Potential improvements to phx-viewport-top/phx-viewport-bottom

Elixir Framework Forums Livebook Forum
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The current live book phx-viewport-bottom uses the following code to check whether or not to load more data:

let isAtViewportBottom = (el, scrollContainer) => {
    let rect = el.getBoundingClientRect();
    return (
        Math.ceil(rect.bottom) >= top(scrollContainer) &&
        Math.ceil(rect.left) >= 0 &&
        Math.floor(rect.bottom) <= bottom(scrollContainer)
    );
};

I’m unsure of the purpose of checking Math.ceil(rect.left) >= 0, this is checking that left edge of the bottom element is not left of the viewport. If you set a negative margin on your list elements this will cause the hook to never load new data. What is the purpose of this check? Can it be removed or improved? I’m just not sure of the intent…