PowerShell-PSReadLine/PSReadLine/ConsoleLib.cs

/********************************************************************++
Copyright (c) Microsoft Corporation.  All rights reserved.
--********************************************************************/

using System;
using System.Text;

namespace Microsoft.PowerShell.Internal
{
    internal class VirtualTerminal : IConsole
    {
        // These two fields are used by PowerShellEditorServices to inject a
        // custom ReadKey implementation. This is not a public API, but it is
        // part of a private contract with that project.
        #pragma warning disable CS0649
        private static Func<bool, ConsoleKeyInfo> _readKeyOverride;
        #pragma warning restore CS0649

        private static Lazy<Func<bool, ConsoleKeyInfo>> _readKeyMethod = new Lazy<Func<bool, ConsoleKeyInfo>>(
            () => _readKeyOverride == null ? Console.ReadKey : _readKeyOverride);

        public int CursorLeft
        {
            get => Console.CursorLeft;
            set => Console.CursorLeft = value;
        }

        public int CursorTop
        {
            get => Console.CursorTop;
            set => Console.CursorTop = value;
        }

        // .NET doesn't fully implement this API on all platforms, so we fake it with a commonly supported escape sequence.
        protected int _unixCursorSize = 25;
        public virtual int CursorSize
        {
            get => PlatformWindows.IsConsoleApiAvailable(input: false, output: true) ? Console.CursorSize : _unixCursorSize;
            set
            {
                if (PlatformWindows.IsConsoleApiAvailable(input: false, output: true))
                {
                    Console.CursorSize = value;
                }
                else
                {
                    _unixCursorSize = value;
                }

                // See the cursor ANSI codes at https://www.real-world-systems.com/docs/ANSIcode.html, searching for 'blinking block'.
                // We write out the ANSI escape sequence even if we are on Windows, where the 'Console.CursorSize' API is supported by .NET.
                // This is because this API works fine in console host, but not in Windows Terminal. The escape sequence will configure the
                // cursor as expected in Windows Terminal, while in console host, the escape sequence works after it's written out, but then
                // will be overwritten by 'CursorSize' when the user continues typing.
                // We use blinking block and blinking underscore, so as to mimic the cursor size 100 and 25 in console host.
                Write(value > 50 ? "\x1b[1 q" : "\x1b[3 q");
            }
        }

        public bool CursorVisible
        {
            get => Console.CursorVisible;
            set => Console.CursorVisible = value;
        }

        public int BufferWidth
        {
            get => Console.BufferWidth;
            set => Console.BufferWidth = value;
        }

        public int BufferHeight
        {
            get => Console.BufferHeight;
            set => Console.BufferHeight = value;
        }

        public int WindowWidth
        {
            get => Console.WindowWidth;
            set => Console.WindowWidth = value;
        }

        public int WindowHeight
        {
            get => Console.WindowHeight;
            set => Console.WindowHeight = value;
        }

        public int WindowTop
        {
            get => Console.WindowTop;
            set => Console.WindowTop = value;
        }

        public ConsoleColor BackgroundColor
        {
            get => Console.BackgroundColor;
            set => Console.BackgroundColor = value;
        }

        public ConsoleColor ForegroundColor
        {
            get => Console.ForegroundColor;
            set => Console.ForegroundColor = value;
        }

        public Encoding OutputEncoding
        {
            // Catch and ignore exceptions - if we can't change the encoding, output is
            // probably redirected, but it can also happen with the legacy console on Windows.
            get { try { return Console.OutputEncoding; } catch { return Encoding.Default; } }
            set { try { Console.OutputEncoding = value; } catch { } }
        }

        private static T _TryIgnoreIOE<T>(Func<T> f)
        {
            int triesLeft = 10;
            while (true)
            {
                try
                {
                    triesLeft--;
                    return f();
                }
                catch (InvalidOperationException)
                {
                    // Ignore it. An IOE could be thrown if the "application does not have a
                    // console or when console input has been redirected"... but we don't
                    // expect PSReadLine to be involved in such a situation. So we are
                    // actually probably running into this Issue (wherein another process
                    // attached to the same console terminated at just the right/wrong time):
                    //
                    //    https://github.com/dotnet/runtime/issues/88697
                    //
                    // In the event there is some *other* pathological situation
                    // happening, we have limited the number of times we will
                    // swallow/retry this exception/operation.

                    if (triesLeft <= 0)
                    {
                        throw;
                    }
                }
            }
        }

        public ConsoleKeyInfo ReadKey()                  => _TryIgnoreIOE(() => _readKeyMethod.Value(true));
        public bool KeyAvailable                         => _TryIgnoreIOE(() => Console.KeyAvailable);
        public void SetWindowPosition(int left, int top) => Console.SetWindowPosition(left, top);
        public void SetCursorPosition(int left, int top) => Console.SetCursorPosition(left, top);
        public virtual void Write(string value)          => Console.Write(value);
        public virtual void WriteLine(string value)      => Console.WriteLine(value);
        public virtual void BlankRestOfLine()            => Console.Write("\x1b[K");
    }
}