Avoid rounding errors in size calculation.

src/GLWpfControl/DxGLFramebuffer.cs

@@ -26,10 +26,10 @@ internal sealed class DxGLFramebuffer : IDisposable {
         public int FramebufferHeight { get; }
 
         /// The width of the element in device-independent pixels
-        public int Width { get; }
+        public double Width { get; }
 
         /// The height of the element in device-independent pixels
-        public int Height { get; }
+        public double Height { get; }
 
         /// The DirectX Render target (framebuffer) handle.
         public IntPtr DxRenderTargetHandle { get; }
@@ -53,7 +53,7 @@ internal sealed class DxGLFramebuffer : IDisposable {
         public ScaleTransform FlipYTransform { get; }
 
 
-        public DxGLFramebuffer([NotNull] DxGlContext context, int width, int height, double dpiScaleX, double dpiScaleY, Format format) {
+        public DxGLFramebuffer([NotNull] DxGlContext context, double width, double height, double dpiScaleX, double dpiScaleY, Format format) {
             DxGlContext = context;
             Width = width;
             Height = height;

src/GLWpfControl/GLWpfControl.cs

@@ -133,7 +133,7 @@ private void SetupRenderSize() {
                 }
             }
             var format = _settings.TransparentBackground ? Format.A8R8G8B8 : Format.X8R8G8B8;
-            _renderer?.SetSize((int) RenderSize.Width, (int) RenderSize.Height, dpiScaleX, dpiScaleY, format);
+            _renderer?.SetSize(RenderSize.Width, RenderSize.Height, dpiScaleX, dpiScaleY, format);
         }
 
         private void OnUnloaded()

src/GLWpfControl/GLWpfControlRenderer.cs

@@ -39,7 +39,7 @@ public GLWpfControlRenderer(GLWpfControlSettings settings)
         }
 
 
-        public void SetSize(int width, int height, double dpiScaleX, double dpiScaleY, Format format) {
+        public void SetSize(double width, double height, double dpiScaleX, double dpiScaleY, Format format) {
             if (_framebuffer == null || _framebuffer.Width != width || _framebuffer.Height != height) {
                 _framebuffer?.Dispose();
                 _framebuffer = null;