Effects scroll exception

Got this when someone was scrolling in my app. I could not make it happen when I tried scrolling directly.

Traceback (most recent call last):
  File "C:\py278_x64\libs\forced_choice\forced_choice\main.py", line 244, in run_app
    app.run()
  File "C:\py278_x64\Python\lib\site-packages\kivy\app.py", line 824, in run
    runTouchApp()
  File "C:\py278_x64\Python\lib\site-packages\kivy\base.py", line 484, in runTouchApp
    EventLoop.window.mainloop()
  File "C:\py278_x64\Python\lib\site-packages\kivy\core\window\window_pygame.py", line 381, in mainloop
    self._mainloop()
  File "C:\py278_x64\Python\lib\site-packages\kivy\core\window\window_pygame.py", line 285, in _mainloop
    EventLoop.idle()
  File "C:\py278_x64\Python\lib\site-packages\kivy\base.py", line 327, in idle
    self.dispatch_input()
  File "C:\py278_x64\Python\lib\site-packages\kivy\base.py", line 312, in dispatch_input
    post_dispatch_input(*pop(0))
  File "C:\py278_x64\Python\lib\site-packages\kivy\base.py", line 271, in post_dispatch_input
    wid.dispatch('on_touch_move', me)
  File "kivy\_event.pyx", line 701, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:6962)
  File "C:\py278_x64\Python\lib\site-packages\kivy\uix\scrollview.py", line 671, in on_touch_move
    if self.dispatch('on_scroll_move', touch):
  File "kivy\_event.pyx", line 701, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:6962)
  File "C:\py278_x64\Python\lib\site-packages\kivy\uix\scrollview.py", line 680, in on_scroll_move
    if self.dispatch_children('on_scroll_move', touch):
  File "kivy\_event.pyx", line 710, in kivy._event.EventDispatcher.dispatch_children (kivy\_event.c:7371)
  File "kivy\_event.pyx", line 706, in kivy._event.EventDispatcher.dispatch_generic (kivy\_event.c:7163)
  File "kivy\_event.pyx", line 710, in kivy._event.EventDispatcher.dispatch_children (kivy\_event.c:7371)
  File "kivy\_event.pyx", line 706, in kivy._event.EventDispatcher.dispatch_generic (kivy\_event.c:7163)
  File "kivy\_event.pyx", line 710, in kivy._event.EventDispatcher.dispatch_children (kivy\_event.c:7371)
  File "kivy\_event.pyx", line 705, in kivy._event.EventDispatcher.dispatch_generic (kivy\_event.c:7130)
  File "kivy\_event.pyx", line 701, in kivy._event.EventDispatcher.dispatch (kivy\_event.c:6962)
  File "C:\py278_x64\Python\lib\site-packages\kivy\uix\scrollview.py", line 704, in on_scroll_move
    self.effect_x.update(touch.x)
  File "C:\py278_x64\Python\lib\site-packages\kivy\effects\scroll.py", line 116, in update
    self.displacement += abs(val - self.history[-1][1])
IndexError: list index out of range

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[bgschaid]

Just wanted to open an issue on this but found this issue (seems that this still happens)

Are there any plans to fix this

As far as I can tell the problem is that the start-method is never called (which initializes self.history in the parent-class). But why that is is above my pay-grade

Simply catching the exception fixes this (there are no effects but I can live with that)

BTW: once self.history was “filled” by another scrolling it doesn’t fail anymore

scroll.py.patch.txt

[bgschaid]

Just wanted to open an issue on this but found this issue (seems that this still happens) Are there any plans to fix this As far as I can tell the problem is that the start-method is never called (which initializes self.history in the parent-class). But why that is is above my pay-grade Simply catching the exception fixes this (there are no effects but I can live with that) BTW: once self.history was “filled” by another scrolling it doesn’t fail anymore scroll.py.patch.txt

hello, i ran into this issue recently, can you please explain how to apply the patch? i am quite new to programming and this is a issue i hardly found info about

If you haven’t used the patch utility then it is easiest to apply the patch by hand: open the file listed on top of the file (probably without the venv in the path. But you find the location by looking at the stacktrace of your failure). Got to approximately line 111 and look for the lines with the “-” i nfron of them. Replace them with the lines with the “+” (without the + obviously)