Add ChromeWidgetMessageInterceptor to WinForms Example

CefSharp.WinForms.Example/BrowserTabUserControl.cs

@@ -1,5 +1,6 @@
 using CefSharp.Example;
 using System;
+using System.Runtime.InteropServices;
 using System.Windows.Forms;
 using CefSharp.WinForms.Internals;
 
@@ -100,9 +101,47 @@ private void SetIsLoading(bool isLoading)
             HandleToolStripLayout();
         }
 
+        [return: MarshalAs(UnmanagedType.Bool)]
+        [DllImport("user32.dll", SetLastError = true)]
+        static extern bool PostMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);
+
         private void OnIsBrowserInitializedChanged(object sender, IsBrowserInitializedChangedEventArgs args)
         {
-
+            if (args.IsBrowserInitialized)
+            {
+                ChromeWidgetMessageInterceptor.SetupLoop((ChromiumWebBrowser)Browser, (message) =>
+                {
+                    const int WM_MOUSEACTIVATE = 0x0021;
+                    const int WM_NCLBUTTONDOWN = 0x00A1;
+
+                    if (message.Msg == WM_MOUSEACTIVATE) {
+                        // The default processing of WM_MOUSEACTIVATE results in MA_NOACTIVATE,
+                        // and the subsequent mouse click is eaten by Chrome.
+                        // This means any .NET ToolStrip or ContextMenuStrip does not get closed.
+                        // By posting a WM_NCLBUTTONDOWN message to a harmless co-ordinate of the
+                        // top-level window, we rely on the ToolStripManager's message handling
+                        // to close any open dropdowns:
+                        // http://referencesource.microsoft.com/#System.Windows.Forms/winforms/Managed/System/WinForms/ToolStripManager.cs,1249
+                        var topLevelWindowHandle = message.WParam;
+                        PostMessage(topLevelWindowHandle, WM_NCLBUTTONDOWN, IntPtr.Zero, IntPtr.Zero);
+                    }
+
+                    // The ChromiumWebBrowserControl does not fire MouseEnter/Move/Leave events, because Chromium handles these.
+                    // However we can hook into Chromium's messaging window to receive the events.
+                    //
+                    //const int WM_MOUSEMOVE = 0x0200;
+                    //const int WM_MOUSELEAVE = 0x02A3;
+                    //
+                    //switch (message.Msg) {
+                    //    case WM_MOUSEMOVE:
+                    //        Console.WriteLine("WM_MOUSEMOVE");
+                    //        break;
+                    //    case WM_MOUSELEAVE:
+                    //        Console.WriteLine("WM_MOUSELEAVE");
+                    //        break;
+                    //}
+                });
+            }
         }
 
         public void ExecuteScript(string script)

CefSharp.WinForms.Example/CefSharp.WinForms.Example.csproj

@@ -77,6 +77,7 @@
     <Compile Include="BrowserTabUserControl.Designer.cs">
       <DependentUpon>BrowserTabUserControl.cs</DependentUpon>
     </Compile>
+    <Compile Include="ChromeWidgetMessageInterceptor.cs" />
     <Compile Include="GeolocationHandler.cs" />
     <Compile Include="KeyboardHandler.cs" />
     <Compile Include="MenuHandler.cs" />

