Page ToC scrolling glitches

[mhsmith]

Describe the bug

Open https://toga.beeware.org/en/stable/reference/api/widgets/canvas, and scroll downward in the page ToC on the right, using the touchpad or mouse wheel, until the scroll bar touches the bottom of the screen:

Notice the ToC is not actually at the bottom. You can continue scrolling for some distance, with the scroll bar disappearing off the bottom edge:

We're still not quite at the bottom of the ToC, but attempting to go any further causes the ToC to suddenly jump back to the top, and for the main page to start scrolling instead:

This can be repeated over and over again, alternating between scrolling the ToC and the main page, until you get to the bottom of the main page. Only then are the last two lines of the ToC visible:

Environment

Chrome 143.0.7499.147 on macOS with a touchpad.

[kattni]

Thanks for the report. I'll look into it when I'm back to things after the holidays.

[kattni]

Oh, wait. I know what's happening. The ToC tracks your location on the page based on header. So, if you scroll the ToC, but not the page, and then start scrolling the page, it will jump back to the location you are on the page as you start scrolling the page. This is a setting, but it is also the setting that enables it to highlight the current header in the ToC, so you know where you are. I don't think we should disable it. I think this needs to be understood as a behavior.

[mhsmith]

OK, that makes sense, but the fact that you can't scroll to the bottom of the ToC until you're at the bottom of the page is still a bug.

[kattni]

Turns out that issue is related to a "feature" of Material that involves JavaScript applying a height directly to the sidebar element. This is the feature that we went to all the trouble of overriding to regain screen-space in the sidebars. I have a "fix" that I think is the best we're going to do. I'll submit a PR when I'm back next week, and ping you on it.