WPF - Fixed Html Dropdown positioning when near bottom of screen (Cleanup) (#4759)

* WPF - Popup Mouse Transform

- Refactor and performance improvements
- WPF Example - Enable popup transform by default

Issue #2820

Author: amaitland

CefSharp.Wpf.Example/Views/BrowserTabView.xaml.cs

@@ -16,6 +16,7 @@
 using CefSharp.Fluent;
 using CefSharp.Wpf.Example.Handlers;
 using CefSharp.Wpf.Example.ViewModels;
+using CefSharp.Wpf.Experimental;
 using CefSharp.Wpf.Experimental.Accessibility;
 
 namespace CefSharp.Wpf.Example.Views
@@ -31,6 +32,8 @@ public BrowserTabView()
 
             DataContextChanged += OnDataContextChanged;
 
+            browser.UsePopupMouseTransform();
+
             //browser.BrowserSettings.BackgroundColor = Cef.ColorSetARGB(0, 255, 255, 255);
 
             //Please remove the comments below to use the Experimental WpfImeKeyboardHandler.

CefSharp.Wpf/ChromiumWebBrowser.cs

@@ -140,11 +140,6 @@ public partial class ChromiumWebBrowser : Control, IRenderWebBrowser, IWpfWebBro
         /// </summary>
         private static bool DesignMode;
 
-        /// <summary>
-        /// The class that coordinates the positioning of the dropdown if wanted.
-        /// </summary>
-        private IMouseAdjustor mouseAdjustor;
-
         // https://github.com/chromiumembedded/cef/issues/3427
         private bool resizeHackIgnoreOnPaint;
         private Structs.Size? resizeHackSize;
@@ -155,6 +150,11 @@ public partial class ChromiumWebBrowser : Control, IRenderWebBrowser, IWpfWebBro
         /// </summary>
         private bool initialFocus;
 
+        /// <summary>
+        /// The class that coordinates the positioning of the dropdown if wanted.
+        /// </summary>
+        internal IMousePositionTransform MousePositionTransform { get; set; }
+
         /// <summary>
         /// When enabled the browser will resize by 1px when it becomes visible to workaround
         /// the upstream issue
@@ -489,14 +489,6 @@ public ChromiumWebBrowser()
             {
                 NoInliningConstructor();
             }
-
-            bool adjust = true;
-
-            if (adjust)
-                this.mouseAdjustor = new MouseAdjustor();
-
-            else
-                this.mouseAdjustor = new NoMouseAdjustor();
         }
 
         /// <summary>
@@ -626,6 +618,7 @@ private void NoInliningConstructor()
             PresentationSource.AddSourceChangedHandler(this, PresentationSourceChangedHandler);
 
             MenuHandler = new ContextMenuHandler();
+            MousePositionTransform = new NoOpMousePositionTransform();
 
             UseLayoutRounding = true;
         }
@@ -1053,7 +1046,7 @@ protected virtual void OnPopupShow(bool isOpen)
             UiThreadRunAsync(() =>
             {
                 popupImage.Visibility = isOpen ? Visibility.Visible : Visibility.Hidden;
-                mouseAdjustor.OnPopupShow(isOpen);
+                MousePositionTransform.OnPopupShow(isOpen);
             });
         }
 
@@ -2125,7 +2118,7 @@ private void SetPopupSizeAndPositionImpl(Rect rect)
             popupImage.Width = rect.Width;
             popupImage.Height = rect.Height;
 
-            Point point = this.mouseAdjustor.UpdatePopupSizeAndPosition(rect, this.viewRect);
+            var point = MousePositionTransform.UpdatePopupSizeAndPosition(rect, viewRect);
 
             Canvas.SetLeft(popupImage, point.X);
             Canvas.SetTop(popupImage, point.Y);
@@ -2295,8 +2288,8 @@ protected override void OnMouseMove(MouseEventArgs e)
                 var point = e.GetPosition(this);
                 var modifiers = e.GetModifiers();
 
-                var adjustedPoint = mouseAdjustor.GetAdjustedMouseCoords(point);
-                browser.GetHost().SendMouseMoveEvent(adjustedPoint.X, adjustedPoint.Y, false, modifiers);
+                MousePositionTransform.TransformMousePoint(ref point);
+                browser.GetHost().SendMouseMoveEvent((int)point.X, (int)point.Y, false, modifiers);
             }
 
             base.OnMouseMove(e);
@@ -2313,11 +2306,11 @@ protected override void OnMouseWheel(MouseWheelEventArgs e)
                 var point = e.GetPosition(this);
                 var modifiers = e.GetModifiers();
                 var isShiftKeyDown = Keyboard.IsKeyDown(Key.LeftShift) || Keyboard.IsKeyDown(Key.RightShift);
-                var adjustedPoint = mouseAdjustor.GetAdjustedMouseCoords(point);
+                MousePositionTransform.TransformMousePoint(ref point);
 
                 browser.SendMouseWheelEvent(
-                    adjustedPoint.X,
-                    adjustedPoint.Y,
+                    (int)point.X,
+                    (int)point.Y,
                     deltaX: isShiftKeyDown ? e.Delta : 0,
                     deltaY: !isShiftKeyDown ? e.Delta : 0,
                     modifiers: modifiers);
@@ -2467,11 +2460,9 @@ private void OnMouseButton(MouseButtonEventArgs e)
                     {
                         clickCount = 1;
                     }
-
 
