spectre.console/src/Spectre.Console/Internal/Ansi/AnsiDetector.cs

using System;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;

/////////////////////////////////////////////////////////////////////////////////////////////////////
// Portions of this code was ported from the supports-ansi project by Qingrong Ke
// https://github.com/keqingrong/supports-ansi/blob/master/index.js
/////////////////////////////////////////////////////////////////////////////////////////////////////

namespace Spectre.Console.Internal
{
    internal static class AnsiDetector
    {
        private static readonly Regex[] _regexes = new[]
        {
            new Regex("^xterm"), // xterm, PuTTY, Mintty
            new Regex("^rxvt"), // RXVT
            new Regex("^eterm"), // Eterm
            new Regex("^screen"), // GNU screen, tmux
            new Regex("tmux"), // tmux
            new Regex("^vt100"), // DEC VT series
            new Regex("^vt102"), // DEC VT series
            new Regex("^vt220"), // DEC VT series
            new Regex("^vt320"), // DEC VT series
            new Regex("ansi"), // ANSI
            new Regex("scoansi"), // SCO ANSI
            new Regex("cygwin"), // Cygwin, MinGW
            new Regex("linux"), // Linux console
            new Regex("konsole"), // Konsole
            new Regex("bvterm"), // Bitvise SSH Client
        };

        public static (bool SupportsAnsi, bool LegacyConsole) Detect(bool upgrade)
        {
            // Github action doesn't setup a correct PTY but supports ANSI.
            if (!string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("GITHUB_ACTION")))
            {
                return (true, false);
            }

            // Running on Windows?
            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                // Running under ConEmu?
                var conEmu = Environment.GetEnvironmentVariable("ConEmuANSI");
                if (!string.IsNullOrEmpty(conEmu) && conEmu.Equals("On", StringComparison.OrdinalIgnoreCase))
                {
                    return (true, false);
                }

                var supportsAnsi = Windows.SupportsAnsi(upgrade, out var legacyConsole);
                return (supportsAnsi, legacyConsole);
            }

            // Check if the terminal is of type ANSI/VT100/xterm compatible.
            var term = Environment.GetEnvironmentVariable("TERM");
            if (!string.IsNullOrWhiteSpace(term))
            {
                if (_regexes.Any(regex => regex.IsMatch(term)))
                {
                    return (true, false);
                }
            }

            return (false, true);
        }

        [SuppressMessage("Design", "CA1060:Move pinvokes to native methods class")]
        internal static class Windows
        {
            [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore")]
            private const int STD_OUTPUT_HANDLE = -11;

            [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore")]
            private const uint ENABLE_VIRTUAL_TERMINAL_PROCESSING = 0x0004;

            [SuppressMessage("StyleCop.CSharp.NamingRules", "SA1310:Field names should not contain underscore")]
            private const uint DISABLE_NEWLINE_AUTO_RETURN = 0x0008;

            [DllImport("kernel32.dll")]
            private static extern bool GetConsoleMode(IntPtr hConsoleHandle, out uint lpMode);

            [DllImport("kernel32.dll")]
            private static extern bool SetConsoleMode(IntPtr hConsoleHandle, uint dwMode);

            [DllImport("kernel32.dll", SetLastError = true)]
            private static extern IntPtr GetStdHandle(int nStdHandle);

            [DllImport("kernel32.dll")]
            public static extern uint GetLastError();

            [SuppressMessage("Design", "CA1031:Do not catch general exception types")]
            public static bool SupportsAnsi(bool upgrade, out bool isLegacy)
            {
                isLegacy = false;

                try
                {
                    var @out = GetStdHandle(STD_OUTPUT_HANDLE);
                    if (!GetConsoleMode(@out, out var mode))
                    {
                        // Could not get console mode.
                        return false;
                    }

                    if ((mode & ENABLE_VIRTUAL_TERMINAL_PROCESSING) == 0)
                    {
                        isLegacy = true;

                        if (!upgrade)
                        {
                            return false;
                        }

                        // Try enable ANSI support.
                        mode |= ENABLE_VIRTUAL_TERMINAL_PROCESSING | DISABLE_NEWLINE_AUTO_RETURN;
                        if (!SetConsoleMode(@out, mode))
                        {
                            // Enabling failed.
                            return false;
                        }
                    }

                    return true;
                }
                catch
                {
                    // All we know here is that we don't support ANSI.
                    return false;
                }
            }
        }
    }
}