wxPython 4: detection of double keystroke

Question

Is there a way with wxPython 4 to recognize double pressing the same key? Especially in my case, I would like to recognize when the SHIFT key is pressed twice in quick succession.

Answer 1

Here is a more general solution

The event EVT_CHAR_HOOK is used instead of EVT_KEY_UP. The problem with EVT_KEY_UP is that it is swallowed when the event is bound to a frame that contains a panel.

The challenge with EVT_CHAR_HOOK is to determine whether the key is actually pressed twice or only held. Therefore the RawKeyFlags are read out. The bit at position 30 indicates whether the key was held or not.

Please note, however, that this solution only works on Windows systems!

import wx

class DoubleKeyStrokeListener(object):
    def __init__(self, parent, keyCode, callback, timeout=500):
        self._monitoredKey = keyCode
        self._callback = callback
        self._timeout = timeout

        self._firstPressRecognized = False
        self._keyTimer = wx.Timer(parent)

        parent.Bind(wx.EVT_CHAR_HOOK, self._OnKeyPressed)
        parent.Bind(wx.EVT_TIMER, self._OnTimer, self._keyTimer)

    def _OnKeyPressed(self, event):
        event.Skip()

        pressedKey = event.GetKeyCode()

        if pressedKey == self._monitoredKey:
            rawFlags = event.GetRawKeyFlags()

            # bit at position 30 is "previous key state" flag
            prevStateBit = rawFlags >> 30 & 1

            if prevStateBit == 1:  # -> key is held
                return

            if self._firstPressRecognized:
                self._firstPressRecognized = False
                self._callback(event)
            else:
                self._firstPressRecognized = True
                self._keyTimer.StartOnce(self._timeout)
        else:
            self._firstPressRecognized = False

    def _OnTimer(self, event):
        self._firstPressRecognized = False
        event.Skip()