E4/Contexts

Contexts

In the general, execution or evaluation contexts, that can provide information to the currently executing code.

IEquinoxContext

Bug 259423 Add notion of "context" that can be injected into objects

IServiceLocator

In Eclipse 3.x we have the notion of part hierarchy: Workbench, WorkbenchWindow, WorkbenchPart (Editor/View), and nested part (MultiPageEditorPart or PageBookView).

Bug 92646 comment #11 [Workbench] [RCP] Allow developers to register Workbench services

There is a description of our services/service locator hierarchy in comment #11, basically we use this model to support 3 things:

• A service behaviour accessed through a local context (not PlatformUI :-)
• Scoping of the service to the local context
• Local service lifecycle, allowing the de-activation of contributions and listener clean up

IContextService contextService = (IContextService) getSite().getService(IContextService.class);
contextService.activateContext("org.eclipse.ui.textScope");

Each service is hierarchical and mirrors the IServiceLocator hierarchy. Services are created lazily on the call to getService(Class). The lookup algorithm is:

1. Check our cache to see if we already have an instance of the service
2. Check our local org.eclipse.ui.services.AbstractServiceFactory to see if we can create a local override version
3. Go to the org.eclipse.ui.services registry, org.eclipse.ui.internal.services.WorkbenchServiceRegistry to see if we can create the service
4. Use the parent locator to try and look up the service

IEvaluationContext

Provided by org.eclipse.core.expressions this is the application context used in 3.x by the IEvaluationService (and hence all declarative expressions like enabledWhen/activeWhen/visibleWhen)