Use sensible defaults for depth/stencil (dotnet#1991)

* Use sensible defaults for depth/stencil

* Slightly adjust the SDL logic to try and encourage system opinions for -1

Author: Perksey

examples/CSharp/Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
     <PropertyGroup>
         <AssemblyName>Tutorial</AssemblyName>
-        <LangVersion>9</LangVersion>
+        <LangVersion>latest</LangVersion>
         <WarningsAsErrors>0618</WarningsAsErrors>
     </PropertyGroup>
 </Project>

src/Windowing/Silk.NET.Windowing.Common/Interfaces/IViewProperties.cs

@@ -78,15 +78,17 @@ public interface IViewProperties
         /// Preferred depth buffer bits of the window's framebuffer.
         /// </summary>
         /// <remarks>
-        /// Pass <c>null</c> or <c>-1</c> to use the system default. 
+        /// Pass <c>-1</c> to always use the system/backend default. Uses <c>24</c> as the default if <c>null</c> and
+        /// <see cref="PreferredStencilBufferBits"/> is also <c>null</c>
         /// </remarks>
         int? PreferredDepthBufferBits { get; }
 
         /// <summary>
         /// Preferred stencil buffer bits of the window's framebuffer.
         /// </summary>
         /// <remarks>
-        /// Pass <c>null</c> or <c>-1</c> to use the system default. 
+        /// Pass <c>-1</c> to always use the system/backend default. Uses <c>8</c> as the default if <c>null</c> and
+        /// <see cref="PreferredDepthBufferBits"/> is also <c>null</c>
         /// </remarks>
         int? PreferredStencilBufferBits { get; }
 
@@ -106,4 +108,4 @@ public interface IViewProperties
         /// </remarks>
         int? Samples { get; }
     }
-}
+}

src/Windowing/Silk.NET.Windowing.Glfw/GlfwWindow.cs

@@ -376,8 +376,18 @@ protected override void CoreInitialize(WindowOptions opts)
             // Set video mode (-1 = don't care)
 
             _glfw.WindowHint(WindowHintInt.RefreshRate, opts.VideoMode.RefreshRate      ?? GLFW.Glfw.DontCare);
-            _glfw.WindowHint(WindowHintInt.DepthBits, opts.PreferredDepthBufferBits     ?? GLFW.Glfw.DontCare);
-            _glfw.WindowHint(WindowHintInt.StencilBits, opts.PreferredStencilBufferBits ?? GLFW.Glfw.DontCare);
+            _glfw.WindowHint(WindowHintInt.DepthBits, opts.PreferredDepthBufferBits switch
+            {
+                null when opts.PreferredStencilBufferBits is null => 24,
+                {} x => x,
+                _ => GLFW.Glfw.DontCare
+            });
+            _glfw.WindowHint(WindowHintInt.StencilBits, opts.PreferredStencilBufferBits switch
+            {
+                null when opts.PreferredDepthBufferBits is null => 8,
+                {} x => x,
+                _ => GLFW.Glfw.DontCare
+            });
 
             _glfw.WindowHint(WindowHintInt.RedBits,   opts.PreferredBitDepth?.X ?? GLFW.Glfw.DontCare);
             _glfw.WindowHint(WindowHintInt.GreenBits, opts.PreferredBitDepth?.Y ?? GLFW.Glfw.DontCare);

src/Windowing/Silk.NET.Windowing.Sdl/SdlView.cs

@@ -149,29 +149,59 @@ protected void CoreInitialize
             IsClosingVal = false;
 
             // Set window GL attributes
-            Sdl.GLSetAttribute(GLattr.DepthSize,
-                    opts.PreferredDepthBufferBits is null || opts.PreferredDepthBufferBits == -1
-                        ? 24 : opts.PreferredDepthBufferBits.Value);
-
-            Sdl.GLSetAttribute(GLattr.StencilSize,
-                    opts.PreferredStencilBufferBits is null || opts.PreferredStencilBufferBits == -1
-                        ? 8 : opts.PreferredStencilBufferBits.Value);
+            if (opts.PreferredDepthBufferBits != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.DepthSize,
+                    opts.PreferredDepthBufferBits ?? 24
+                );
+            }
 
-            Sdl.GLSetAttribute(GLattr.RedSize,
-                    opts.PreferredBitDepth is null || opts.PreferredBitDepth.Value.X == -1
-                        ? 8 : opts.PreferredBitDepth.Value.X);
+            if (opts.PreferredStencilBufferBits != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.StencilSize,
+                    opts.PreferredStencilBufferBits ?? 8
+                );
+            }
 
-            Sdl.GLSetAttribute(GLattr.GreenSize,
-                    opts.PreferredBitDepth is null || opts.PreferredBitDepth.Value.Y == -1
-                        ? 8 : opts.PreferredBitDepth.Value.Y);
+            if (opts.PreferredBitDepth?.X != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.RedSize,
+                    opts.PreferredBitDepth?.X ?? 8
+                );
+            }
 
-            Sdl.GLSetAttribute(GLattr.BlueSize,
-                    opts.PreferredBitDepth is null || opts.PreferredBitDepth.Value.Z == -1
-                        ? 8 : opts.PreferredBitDepth.Value.Z);
+            if (opts.PreferredBitDepth?.Y != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.GreenSize,
+                    opts.PreferredBitDepth?.Y ?? 8
+                );
+            }
 
-            Sdl.GLSetAttribute(GLattr.AlphaSize,
-                    opts.PreferredBitDepth is null || opts.PreferredBitDepth.Value.W == -1
-                        ? 8 : opts.PreferredBitDepth.Value.W);
+            if (opts.PreferredBitDepth?.Z != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.BlueSize,
+                    opts.PreferredBitDepth?.Z ?? 8
+                );
+            }
+            
+            if (opts.PreferredBitDepth?.W != -1)
+            {
+                Sdl.GLSetAttribute
+                (
+                    GLattr.AlphaSize,
+                    opts.PreferredBitDepth?.W ?? 8
+                );
+            }
 
             Sdl.GLSetAttribute(GLattr.Multisamplebuffers, (opts.Samples == null || opts.Samples == -1) ? 0 : 1);
             Sdl.GLSetAttribute(GLattr.Multisamplesamples, (opts.Samples == null || opts.Samples == -1) ? 0 : opts.Samples.Value);