I’m playing around with a Kivy Scrollview, adding scrollbars, etc, and getting a strange crash. I don’t specifically think it’s a bug, it’s probably some configuration element on Scrollviews that I’m missing, but who knows?
Given this code:
""" Source: https://stackoverflow.com/questions/35626320/kivy-image-scrolling """ from kivy.app import App from kivy.uix.image import Image from kivy.uix.scrollview import ScrollView from kivy.core.window import Window class TutorialApp(App): def build(self): some_img = Image(source='/home/data/map/Map_07C.jpg', size_hint=(None, None), keep_ratio=True, size=(Window.width * 2, Window.height * 2)) sv = ScrollView(size=Window.size, bar_width=50, scroll_type=['bars', 'content'], effect_cls='ScrollEffect') sv.add_widget(some_img) return sv if __name__ == "__main__": TutorialApp().run()
if I click or touch the Scrollbars in any way, I get this error:
File "kivy_env/lib/python3.8/site-packages/kivy/uix/scrollview.py", line 908, in on_scroll_move self.effect_x.update(touch.x) File "kivy_env/lib/python3.8/site-packages/kivy/effects/scroll.py", line 116, in update self.displacement += abs(val - self.history[-1]) IndexError: list index out of range
However – if I first click the bitmap being scrolled, I can use the scrollbars with no problem.
So what’s up? Is there some Scrollview configuration I’m missing? (It took me a while to even find the
scroll_type option to enable the bars, at first I could only mouse-drag the bitmap). Or is it a bug – given that it’s referencing
history[-1], maybe that doesn’t exist yet?
Yep, it’s a bug. Just searched the Kivy repo on Github, found:
The link does have a “workaround” patch, that you can manually apply to the installed library. Just tested the patch, it fixes my problem. Basically puts a try/except/return block around the line with