Use device scale factor to support higher DPI on WPF

CefSharp.Core/Internals/RenderClientAdapter.h

@@ -53,6 +53,25 @@ namespace CefSharp
             // CefClient
             virtual CefRefPtr<CefRenderHandler> GetRenderHandler() OVERRIDE{ return this; };
 
+            // CefRenderHandler
+            virtual DECL bool GetScreenInfo(CefRefPtr<CefBrowser> browser, CefScreenInfo& screen_info) OVERRIDE
+            {
+                if ((IRenderWebBrowser^)_renderWebBrowser == nullptr)
+                {
+                    return false;
+                }
+
+                auto scaleFactor = _renderWebBrowser->GetScreenInfoScaleFactor();
+
+                if (screen_info.device_scale_factor == scaleFactor)
+                {
+                    return false;
+                }
+
+                screen_info.device_scale_factor = scaleFactor;
+                return true;
+            }
+
             // CefRenderHandler
             virtual DECL bool GetViewRect(CefRefPtr<CefBrowser> browser, CefRect& rect) OVERRIDE
             {

CefSharp.Core/ManagedCefBrowserAdapter.h

@@ -646,6 +646,16 @@ namespace CefSharp
             }
         }
 
+        void NotifyScreenInfoChanged()
+        {
+            auto browser = _clientAdapter->GetCefBrowser();
+
+            if (browser != nullptr)
+            {
+                browser->GetHost()->NotifyScreenInfoChanged();
+            }
+        }
+
         void RegisterJsObject(String^ name, Object^ object)
         {
             _javaScriptObjectRepository->Register(name, object);

CefSharp.OffScreen/ChromiumWebBrowser.cs

@@ -387,6 +387,11 @@ public BitmapInfo CreateBitmapInfo(bool isPopup)
             return new GdiBitmapInfo { IsPopup = isPopup, BitmapLock = bitmapLock };
         }
 
+        float IRenderWebBrowser.GetScreenInfoScaleFactor()
+        {
+            return 1F;
+        }
+
         void IRenderWebBrowser.InvokeRenderAsync(BitmapInfo bitmapInfo)
         {
             lock (bitmapLock)

CefSharp.Wpf/ChromiumWebBrowser.cs

@@ -30,6 +30,8 @@ public class ChromiumWebBrowser : ContentControl, IRenderWebBrowser, IWpfWebBrow
         private bool ignoreUriChange;
         private bool browserCreated;
         private Matrix matrix;
+        private float deviceScaleFactor;
+        private ScaleTransform imageTransform;
 
         private Image image;
         private Image popupImage;
@@ -494,6 +496,8 @@ public ChromiumWebBrowser()
             UndoCommand = new DelegateCommand(Undo);
             RedoCommand = new DelegateCommand(Redo);
 
+            deviceScaleFactor = 1.0F;
+            imageTransform = new ScaleTransform();
             managedCefBrowserAdapter = new ManagedCefBrowserAdapter(this, true);
 
             disposables.Add(managedCefBrowserAdapter);
@@ -655,8 +659,13 @@ private void PresentationSourceChangedHandler(object sender, SourceChangedEventA
                 if (source != null)
                 {
                     matrix = source.CompositionTarget.TransformToDevice;
+                    deviceScaleFactor = (float)matrix.M11;
                     sourceHook = SourceHook;
                     source.AddHook(sourceHook);
+
+                    managedCefBrowserAdapter.NotifyScreenInfoChanged();
+                    imageTransform.ScaleX = 1 / matrix.M11;
+                    imageTransform.ScaleY = 1 / matrix.M22;
                 }
             }
             else if (args.OldSource != null)
@@ -743,7 +752,7 @@ private Image CreateImage()
             img.HorizontalAlignment = HorizontalAlignment.Left;
             img.VerticalAlignment = VerticalAlignment.Top;
             //Scale Image based on DPI settings
-            img.LayoutTransform = new ScaleTransform(1 / matrix.M11, 1 / matrix.M22);
+            img.LayoutTransform = imageTransform;
 
             return img;
         }
@@ -811,6 +820,11 @@ public BitmapInfo CreateBitmapInfo(bool isPopup)
             return BitmapFactory.CreateBitmap(isPopup);
         }
 
+        float IRenderWebBrowser.GetScreenInfoScaleFactor()
+        {
+            return deviceScaleFactor;
+        }
+
         void IRenderWebBrowser.InvokeRenderAsync(BitmapInfo bitmapInfo)
         {
             UiThreadRunAsync(delegate

CefSharp/Internals/IRenderWebBrowser.cs

@@ -11,6 +11,8 @@ public interface IRenderWebBrowser : IWebBrowserInternal
         int Width { get; }
         int Height { get; }
 
+        float GetScreenInfoScaleFactor();
+
         BitmapInfo CreateBitmapInfo(bool isPopup);
         void InvokeRenderAsync(BitmapInfo bitmapInfo);