diff --git a/gtk/IconFactory.custom b/gtk/IconFactory.custom
new file mode 100644
index 000000000..9e2e992df
--- /dev/null
+++ b/gtk/IconFactory.custom
@@ -0,0 +1,18 @@
+                [DllImport("libgtk-win32-2.0-0.dll")]
+                extern static void gtk_icon_size_lookup (IconSize size, out int width, out int height);
+
+                /// <summary> Query icon dimensions </summary>
+                /// <remarks> Queries dimensions for icons of the specified size. </remarks>
+                public void LookupIconSize (IconSize size, out int width, out int height)
+                {
+                    gtk_icon_size_lookup (size, out width, out height);
+                }
+
+                /// <summary> Query icon dimensions </summary>
+                /// <remarks> Queries dimensions for icons of the specified size. </remarks>
+                public System.Drawing.Size LookupIconSize (IconSize size)
+                {
+                    int width, height;
+                    gtk_icon_size_lookup (size, out width, out height);
+                    return new System.Drawing.Size(width, height);
+                }