Scroll bug on lines with tabs

[fabienferre91]

Go to: http://codemirror.net/demo/visibletabs.html
(Chrome Version 56.0.2924.87)

1/ Clean content
2/ Add this as the first line : 123456789 123456789 123456789 12
3/ On second line, press TAB key 16 times and add 123456789 1234567
4/ Horizontal scrollbar should appear
5/ Put cursor at the end of the second line
6/ Press DEL to remove the '7' char

=> End of second line is truncated

I dig into the source code, and I noticed that lineLength function (src/line/spans.js) doesn't take tabs into account. Maybe I misunderstood something but I have fix this with :

  function lineLength(line, tabSize) {
    if (line.height == 0) return 0;
    // take tabs into account
    var text = line.text.replace(/\t/g, Array(tabSize).fill(" "));
    var len = text.length, merged, cur = line;

[adrianheine]

I can reproduce truncated characters with roughly the steps you described in Firefox 51. The first line has to have more characters than the second.

[peterkroon]

Reproduced on Windows 10 Chrome stable
"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36"

Reproduced on Windows 10 Firefox stable
"Mozilla/5.0 (Windows NT 10.0; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0"