Incorrect ANSI escape codes

[JayJeckel]

While moving a bunch of in-house console apps to dotnet core using System.CommandLine, I've come across a few bugs in the System.CommandLine.Rendering.Ansi class.

• Ansi.Color.Background class isn't marked static.
• Ansi.Cursor.Scroll class isn't marked static.
• Ansi.Cursor.Move.NextLine() is missing the open bracket [ after the escape, ie $"{Esc}{line}E"; should be $"{Esc}[{line}E";.

According to the ms docs Console Virtual Terminal Sequences and the wikipedia ANSI escape code article, the following also need correcting.

• Ansi.Cursor.Scroll.UpOne() should be A instead of D. Up one line is A, while D is left one character.
• Ansi.Cursor.Scroll.DownOne() should be B instead of M. Down one line is B, while M is the reverse of \n and moves up one line.
• Ansi.Cursor.SavePosition should be s instead of 7.
• Ansi.Cursor.RestorePosition should be u instead of 8.

[hackf5]

What you say may be correct, however the current implementation works, apart from Ansi.Cursor.Move.NextLine(), which is indeed broken.

I've added a new sample to the RenderingPlayground that demonstrates this. If you get this branch https://github.com/hackf5/command-line-api/tree/bug-970-ansi-escape-codes and run the RenderingPlayground sample it will load the new Cursor sample by default. This sample demonstrates that the cursor currently works as expected (I've fixed NextLine()) on Windows at least.

I would be happy to tidy this up and add some unit tests in order to close this bug.

[hackf5]

I've reread the spec and

• Ansi.Cursor.SavePosition = 7
• Ansi.Cursor.RestorePosition = 8

are fine; see here.

However, to be explicit I think that scroll up and down are better represented as:

• Up = [S
• Down = [T

since this exactly matches the spec.

I've updated the sample.

I will update the test cases later and submit a PR.