Added drmModeGetConnectorCurrent, added new StartLinuxDrm with LinuxDrmOptions

src/Linux/Avalonia.LinuxFramebuffer/LinuxDrmOptions.cs

@@ -0,0 +1,46 @@
+using Avalonia.LinuxFramebuffer.Output;
+using Avalonia.Media;
+using JetBrains.Annotations;
+
+namespace Avalonia.LinuxFramebuffer
+{
+    public class LinuxDrmOptions
+    {
+        /// <summary>
+        /// Path for DrmCard to use, if no <see cref="OutputBackend"/> is passed.
+        /// Default: null
+        /// </summary>
+        [CanBeNull] public string Card { get; set; }
+        
+        /// <summary>
+        /// True to call drmModeGetConnector for all available connectors, otherwise drmModeGetConnectorCurrent is called to get the kernel-cached connected connector.
+        /// Info: since some hardware might have incorrect connector information on startup for some reason, you may need to set this parameter to true.
+        /// Default: False
+        /// </summary>
+        public bool DrmConnectorsForceProbe { get; set; } = false;
+        
+        /// <summary>
+        /// Scaling factor.
+        /// Default: 1.0
+        /// </summary>
+        public double Scaling { get; set; } = 1.0;
+        
+        /// <summary>
+        /// If true an two cycle buffer swapping is processed at init.
+        /// Default: True
+        /// </summary>
+        public bool EnableInitialBufferSwapping { get; set; } = true;
+        
+        /// <summary>
+        /// Color for <see cref="EnableInitialBufferSwapping"/>
+        /// Default: R0 G0 B0 A0
+        /// </summary>
+        public Color InitialBufferSwappingColor { get; set; } = new Color(0, 0, 0, 0);
+        
+        /// <summary>
+        /// IOutputBackend. If Null, a new DrmOutput for <see cref="Card"/> with <see cref="Scaling"/> will be created.
+        /// Default: null
+        /// </summary>
+        [CanBeNull] public IOutputBackend OutputBackend { get; set; }
+    }
+}

src/Linux/Avalonia.LinuxFramebuffer/LinuxFramebufferPlatform.cs

@@ -140,6 +140,14 @@ public static class LinuxFramebufferPlatformExtensions
 
     public static int StartLinuxDrm<T>(this T builder, string[] args, string card = null, double scaling = 1)
         where T : AppBuilderBase<T>, new() => StartLinuxDirect(builder, args, new DrmOutput(card) {Scaling = scaling});
+
+    public static int StartLinuxDrm<T>(this T builder, string[] args, [CanBeNull] LinuxDrmOptions drmOptions)
+        where T : AppBuilderBase<T>, new()
+    {
+        drmOptions ??= new LinuxDrmOptions();
+        drmOptions.OutputBackend ??= new DrmOutput(drmOptions) {Scaling = drmOptions.Scaling};
+        return StartLinuxDirect(builder, args, drmOptions.OutputBackend);
+    }
     
     public static int StartLinuxDirect<T>(this T builder, string[] args, IOutputBackend backend)
         where T : AppBuilderBase<T>, new()

src/Linux/Avalonia.LinuxFramebuffer/Output/Drm.cs

@@ -162,6 +162,8 @@ namespace Avalonia.LinuxFramebuffer.Output
         [DllImport(libdrm, SetLastError = true)]
         public static extern drmModeConnector* drmModeGetConnector(int fd, uint connector);
         [DllImport(libdrm, SetLastError = true)]
+        public static extern drmModeConnector* drmModeGetConnectorCurrent(int fd, uint connector);
+        [DllImport(libdrm, SetLastError = true)]
         public static extern void drmModeFreeConnector(drmModeConnector* res);
         
         [DllImport(libdrm, SetLastError = true)]

src/Linux/Avalonia.LinuxFramebuffer/Output/DrmBindings.cs

@@ -84,7 +84,7 @@ namespace Avalonia.LinuxFramebuffer.Output
     {
         public List<DrmConnector> Connectors { get; }= new List<DrmConnector>();
         internal Dictionary<uint, DrmEncoder> Encoders { get; } = new Dictionary<uint, DrmEncoder>();
-        public DrmResources(int fd)
+        public DrmResources(int fd, bool connectorsForceProbe = false)
         {
             var res = drmModeGetResources(fd);
             if (res == null)
@@ -107,7 +107,7 @@ namespace Avalonia.LinuxFramebuffer.Output
             
             for (var c = 0; c < res->count_connectors; c++)
             {
-                var conn = drmModeGetConnector(fd, res->connectors[c]);
+                var conn = connectorsForceProbe ? drmModeGetConnector(fd, res->connectors[c]) : drmModeGetConnectorCurrent(fd, res->connectors[c]);
                 Connectors.Add(new DrmConnector(conn));
                 drmModeFreeConnector(conn);
             }
@@ -168,7 +168,7 @@ namespace Avalonia.LinuxFramebuffer.Output
             }
         }
 
