Now using SdlInit to manage subsystem initialization/destruction; added a Canvas object to handle graphics.

DotSDL/Graphics/Canvas.cs

@@ -0,0 +1,43 @@
+namespace DotSDL.Graphics {
+    /// <summary>
+    /// A representation of the contents of the SDL window, with a number of
+    /// helper routines.
+    /// </summary>
+    public class Canvas {
+        /// <summary>
+        /// The raw pixels in the <see cref="Canvas"/>.
+        /// </summary>
+        public Color[] Pixels;
+
+        /// <summary>
+        /// Gets the width of the <see cref="Canvas"/>.
+        /// </summary>
+        public int Width { get; private set; }
+
+        /// <summary>
+        /// Gets the height of the <see cref="Canvas"/>.
+        /// </summary>
+        public int Height { get; private set; }
+
+        /// <summary>
+        /// Initialization a new <see cref="Canvas"/>.
+        /// </summary>
+        /// <param name="width">The width of the <see cref="Canvas"/>.</param>
+        /// <param name="height">The height of the <see cref="Canvas"/>.</param>
+        internal Canvas(int width, int height) {
+            SetSize(width, height);
+        }
+
+        /// <summary>
+        /// Resizes the <see cref="Canvas"/>.
+        /// </summary>
+        /// <param name="width">The new width of the <see cref="Canvas"/>.</param>
+        /// <param name="height">The new height of the <see cref="Canvas"/>.</param>
+        internal void SetSize(int width, int height) {
+            Width = width;
+            Height = height;
+
+            Pixels = new Color[Width * Height];
+        }
+    }
+}

DotSDL/Graphics/SdlWindow.cs

@@ -6,6 +6,8 @@ namespace DotSDL.Graphics {
     /// Represents an SDL window.
     /// </summary>
     public class SdlWindow {
+        private readonly SdlInit sdlInit = SdlInit.Instance;
+
         private readonly IntPtr _window;
         private readonly IntPtr _renderer;
         private readonly IntPtr _texture;
@@ -15,7 +17,7 @@ namespace DotSDL.Graphics {
         public int Width { get; }
         public int Height { get; }
 
-        private Color[] _pixels;
+        private Canvas _canvas;
 
         /// <summary>Indicates that the window manager should position the window.</summary>
         public const int WindowPosUndefined = 0x1FFF0000;
@@ -30,21 +32,22 @@ namespace DotSDL.Graphics {
         }
 
         public SdlWindow(string name, Point position, int width, int height) {
+            sdlInit.InitSubsystem(Init.SubsystemFlags.Video);
+
             _window = Video.CreateWindow(name, position.X, position.Y, width, height, Video.WindowFlags.Hidden);
             _renderer = Render.CreateRenderer(_window, -1, Render.RendererFlags.Accelerated);
             _texture = Render.CreateTexture(_renderer, Pixels.PixelFormatArgb8888, Render.TextureAccess.Streaming, width, height);
 
-            // TODO: Support other pixel formats.
-            _pixels = new Color[width * height];
+            _canvas = new Canvas(width, height);
 
             Width = width;
             Height = height;
         }
 
         private unsafe void BaseDraw() {
-            OnDraw(ref _pixels);  // Call the overridden Draw function.
+            OnDraw(ref _canvas);  // Call the overridden Draw function.
 
-            fixed(void* pixelsPtr = _pixels) {
+            fixed(void* pixelsPtr = _canvas.Pixels) {
                 var ptr = (IntPtr)pixelsPtr;
                 Render.UpdateTexture(_texture, IntPtr.Zero, ptr, Width * 4);
             }
@@ -73,7 +76,7 @@ namespace DotSDL.Graphics {
         /// <summary>
         /// Fired every time the window is drawn to.
         /// </summary>
-        protected virtual void OnDraw(ref Color[] pixels) {}
+        protected virtual void OnDraw(ref Canvas canvas) {}
 
         /// <summary>
         /// Fired before the window is shown.

DotSDL/SdlInit.cs

@@ -10,6 +10,11 @@ namespace DotSDL {
         private static readonly Lazy<SdlInit> Singleton = new Lazy<SdlInit>(() => new SdlInit());
         internal static SdlInit Instance => Singleton.Value;
 
+        // Subsystem initialization is ref counted in SDL2, and there really
+        // isn't much point in shutting down a specific subsystem after it's
+        // been started. We'll use a stack to ensure that everything is taken
+        // down in the order that it's been brought up and that QuitSubsystem
+        // has been called the appropriate number of times.
         private readonly Stack<Init.SubsystemFlags> _subsystems = new Stack<Init.SubsystemFlags>();
 
         private SdlInit() {

Samples/Sample.BasicPixels/Window.cs

@@ -87,13 +87,13 @@ namespace DotSDL.Sample.BasicPixels {
             return (Width * y) + x;
         }
 
