Add ability to dynamically disable a right click popup menu item for Tree

Originally by andrewv

Hi,

Currently (as I understand it), right click popup menu items on a Tree popup are rendered, based on the Action getIcon() and getCaption() values. I am unable to find any way to disable the individual menu items, like I can for items in the new MenuBar (by calling MenuItem.setCommand(null).

The only workaround I can think of for the moment, is to use HTML for the caption, and change the caption text colour to be (say grey - to "look" disabled), and perform no processing in the Action.Handler.handleAction() when the right click menu item is clicked.

Are you planning to add an explicit isEnabled(), or similar mechanism to the Action interface, to allow a menu item in the right click popup menu to be dynamically disabled ? If not, can you think of any better workarounds ?

Thanks
Andrew

Imported from https://dev.vaadin.com/ issue #2461

Start with the Tree right-click popup implementation and the Action interface, then compare it with MenuBar's MenuItem.setCommand(null) behavior. Done means individual Tree popup menu items can be dynamically disabled and render as disabled rather than merely ignoring clicks.