |  2 ++
 libgimp/gimptilebackendplugin.c |  2 +-
 3 files changed, 16 insertions(+), 1 deletion(-)
---
diff --git a/libgimp/gimptile.c b/libgimp/gimptile.c
index bdcedcf773..5441551de8 100644
--- a/libgimp/gimptile.c
+++ b/libgimp/gimptile.c
@@ -99,6 +99,19 @@ gimp_tile_ref_zero (GimpTile *tile)
   gimp_tile_cache_insert (tile);
 }
 
+void
+_gimp_tile_ref_noinit (GimpTile *tile)
+{
+  g_return_if_fail (tile != NULL);
+
+  tile->ref_count++;
+
+  if (tile->ref_count == 1)
+    tile->data = g_new (guchar, tile->ewidth * tile->eheight * tile->bpp);
+
+  gimp_tile_cache_insert (tile);
+}
+
 void
 gimp_tile_unref (GimpTile *tile,
                  gboolean  dirty)
diff --git a/libgimp/gimptile.h b/libgimp/gimptile.h
index 55f6b23740..64b5dd88a9 100644
--- a/libgimp/gimptile.h
+++ b/libgimp/gimptile.h
@@ -62,6 +62,8 @@ void    gimp_tile_cache_ntiles (gulong     ntiles);
 
 /*  private function  */
 
+G_GNUC_INTERNAL void _gimp_tile_ref_noinit           (GimpTile     *tile);
+
 G_GNUC_INTERNAL void _gimp_tile_cache_flush_drawable (GimpDrawable *drawable);
 
 
diff --git a/libgimp/gimptilebackendplugin.c b/libgimp/gimptilebackendplugin.c
index e089deafda..9116693aaa 100644
--- a/libgimp/gimptilebackendplugin.c
+++ b/libgimp/gimptilebackendplugin.c
@@ -261,7 +261,7 @@ gimp_tile_write_mul (GimpTileBackendPlugin *backend_plugin,
           gimp_tile = gimp_drawable_get_tile (priv->drawable,
                                               priv->shadow,
                                               y+v, x+u);
-          gimp_tile_ref (gimp_tile);
+          _gimp_tile_ref_noinit (gimp_tile);
 
           {
             gint ewidth           = gimp_tile->ewidth;