[Matplotlib-users] Key Press and Key Release Events in TkInter

[Gregory Key]

So basically in tkinter the key_release_event is useless.

Thanks I'll do some experimenting with the information you have given
me.

On Thu, 2017-02-02 at 14:07 -0600, Joe Kington wrote:
> That's a common "gotcha" when trying to detect a held key on a
> keyboard.  Your operating system (or the actual hardware in your
> keyboard in some cases) interprets a held key as multiple keypresses
> and fires off events accordingly (e.g., that's why holding down "a"
> will give "aaaaaaaaa" when typing).
> 
> I think Qt handles this automatically, but I could be wrong. Tk
> doesn't do it automatically.
> 
> Usually, you'd detect a held key by keeping track of the either the
> last key press event or the time since the last keypress event.
>  "Debouncing" is the term you'll want to search for.  In tkinter, you
> can bind a function to fire after idle (effectively checking if the
> key was ever released).  Alternatively, for the matplotlib side, I
> think you can bind to the idle event and do the same thing without
> needing to rely on anything tkinter-specific (Untested).
> 
> Hope that helps a bit, anyway.
> -Joe
> 
> On Tue, Jan 31, 2017 at 3:05 PM, Gregory Key <gregk3172 at outlook.com>
> wrote:
> > I am running Python 3.5.2 and MatPlotLib 2.0.0 on Ubuntu 16.10.
> > 
> > I am developing a program that uses matplotlib embedded in tkinter
> > to
> > plot vibration data in a bode plot, phase and amplitude versus
> > rotor
> > speed. I adapted the data browser given in the matplotlib
> > documentation
> >             as example 91.2 data_browser.py to browse the data. The
> > browser worked but I wanted to modify it so that holding down the
> > next
> > or previous key would scroll through the data instead of having to
> > continously press and release the keys. My plan was to use the
> > key_press_event to start a timer which would call a scroll method
> > and
> > then use the key_release event to stop the timer and stop
> > scrolling. I
> > couldn't make this scheme work so I did some investigating on the
> > key_press_event and key_release_event in tkinter. I used example
> > 91.5
> > keypress_demo.py given in the matplotlib documentation but I added
> > a
> > key_release_event method to it. What I found was that the key
> > events
> > don't work the way I would expect them to work. If you press and
> > release a key things work as expected. When a key is pressed the
> > key_press_event fires and when it is released the key_release_event
> > fires. If a key is pressed and held however the key_press_event
> > fires
> > followed immediately by a key_release_event even though the key has
> > not
> > been released. As long as the key is held down it will continue to
> > fire
> > key_press_event followed by key_release_event. Is this the way it
> > is
> > supposed to work?
> > 
> > Thanks
> > Greg Key
> > _______________________________________________
> > Matplotlib-users mailing list
> > Matplotlib-users at python.org
> > https://mail.python.org/mailman/listinfo/matplotlib-users
> > 
> 
>