[gimp/gimp-2-10] Issue #4484: Add reflection option for mandala symmetry

[Jehan <jehanp src gnome org>]

commit ec10b374219fa474049eec92e37c77658448c3ee
Author: Elad Shahar <dawn ever gmail com>
Date:   Sat Jan 11 07:51:27 2020 +0200

    Issue #4484: Add reflection option for mandala symmetry
    
    (cherry picked from commit 36dd48aea64308d7a911c26d2faef69b1b880be4)

 app/core/gimpsymmetry-mandala.c | 26 +++++++++++++++++++++++++-
 app/core/gimpsymmetry-mandala.h |  1 +
 2 files changed, 26 insertions(+), 1 deletion(-)
---
diff --git a/app/core/gimpsymmetry-mandala.c b/app/core/gimpsymmetry-mandala.c
index c8c4b0e2ea..6c575b02ce 100644
--- a/app/core/gimpsymmetry-mandala.c
+++ b/app/core/gimpsymmetry-mandala.c
@@ -51,6 +51,7 @@ enum
   PROP_CENTER_Y,
   PROP_SIZE,
   PROP_DISABLE_TRANSFORMATION,
+  PROP_ENABLE_REFLECTION,
 };
 
 
@@ -154,6 +155,14 @@ gimp_mandala_class_init (GimpMandalaClass *klass)
                             FALSE,
                             GIMP_PARAM_STATIC_STRINGS |
                             GIMP_SYMMETRY_PARAM_GUI);
+
+  GIMP_CONFIG_PROP_BOOLEAN (object_class, PROP_ENABLE_REFLECTION,
+                            "enable-reflection",
+                            _("Enable reflection"),
+                            _("Enable reflection"),
+                            FALSE,
+                            GIMP_PARAM_STATIC_STRINGS |
+                            GIMP_SYMMETRY_PARAM_GUI);
 }
 
 static void
@@ -243,6 +252,10 @@ gimp_mandala_set_property (GObject      *object,
       mandala->disable_transformation = g_value_get_boolean (value);
       break;
 
+    case PROP_ENABLE_REFLECTION:
+      mandala->enable_reflection = g_value_get_boolean (value);
+      break;
+
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
       break;
@@ -271,6 +284,9 @@ gimp_mandala_get_property (GObject    *object,
     case PROP_DISABLE_TRANSFORMATION:
       g_value_set_boolean (value, mandala->disable_transformation);
       break;
+    case PROP_ENABLE_REFLECTION:
+      g_value_set_boolean (value, mandala->enable_reflection);
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
       break;
@@ -457,7 +473,15 @@ gimp_mandala_update_strokes (GimpSymmetry *sym,
       gimp_matrix3_translate (&matrix,
                               - mandala->center_x,
                               - mandala->center_y);
-      gimp_matrix3_rotate (&matrix, - i * 2.0 * G_PI / (gdouble) mandala->size);
+      if ( mandala->enable_reflection && i % 2 == 1 )
+        {
+          gimp_matrix3_scale (&matrix, -1, 1);
+          gimp_matrix3_rotate (&matrix, G_PI - (i+1) * 2.0 * G_PI / (gdouble) mandala->size);
+        }
+      else
+        {
+          gimp_matrix3_rotate (&matrix, - i * 2.0 * G_PI / (gdouble) mandala->size);
+        }
       gimp_matrix3_translate (&matrix,
                               mandala->center_x,
                               mandala->center_y);
diff --git a/app/core/gimpsymmetry-mandala.h b/app/core/gimpsymmetry-mandala.h
index d7486f5b68..0978a40593 100644
--- a/app/core/gimpsymmetry-mandala.h
+++ b/app/core/gimpsymmetry-mandala.h
@@ -43,6 +43,7 @@ struct _GimpMandala
   gdouble       center_y;
   gint          size;
   gboolean      disable_transformation;
+  gboolean      enable_reflection;
 
   GimpGuide    *horizontal_guide;
   GimpGuide    *vertical_guide;