On 20.06.2012, at 21:32, William wrote:
>> Hello, I'm fairly new to FLTK but I am having some trouble getting a
>> Fl_Valuator to update from a callback. I currently have the following
>> callback on a button:
>>
>> {
>> boost::thread t(boost::bind(&MotorControl::Sweep, motor_control));
>> }
>>
>> This should call the MotorControl::Sweep method in a separate thread.
>> Within this method I issue the value(int) method on a few Fl_Valuators to
>> change their values. There is also a boost sleep command between these
>> method calls.
>>
>> My issue is if I do not move the mouse, the Fl_Valuators (which are
>> horizontal sliders) do not update their positions. When I do move the
>> mouse, the sliders instantly jump to their correct values.
>>
>> How can I get the "Fl_Value_Slider"s to update correctly without me moving
>> the mouse?
>>
>> Thank you!
>
>
> I found a solution that seems to work. Calling Fl::check(); after setting
> with value(int) does the trick.
There may be two issues here:
1: since you are using threads, make sure that you don't create or delete
windows from within a thread. All FLTK calls should be done in the main thread.
That is a restriction of the underlying system calls. If you need to do FLTK
stuff in threads, you need to use Fl::lock, ::unlock, and ::awake.
2: your mein thread must return from callbacks quickly. I don;t know much about
boost, but if the call above blocks the FLTK main loop, you will not get any
updates until you return from the callback (or call Fl::check() or Fl::wait(),
but that has its own issues).
- Matthias
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