libgimp: new gimp_procedure_dialog_get_preview_from_drawable() function.

This allows plug-in developers to create GimpPreviewDrawable widgets
with the procedure dialog API.

libgimp/gimpproceduredialog.c

@@ -1373,6 +1373,46 @@ gimp_procedure_dialog_get_size_entry (GimpProcedureDialog       *dialog,
   return widget;
 }
 
+/**
+ * gimp_procedure_dialog_get_drawable_preview:
+ * @dialog:     the #GimpProcedureDialog.
+ * @preview_id: the ID of #GimpDrawablePreview.
+ * @drawable:   the #GimpDrawable.
+ *
+ * Gets or creates a new #GimpDrawablePreview for @drawable.
+ * If a widget with the @preview_id has already been created for
+ * this procedure, it will be returned instead.
+ *
+ * The @preview_id ID can later be used together with property names
+ * to be packed in other containers or inside @dialog itself.
+
+ * Returns: (transfer none): the #GtkWidget representing @preview_id. The
+ *                           object belongs to @dialog and must not be
+ *                           freed.
+ */
+GtkWidget *
+gimp_procedure_dialog_get_drawable_preview (GimpProcedureDialog *dialog,
+                                            const gchar         *preview_id,
+                                            GimpDrawable        *drawable)
+{
+  GtkWidget *w = g_hash_table_lookup (dialog->priv->widgets, preview_id);
+
+  if (w != NULL)
+    {
+      g_warning ("%s: preview_from_drawable identifier '%s' was already configured.",
+                 G_STRFUNC, preview_id);
+      return w;
+    }
+
+  w = gimp_drawable_preview_new_from_drawable (drawable);
+
+  g_hash_table_insert (dialog->priv->widgets, g_strdup (preview_id), w);
+  if (g_object_is_floating (w))
+    g_object_ref_sink (w);
+
+  return w;
+}
+
 /**
  * gimp_procedure_dialog_get_label:
  * @dialog:    the #GimpProcedureDialog.

libgimp/gimpproceduredialog.h

@@ -113,6 +113,11 @@ GtkWidget * gimp_procedure_dialog_get_file_chooser  (GimpProcedureDialog *dialog
                                                      const gchar         *property,
                                                      GtkFileChooserAction action);
 
+GtkWidget * gimp_procedure_dialog_get_drawable_preview
+                                                    (GimpProcedureDialog *dialog,
+                                                     const gchar         *preview_id,
+                                                     GimpDrawable        *drawable);
+
 GtkWidget * gimp_procedure_dialog_fill_box          (GimpProcedureDialog *dialog,
                                                      const gchar         *container_id,
                                                      const gchar         *first_property,

libgimp/gimpui.def

@@ -47,6 +47,7 @@ EXPORTS
 	gimp_procedure_dialog_fill_paned
 	gimp_procedure_dialog_fill_scrolled_window
 	gimp_procedure_dialog_get_color_widget
+	gimp_procedure_dialog_get_drawable_preview
 	gimp_procedure_dialog_get_file_chooser
 	gimp_procedure_dialog_get_int_combo
 	gimp_procedure_dialog_get_int_radio