E4/Eclipse Application Services

a.k.a. "the twenty things"

This page is obsolete
See Eclipse4 for updated information.

This is a list of "recommended APIs" - things that we expect most Eclipse plug-ins would make use of (if applicable). The goal is to reduce bloat by focusing on a smaller subset of core recommended Services and APIs. If these Services and APIs are also structured in a similar and consistent manner, it will also simplify understanding.

Note that "the Workbench", "PlatformUI" or "Platform" are not on this list. Think of which services you would want to use from within your contributed view or editor.

We believe that these services should be offered as separate, independent APIs, so that clients can make use of some of them without having to buy into all of them. Structuring them as individual services also makes it easier to use them from other languages / environments such as e.g. JavaScript.

All of the services below are described from the point of view of an individual component. Under Life Cycle, we explain how components are initialized, disposed, and how they are passed references to the services they require.

Application Services

Core

Name	Description	Priority	Status
Acess to application model	Clients need to be able to retrieve model elements to access the current state of the application or to change this state.	High	EModelService API completed (can be used by injection).
Reading/Writing of Preferences	Clients need to be able to retrieve preferences (and sometimes, change preferences) regardless of where the preferences are stored.	High	Simplified client API (preferences by injection) completed. Provider-side API uses the 3.x API.
Adapting Objects	The adapter pattern should be supported.	High	Simplified client API completed. Provider-side API and more complex scenarios use IAdapterManager API.
Logging and Tracing	Components should be able to easily access a logger or provide tracing mechanisms to help with debugging.	High	Simplified client API backed by multiple loggers. Work to be completed via bug 298660
String Localization	The Eclipse Platform needs to ensure that localization can easily be done by product teams.	High	The need for 4.0 is come up with a story for externalizing strings in the model xmi. See bug 226340 and bug 244468 for more information.
Scheduling Work/Reporting Progress	A component should be able to schedule work in the foreground or in the background.	High	Deferred to 4.1. In 4.0, clients should use equinox futures, IRunnableWithProgress, JFace Modal Context, and Jobs framework. Some cleanup work to be done in bug 304244
Error (Status) Handling	Need a consistent way for components to report warnings / unexpected errors.	High	Simplified client API with providers using 3.x API.
Commands/Handlers	Clients should be able to register handles for global commands like cut/copy/paste.	High
Eventing System	Clients should be able to monitor events easily without having a myriad of different kinds of listeners.	High	See bug 288999.
Participating in Undo/Redo Support	Clients should be able to push operations to the undo/redo service and have it be tie in with other operations on the stack automatically.	High	Deferred to 4.1. In 4.0, clients should use the operations framework in org.eclipse.core.commands. Some cleanup work to do to describe the "pure 4.0" story is tracked in bug 315703
Authentication/Single Sign-on	A component should be able to request authentication in a way that the end user perceives as consistent. Different backends can have different requirements, will need to support multiple mechanisms.	High	Deferred to 4.1.
BiDi	A means for processing strings for display in non-LTR languages.	High	Need to determine if existing 3.x support is enough.

User Interface

Name	Description	Priority	Status
Receiving Input	Model objects (parts?) should be able to define an input.	High	DI can be used to define an input similar to consuming selection.
Providing Selection Information	Different parts of the model should be able to react to current active selection of other parts.	High	DI can be used in this case. Currently the model would define 'selection' as a variable that is modifiable by an IEclipseContext. In 3.x there is ISelectionService.
Persisting State and Data	The user interface must be able to remember things like its size and layouts when it has been recreated.	High	In 3.x, IDialogSettings and IMemento is used.
Managing Shared Resources	There should be a mechanism to pool identical resources together and share them to keep memory footprint low.	High	3.x version would be JFace's AbstractResourceManager and friends.
Participating in Editor/Saveable Part Life Cycle	Management of dirty state, save management, prompting to save unsaved resources, etc.	High	A save handler will invoke a doSave() method on a part's implementing client object directly.
Updating UI Elements	Components should be able to modify model objects directly and the UI should update if necessary	High	The client should modify model objects directly and they should update the UI.
Notifications	Inform the user of events in the application that may require attention, regardless of whether the application is visible or not.	High	No progress. See Platform UI/Notifications for ideas.
Status Reporting	Users should be able to easily check the status of operations/requests. In 3.x this is done in the status line and the 'Progress' view.	High	No progress. Can we merge this one with "Notifications"?
Part Service	Clients need to be able to perform simple part-related operations like "bring to top", "activate", and "show part X".	High	bug 295003 Seems to be related to "Show In".

