Improve ImGui fractional scaling support (#2614)

* Improve ImGui fractional scaling support

* Update window size in SetPerFrameImGuiData, Resize not raised on Wayland

Author: jaredh

src/Input/Silk.NET.Input/Silk.NET.Input.csproj

@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
-        <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0;net6.0;net7.0-android;net7.0-ios;net7.0-maccatalyst</TargetFrameworks>
+        <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1;net5.0;net6.0;net7.0-android</TargetFrameworks>
+        <TargetFrameworks Condition="!$([MSBuild]::IsOsPlatform('Linux'))">$(TargetFrameworks);net7.0-ios;net7.0-maccatalyst</TargetFrameworks>
         <SilkMetapackage>true</SilkMetapackage>
     </PropertyGroup>
 

src/OpenGL/Extensions/Silk.NET.OpenGL.Extensions.ImGui/ImGuiController.cs

@@ -236,12 +236,19 @@ public void Update(float deltaSeconds)
         private void SetPerFrameImGuiData(float deltaSeconds)
         {
             var io = ImGuiNET.ImGui.GetIO();
+            var size = _view.Size;
+            var framebufferSize = _view.FramebufferSize;
+
+            // Update here since Resize isn't raised on all platforms
+            _windowWidth = size.X;
+            _windowHeight = size.Y;
+
             io.DisplaySize = new Vector2(_windowWidth, _windowHeight);
 
             if (_windowWidth > 0 && _windowHeight > 0)
             {
-                io.DisplayFramebufferScale = new Vector2(_view.FramebufferSize.X / _windowWidth,
-                    _view.FramebufferSize.Y / _windowHeight);
+                io.DisplayFramebufferScale = new Vector2((float) framebufferSize.X / _windowWidth,
+                    (float) framebufferSize.Y / _windowHeight);
             }
 
             io.DeltaTime = deltaSeconds; // DeltaTime is in seconds.
@@ -427,6 +434,9 @@ private unsafe void SetupRenderState(ImDrawDataPtr drawDataPtr, int framebufferW
             _gl.PolygonMode(GLEnum.FrontAndBack, GLEnum.Fill);
 #endif
 
+            // Setup viewport, orthographic projection matrix
+            _gl.Viewport(0, 0, (uint) framebufferWidth, (uint) framebufferHeight);
+
             float L = drawDataPtr.DisplayPos.X;
             float R = drawDataPtr.DisplayPos.X + drawDataPtr.DisplaySize.X;
             float T = drawDataPtr.DisplayPos.Y;
@@ -488,6 +498,8 @@ private unsafe void RenderImDrawData(ImDrawDataPtr drawDataPtr)
             _gl.GetInteger(GLEnum.PolygonMode, lastPolygonMode);
 #endif
 
+            Span<int> lastViewport = stackalloc int[4];
+            _gl.GetInteger(GLEnum.Viewport, lastViewport);
             Span<int> lastScissorBox = stackalloc int[4];
             _gl.GetInteger(GLEnum.ScissorBox, lastScissorBox);
 
@@ -637,6 +649,7 @@ private unsafe void RenderImDrawData(ImDrawDataPtr drawDataPtr)
             _gl.PolygonMode(GLEnum.FrontAndBack, (GLEnum) lastPolygonMode[0]);
 #endif
 
+            _gl.Viewport(lastViewport[0], lastViewport[1], (uint) lastViewport[2], (uint) lastViewport[3]);
             _gl.Scissor(lastScissorBox[0], lastScissorBox[1], (uint) lastScissorBox[2], (uint) lastScissorBox[3]);
         }
 

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

@@ -2063,6 +2063,38 @@ public unsafe partial WindowHandle* CreateWindow
         /// </remarks>
         public unsafe partial void GetFramebufferSize(WindowHandle* window, out int width, out int height);
 
+        /// <summary>
+        /// <para>
+        /// This function retrieves the content scale for the specified window.
+        /// </para>
+        /// <para>
+        /// The content scale is the ratio between the current DPI and the platform's default DPI.
+        /// </para>
+        /// <para>
+        /// If you scale all pixel dimensions by this scale then your content should appear at an appropriate size.
+        /// This is especially important for text and any UI elements.
+        /// </para>
+        /// <para>
+        /// On platforms where each monitor can have its own content scale, the window content scale
+        /// depends on which monitor the system considers the window to be on.
+        /// </para>
+        /// </summary>
+        /// <param name="window">The window to query.</param>
+        /// <param name="xscale">Where to store the x-axis content scale, or <c>out _</c>.</param>
+        /// <param name="yscale">Where to store the y-axis content scale, or <c>out _</c>.</param>
+        /// <remarks>
+        /// <para>
+        /// This function must only be called from the main thread.
+        /// </para>
+        /// <para>
+        /// Possible errors include <see cref="ErrorCode.NotInitialized" /> and <see cref="ErrorCode.PlatformError" />.
+        /// </para>
+        /// </remarks>
+        /// <seealso cref="GetMonitorContentScale" />
+        // ReSharper disable IdentifierTypo
+        public unsafe partial void GetWindowContentScale(WindowHandle* window, out float xscale, out float yscale);
+        // ReSharper enable IdentifierTypo
+
         /// <summary>
         /// <para>
         /// This function returns the value of an input option for the specified window.