Symbols are edited using a property editor. This editor is created by VWTk by looking at the symbols and deciding which ones are editable. (The technically inclined may like to know that symbol properties are edited (or for that matter, created, or animated) entirely by reflective invocation. VWTk uses JDK1.5 annotations to figure out editable properties.)
The property editor can be brought up in two ways:
If multiple symbols are selected, then the property editor will contain properties common to the selected group of symbols. In other words, it performs a "set intersection" of the properties. If nothing happens when you double click, it is because VWTk did not find any selected symbols.
Why this difference in behavior in the two cases? This is done because one might accidentally double click on the canvas while trying to select a symbol or zooming, panning, etc. It is very annoying to bring up a dialog saying nothing is selected everytime this happens, so the policy is for VWTk to ignore it. This may be changed in the future.
Once a property editor is brought up, it is "bound" to the symbols you selected before bringing it up. You can see what it affects by clicking "Selection details" in the property editor. Every property editor window is unique and is "bound" to a different group of symbols. So, for example, if you want to focus on a particular group of users, you can select them using the selection tool in the avatars panel, create a property editor and keep it open as long as you are working with the data.
