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Re: [fltk.general] Get current value from Fl_Value_Slider

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Re: Get current value from Fl_Value_Slider Albrecht Schlosser Oct 16, 2020  
 
On 10/16/20 5:48 PM Dave Branson wrote:
I am new to the use of FLTK, and am having a problem with my initial test use of the Value Slider widget.  I am attempting to use this slider to extract values for a controls project, but cannot seem to grab the current value as the slider is exercised.  A sample of my test code is below.  Any advise would be welcomed.

Hi Dave,

it's great that you posted your code, but an image is not very helpful. You can attach your source file (.cxx, .cpp, whatever) here w/o issues. If we had the source code we could easily (test and) modify it to show you how to proceed.

Another important info would be the OS and compiler/toolchain you're using. If it's Windows (maybe VS ?), then printf doesn't work as you may assume.

That said, your code does only print the value right at the beginning of the program (what does it print, BTW?) but not during runtime when the slider is moved.

(See also Ian's post which I saw while writing this.)

I understand that the latter is what you want. If you want to access the value during runtime you need either a callback or another means like a button or timer to access the value whenever you need. The most direct way would likely be a callback with an appropriate when() condition that gets triggered when the slider is moved, something like (untested!):

void slider_cb(Fl_Widget *w, void *v) {

  Fl_Value_Slider *sl = (Fl_Value_Slider *)w;
  printf("Slider value = %d\n", sl->value());

}

But note, this is not going to output anything if you're using Windows. Please ask again if you need further advice.

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