There is UpToDateStatusProvider that ought to report when annotations / decorations for an opened editor are being compujed.
But Java hints and CSL hints (= groovy, php, ...) do not implement this interface properly: it contains a stub, which reports "DONE" always.
Maven implementation was partially broken and I broke it completely transitioning to Parsing API, so it became the same as Java+CSL.
The general idea how to fix that is to provide some SPI / event source from Parsing API that would inform about source(s) being parsed and task(s) being applied on it. Then the Hint infrastructure could convert that to UpToDateStatusProvider that fires PENDING if there are some 'marked' tasks (i.e. by a mixin interface) before the tasks are run and fires DONE after all the tasks finish.
// cc: jlahoda