How to Detect If Current Terminal Supports 16-Color or 256-Color in Go?

Question

We got many popular packages in Go to render colorized text in terminal, like fatih/color, gookit/color, lucasb-eyer/go-colorful.

However I'm facing a problem that --- apart from seeing with my own eyes, how to detect if current terminal supports 16-Color or 256-Color programmatically in Go (even on Windows)?

Answer 1

As mentioned in "Determine whether the current Linux console supports 256 colours?" (and that is on Linux, the same portability issue would exist on Windows)

As an example of non-portable option, you could use curses (on Linux), as discussed here and implemented in curses.go:

Looking at tput colors and tigetnum('colors') (which return numbers like 1, 8, 256, or greater) are more along the lines of feature testing, which is less hacky and more future-proof.

func Init(theme *ColorTheme, black bool, mouse bool) {
    {
        in, err := os.OpenFile("/dev/tty", syscall.O_RDONLY, 0)
        if err != nil {
            panic("Failed to open /dev/tty")
        }
        _in = in
        // Break STDIN
        // syscall.Dup2(int(in.Fd()), int(os.Stdin.Fd()))
    }

    C.setlocale(C.LC_ALL, C.CString(""))
    _screen = C.c_newterm()
    if _screen == nil {
        fmt.Println("Invalid $TERM: " + os.Getenv("TERM"))
        os.Exit(2)
    }
    C.set_term(_screen)
    if mouse {
        C.mousemask(C.ALL_MOUSE_EVENTS, nil)
    }
    C.noecho()
    C.raw() // stty dsusp undef

    if theme != nil {
        C.start_color()
        var baseTheme *ColorTheme
        if C.tigetnum(C.CString("colors")) >= 256 {
            baseTheme = Dark256
        } else {
            baseTheme = Default16
        }
        initPairs(baseTheme, theme, black)
        _color = attrColored
    } else {
        _color = attrMono
    }
}