> If you have an Fl_Choice widget, and pop up its menu, you > can dismiss the menu sub-window by clicking anywhere at > all, so it seems fltk can handle it somehow. > > Here's another example. Without the sub-window, grab() > makes all the events visible, as expected. Compare it to > the original. > > Doesn't that mean it's supposed to get events external to the window?
Yes, but this looks under the hood little bit different. When you start your application, you usually have main window and it's children (or widgets). This means that fltk internally build some kind of tree so it can communicate with them, and eventually when main application quits, nicely delete every one of them. Those childrens can be sub-windows too; no matter where they are placed (even on another screen), as long as fltk see them as it's children, it can send to them and receive from them events. Fl::grab() will instruct main window (you can see it as root in above tree) to 'route' events to one of it's sub-windows. Hoping now is little bit clear how Fl::grab() works :-) On other hand, communication between two applications (or two instances of the same), can be accomplished only via either system specific messages or some kind of IPC calls. For example, when you starts two instances of fluid, they can't send events to each other via plain fltk calls. The same applies for window manager borders (you can see them as children of window manager application) so to get events from them you have to communicate with window manager itself. Another solution exists and is extremely system specific. On X11 there is a way to listen specific events that occurs on the screen; registering your own event handler via Fl::add_handler(), events will be reported there for all visible windows on that screen (not fltk ones only) and you must find out who triggered them; this can be in some cases simple, but in some very tricky, not to say how this solution introduce a lot of event noise in Fl::add_handler(). Those events will not be fltk-like (FL_PUSH and etc.), but system one, like KeyPress, KeyRelease...) To complicate matter more, events in main fltk application window will be reported in Fl_Window::handle(), but not in Fl::add_handler(). I'm hoping this quick explaination didn't introduce more confusion :-). -- Sanel _______________________________________________ fltk mailing list [email protected] http://lists.easysw.com/mailman/listinfo/fltk
