Kevin, I think that 'simple' RCP apps may not want CSS styling even though they use the SWT renderers. There seems to be some question of the footprint, This would mean that the (swt) renderers now have the same issue...what's the best way of setting up the optional dependency. At least ther're in a position to perform any initialization necessary at the proper time (i.e. before any widgets are created).
I still think that the service approach would work, the difference being that it's the swt renderers that would get/initialize the service rather than the workbench. There's still some issue of how to get the 'ApplicationCSS' product variable but that should be doable (using the Context?). Eric Kevin McGuire/Ottawa/i...@ibmca Sent by: [email protected] 04/07/2009 10:48 AM Please respond to E4 Project developer mailing list <[email protected]> To E4 Project developer mailing list <[email protected]> cc Subject Re: [e4-dev] Re: CSS relationship to e4 workbench Eric and I discussed this in person, so to relay the discussion: - The CSS support needs to be initialized very early, prior to any widget creation. - The services so far are for use by the parts. We have a styling service at present that sets the CSS id/cass. This may never get called for a given part and thus is not a good candidate for CSS engine init. Eric observed correctly that the real relationship is between CSS and the SWT renderers. Thus I think the services aren't the right mechanism for this initialization. - My argument, which I think Eric agreed with, is that if we're talking about workbench model + SWT then we might as well also be talking about CSS for any practical use of the workbench + SWT. - It's possible that the same model though could be used with a different renderer and therefore maybe you don't want to use CSS. Thus again it seems reasonable to pair renderer + styling engine (or different renderer + different styling engine). - Currently the optional dependencies and reflective code are in org.eclipse.e4.ui.workbench.swt. Thus I think it's ok to make the use of CSS explicit there. - Eric observed that most if not all the contents of that project could be moved to workbench.renderers.swt. We also noted that many of the classes in the project seem like left over experiments to be deleted. Eric chime in if I missed anything. Regards, Kevin Eric Moffatt/Ottawa/i...@ibmca Sent by: [email protected] 04/07/2009 09:22 AM Please respond to E4 Project developer mailing list <[email protected]> To E4 Project developer mailing list <[email protected]> cc Subject Re: [e4-dev] Re: CSS relationship to e4 workbench The way we handle this for the legacy code (also an optional dependency) is that the legacy bundle registers a service using the org.eclipse.e4.services extension point. Then code that needs to gets the service from the global context. A returned 'null' means that the bundle isn't there and the code can take appropriate actions (if any). This mechanism uses the service layer/context rather than reflection to determine the availability of the necessary classes. It also avoids the eager loading cases since services themselves are lazy loaded. Not sure if this will help in the CSS case but it might provide some avenues to look at... Eric Ed Merks <[email protected]> Sent by: [email protected] 04/07/2009 06:11 AM Please respond to E4 Project developer mailing list <[email protected]> To E4 Project developer mailing list <[email protected]> cc Subject Re: [e4-dev] Re: CSS relationship to e4 workbench Gunnar, Well, you still have to be careful about Java wanting to load classes that might not be available. Certainly EMF makes quite heavy use of the type of pattern you describe, i.e., non-reflective code guarded by tests for availability of the classes used in that code. That's how we support stand alone execution with no Eclipse dependencies. Often it's necessary to put the logic in a separate class to prevent Java from eagerly loading it. It's obviously very important to test for proper behavior when the classes aren't available. Cheers, Ed Gunnar Wagenknecht wrote: Kevin McGuire schrieb: 1) The use of optional dependencies is cool, but makes writing more code here tricky since it must be reflective which is brutal to write (I believe Boris has a "reflectify" refactor but that only helps the first time and change/debug is still a challenge). It also is a potential point of introducing errors if we forget to add the CSS plugins to the product since the tooling won't warn you of their absence (being optional). The trick is to only use reflection to verify that an optional dependency is satisfied. Thereafter it's totally fine to call out to a different class which uses the API provided by the optional dependencies directly. An example of this can be found in the Equinox Preferences bundle. org.eclipse.core.internal.preferences.Activator#start org.eclipse.core.internal.preferences.Activator#addingService OSGi services actually do support this very well because you only need to reference the service class by name. -Gunnar _______________________________________________ e4-dev mailing list [email protected] https://dev.eclipse.org/mailman/listinfo/e4-dev _______________________________________________ e4-dev mailing list [email protected] https://dev.eclipse.org/mailman/listinfo/e4-dev _______________________________________________ e4-dev mailing list [email protected] https://dev.eclipse.org/mailman/listinfo/e4-dev
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