Pass FG rights to extensions when we access them (#38068)

Calling Win32 APIs from C# is usually easy! but mixing C#+WinRT+COM is dark and full of terrors

Closes zadjii-msft#546


Co-authored-by: Manodasan Wignarajah <[email protected]>

Author: zadjii-msft

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/ShellViewModel.cs

@@ -2,6 +2,8 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Runtime.InteropServices;
+using System.Runtime.Versioning;
 using CommunityToolkit.Common;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
@@ -13,7 +15,7 @@
 using Microsoft.CmdPal.UI.ViewModels.Models;
 using Microsoft.CommandPalette.Extensions;
 using Microsoft.Extensions.DependencyInjection;
-using Windows.Win32;
+using WinRT;
 
 namespace Microsoft.CmdPal.UI.ViewModels;
 
@@ -148,14 +150,16 @@ public void SetActiveExtension(IExtensionWrapper? extension)
             // need to handle that
             _activeExtension = extension;
 
-            var extensionComObject = _activeExtension?.GetExtensionObject();
-            if (extensionComObject != null)
+            var extensionWinRtObject = _activeExtension?.GetExtensionObject();
+            if (extensionWinRtObject != null)
             {
                 try
                 {
                     unsafe
                     {
-                        var hr = PInvoke.CoAllowSetForegroundWindow(extensionComObject);
+                        var winrtObj = (IWinRTObject)extensionWinRtObject;
+                        var intPtr = winrtObj.NativeObject.ThisPtr;
+                        var hr = Native.CoAllowSetForegroundWindow(intPtr);
                         if (hr != 0)
                         {
                             Logger.LogWarning($"Error giving foreground rights: 0x{hr.Value:X8}");
@@ -174,4 +178,18 @@ public void GoHome()
     {
         SetActiveExtension(null);
     }
+
+    // You may ask yourself, why aren't we using CsWin32 for this?
+    // The CsWin32 projected version includes some object marshalling, like so:
+    //
+    // HRESULT CoAllowSetForegroundWindow([MarshalAs(UnmanagedType.IUnknown)] object pUnk,...)
+    //
+    // And if you do it like that, then the IForegroundTransfer interface isn't marshalled correctly
+    internal sealed class Native
+    {
+        [DllImport("OLE32.dll", ExactSpelling = true)]
+        [DefaultDllImportSearchPaths(DllImportSearchPath.System32)]
+        [SupportedOSPlatform("windows5.0")]
+        internal static extern unsafe global::Windows.Win32.Foundation.HRESULT CoAllowSetForegroundWindow(nint pUnk, [Optional] void* lpvReserved);
+    }
 }

src/modules/cmdpal/Microsoft.CmdPal.UI/Pages/ShellPage.xaml.cs

@@ -130,14 +130,36 @@ private void PerformCommand(PerformCommandMessage message)
         // Or the command may be a stub. Future us problem.
         try
         {
+            // In the case that we're coming from a top-level command, the
+            // current page's host is the global instance. We only really want
+            // to use that as the host of last resort.
             var pageHost = ViewModel.CurrentPage?.ExtensionHost;
+            if (pageHost == CommandPaletteHost.Instance)
+            {
+                pageHost = null;
+            }
+
             var messageHost = message.ExtensionHost;
 
             // Use the host from the current page if it has one, else use the
             // one specified in the PerformMessage for a top-level command,
             // else just use the global one.
-            var host = pageHost ?? messageHost ?? CommandPaletteHost.Instance;
+            CommandPaletteHost host;
+
+            // Top level items can come through without a Extension set on the
+            // message. In that case, the `Context` is actually the
+            // TopLevelViewModel itself, and we can use that to get at the
+            // extension object.
             extension = pageHost?.Extension ?? messageHost?.Extension ?? null;
+            if (extension == null && message.Context is TopLevelViewModel topLevelViewModel)
+            {
+                extension = topLevelViewModel.ExtensionHost?.Extension;
+                host = pageHost ?? messageHost ?? topLevelViewModel?.ExtensionHost ?? CommandPaletteHost.Instance;
+            }
+            else
+            {
+                host = pageHost ?? messageHost ?? CommandPaletteHost.Instance;
+            }
 
             if (extension != null)
             {