windows: detect ANSI support in more terminals

[nolanderc]

Checks if the underlying console supports ANSI escape sequences.

Resolves an issue where bold text would render as completely white in Windows Terminal, which was unreadable on a light background.

[perillo]

@nolanderc Does #15206 fix this issue?

[nolanderc]

@perillo I don’t think so, because the code emitting the colors uses hardcoded values for windows unless ANSI escapes are detected. That is, even with the linked PR, the hardcoded values would still be used:

zig/lib/std/debug.zig

Line 662 in 2568da2

pubfnsetColor(conf: Config, out_stream: anytype, color: Color) !void {

[perillo]

@perillo I don’t think so, because the code emitting the colors uses hardcoded values for windows unless ANSI escapes are detected. That is, even with the linked PR, the hardcoded values would still be used:

Color codes are all hardcoded.

On Windows we have:

 .White, .Bold => windows.FOREGROUND_RED | windows.FOREGROUND_GREEN | windows.FOREGROUND_BLUE | windows.FOREGROUND_INTENSITY

and on an ANSI compatible terminal, we have

"\x1b[37;1m"

that corresponds to white color with bold or increased intensity.

So it seems the issue is the use of ANSI colors on a terminal having a white background/light color theme.

[nolanderc]

Ah yes, I seem to have forgotten to add a line to my commit... Originally, I had intended to split the white and bold styles into their own escape sequences. That way foreground colors are not overriden by the bold style, instead using the default (white on dark backgrounds, black on light ones).

[nolanderc]

Nevermind, that was already there... 😅

[squeek502]

I am in full support of this. @nolanderc you might want to rebase this branch on latest master so that it passes CI to make it more likely to get merged.

---

The new build runner means that on Windows the SetConsoleTextAttribute colors are not preserved when a test case fails. In combination with #13816 / #13723, this makes the output for expectEqualSlices much less useful.

With the changes in this PR, the colors are preserved (at least with Windows Terminal).

Before this PR:

After this PR:

[squeek502]

This is redundant and can (should?) be removed, the implementation of os.isatty on Windows is:

if (isCygwinPty(handle))
returntrue;
varout: windows.DWORD=undefined;
returnwindows.kernel32.GetConsoleMode(handle, &out) !=0;

[andrewrk]

Closing abandoned PR (CI failures, unaddressed review comments). @squeek502 please feel free to pick this up in a new PR if you are interested.