Fix focus not restored after Storage Pickers dialog closes

dev/Interop/StoragePickers/FileOpenPicker.cpp

@@ -128,6 +128,9 @@ namespace winrt::Microsoft::Windows::Storage::Pickers::implementation
 
         CaptureParameters(parameters);
 
+        // Capture focus on the UI thread so it can be restored after the dialog closes (issue #6505).
+        PickerCommon::DialogFocusRestorer focusRestorer{};
+
         auto cancellationToken = co_await winrt::get_cancellation_token();
         cancellationToken.enable_propagation(true);
         co_await winrt::resume_background();
@@ -176,6 +179,9 @@ namespace winrt::Microsoft::Windows::Storage::Pickers::implementation
 
         CaptureParameters(parameters);
 
+        // Capture focus on the UI thread so it can be restored after the dialog closes (issue #6505).
+        PickerCommon::DialogFocusRestorer focusRestorer{};
+
         auto cancellationToken = co_await winrt::get_cancellation_token();
         cancellationToken.enable_propagation(true);
         co_await winrt::resume_background();

dev/Interop/StoragePickers/FileSavePicker.cpp

@@ -154,6 +154,9 @@ namespace winrt::Microsoft::Windows::Storage::Pickers::implementation
 
         CaptureParameters(parameters);
 
+        // Capture focus on the UI thread so it can be restored after the dialog closes (issue #6505).
+        PickerCommon::DialogFocusRestorer focusRestorer{};
+
         auto defaultFileExtension = m_defaultFileExtension;
         auto suggestedFolder = m_suggestedFolder;
         auto suggestedFileName = m_suggestedFileName;

dev/Interop/StoragePickers/FolderPicker.cpp

@@ -104,7 +104,10 @@ namespace winrt::Microsoft::Windows::Storage::Pickers::implementation
 
         PickerCommon::PickerParameters parameters{};
         CaptureParameters(parameters);
-
+
+        // Capture focus on the UI thread so it can be restored after the dialog closes (issue #6505).
+        PickerCommon::DialogFocusRestorer focusRestorer{};
+
         auto cancellationToken = co_await winrt::get_cancellation_token();
         cancellationToken.enable_propagation(true);
         co_await winrt::resume_background();
@@ -164,7 +167,10 @@ namespace winrt::Microsoft::Windows::Storage::Pickers::implementation
 
         PickerCommon::PickerParameters parameters{};
         CaptureParameters(parameters);
-
+
+        // Capture focus on the UI thread so it can be restored after the dialog closes (issue #6505).
+        PickerCommon::DialogFocusRestorer focusRestorer{};
+
         auto cancellationToken = co_await winrt::get_cancellation_token();
         cancellationToken.enable_propagation(true);
         co_await winrt::resume_background();

dev/Interop/StoragePickers/ManualTests/README.md

@@ -77,3 +77,22 @@ else
 }
 ```
 Expect to print out all selected folders.
+
+### Keyboard focus is restored after the dialog closes
+Run from a WinUI 3 app with a button whose Click handler opens a picker. This applies to every pick
+method: `FileOpenPicker.PickSingleFileAsync` / `PickMultipleFilesAsync`, `FileSavePicker.PickSaveFileAsync`,
+and `FolderPicker.PickSingleFolderAsync` / `PickMultipleFoldersAsync`.
+
+Test code (C++), in the button's Click handler:
+```C++
+winrt::Microsoft::Windows::Storage::Pickers::FileOpenPicker picker{ AppWindow().Id() };
+co_await picker.PickSingleFileAsync();
+```
+
+1. Click the button. The file dialog opens.
+2. Pick a file and confirm. The dialog closes.
+3. Without touching the mouse, press Enter.
+
+    **Expected behavior - with the fix:** Enter re-invokes the button and the dialog reopens.
+
+    **Example of unexpected behavior - without the fix:** Enter does nothing.

dev/Interop/StoragePickers/PickerCommon.cpp

@@ -144,6 +144,27 @@ namespace {
 namespace PickerCommon {
     using namespace winrt;
 
+    DialogFocusRestorer::DialogFocusRestorer()
+    {
+        // Capture on the UI thread: GetFocus returns the focused window of the calling
+        // thread's message queue, which is the WinUI content island hosting the focused element.
+        m_focusedWindow = ::GetFocus();
+        m_dispatcherQueue = winrt::Microsoft::UI::Dispatching::DispatcherQueue::GetForCurrentThread();
+    }
+
+    DialogFocusRestorer::~DialogFocusRestorer()
+    {
+        if (m_focusedWindow && m_dispatcherQueue)
+        {
+            HWND focusedWindow = m_focusedWindow;
+            // Marshal back to the UI thread so SetFocus runs on the thread that owns the window.
+            m_dispatcherQueue.TryEnqueue([focusedWindow]()
+            {
+                ::SetFocus(focusedWindow);
+            });
+        }
+    }
+
     void CALLBACK WslNodeRevealer::PollTimerProc(HWND hwnd, UINT, UINT_PTR timerId, DWORD) noexcept
     {
         reinterpret_cast<WslNodeRevealer*>(timerId)->RevealWslNodeWhenReady(hwnd);

dev/Interop/StoragePickers/PickerCommon.h

@@ -8,6 +8,7 @@
 #include <winrt/Windows.Security.Cryptography.h>
 #include <winrt/Windows.Security.Cryptography.Core.h>
 #include <winrt/Microsoft.UI.Windowing.h>
+#include <winrt/Microsoft.UI.Dispatching.h>
 
 namespace PickerCommon {
     winrt::hstring GetPathFromShellItem(winrt::com_ptr<IShellItem> shellItem);
@@ -32,6 +33,27 @@ namespace PickerCommon {
     void ValidateFolderPath(winrt::hstring const& path, std::string const& propertyName);
     void ValidateInitialFileTypeIndex(int const& value);
 
+    // Restores keyboard focus to the WinUI window after a COM file dialog closes.
+    //
+    // These dialogs run on a background thread (winrt::resume_background), so the SetFocus they
+    // perform on close comes from a thread that does not own the window and is ignored, leaving the
+    // window unable to receive key presses until the user clicks it again (issue #6505).
+    //
+    // Construct this RAII helper on the UI thread before switching to the background thread: it
+    // captures the focused window at construction and, on destruction, marshals SetFocus back to
+    // the UI thread via its DispatcherQueue, restoring focus once the dialog has closed.
+    struct DialogFocusRestorer
+    {
+        DialogFocusRestorer();
+        ~DialogFocusRestorer();
+        DialogFocusRestorer(DialogFocusRestorer const&) = delete;
+        DialogFocusRestorer& operator=(DialogFocusRestorer const&) = delete;
+
+    private:
+        HWND m_focusedWindow{ nullptr };
+        winrt::Microsoft::UI::Dispatching::DispatcherQueue m_dispatcherQueue{ nullptr };
+    };
+
     // Shows the WSL node in the navigation pane of COM file dialogs that hide it by default.
     // The WSL node was hidden in FileSavePicker (IFileSaveDialog) and FolderPicker (IFileOpenDialog + FOS_PICKFOLDERS + FOS_FORCEFILESYSTEM);
     // It takes time for the navigation pane to load nodes.