[easytag] Factor out EtPicture comparison to new function

[David King <davidk src gnome org>]

commit 7cafddad51ebe49ba893c69097ea53b8ebdc8c34
Author: David King <amigadave amigadave com>
Date:   Mon Jun 29 20:37:17 2015 +0100

    Factor out EtPicture comparison to new function
    
    Move the code to check for differences between two EtPicture instances
    into EtPicture from File_Tag.

 src/file_tag.c |   15 +--------------
 src/picture.c  |   39 ++++++++++++++++++++++++++++++++++++++-
 src/picture.h  |    3 ++-
 3 files changed, 41 insertions(+), 16 deletions(-)
---
diff --git a/src/file_tag.c b/src/file_tag.c
index 8239bef..b0cf164 100644
--- a/src/file_tag.c
+++ b/src/file_tag.c
@@ -456,20 +456,7 @@ et_file_tag_detect_difference (const File_Tag *FileTag1,
     for (pic1 = FileTag1->picture, pic2 = FileTag2->picture; ;
          pic1 = pic1->next, pic2 = pic2->next)
     {
-        if( (pic1 && !pic2) || (!pic1 && pic2) )
-            return TRUE;
-        if (!pic1 || !pic2)
-            break; // => no changes
-        //if (!pic1->data || !pic2->data)
-        //    break; // => no changes
-
-        if (!g_bytes_equal (pic1->bytes, pic2->bytes))
-        {
-            return TRUE;
-        }
-        if (pic1->type != pic2->type)
-            return TRUE;
-        if (et_normalized_strcmp0 (pic1->description, pic2->description) != 0)
+        if (et_picture_detect_difference (pic1, pic2))
         {
             return TRUE;
         }
diff --git a/src/picture.c b/src/picture.c
index 2fedee2..74f1a82 100644
--- a/src/picture.c
+++ b/src/picture.c
@@ -1,5 +1,5 @@
 /* EasyTAG - Tag editor for audio files
- * Copyright (C) 2014  David King <amigadave amigadave com>
+ * Copyright (C) 2014-2015  David King <amigadave amigadave com>
  * Copyright (C) 2000-2003  Jerome Couderc <easytag gmail com>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -237,6 +237,43 @@ Picture_Type_String (EtPictureType type)
     }
 }
 
+gboolean
+et_picture_detect_difference (const EtPicture *a,
+                              const EtPicture *b)
+{
+    if (!a && !b)
+    {
+        return FALSE;
+    }
+
+    if ((a && !b) || (!a && b))
+    {
+        return TRUE;
+    }
+
+    if (a->type != b->type)
+    {
+        return TRUE;
+    }
+
+    if ((a->width != b->width) || (a->height != b->height))
+    {
+        return TRUE;
+    }
+
+    if (et_normalized_strcmp0 (a->description, b->description) != 0)
+    {
+        return TRUE;
+    }
+
+    if (!g_bytes_equal (a->bytes, b->bytes))
+    {
+        return TRUE;
+    }
+
+    return FALSE;
+}
+
 gchar *
 et_picture_format_info (const EtPicture *pic,
                         ET_Tag_Type tag_type)
diff --git a/src/picture.h b/src/picture.h
index 34a8ab5..5f62bc5 100644
--- a/src/picture.h
+++ b/src/picture.h
@@ -1,5 +1,5 @@
 /* EasyTAG - tag editor for audio files
- * Copyright (C) 2014  David King <amigadave amigadave com>
+ * Copyright (C) 2014-2015  David King <amigadave amigadave com>
  * Copyright (C) 2000-2003  Jerome Couderc <easytag gmail com>
  *
  * This program is free software; you can redistribute it and/or modify it
@@ -92,6 +92,7 @@ void et_picture_free (EtPicture *pic);
 Picture_Format Picture_Format_From_Data (const EtPicture *pic);
 const gchar   *Picture_Mime_Type_String (Picture_Format format);
 const gchar * Picture_Type_String (EtPictureType type);
+gboolean et_picture_detect_difference (const EtPicture *a, const EtPicture *b);
 gchar * et_picture_format_info (const EtPicture *pic, ET_Tag_Type tag_type);
 
 GBytes * et_picture_load_file_data (GFile *file, GError **error);