-        protected override void OnDraw(ref Color[] pixels) {
+        protected override void OnDraw(ref Canvas canvas) {
             const byte min = 128, max = 255;
             const int offsetX = 96, offsetY = 80;
 
-            DrawBackground(ref pixels);
+            DrawBackground(ref canvas.Pixels);
             // D
-            DrawSequence(ref pixels, RandomColor(min, max),
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max),
                 new Line { Start = new Point { X = offsetX, Y = offsetY + 96 }, End = new Point { X = offsetX, Y = offsetY } },
                 new Line { Start = new Point { X = offsetX, Y = offsetY }, End = new Point { X = offsetX + 32, Y = offsetY } },
                 new Line { Start = new Point { X = offsetX + 32, Y = offsetY }, End = new Point { X = offsetX + 48, Y = offsetY + 16 } },
@@ -102,7 +102,7 @@ namespace DotSDL.Sample.BasicPixels {
                 new Line { Start = new Point { X = offsetX + 32, Y = offsetY + 96 }, End = new Point { X = offsetX, Y = offsetY + 96 } }
             );
             // o
-            DrawSequence(ref pixels, RandomColor(min, max),
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max),
                 new Line { Start = new Point { X = offsetX + 64, Y = offsetY + 88}, End = new Point { X = offsetX + 64, Y = offsetY + 56 } },
                 new Line { Start = new Point { X = offsetX + 64, Y = offsetY + 56}, End = new Point { X = offsetX + 72, Y = offsetY + 48 } },
                 new Line { Start = new Point { X = offsetX + 72, Y = offsetY + 48}, End = new Point { X = offsetX + 80, Y = offsetY + 48 } },
@@ -113,13 +113,13 @@ namespace DotSDL.Sample.BasicPixels {
                 new Line { Start = new Point { X = offsetX + 72, Y = offsetY + 96}, End = new Point { X = offsetX + 64, Y = offsetY + 88 } }
             );
             // t
-            DrawSequence(ref pixels, RandomColor(min, max), 
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max), 
                 new Line { Start = new Point { X = offsetX + 104 + 12, Y = offsetY + 24}, End = new Point { X = offsetX + 104 + 12, Y = offsetY + 96 } },
                 new Line { Start = new Point { X = offsetX + 104, Y = offsetY + 48}, End = new Point { X = offsetX + 104 + 24, Y = offsetY + 48 } }
             );
 
             // S
-            DrawSequence(ref pixels, RandomColor(min, max),
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max),
                 new Line { Start = new Point { X = offsetX + 144 + 48, Y = offsetY }, End = new Point { X = offsetX + 144, Y = offsetY } },
                 new Line { Start = new Point { X = offsetX + 144, Y = offsetY }, End = new Point { X = offsetX + 144, Y = offsetY + 48 } },
                 new Line { Start = new Point { X = offsetX + 144, Y = offsetY + 48 }, End = new Point { X = offsetX + 144 + 48 , Y = offsetY + 48 } },
@@ -127,7 +127,7 @@ namespace DotSDL.Sample.BasicPixels {
                 new Line { Start = new Point { X = offsetX + 144 + 48, Y = offsetY + 96 }, End = new Point { X = offsetX + 144, Y = offsetY + 96 } }
             );
             // D
-            DrawSequence(ref pixels, RandomColor(min, max),
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max),
                 new Line { Start = new Point { X = offsetX + 208, Y = offsetY + 96 }, End = new Point { X = offsetX + 208, Y = offsetY } },
                 new Line { Start = new Point { X = offsetX + 208, Y = offsetY }, End = new Point { X = offsetX + 208 + 32, Y = offsetY } },
                 new Line { Start = new Point { X = offsetX + 208 + 32, Y = offsetY }, End = new Point { X = offsetX + 208 + 48, Y = offsetY + 16 } },
@@ -136,7 +136,7 @@ namespace DotSDL.Sample.BasicPixels {
                 new Line { Start = new Point { X = offsetX + 208 + 32, Y = offsetY + 96 }, End = new Point { X = offsetX + 208, Y = offsetY + 96 } }
             );
             // L
-            DrawSequence(ref pixels, RandomColor(min, max),
+            DrawSequence(ref canvas.Pixels, RandomColor(min, max),
                 new Line { Start = new Point { X = offsetX + 272, Y = offsetY }, End = new Point { X = offsetX + 272, Y = offsetY + 96} },
                 new Line { Start = new Point { X = offsetX + 272, Y = offsetY + 96 }, End = new Point { X = offsetX + 272 + 48, Y = offsetY + 96} }
             );