Steps to Reproduce

According to the javadoc of Window it is possible to specify the position of the Window based on a combination of values e.g. "left,center'.

https://www.zkoss.org/javadoc/8.0.0/zk/org/zkoss/zul/Window.html#setPosition(java.lang.String)

However it is impossible to define the position inside the parent element.

As you can try in the fiddle (https://zkfiddle.org/sample/3phlhus/2-Center-Window-in-Parent#source-2) you can either specify "parent" which places the window in the top left corner of the parent element or "center" which places it in the middle. But the combination to center it inside the parent component does not work "parent,center".

Window win = new Window();
win.setTitle("Should be centered in parent");
win.setParent(container);
win.setPosition("parent,center");
win.doPopup();

Current Result

The combination "parent,center" to center it inside the parent component does not work.

Expected Result

Window component should be correctly centered inside the parent component.

Debug Information

Workaround