automatic scroll down breaks sometimes

[nitzantomer]

not quite sure when, find a way to reproduce first.

[TomZelazny]

This is because of the checkOverflow function in output.tsx:

private checkOverflow(): boolean {
	var node: any = ReactDOM.findDOMNode(this);
	return node.scrollTop + node.offsetHeight === node.scrollHeight;
}

it seems as though under certain conditions return node.scrollTop + node.offsetHeight === node.scrollHeight; does not correctly check if the scrollbar is at the bottom of the page. for instance screen resizes (opening the console, zooming in/out, resizing the window) or zoomed windows.

an elegant fix (which makes having to check for overflow obsolete ) is changing

main#ui article.terminal section.output{
    ....
    flex-direction: column;
    ....

into

main#ui article.terminal section.output{
    ....
    flex-direction: column-reverse;
    ....

but it seems to break the scrollbar. If anyone has any ideas on why checkOverflow is wrong I'd be happey to hear.

[nitzantomer]

You're right, it breaks the scrollbar.

I flowed your advice and changed it to: Math.ceil(this.element.scrollTop + this.element.offsetHeight) >= this.element.scrollHeight I also updated the scrollbar lib version and removed a use of deprecated react feature.

The PR is here: https://github.com/fugazi-io/webclient/pull/33

[TomZelazny]

After testing, the Math.ceil does not fix the problem, any fix that uses scrollTop, offestHeight and scollHeight or other browser window properties seems pretty susceptible to alot of edge cases. I am currently abroad for work so I can't really test this properly but I think it would be much simpler and more elegant to use a css solution (and just fix the css for the scrollbar so it does not disappear). If you can reopen the issue I'll work on fixing it when I get back.

[nitzantomer]

@TomZelazny Sorry, I forgot about it... Re-opened it, if you still wanna take a look. I agree that a css only solution is the best, but it might be tricky..

[nitzantomer]

Scrolling related PR: https://github.com/fugazi-io/webclient/pull/58 Not sure if it fixed this bug completely