[platform-update-dev] custom install handler accessing eclipse ui classe

[Dorian Birsan <birsan@xxxxxxxxxx>]

There has been some discussion on supporting
custom install handler accessing the eclipse ui classes.
The associated bug (https://bugs.eclipse.org/bugs/show_bug.cgi?id=73424)
has been fixed as follows:

- the custom install handler specified
in a jar file included by the feature 
will have access to both the org.eclipse.update.core and org.eclipse.ui
plugins class loaders (previously only org.eclipse.update.core was available)

- the custom install handler can, therefore, use any classes/interfaces
exposed by the org.eclipse.ui

- as the install handler code may be invoked on a non-ui thread, the 
implementer may need to wrap the UI code with a Display.asyncExec()/synchExec()

- update supports headless updates (i.e. command line driver installs,
etc.) 
which may not involve the ui plugins. It is the implementer's responsibility
to ensure the install handler can function under that environment (you
can 
check if the org.eclipse.ui bundle exists and is active, etc.)


-Dorian