Merge pull request #920 from rassilon/issue918

Fix #918 by adding extension method to cast from IntPtr to Int32

Author: rassilon

CefSharp.WinForms/Internals/ParentFormMessageInterceptor.cs

@@ -6,6 +6,7 @@
 using System.Drawing;
 using System.Runtime.InteropServices;
 using System.Windows.Forms;
+using CefSharp.Internals;
 
 namespace CefSharp.WinForms.Internals
 {
@@ -149,8 +150,14 @@ protected override void WndProc(ref Message m)
                 }
                 case NativeMethods.WM_MOVE:
                 {
-                    x = (m.LParam.ToInt32() & 0xffff);
-                    y = ((m.LParam.ToInt32() >> 16) & 0xffff);
+                    // Convert IntPtr into 32bit int safely without 
+                    // exceptions:
+                    int dwLParam = m.LParam.CastToInt32();
+
+                    // Extract coordinates from lo/hi word:
+                    x = dwLParam & 0xffff;
+                    y = (dwLParam >> 16) & 0xffff;
+
                     isMovingMessage = true;
                     break;
                 }

CefSharp/CefSharp.csproj

@@ -92,6 +92,7 @@
     <Compile Include="CefFileDialogMode.cs" />
     <Compile Include="DefaultResourceHandlerFactory.cs" />
     <Compile Include="IJavascriptCallback.cs" />
+    <Compile Include="Internals\IntPtrExtensions.cs" />
     <Compile Include="Internals\JavascriptCallbackProxy.cs" />
     <Compile Include="Internals\JavascriptCallback.cs" />
     <Compile Include="Internals\JavascriptCallbackEndpointBehavior.cs" />

CefSharp/Internals/IntPtrExtensions.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace CefSharp.Internals
+{
+    public static class IntPtrExtensions
+    {
+        /// <summary>
+        /// Do an unchecked conversion from IntPtr to int
+        /// so overflow exceptions don't get thrown.
+        /// </summary>
+        /// <param name="intPtr"></param>
+        /// <returns></returns>
+        public static int CastToInt32(this IntPtr intPtr)
+        {
+            return unchecked((int)intPtr.ToInt64());
+        }
+    }
+}