Today I added some aid for supporting cancellation of items to asyncworker. It goes like this (check the link):
What will happen is that first the item will be created and then (at some point) launched. Upon some_event will a request to cancel the item be set. If such a request is set and a cancellation point happens, the item will be cancelled. You can pass a boolean to the cancellation point that will tell the asyncworker-library whether to still launch the callback (for cleaning up). Once cancelled or really finished, the “item_finished” signal will be emitted (and the handler will therefor happen).
ps. I also created the build-environment for the gtk-doc stuff. You can preview the API-docs here