E4 RCP How to set Toolbar item from preferences on start-up

Eclipse E4 (4.4.2), I have a Handled Tool Item defined in the Application model at,
Windows and Dialogs -> TrimBars -> Window Trim -> Toolbar

The Type of the item is Check. An option of the item call Selected, assigns the default selection of the Toolbar item when the RCP application is launched. I am persisting the current state of the tool bar item in org.eclipse.core.runtime.preferences.InstanceScope (other non-UI preferences as also stored here).

Is there a way to set the selection state of the tool bar item when the application is re-launched to the value stored in my preferences? i.e. if tool bar item is selected on exiting the application it is selected on launching, if tool bar item is de-selected on existing the application it is not selected on launching.

Solution

There is no standard way since the Eclipse Application Platform doesn't know anything about the preferences.

You could use a model processor defined using the org.eclipse.e4.workbench.model extension point to add code to initialize the item.

<extension
     id="themeContribution"
     point="org.eclipse.e4.workbench.model">
  <processor
        beforefragment="false"
        class="package.ItemProcessor">
     <element
           id="item.id">
     </element>
  </processor>

Alternatively you should be able to write code to set the tool bar item value from the preferences in the @ProcessAdditions method of your application LifeCycle class (assuming you have one). Note the @PostContextCreate method is probably called to early for this.