Emit a signal prior to opening context menus
Currently there's no way for apps to know when a context menu is going to open.
That makes difficult to dynamically add entries depending on contextual information: a textview may want to add a special entry if the user right-clicks a link, for example. Or suggest spellchecking corrections. The usecases are multiple. I suggest adding a signal, but exposing a vfunc could work as well.
The alternative right now is to override the whole menu, which for complex things like TextViews is not exactly an easy task, and could be avoided altogether if such signal was to be implemented.