CefSharp.WinForms.Example/ChromeWidgetMessageInterceptor.cs

@@ -0,0 +1,152 @@
+// Copyright © 2010-2015 The CefSharp Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
+
+using System;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Windows.Forms;
+
+namespace CefSharp.WinForms.Example
+{
+    /// <summary>
+    /// Intercepts Windows messages sent to the ChromiumWebBrowser control's widget sub-window.
+    /// 
+    /// It is necessary to listen to the widget sub-window because it receives all Windows messages
+    /// and forwards them to CEF, rather than the ChromiumWebBrowser.Handle.
+    /// 
+    /// The supplied Action delegate is fired upon each message.
+    /// </summary>
+    class ChromeWidgetMessageInterceptor : NativeWindow
+    {
+        private readonly ChromiumWebBrowser browser;
+        private Action<Message> forwardAction;
+
+        private ChromeWidgetMessageInterceptor(ChromiumWebBrowser browser, IntPtr chromeWidgetHostHandle, Action<Message> forwardAction)
+        {
+            AssignHandle(chromeWidgetHostHandle);
+
+            this.browser = browser;
+            browser.HandleDestroyed += BrowserHandleDestroyed;
+
+            this.forwardAction = forwardAction;
+        }
+
+        /// <summary>
+        /// Asynchronously wait for the Chromium widget window to be created for the given ChromiumWebBrowser,
+        /// and when created hook into its Windows message loop.
+        /// </summary>
+        /// <param name="browser">The browser to intercept Windows messages for.</param>
+        /// <param name="forwardAction">This action will be called whenever a Windows message is received.</param>
+        internal static void SetupLoop(ChromiumWebBrowser browser, Action<Message> forwardAction)
+        {
+            Task.Factory.StartNew(() =>
+            {
+                try
+                {
+                    bool foundWidget = false;
+                    while (!foundWidget)
+                    {
+                        browser.Invoke((Action)(() =>
+                        {
+                            IntPtr chromeWidgetHostHandle;
+                            if (ChromeWidgetHandleFinder.TryFindHandle(browser, out chromeWidgetHostHandle))
+                            {
+                                foundWidget = true;
+                                new ChromeWidgetMessageInterceptor(browser, chromeWidgetHostHandle, forwardAction);
+                            }
+                            else
+                            {
+                                // Chrome hasn't yet set up its message-loop window.
+                                Thread.Sleep(10);
+                            }
+                        }));
+                    }
+                }
+                catch
+                {
+                    // Errors are likely to occur if browser is disposed, and no good way to check from another thread
+                }
+            });
+        }
+
+        private void BrowserHandleDestroyed(object sender, EventArgs e)
+        {
+            ReleaseHandle();
+
+            browser.HandleDestroyed -= BrowserHandleDestroyed;
+            forwardAction = null;
+        }
+
+        protected override void WndProc(ref Message m)
+        {
+            base.WndProc(ref m);
+
+            if (forwardAction != null)
+            {
+                forwardAction(m);
+            }
+        }
+    }
+
+    class ChromeWidgetHandleFinder
+    {
+        private delegate bool EnumWindowProc(IntPtr hwnd, IntPtr lParam);
+
+        [DllImport("user32")]
+        [return: MarshalAs(UnmanagedType.Bool)]
+        private static extern bool EnumChildWindows(IntPtr window, EnumWindowProc callback, IntPtr lParam);
+
+        private readonly IntPtr mainHandle;
+        private string seekClassName;
+        private IntPtr descendantFound;
+
+        private ChromeWidgetHandleFinder(IntPtr handle)
+        {
+            this.mainHandle = handle;
+        }
+
+        private IntPtr FindDescendantByClassName(string className)
+        {
+            descendantFound = IntPtr.Zero;
+            seekClassName = className;
+
+            EnumWindowProc childProc = new EnumWindowProc(EnumWindow);
+            EnumChildWindows(this.mainHandle, childProc, IntPtr.Zero);
+
+            return descendantFound;
+        }
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        public static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount);
+
+        private bool EnumWindow(IntPtr hWnd, IntPtr lParam)
+        {
+            StringBuilder buffer = new StringBuilder(128);
+            GetClassName(hWnd, buffer, buffer.Capacity);
+
+            if (buffer.ToString() == seekClassName)
+            {
+                descendantFound = hWnd;
+                return false;
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Chrome's message-loop Window isn't created synchronously, so this may not find it.
+        /// If so, you need to wait and try again later.
+        /// </summary>
+        public static bool TryFindHandle(ChromiumWebBrowser browser, out IntPtr chromeWidgetHostHandle)
+        {
+            var browserHandle = browser.Handle;
+            var windowHandleInfo = new ChromeWidgetHandleFinder(browserHandle);
+            const string chromeWidgetHostClassName = "Chrome_RenderWidgetHostHWND";
+            chromeWidgetHostHandle = windowHandleInfo.FindDescendantByClassName(chromeWidgetHostClassName);
+            return chromeWidgetHostHandle != IntPtr.Zero;
+        }
+    }
+}