Study to demonstrate the behaviour of key repeats for different event loops and OSes.

Author: Anustuv Pal

MacOS tkinter

On MacOS running a tkinter event loop, when a key is pressed, the on_press and on_release register a sequence of key release and key press events.

MacOS pynput

On MacOS running a pynput event loop, when a key is pressed, the on_press and on_release register simple key presses, and one key release when the user actually releases the key.

Windows tk & pynput

Tests on Windows shows that for both tkinter and pynput, the behaviour is the simpler one shown by the pynput event above.

Observations

We see two different behaviours. We will call them "releasing" (MacOS tk) and "non-releasing" (others).

Filtering key repeats

Filtering key repeats for the non-releasing model is simple.

• Keep track of a pressed key
• on_press don't press if the key is already pressed
• on_release release the key

Filtering key repeats for the releasing model is bit more involved.

• For each key the user interacts with record the time of press and release
• on-press check that it was last released > 2ms ago, then press
• on_release wait ~2 ms to see if on_press comes, else release the key.