[gimp] app: do not copy needlessly paint_mask GimpTempBuf.

[Jehan Pagès <jehanp src gnome org>]

commit 04a798d786617257ffa2b75ad24a14afd7b5c087
Author: Jehan <jehan girinstud io>
Date:   Sat Mar 31 16:36:55 2018 +0200

    app: do not copy needlessly paint_mask GimpTempBuf.
    
    We are not doing any write operation on this mask data so copying all
    the data just to read it and unreffing it in the end is only a cost on
    performance.
    See also bug 694917.

 app/paint/gimppaintcore-loops.c |   14 ++++++--------
 1 files changed, 6 insertions(+), 8 deletions(-)
---
diff --git a/app/paint/gimppaintcore-loops.c b/app/paint/gimppaintcore-loops.c
index a58b3f3..b6b60fc 100644
--- a/app/paint/gimppaintcore-loops.c
+++ b/app/paint/gimppaintcore-loops.c
@@ -47,12 +47,11 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
   const gint   mask_stride       = gimp_temp_buf_get_width (paint_mask);
   const gint   mask_start_offset = mask_y_offset * mask_stride + mask_x_offset;
   const Babl  *mask_format       = gimp_temp_buf_get_format (paint_mask);
-  GimpTempBuf *modified_mask     = gimp_temp_buf_copy (paint_mask);
   gint         width;
   gint         height;
 
-  width  = gimp_temp_buf_get_width (modified_mask);
-  height = gimp_temp_buf_get_height (modified_mask);
+  width  = gimp_temp_buf_get_width (paint_mask);
+  height = gimp_temp_buf_get_height (paint_mask);
 
   roi.x = x_offset;
   roi.y = y_offset;
@@ -67,7 +66,7 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
     {
       if (mask_format == babl_format ("Y u8"))
         {
-          const guint8 *mask_data = (const guint8 *) gimp_temp_buf_get_data (modified_mask);
+          const guint8 *mask_data = (const guint8 *) gimp_temp_buf_get_data (paint_mask);
           mask_data += mask_start_offset;
 
           while (gegl_buffer_iterator_next (iter))
@@ -92,7 +91,7 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
         }
       else if (mask_format == babl_format ("Y float"))
         {
-          const gfloat *mask_data = (const gfloat *) gimp_temp_buf_get_data (modified_mask);
+          const gfloat *mask_data = (const gfloat *) gimp_temp_buf_get_data (paint_mask);
           mask_data += mask_start_offset;
 
           while (gegl_buffer_iterator_next (iter))
@@ -124,7 +123,7 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
     {
       if (mask_format == babl_format ("Y u8"))
         {
-          const guint8 *mask_data = (const guint8 *) gimp_temp_buf_get_data (modified_mask);
+          const guint8 *mask_data = (const guint8 *) gimp_temp_buf_get_data (paint_mask);
           mask_data += mask_start_offset;
 
           while (gegl_buffer_iterator_next (iter))
@@ -150,7 +149,7 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
         }
       else if (mask_format == babl_format ("Y float"))
         {
-          const gfloat *mask_data = (const gfloat *) gimp_temp_buf_get_data (modified_mask);
+          const gfloat *mask_data = (const gfloat *) gimp_temp_buf_get_data (paint_mask);
           mask_data += mask_start_offset;
 
           while (gegl_buffer_iterator_next (iter))
@@ -179,7 +178,6 @@ combine_paint_mask_to_canvas_mask (const GimpTempBuf *paint_mask,
           g_warning("Mask format not supported: %s", babl_get_name (mask_format));
         }
     }
-  gimp_temp_buf_unref (modified_mask);
 }
 
 void