Say I have scrolled horizontally rightward how do I get the first visible line number?

[nyngwang]

As title.

My trying: I found that vim.fn.virtcol('.') can give what I want only if I place my cursor at the first visible column after, e.g. z10l, in the first place. Now the problem becomes what should I pass to virtcol.

[luukvbaal]

vim.fn.winsaveview() contains the leftcol field, that should be what you're looking for.

[nyngwang]

Thank you!