-                    var adjustedPoint = mouseAdjustor.GetAdjustedMouseCoords(point);
-                    browser.GetHost().SendMouseClickEvent(adjustedPoint.X, adjustedPoint.Y, (MouseButtonType)e.ChangedButton, mouseUp, clickCount, modifiers);
-                    // browser.GetHost().SendMouseClickEvent(mouseTeleport.originalRect.X + mouseTeleport.originalRect.Width, (int)point.Y, (MouseButtonType)e.ChangedButton, mouseUp, clickCount, modifiers);
+                    MousePositionTransform.TransformMousePoint(ref point);
+                    browser.GetHost().SendMouseClickEvent((int)point.X, (int)point.Y, (MouseButtonType)e.ChangedButton, mouseUp, clickCount, modifiers);
                 }
 
                 e.Handled = true;

CefSharp.Wpf/Experimental/ExperimentalExtensions.cs

@@ -0,0 +1,12 @@
+using CefSharp.Wpf.Internals;
+
+namespace CefSharp.Wpf.Experimental
+{
+    public static class ExperimentalExtensions
+    {
+        public static void UsePopupMouseTransform(this ChromiumWebBrowser chromiumWebBrowser)
+        {
+            chromiumWebBrowser.MousePositionTransform = new MousePositionTransform();
+        }
+    }
+}

CefSharp.Wpf/IMouseAdjustor.cs

@@ -0,0 +1,14 @@
+using CefSharp.Structs;
+
+namespace CefSharp.Wpf.Internals
+{
+    /// <summary>
+    /// Implement this interface to control transform the mouse position
+    /// </summary>
+    public interface IMousePositionTransform
+    {
+        System.Windows.Point UpdatePopupSizeAndPosition(Rect originalRect, Rect viewRect);
+        void OnPopupShow(bool isOpen);
+        void TransformMousePoint(ref System.Windows.Point point);
+    }
+}

CefSharp.Wpf/Internals/IMousePositionTransform.cs

@@ -2,28 +2,7 @@
 
 namespace CefSharp.Wpf.Internals
 {
-    public class NoMouseAdjustor : IMouseAdjustor
-    {
-        public virtual void Dispose()
-        {
-        }
-
-        public System.Windows.Point UpdatePopupSizeAndPosition(Rect originalRect, Rect viewRect)
-        {
-            return new System.Windows.Point(originalRect.X, originalRect.Y);
-        }
-
-        public void OnPopupShow(bool isOpen)
-        {
-        }
-
-        public Point GetAdjustedMouseCoords(System.Windows.Point point)
-        {
-            return new Point((int)point.X, (int)point.Y);
-        }
-    }
-
-    public class MouseAdjustor : IMouseAdjustor
+    public sealed class MousePositionTransform : IMousePositionTransform
     {
         /// <summary>
         /// The x-offset.
@@ -50,20 +29,13 @@ public class MouseAdjustor : IMouseAdjustor
         /// </summary>
         private bool isOpen;
 
-        /// <summary>
-        /// This method is required for the interface.
-        /// </summary>
-        public virtual void Dispose()
-        {
-        }
-
         /// <summary>
         /// Updates the size and the position of the popup.
         /// </summary>
         /// <param name="originalRect"></param>
         /// <param name="viewRect"></param>
         /// <returns>The adjusted point.</returns>
-        public System.Windows.Point UpdatePopupSizeAndPosition(Rect originalRect, Rect viewRect)
+        System.Windows.Point IMousePositionTransform.UpdatePopupSizeAndPosition(Rect originalRect, Rect viewRect)
         {
             int x = originalRect.X,
                 prevX = originalRect.X,
@@ -124,7 +96,7 @@ public System.Windows.Point UpdatePopupSizeAndPosition(Rect originalRect, Rect v
         /// Resets the offsets and original-rect.
         /// <param name="isOpen">If the popup is open or not.</param>
         /// </summary>
-        public void OnPopupShow(bool isOpen)
+        void IMousePositionTransform.OnPopupShow(bool isOpen)
         {
             if (!isOpen)
             {
@@ -142,16 +114,14 @@ public void OnPopupShow(bool isOpen)
         /// Adjusts the mouse-coordinates when the popup is visible.
         /// </summary>
         /// <param name="point">The original point.</param>
-        /// <returns>The adjusted point if needed, else the original point.</returns>
-        public Point GetAdjustedMouseCoords(System.Windows.Point point)
+        /// <returns>The transformed point if needed, else the original point.</returns>
+        void IMousePositionTransform.TransformMousePoint(ref System.Windows.Point point)
         {
-            if (!this.isOpen)
-                return new Point((int)point.X, (int)point.Y);
-
-            if (!this.IsInsideOriginalRect(point) && IsInsideAdjustedRect(point))
-                return new Point((int)point.X + this.xOffset, (int)point.Y + this.yOffset);
+            if (!isOpen)
+                return;
 
-            return new Point((int)point.X, (int)point.Y);
+            if (!IsInsideOriginalRect(point) && IsInsideAdjustedRect(point))
+                point = new System.Windows.Point((int)point.X + this.xOffset, (int)point.Y + this.yOffset);
         }
 
         /// <summary>

CefSharp.Wpf/Internals/MouseAdjustor.cs renamed to CefSharp.Wpf/Internals/MousePositionTransform.cs

@@ -0,0 +1,21 @@
+using CefSharp.Structs;
+
+namespace CefSharp.Wpf.Internals
+{
+    public sealed class NoOpMousePositionTransform : IMousePositionTransform
+    {
+        System.Windows.Point IMousePositionTransform.UpdatePopupSizeAndPosition(Rect originalRect, Rect viewRect)
+        {
+            return new System.Windows.Point(originalRect.X, originalRect.Y);
+        }
+
+        void IMousePositionTransform.OnPopupShow(bool isOpen)
+        {
+        }
+
+        void IMousePositionTransform.TransformMousePoint(ref System.Windows.Point point)
+        {
+            
+        }
+    }
+}