Table of contents and footer can overlap when using `stickysidebar`

[tyralla]

Describe the bug

The problem occurs when the content of a page is "shorter" than the table of contents.

Here is a real example (that occurs in combination with fulltoc):

And this is my minimal example (without fulltoc):

How to Reproduce

conf.py

project = 'test'
copyright = '2023, me'
author = 'me'
release = '0.0'

extensions = []

templates_path = ['_templates']
exclude_patterns = []

html_theme = 'classic'
html_static_path = ['_static']
html_theme_options = {"stickysidebar": True}

index.rst

page 1
======

.. toctree::
   :hidden:

   page2

page2

page 2
======

Environment Information

Platform:              win32; (Windows-10-10.0.19045-SP0)
Python version:        3.11.2 (tags/v3.11.2:878ead1, Feb  7 2023, 16:38:35) [MSC v.1934 64 bit (AMD64)])
Python implementation: CPython
Sphinx version:        7.1.2
Docutils version:      0.20.1
Jinja2 version:        3.1.2
Pygments version:      2.14.0

Sphinx extensions

No response

Additional context

No response

[picnixz]

I had a quick look at the CSS/HTML and I think the way that the side-bar is rendered may not necessarily be correct. The issue lies in the position: fixed instead of a position: sticky. However, with position: sticky, when the content is of normal length, the sidebar is not sticky at all and stays at the top of the page (and hence is hidden when scrolling down). AFAICT, this is due to the fact that both the content and the sidebar are actually in the same container but I'm not well-versed enough in HTML/CSS to know how to properly fix it so anyone who's willing to help is welcomed.

[tyralla]

Thanks for having a look at this. Unfortunately, this internet stuff is definitely not my expertise, so I hope someone else is interested.

[tyralla]

@parvumflumen provided a fix which he added to our project as a custom theme:

I have no idea if the modified theme would work well in other projects with different configurations, but maybe it does or can at least serve as a starting point for improving the original Sphinx theme.

[picnixz]

They are welcome to submit a PR if they think this can help in improving the current HTML/CSS, though I won't be able to review anything major until late september. Or they could discuss what should be done / has been done on this issue directly.

cc @parvumflumen