[gimp] app: add gimp_gegl_buffer_set_extent()

[Ell <ell src gnome org>]

commit 90610ac87e2fa652c8d0c0b88e58810f036adedb
Author: Ell <ell_se yahoo com>
Date:   Tue Aug 13 17:06:23 2019 +0300

    app: add gimp_gegl_buffer_set_extent()
    
    .... as a drop-in replacement for gegl_buffer_set_extent(), which,
    in addition to setting the buffer's extent, clears any now-out-of-
    bounds tiles, to free memory.

 app/gegl/gimp-gegl-utils.c | 29 +++++++++++++++++++++++++++++
 app/gegl/gimp-gegl-utils.h |  3 +++
 2 files changed, 32 insertions(+)
---
diff --git a/app/gegl/gimp-gegl-utils.c b/app/gegl/gimp-gegl-utils.c
index acc06be313..0340358ff0 100644
--- a/app/gegl/gimp-gegl-utils.c
+++ b/app/gegl/gimp-gegl-utils.c
@@ -283,3 +283,32 @@ gimp_gegl_buffer_dup (GeglBuffer *buffer)
 
   return new_buffer;
 }
+
+gboolean
+gimp_gegl_buffer_set_extent (GeglBuffer          *buffer,
+                             const GeglRectangle *extent)
+{
+  GeglRectangle aligned_old_extent;
+  GeglRectangle aligned_extent;
+  GeglRectangle diff_rects[4];
+  gint          n_diff_rects;
+  gint          i;
+
+  g_return_val_if_fail (GEGL_IS_BUFFER (buffer), FALSE);
+  g_return_val_if_fail (extent != NULL, FALSE);
+
+  gegl_rectangle_align_to_buffer (&aligned_old_extent,
+                                  gegl_buffer_get_extent (buffer), buffer,
+                                  GEGL_RECTANGLE_ALIGNMENT_SUPERSET);
+  gegl_rectangle_align_to_buffer (&aligned_extent,
+                                  extent, buffer,
+                                  GEGL_RECTANGLE_ALIGNMENT_SUPERSET);
+
+  n_diff_rects = gegl_rectangle_subtract (diff_rects,
+                                          &aligned_old_extent, &aligned_extent);
+
+  for (i = 0; i < n_diff_rects; i++)
+    gegl_buffer_clear (buffer, &diff_rects[i]);
+
+  return gegl_buffer_set_extent (buffer, extent);
+}
diff --git a/app/gegl/gimp-gegl-utils.h b/app/gegl/gimp-gegl-utils.h
index 29654c36f6..a219736e18 100644
--- a/app/gegl/gimp-gegl-utils.h
+++ b/app/gegl/gimp-gegl-utils.h
@@ -49,5 +49,8 @@ gboolean     gimp_gegl_param_spec_has_key            (GParamSpec          *pspec
 
 GeglBuffer * gimp_gegl_buffer_dup                    (GeglBuffer          *buffer);
 
+gboolean     gimp_gegl_buffer_set_extent             (GeglBuffer          *buffer,
+                                                      const GeglRectangle *extent);
+
 
 #endif /* __GIMP_GEGL_UTILS_H__ */