libgimp: new utility method gimp_procedure_config_get_choice_id().

This is just a method to simplify transforming a GimpChoice argument into an
enum value, which is easier to deal with, in C. It also allows to benefit from
switch() warnings or the like to make sure no cases are missing.

libgimp/gimp.def

@@ -728,6 +728,7 @@ EXPORTS
 	gimp_procedure_config_begin_run
 	gimp_procedure_config_end_export
 	gimp_procedure_config_end_run
+	gimp_procedure_config_get_choice_id
 	gimp_procedure_config_get_procedure
 	gimp_procedure_config_get_type
 	gimp_procedure_config_get_values

libgimp/gimpprocedureconfig.c

@@ -897,6 +897,59 @@ gimp_procedure_config_save_metadata (GimpProcedureConfig *config,
     }
 }
 
+/**
+ * gimp_procedure_config_get_choice_id:
+ * @config:        a #GimpProcedureConfig
+ * @property_name: the name of a [struct@ParamSpecChoice] property.
+ *
+ * A utility function which will get the current string value of a
+ * [struct@ParamSpecChoice] property in @config and convert it to the integer ID
+ * mapped to this value.
+ * This makes it easy to work with an Enum type locally, within a plug-in code.
+ *
+ * Since: 3.0
+ **/
+gint
+gimp_procedure_config_get_choice_id (GimpProcedureConfig *config,
+                                     const gchar         *property_name)
+{
+  GParamSpec          *param_spec;
+  GimpParamSpecChoice *cspec;
+  gchar               *value = NULL;
+  gint                 id;
+
+  param_spec = g_object_class_find_property (G_OBJECT_GET_CLASS (config),
+                                             property_name);
+
+  if (! param_spec)
+    {
+      g_warning ("%s: %s has no property named '%s'",
+                 G_STRFUNC,
+                 g_type_name (G_TYPE_FROM_INSTANCE (config)),
+                 property_name);
+      return 0;
+    }
+
+  if (! g_type_is_a (G_TYPE_FROM_INSTANCE (param_spec), GIMP_TYPE_PARAM_CHOICE))
+    {
+      g_warning ("%s: property '%s' of %s is not a GimpParamSpecChoice.",
+                 G_STRFUNC,
+                 param_spec->name,
+                 g_type_name (param_spec->owner_type));
+      return 0;
+    }
+
+  cspec = GIMP_PARAM_SPEC_CHOICE (param_spec);
+  g_object_get (config,
+                property_name, &value,
+                NULL);
+  id = gimp_choice_get_id (cspec->choice, value);
+
+  g_free (value);
+
+  return id;
+}
+
 
 /*  private functions  */
 

libgimp/gimpprocedureconfig.h

@@ -98,6 +98,12 @@ void    gimp_procedure_config_save_metadata (GimpProcedureConfig  *config,
                                              GFile                *file);
 
 
+/* Utility functions */
+
+gint    gimp_procedure_config_get_choice_id (GimpProcedureConfig  *config,
+                                             const gchar          *property_name);
+
+
 G_END_DECLS
 
 #endif /* __GIMP_PROCEDURE_CONFIG_H__ */