Round corner in metacity theme?

[Deling Ren <lg+gnome home homeunix org>]

Dear all, I am trying to make a metacity theme with rounded corners
following this document
http://developer.gnome.org/doc/tutorials/metacity/metacity-themes.html by
Havoc Pennington. But specifying rounded corners in frame geometry simply
has no effect. I took a look at Bluecurve theme and didn't see anything
special there. Here is mine, which basically draw nothing yet:

<?xml version="1.0"?>
<metacity_theme>
    <info>
        <name>Test</name>
        <author>Test</author>
        <copyright>Copyright</copyright>
        <date>Someday</date>
        <description>Something</description>
    </info>

    <frame_geometry name="normal" rounded_top_left="true"
rounded_top_right="true">
        <distance name="left_width" value="6"/>
        <distance name="right_width" value="6"/>
        <distance name="bottom_height" value="6"/>
        <distance name="left_titlebar_edge" value="1"/>
        <distance name="right_titlebar_edge" value="1"/>
        <distance name="title_vertical_pad" value="3"/>
        <border name="title_border" left="0" right="0" top="1"
bottom="0"/>
        <border name="button_border" left="0" right="0" top="1"
bottom="0"/>
        <aspect_ratio name="button" value="1"/>
    </frame_geometry>

    <draw_ops name="blank">
    </draw_ops>

    <frame_style name="default" geometry="normal">
        <button function="minimize" state="normal" draw_ops="blank"/>
        <button function="minimize" state="pressed" draw_ops="blank"/>
        <button function="maximize" state="normal" draw_ops="blank"/>
        <button function="maximize" state="pressed" draw_ops="blank"/>
        <button function="menu" state="normal" draw_ops="blank"/>
        <button function="menu" state="pressed" draw_ops="blank"/>
        <button function="close" state="normal" draw_ops="blank"/>
        <button function="close" state="pressed" draw_ops="blank"/>
    </frame_style>

    <frame_style_set name="normal">
        <frame focus="yes" state="normal" resize="both" style="default"/>
        <frame focus="no" state="normal" resize="both" style="default"/>
        <frame focus="yes" state="maximized" style="default"/>
        <frame focus="no" state="maximized" style="default"/>
        <frame focus="yes" state="shaded" style="default"/>
        <frame focus="no" state="shaded" style="default"/>
        <frame focus="yes" state="maximized_and_shaded" style="default"/>
        <frame focus="no" state="maximized_and_shaded" style="default"/>
    </frame_style_set>

    <window type="normal" style_set="normal"/>
    <window type="dialog" style_set="normal"/>
    <window type="modal_dialog" style_set="normal"/>
    <window type="menu" style_set="normal"/>
    <window type="utility" style_set="normal"/>
    <window type="border" style_set="normal"/>

    <menu_icon function="close" state="normal" draw_ops="blank"/>
    <menu_icon function="maximize" state="normal" draw_ops="blank"/>
    <menu_icon function="unmaximize" state="normal" draw_ops="blank"/>
    <menu_icon function="minimize" state="normal" draw_ops="blank"/>
</metacity_theme>


Any suggestions? Thanks a lot.

Deling