Eclipse RCP: How to order perspective buttons belonging to different plugins?

Question

My application has 5 plugins. Each plugin has a perspective of it's own and hence each perspective extension definition is under individual plugin's plugin.xml.

Now, I want to control the order in which these perspectives appear in my application. How to do it?

There is one main plugin that holds "ApplicationWorkBenchAdvisor.java". This has initialize() method in which I am iterating through the perspective registry using

PlatformUI.getWorkbench().getPerspectiveRegistry().getPerspectives();

and then appending perspective ids in a comma separated fashion to a String variable (pbar) which is used later like this.

PlatformUI.getPreferenceStore().setDefault(IWorkbenchPreferenceConstants.PERSPECTIVE_BAR_EXTRAS, pbar);
PlatformUI.getPreferenceStore().setValue(IWorkbenchPreferenceConstants.PERSPECTIVE_BAR_EXTRAS, pbar);

When iterating thourgh the perspective registry, I can compare perspective ids and sort it(when adding to 'pbar' by comparing ids) the way I want it to appear but, I don't want to do this ordering here as it appears like a dirty way.

Is there any other place where we can fix the order in which perspectives appear? (Each perspective resides in different plugin).

ADDED

1) Could we also control the ordering in the perspective switcher?

2) Is there a way to control entry into perspective registry to in inflict the desired order. If not could we write back into perspective registry?

Answer 1

To sum up all the observations and findings,

1) It is not possible to alter entries in the perspective registry. It is read-only.

2) To make perspective appear in the order that we want on perspective bar, we can achieve it by adding an entry in plugin_customization.ini (or preferences.ini) as shown below.

org.eclipse.ui/PERSPECTIVE_BAR_EXTRAS=perspectiveId1,perspectiveId2,perspectiveId3

3) If we want to fetch this ordered list, we can't fetch it directly. But as this ini file entry internally gets recorded in PreferenceStore we can fetch the same value from PreferenceStore using the following API as shown below.

PlatformUI.getPreferenceStore().getDefault( 
    IWorkbenchPreferenceConstants.PERSPECTIVE_BAR_EXTRAS);

Why would someone need to access the entry defined in ini file at all?

Well, in my case I had a view in which i had to display links to every perspective. As my perspective bar was sorted in desired order, I also wanted to maintain the same order in my view while displaying links to perspectives.

4) There is no known way to inflict the same sort order in the display of default perspective switcher. While a new custom perspective switcher can be written to achieve the desired effect.