-        public DrmResources GetResources() => new DrmResources(Fd);
+        public DrmResources GetResources(bool connectorsForceProbe = false) => new DrmResources(Fd, connectorsForceProbe);
         public void Dispose()
         {
             close(Fd);

src/Linux/Avalonia.LinuxFramebuffer/Output/DrmOutput.cs

@@ -15,20 +15,34 @@ namespace Avalonia.LinuxFramebuffer.Output
 {
     public unsafe class DrmOutput : IGlOutputBackend, IGlPlatformSurface
     {
+        private LinuxDrmOptions _options;
         private DrmCard _card;
         public PixelSize PixelSize => _mode.Resolution;
-        public double Scaling { get; set; }
+
+        public double Scaling
+        {
+            get => _options.Scaling;
+            set => _options.Scaling = value;
+        }
         public IGlContext PrimaryContext => _deferredContext;
 
         private EglPlatformOpenGlInterface _platformGl;
         public IPlatformOpenGlInterface PlatformOpenGlInterface => _platformGl;
 
-        public DrmOutput(string path = null)
+        public DrmOutput(LinuxDrmOptions drmOptions)
         {
-            var card = new DrmCard(path);
+            _options = drmOptions;
+            CreateDrmOutput(_options.Card, _options.DrmConnectorsForceProbe);
+        }
+        public DrmOutput(string path = null) : this(new LinuxDrmOptions() { Card = path })
+        {
+        }
 
-            var resources = card.GetResources();
+        private void CreateDrmOutput(string path = null, bool connectorsForceProbe = false)
+        {
+            var card = new DrmCard(path);
 
+            var resources = card.GetResources(connectorsForceProbe);
 
             var connector =
                 resources.Connectors.FirstOrDefault(x => x.Connection == DrmModeConnection.DRM_MODE_CONNECTED);
@@ -144,7 +158,9 @@ namespace Avalonia.LinuxFramebuffer.Output
 
             using (_deferredContext.MakeCurrent(_eglSurface))
             {
-                _deferredContext.GlInterface.ClearColor(0, 0, 0, 0);
+                _deferredContext.GlInterface.ClearColor(_options.InitialBufferSwappingColor.R,
+                    _options.InitialBufferSwappingColor.G, _options.InitialBufferSwappingColor.B,
+                    _options.InitialBufferSwappingColor.A);
                 _deferredContext.GlInterface.Clear(GlConsts.GL_COLOR_BUFFER_BIT | GlConsts.GL_STENCIL_BUFFER_BIT);
                 _eglSurface.SwapBuffers();
             }
@@ -162,13 +178,18 @@ namespace Avalonia.LinuxFramebuffer.Output
             _mode = mode;
             _currentBo = bo;
             
-            // Go trough two cycles of buffer swapping (there are render artifacts otherwise)
-            for(var c=0;c<2;c++)
-                using (CreateGlRenderTarget().BeginDraw())
-                {
-                    _deferredContext.GlInterface.ClearColor(0, 0, 0, 0);
-                    _deferredContext.GlInterface.Clear(GlConsts.GL_COLOR_BUFFER_BIT | GlConsts.GL_STENCIL_BUFFER_BIT);
-                }
+            if (_options.EnableInitialBufferSwapping)
+            {
+                //Go trough two cycles of buffer swapping (there are render artifacts otherwise)
+                for(var c=0;c<2;c++)
+                    using (CreateGlRenderTarget().BeginDraw())
+                    {
+                        _deferredContext.GlInterface.ClearColor(_options.InitialBufferSwappingColor.R,
+                            _options.InitialBufferSwappingColor.G, _options.InitialBufferSwappingColor.B,
+                            _options.InitialBufferSwappingColor.A);
+                        _deferredContext.GlInterface.Clear(GlConsts.GL_COLOR_BUFFER_BIT | GlConsts.GL_STENCIL_BUFFER_BIT);
+                    }
+            }
             
         }