[gimp] Bug 795185 - Corrective rotation guides are incorrect in GIMP 2.10.

[Jehan Pagès <jehanp src gnome org>]

commit b91742a84fe78fb6e5b99cb147cb35ec2504b2c6
Author: Jehan <jehan girinstud io>
Date:   Thu Apr 12 12:13:38 2018 +0200

    Bug 795185 - Corrective rotation guides are incorrect in GIMP 2.10.
    
    Most expected behavior in normal transform is to see the preview,
    whereas you usually don't want to see it in corrective mode. In 2.8
    actually, it seems like it was not even possible to see the image
    preview in corrective mode.
    
    So let's set "show-preview" to these defaults when "direction" property
    is updated.  It is still possible to change it manually for any specific
    use cases (i.e. you can hide the preview in normal transform, and
    oppositely you can show it in corrective transform), but at least now
    defaults are sane.

 app/tools/gimptransformoptions.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/app/tools/gimptransformoptions.c b/app/tools/gimptransformoptions.c
index 7decf77..5fd7a1e 100644
--- a/app/tools/gimptransformoptions.c
+++ b/app/tools/gimptransformoptions.c
@@ -254,6 +254,14 @@ gimp_transform_options_set_property (GObject      *object,
       break;
     case PROP_DIRECTION:
       options->direction = g_value_get_enum (value);
+
+      /* Expected default for corrective transform is to see the
+       * original image only.
+       */
+      g_object_set (options,
+                    "show-preview",
+                    options->direction != GIMP_TRANSFORM_BACKWARD,
+                    NULL);
       break;
     case PROP_INTERPOLATION:
       options->interpolation = g_value_get_enum (value);