🚀 go-pugleaf

I'm attempting to set the icon property of a JButton in the inspector.
I've created class ZoomIcon, which extends Object and implements Icon. A
ZoomIcon instance draws a plus sign or a minus sign when its paintIcon
method is invoked (intended to save a couple of gif downloads).

In a test JFrame, having only the single JButton on it, I create an
instance of ZoomIcon by:

Icon plusSign = new ZoomIcon(ZoomIcon.PlusSign);

In its drop down menu, the 'icon' property editor of the JButton's
inspector shows plusSign, BUT .... when I select plus sign from the drop
down,  the inspector flickers and fails to assign it to the property.

1. Given that the property editor accepted the ZoomIcon, which IDE
component subsequently rejected it ?

2. Is there a diagrnostic/logging trace that would show why the property
was rejected ?

3 What conditions can cause reject of a property assignment from the
drop down list.?

I've pored over the archives to no avail, except that a similar problem
has been reported before <34F1CA3B.91027487@csi.com>, but there is no
resolution of it in the archive.

Thanks in advance for any help you can give.