Kivy Virtual Keyboard very slow on RaspberryPi 3B+

[Piyush]

Dear KivyGurus,

Would appreciate if anyone can have any pointers on this one. We have coded Kivy's Virtual Keyboard with Python 3.7,  on our Raspberry Pi 3B+ but it is very slow. In comparison if we install something like Matchbox or florence keyboard on Raspbian desktop, they work fluently. The CPU is may be around 50% utilized and the 1 GB RAM is also sufficiently free. 

It has been slow right from the moment we started using it.

Is there any specific setting we need to be aware of ? I apologize in advance if the information I share is not enough but do let me know and I'll share as much as possible.  we are not doing anything fancy but using but using these 4 functions (took them from good Samaritans on stackoverflow i think). 

from kivy.uix.vkeyboard import VKeyboard

self._keyboard = Window.request_keyboard(self._keyboard_closed, self, 'text')

if self._keyboard.widget:

self.vkeyboard = self._keyboard.widget

self.vkeyboard.background_color = [0.8, 0.82, 0.83, 1]

self.vkeyboard.font_size=20

self.vkeyboard.layout = 'keyboard.json'

self.vkeyboard.text_color = [0, 0, 0.83, 1]

def _keyboard_closed(self):

print('My keyboard have been closed!')

self._keyboard.unbind(on_key_down=self._on_keyboard_down)

self._keyboard = None

def _on_keyboard_down(self, keyboard, keycode, text, modifiers):

print('The key', keycode, 'have been pressed')

print(' - text is %r' % text)

print(' - modifiers are %r' % modifiers)

if keycode[1] == 'escape':

keyboard.release()

def process_key_on(self, touch):

if not touch:

return

x, y = self.to_local(*touch.pos)

key = self.get_key_at_pos(x, y)

if not key:

return

key_data = key[0]

displayed_char, internal, special_char, size = key_data

line_nb, key_index = key[1]

# save pressed key on the touch

ud = touch.ud[self.uid] = {}

ud['key'] = key

# for caps lock or shift only:

uid = touch.uid

if special_char is not None:

# Do not repeat special keys

if special_char in ('capslock', 'shift', 'layout', 'special'):

if self._start_repeat_key_ev is not None:

self._start_repeat_key_ev.cancel()

self._start_repeat_key_ev = None

self.repeat_touch = None

if special_char == 'capslock':

self.have_shift = False

self.have_special = False

self.have_capslock = not self.have_capslock

uid = -1

elif special_char == 'shift':

self.have_capslock = False

self.have_special = False

self.have_shift = not self.have_shift

uid = -1

elif special_char == 'special':

#self.have_special = True

self.have_capslock = False

self.have_shift = False

self.have_special = not self.have_special

uid = -1

elif special_char == 'layout':

self.change_layout()

# send info to the bus

b_keycode = special_char

b_modifiers = self._get_modifiers()

if self.get_parent_window().__class__.__module__ == \

'kivy.core.window.window_sdl2' and internal:

self.dispatch('on_textinput', internal)

else:

self.dispatch('on_key_down', b_keycode, internal, b_modifiers)

if special_char is not None and special_char != 'shift' and self.have_shift:

self.have_shift = False

self.active_keys = []

# elif special_char is not None and special_char != 'special' and self.have_special:

# self.have_special = False

# self.active_keys = []

else:

# save key as an active key for drawing

self.active_keys[uid] = key[1]

self.refresh_active_keys_layer()

def process_key_up(self, touch):

uid = touch.uid

if self.uid not in touch.ud:

return

# save pressed key on the touch

key_data, key = touch.ud[self.uid]['key']

displayed_char, internal, special_char, size = key_data

# send info to the bus

b_keycode = special_char

b_modifiers = self._get_modifiers()

self.dispatch('on_key_up', b_keycode, internal, b_modifiers)

if special_char in ('shift', 'capslock','special'):

uid = -1

if uid in self.active_keys:

self.active_keys.pop(uid, None)

if special_char == 'shift' and self.have_shift:

self.active_keys[-1] = key

elif special_char == 'special' and self.have_special:

#self.have_special = False

self.active_keys[-1] = key

if special_char == 'capslock' and self.have_capslock:

self.active_keys[-1] = key

self.refresh_active_keys_layer()

VKeyboard.process_key_on = process_key_on

VKeyboard.process_key_up = process_key_up