Mathew Robertson wrote:
Why not use boost::signals for your event interface. It is much better than hand-coded actions and listeners, since any type of function can handle an event. The technology is already in Boost so why re-invent the wheel.
The signals library looks very good, but it solves half the problem. You need to work out what types of signals are raised: MouseUp MouseDown MouseDoubleClick MouseMove and have a signal for each. This would mean that you could have hundreds of signals!
What makes this worse is that you often want to synthesise other events eg:
- MouseClick+LeftAlt - MouseMove-Left-Down (think 'mouse gestures') - etc
Just create a boost::signal<> for the mouse click and pass along all the information about the keyboard with it to the handler. Let the handler decide what should then be done with it. The handler could also be you, internally, ready to trigger a new event for some special situation. The point being that if you decide to have X number of events for a particular class, and you decide that some subset of X can be handled by the user, you are going to have to trigger those events anyway, so having subset-X boost::signals to do it by is no less of a cost than any other way. Remember also that boost::signal<> are just variabales like anything else and can be inherited like anything else by a specific derived class over a broader base class. There is no reason, if you have a particular mouse event as a boost::signal<> for a base class type of "window" to have to create another mouse event of the exact same type, as a boost::signal<>, for the derived class.