Remotely/Desktop.Linux/Services/ScreenCapturerLinux.cs

using Remotely.Desktop.Core.Interfaces;
using Remotely.Desktop.Linux.Native;
using Remotely.Shared.Utilities;
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text.Json;
using System.Threading;

namespace Remotely.Desktop.Linux.Services
{
    public class ScreenCapturerLinux : IScreenCapturer
    {
        private readonly object _screenBoundsLock = new();
        private readonly Dictionary<string, LibXrandr.XRRMonitorInfo> _x11Screens = new();
        public ScreenCapturerLinux()
        {
            Display = LibX11.XOpenDisplay(null);
            Init();
        }

        public event EventHandler<Rectangle> ScreenChanged;

        public bool CaptureFullscreen { get; set; } = true;
        public Rectangle CurrentScreenBounds { get; private set; }
        public IntPtr Display { get; private set; }
        public string SelectedScreen { get; private set; }

        public void Dispose()
        {
            LibX11.XCloseDisplay(Display);
            GC.SuppressFinalize(this);
        }
        public IEnumerable<string> GetDisplayNames() => _x11Screens.Keys.Select(x => x.ToString());

        public Bitmap GetNextFrame()
        {
            lock (_screenBoundsLock)
            {
                try
                {
                    return GetX11Capture();
                }
                catch (Exception ex)
                {
                    Logger.Write(ex);
                    Init();
                    return null;
                }
            }
        }
        public int GetScreenCount() => _x11Screens.Count;

        public int GetSelectedScreenIndex() => int.Parse(SelectedScreen ?? "0");

        public Rectangle GetVirtualScreenBounds()
        {
            int width = 0;
            for (var i = 0; i < GetScreenCount(); i++)
            {
                width += LibX11.XWidthOfScreen(LibX11.XScreenOfDisplay(Display, i));
            }
            int height = 0;
            for (var i = 0; i < GetScreenCount(); i++)
            {
                height += LibX11.XHeightOfScreen(LibX11.XScreenOfDisplay(Display, i));
            }
            return new Rectangle(0, 0, width, height);
        }

        public void Init()
        {
            try
            {
                CaptureFullscreen = true;
                _x11Screens.Clear();
               
                var monitorsPtr = LibXrandr.XRRGetMonitors(Display, LibX11.XDefaultRootWindow(Display), true, out var monitorCount);

                var monitorInfoSize = Marshal.SizeOf<LibXrandr.XRRMonitorInfo>();

                for (var i = 0; i < monitorCount; i++)
                {
                    var monitorPtr = new IntPtr(monitorsPtr.ToInt64() + i * monitorInfoSize);
                    var monitorInfo = Marshal.PtrToStructure<LibXrandr.XRRMonitorInfo>(monitorPtr);

                    Logger.Write($"Found monitor: " +
                        $"{monitorInfo.width}," +
                        $"{monitorInfo.height}," +
                        $"{monitorInfo.x}, " +
                        $"{monitorInfo.y}");

                    _x11Screens.Add(i.ToString(), monitorInfo);
                }

                LibXrandr.XRRFreeMonitors(monitorsPtr);

                if (string.IsNullOrWhiteSpace(SelectedScreen) ||
                    !_x11Screens.ContainsKey(SelectedScreen))
                {
                    SelectedScreen = _x11Screens.Keys.First();
                    RefreshCurrentScreenBounds();
                }
            }
            catch (Exception ex)
            {
                Logger.Write(ex);
            }
        }
        public void SetSelectedScreen(string displayName)
        {
            lock (_screenBoundsLock)
            {
                try
                {
                    Logger.Write($"Setting display to {displayName}.");
                    if (displayName == SelectedScreen)
                    {
                        return;
                    }
                    if (_x11Screens.ContainsKey(displayName))
                    {
                        SelectedScreen = displayName;
                    }
                    else
                    {
                        SelectedScreen = _x11Screens.Keys.First();
                    }

                    RefreshCurrentScreenBounds();

                }
                catch (Exception ex)
                {
                    Logger.Write(ex);
                }
            }
        }

        private Bitmap GetX11Capture()
        {
            var currentFrame = new Bitmap(CurrentScreenBounds.Width, CurrentScreenBounds.Height, PixelFormat.Format32bppArgb);

            var window = LibX11.XDefaultRootWindow(Display);

            var imagePointer = LibX11.XGetImage(Display,
                window,
                CurrentScreenBounds.X,
                CurrentScreenBounds.Y,
                CurrentScreenBounds.Width,
                CurrentScreenBounds.Height,
                ~0,
                2);

            var image = Marshal.PtrToStructure<LibX11.XImage>(imagePointer);

            var bd = currentFrame.LockBits(new Rectangle(0, 0, CurrentScreenBounds.Width, CurrentScreenBounds.Height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);
            unsafe
            {
                byte* scan1 = (byte*)bd.Scan0.ToPointer();
                byte* scan2 = (byte*)image.data.ToPointer();
                var bytesPerPixel = Bitmap.GetPixelFormatSize(currentFrame.PixelFormat) / 8;
                var totalSize = bd.Height * bd.Width * bytesPerPixel;
                for (int counter = 0; counter < totalSize - bytesPerPixel; counter++)
                {
                    scan1[counter] = scan2[counter];
                }
            }

            currentFrame.UnlockBits(bd);
            Marshal.DestroyStructure<LibX11.XImage>(imagePointer);
            LibX11.XDestroyImage(imagePointer);

            return currentFrame;
        }

        private void RefreshCurrentScreenBounds()
        {
            var screen = _x11Screens[SelectedScreen];

            Logger.Write($"Setting new screen bounds: " +
                 $"{screen.width}," +
                 $"{screen.height}," +
                 $"{screen.x}, " +
                 $"{screen.y}");

            CurrentScreenBounds = new Rectangle(screen.x, screen.y, screen.width, screen.height);
            CaptureFullscreen = true;
            ScreenChanged?.Invoke(this, CurrentScreenBounds);
        }
    }
}