Support touch in autohide_sidebar.css

[firai]

There doesn't seem to be a way to activate the width expansion using touch when using autohide_sidebar.css currently. This is useful on non-Android tablets and 2-in-1s. Maybe one way of doing this is to add the :active pseudo-class?

[MrOtherGuy]

I really don't know how that would work. While you might get the contents to show with :active - I don't see how you could then actually use the contents, because you are already in the process of "clicking" it. To do anything useful you would have to release the activeness and then do whatever, but then it isn't active anymore...

Also, :active shouldn't work when the contents of the sidebar is a separate document. We need to apply rules to the sidebar itself which is in the main window document, but the contents of the sidebar - what you would click or touch - are in a separate document, and the active pseudo-class doesn't get across document boundary.