diff --git a/wmdocklib/__init__.py b/wmdocklib/__init__.py
index e59d054..0c0c814 100644
--- a/wmdocklib/__init__.py
+++ b/wmdocklib/__init__.py
@@ -50,6 +50,14 @@ class DockApp:
             self.redraw()
             time.sleep(0.3)
 
+    def open_xwindow(self):
+        """Open the X window of given width and height.
+
+        The XBM mask is here created from the upper left rectangle of the
+        XPM using the given width and height."""
+        pywmgeneral.open_xwindow(len(sys.argv), sys.argv, self.width,
+                                 self.height)
+
     def prepare_pixmaps(self, background=None, patterns=None, style='3d',
                         margin=3):
 
diff --git a/wmdocklib/helpers.py b/wmdocklib/helpers.py
index 1da738b..676cdfd 100644
--- a/wmdocklib/helpers.py
+++ b/wmdocklib/helpers.py
@@ -283,14 +283,6 @@ def init_pixmap(background=None, patterns=None, style='3d', width=64,
     return char_width, char_height, charset_start, charset_width
 
 
-def open_xwindow(argv, w, h):
-    """Open the X window of given width and height.
-
-    The XBM mask is here created from the upper left rectangle of the
-    XPM using the given width and height."""
-    pywmgeneral.open_xwindow(len(argv), argv, w, h)
-
-
 def redraw():
     """Redraw the window."""
     pywmgeneral.redraw_window()