Commands in Eclipse: some advanced patterns

This presentation was about the commands framework in Eclipse.  While titled as advanced, I found that most of the patterns were things that I've already came across, and solved.

Commands/Handlers:

• Command provides enabled state, and any arbitrary state
• Handler controls commands enabled state
• Can be global or local (based on state)
• Keybindings can point to different handlers base on state
• Menus and toolbars expose commands to user visually
• Programatically done through Eclipse services (not OSGi services)

Patterns:

• Using a parameter:
• Static string key/value pair
• Used to change behaviour of handler
• Can support other types, via parameter convertor
• Toggle
• Handler's duty to change command state
• HandlerUtil.toggleCommandState()
• Radio
• Command needs parameter for state, managed by handler
• Tool item drop down
• Usually a command with parameter, filled by menu ID
• Dynamic sections in menu
• Command contribution items
• Operating on selection
• Use core expressions
• Use core expressions with a property tester for more complicated tests
• Control in toolbar
• Contribution filling in a composite, has to handle orientation, not part of a part
• Property tester
• Used for complicated tests done in code
• Best to try to avoid these since plug-in needs to be loaded for them to work
• API to cause reevaluation
• Use handler services to update application state
• Use services to access commands and handlers from platform; don't try to access them directly.
• Don't call execute commands/handlers directly, instead invoke them via services

Commands in E4 and 3 are very similar.