Neither location mentions what should I think be by far the main purpose of scrollbar-gutter: avoiding layout shift when you open a modal and disable the page’s

Neither location mentions what should I think be by far the main purpose of scrollbar-gutter: avoiding layout shift when you open a modal and disable the page’s scrollbar to avoid confusion. Perhaps the best solution there would be some way of designating a certain scrollable area as the document scrollable area when the body element doesn’t have scrollbars, so that Up/Down/PageUp/PageDown/Space/Shift+Space all act as though it were focused when the body is focused. That way, you could have the modal exist in the DOM after the main scrolling area, rather than inside it, and you wouldn’t need to worry about document scrollbars or overscroll behaviour. Multi-pane views (very common in desktop apps) are normally a bit of a mess on the web, and it’s always a pain when you come across a web page that has shunned the body scrollable area and put everything in something like a <main style="overflow:auto">, so that you have to focus that before keyboard scrolling works. I should finish my draft blog post from a year or two ago where I explored the space and all the hoops you have to jump through to have it work almost perfectly, though it still requires some client-side JavaScript to redirect body focus to the correct element.