Advanced

Name	Description	Priority	Status
Shell Provider	Dialogs/Windows need to be parented off of the proper window.	High	In 3.x there is JFace's IShellProvider interface. Also see bug 231150 and bug 303132.
Reacting to Workbench Model Changes.	Clients should be able to listen for changes in the workbench model.	High	See IEventBroker.
Participating in Label and Icon Decoration	Components should be able to contribute decorations to provide information to the user in a way that does not necessarily draw the user's attention.	High	Deferred to 4.1. For 4.0, decorations are only available via the compatibility layer, which uses the 3.x IDecoratorManager and an extension point for contributing decorators.
Reacting to Changes to the Context	The Eclipse Platform needs to be able to react to bundles coming and going on-the-fly at runtime.	High	Deferred to 4.1. 3.x version would be the IExtensionTracker.
Dynamically Contributing to the Workbench Model	Clients should be able to add tool items, menus, parts, and other such model objects to the workbench.	High	Boris to review what's there
Object Contributions	Actions that can be contributed to objects of a certain type.	High	Boris to review what's implemented
Focus Service	It should be possible to drive and enhance the presentation of the model/workbench based on the current "focus".	High	No progress.

Domain-Specific

Name	Description	Priority	Status
Workspace/Resources	Components should be able to create folders and files via interacting with the user's workspace.	High	No progress. 3.x API in the org.eclipse.core.resources bundle.
Database Connection	N/A	High	No progress.
Getting Hold of the Domain Model	Clients should be able to retrieve the model, say, in the form of an EMF model.	High	No progress.

Not Sure About These

• String comparison/collation.
• "Show In" support.
• Hyperlink detection.
• Opening a web page. (Eclipse 3.x: IWorkbenchBrowserSupport)

Other Services not yet Decided on

• From Architecture Council/Minutes May 15 2008#Eclipse Application Model:
  • Capabilities
  • Content Types, Associations
  • Markers
  • Workspace, Resources (related to Team Support)
  • Launching Framework
  • Core Variables / Launch String Substitution
  • EFS (core.filesystem)
  • OSGi Stuff (NLS, ServiceTracker, Bundle States / Activator / Classloader; Log; State Location)

There has been a discussion about if this list is too large. The conclusion is that you can build applications with subsets, but bigger applications usually need most of them. Instead of reducing the list further we want to make sure that in future there is only exactly one way to do a thing, not multiple as it is today.

Thoughts, Comments and Discussion

Data model (a rest service)

- Adapting object
- Selection (currentSelection)
- UI Contributions
- Decorations
- Common UI Elements
- Persist State 
- Extension Registry
- roles

Command Bus (a javascript function)

- Selection (change)
- Undo/Redo
- Handlers
- Dynamic enablement
- Notification Service
- Focus service
- logging
- usage monitoring

• From Architecture Council/Minutes May 15 2008#Eclipse Application Model:
  • Besides the List of Services we're compiling now by hand, we'll need a strong way of describing the Services for E4 -- as a medium for newcomers to understand Eclipse -- perhaps Tooling to make Service Descriptions machine readable / usable. In the beginning, Every Service should have a Wiki page describing it and the Architecture behind it (probably linked from this Summary Page.