Re: [fltk.general] RFC: Tracking the focus widget - would this be useful ?
On 01/04/13 05:22, Albrecht Schlosser wrote: I'd like to know if there are more FLTK users who have the need to track the widget that currently has the focus. I wouldn't be against it.. sounds reasonable. I could imagine something like a callback that could be called whenever the current focus widget (Fl::focus()) changes. This could be something like: Fl::register_focus[_tracking] (my_widget,callback,arg) Seems like: Fl::add_focus_callback(cb, data); Fl::remove_focus_callback(cb,data); ..would make sense. void callback (Fl_Widget *w, long or void * arg, Fl_Widget *focus) The last argument is just to avoid calling Fl::focus() each time the callback is called, but could also be removed. I'd prefer the user's callback code do the Fl::focus() call (if it needs it) rather than a third arg so as to be consistent with Fl_Callback and it's always easier to remember shorter arg lists. Plus whatever few cycles are saved by preventing the user from calling Fl::focus() are probably undone by the stack manipulations of handling a third arg in the callback.. ___ fltk mailing list fltk@easysw.com http://lists.easysw.com/mailman/listinfo/fltk
Re: [fltk.general] RFC: Tracking the focus widget - would this be useful ?
On 06.01.2013 09:01, Greg Ercolano wrote:
On 01/04/13 05:22, Albrecht Schlosser wrote:
I'd like to know if there are more FLTK users who have the need
to track the widget that currently has the focus.
I wouldn't be against it.. sounds reasonable.
I could imagine something like a callback that could be called
whenever the current focus widget (Fl::focus()) changes. This
could be something like:
Fl::register_focus[_tracking] (my_widget,callback,arg)
Seems like:
Fl::add_focus_callback(cb, data);
Fl::remove_focus_callback(cb,data);
..would make sense.
void callback (Fl_Widget *w, long or void * arg, Fl_Widget *focus)
The last argument is just to avoid calling Fl::focus() each time
the callback is called, but could also be removed.
I'd prefer the user's callback code do the Fl::focus() call
(if it needs it) rather than a third arg so as to be consistent
with Fl_Callback and it's always easier to remember shorter arg lists.
Agreed, 100%. All good points.
Plus whatever few cycles are saved by preventing the user from calling
Fl::focus() are probably undone by the stack manipulations of handling
a third arg in the callback..
Yep, you're right, thanks. Calling Fl::focus() is a simple pointer
assignment, usually handled inline:
From FL/Fl.H:
static Fl_Widget* focus() {return focus_;}
Note also that I currently believe that the first argument I had in my
register... method should be dropped, because it's useless or redundant.
If someone would want to save the widget that is interested in the focus
change somewhere, s/he could use the data arg for this or save it
elsewhere.
Albrecht
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Re: [fltk.general] RFC: Tracking the focus widget - would this be useful ?
All, I'd like to know if there are more FLTK users who have the need to track the widget that currently has the focus. If this was a common problem, we could probably add something to FLTK to make this easier. It's not easy with current FLTK methods, as can be seen in the current discussion with the title scroll to focus in Fl_Scroll in fltk.general. I, for one, agree. Having a focus callback would be handy. Currently, I template/subclass every widget that I need to have this sort of ability. If others are interested, and the weight of the additional code is trivial, I think it's worth it. Denton ___ fltk mailing list fltk@easysw.com http://lists.easysw.com/mailman/listinfo/fltk
[fltk.general] RFC: Tracking the focus widget - would this be useful ?
All, I'd like to know if there are more FLTK users who have the need to track the widget that currently has the focus. If this was a common problem, we could probably add something to FLTK to make this easier. It's not easy with current FLTK methods, as can be seen in the current discussion with the title scroll to focus in Fl_Scroll in fltk.general. http://www.fltk.org/newsgroups.php?gfltk.general+Q%22scroll+to+focus+in+Fl_Scroll%22 I could imagine something like a callback that could be called whenever the current focus widget (Fl::focus()) changes. This could be something like: Fl::register_focus[_tracking] (my_widget,callback,arg) to register interest in focus changes. In this case, each focus change would call the callback function like this: void callback (Fl_Widget *w, long or void * arg, Fl_Widget *focus) The last argument is just to avoid calling Fl::focus() each time the callback is called, but could also be removed. The first argument would be the widget (my_widget) the callback was registered for (this could also be NULL, if my_widget was NULL in the call to register_focus[...]. ... or something like that ... Any ideas, comments, wishes ? Albrecht ___ fltk mailing list fltk@easysw.com http://lists.easysw.com/mailman/listinfo/fltk
