In case I'm not the only one who was unfamiliar with the term FFI:
http://en.wikipedia.org/wiki/Foreign_function_interface
-scott.
On Wed, 2009-02-11 at 00:50 +0800, Evan Laforge wrote:
> I have a haskell + fltk app. However, the route I took was to write
> the gui in c++, and then write an API to talk to it in C (just a set
> of 15 or so very short functions), and then FFI that API into haskell.
> I also have a C wrapper for Fl::run(), fork off my various haskell
> threads and then the main one calls Fl::wait() in a loop. Other
> threads can ship 'Fltk a' values (just a newtype for 'IO a' actually)
> to the main thread via a function that drops the action in an MVar and
> then calls Fl::awake() to break the wait(), which then runs the action
> and goes back to wait().
>
> Events go back to haskell via a queue on the fltk side that's read
> from by another API function on an event handler thread that drops it
> into a TChan, which is merged with several other TChans which is what
> the main event loop (in haskell) reads from. The main event loop
> pulls something out of the TChans and does whatever, which might wind
> up calling API functions which get shipped over to the Fl::wait()
> thread as above. Actually, the the event loop is pure and actions are
> run outside of it by diffing before and after states, but anyway.
>
> I wasn't sure if it would work, but it seems to be pretty ok so far.
> It's not very fast if there are 100s of events coming in per second,
> but for low bandwidth like mouse drags it's fine. There are also some
> occasional performance hiccups but I haven't put any effort into
> tracking those down yet. In theory if I track down a latency issue
> that I can't solve in haskell for whatever reason, I can just push it
> down into c++ and expose it via the API.
>
> Anyway, I tried this approach because I like the idea of a narrow API
> between the GUI and the rest of the program. In theory if I ever
> didn't like fltk I could swap out something else, but mostly it lets
> me write the low level GUI stuff in c++ without lots of painful FFI
> wrapping. Maybe it would work for your app?
>
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