[gegl] buffer: add gegl_buffer_share_storage()

[Ell <ell src gnome org>]

commit 337eab200514d0837a8c5d5471477839367b2ffd
Author: Ell <ell_se yahoo com>
Date:   Thu Feb 20 12:35:34 2020 +0200

    buffer: add gegl_buffer_share_storage()
    
    ... which checks if a pair of buffers share the same underlying
    tile storage.  This can be used, e.g., for certain optimizations,
    as will be done in GIMP.

 gegl/buffer/gegl-buffer.c | 10 ++++++++++
 gegl/buffer/gegl-buffer.h | 12 ++++++++++++
 2 files changed, 22 insertions(+)
---
diff --git a/gegl/buffer/gegl-buffer.c b/gegl/buffer/gegl-buffer.c
index 8a482af7f..826b00b41 100644
--- a/gegl/buffer/gegl-buffer.c
+++ b/gegl/buffer/gegl-buffer.c
@@ -1182,6 +1182,16 @@ gegl_buffer_unlock (GeglBuffer *buffer)
 }
 #endif
 
+gboolean
+gegl_buffer_share_storage (GeglBuffer *buffer1,
+                           GeglBuffer *buffer2)
+{
+  g_return_val_if_fail (GEGL_IS_BUFFER (buffer1), FALSE);
+  g_return_val_if_fail (GEGL_IS_BUFFER (buffer2), FALSE);
+
+  return buffer1->tile_storage == buffer2->tile_storage;
+}
+
 void
 gegl_buffer_emit_changed_signal (GeglBuffer          *buffer,
                                  const GeglRectangle *rect)
diff --git a/gegl/buffer/gegl-buffer.h b/gegl/buffer/gegl-buffer.h
index 308fc892a..51d5512ad 100644
--- a/gegl/buffer/gegl-buffer.h
+++ b/gegl/buffer/gegl-buffer.h
@@ -697,6 +697,18 @@ void            gegl_buffer_linear_close      (GeglBuffer    *buffer,
 const GeglRectangle * gegl_buffer_get_abyss   (GeglBuffer           *buffer);
 
 
+/**
+ * gegl_buffer_share_storage:
+ * @buffer1: a #GeglBuffer.
+ * @buffer2: a #GeglBuffer.
+ *
+ * Checks if a pair of buffers share the same underlying tile storage.
+ *
+ * Returns TRUE if @buffer1 and @buffer2 share the same storage.
+ */
+gboolean gegl_buffer_share_storage (GeglBuffer *buffer1,
+                                    GeglBuffer *buffer2);
+
 
 /**
  * gegl_buffer_signal_connect: