Add UnhandledKeyPressed.md

specs/UnhandledKeyPressed.md

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+
+# Background
+Consumers of the old [WebBrowser](https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.webbrowser?view=windowsdesktop-7.0) control that relied on the [OnKeyDown](https://learn.microsoft.com/previous-versions/aa752133(v=vs.85)) API that allowed them to receive and handle key events not handled by the browser, [requested](https://github.com/MicrosoftEdge/WebViewFeedback/issues/468) same ability in WebView2. 
+
+# Description
+The `UnhandledKeyPressed` event allows developers to subscribe event handlers to be run when a key event is not handled by the browser (including DOM and browser accelerators).
+
+`UnhandledKeyPressed` event can be triggered by all keys, which is different from [AcceleratorKeyPressed](https://learn.microsoft.com/en-us/dotnet/api/microsoft.web.webview2.core.corewebview2acceleratorkeypressedeventargs?view=webview2-dotnet-1.0.705.50) event.
+
+`UnhandledKeyPressed` event is async, which means [GetKeyState](https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getkeystate) does not return the exact key state when the key event is fired. Use `UnhandledKeyPressedEventArgs.Modifiers` instead to verify whether Ctrl or Alt is down in this situation.
+
+# Examples
+## C++
+
+```cpp
+auto controller5 = m_controller.try_query<ICoreWebView2Controller5>();
+if (controller5)
+{
+    CHECK_FAILURE(controller5->add_UnhandledKeyPressed(
+        Callback<ICoreWebView2UnhandledKeyPressedEventHandler>(
+            [this](
+                ICoreWebView2Controller* sender,
+                ICoreWebView2UnhandledKeyPressedEventArgs* args) -> HRESULT
+            {
+                COREWEBVIEW2_KEY_EVENT_KIND kind;
+                CHECK_FAILURE(args->get_KeyEventKind(&kind));
+
+                // We only care about key down events.
+                if (kind == COREWEBVIEW2_KEY_EVENT_KIND_KEY_DOWN ||
+                    kind == COREWEBVIEW2_KEY_EVENT_KIND_SYSTEM_KEY_DOWN)
+                {
+                    COREWEBVIEW2_KEY_PRESSED_FLAG_KIND flag;
+                    CHECK_FAILURE(args->get_Modifiers(&flag));
+                    if (flag & COREWEBVIEW2_KEY_EVENT_FLAG_CONTROL_DOWN)
+                    {
+                        UINT key;
+                        CHECK_FAILURE(args->get_VirtualKey(&key));
+                        // Check if the key is one we want to handle.
+                        if (key == 'Z')
+                        {
+                            MessageBox(
+                                nullptr,
+                                L"Key combination Ctrl + Z unhandled by browser is "
+                                L"triggered.",
+                                L"", MB_OK);
+                        }
+                        else if (key >= 'A' && key <= 'Z')
+                        {
+                            OutputDebugString((std::wstring(L"Ctrl +") + (wchar_t)key +
+                                                L" not handled by browser is triggered.")
+                                                  .c_str());
+                        }
+                    }
+                }
+                return S_OK;
+            })
+            .Get(),
+        &m_unhandledKeyPressedToken));
+}
+```
+
+## C#
+
+```csharp
+private CoreWebView2Controller controller;
+void RegisterKeyEventHandlers()
+{
+    if (controller != null)
+    {
+        controller.UnhandledKeyPressed += CoreWebView2Controller_UnhandledKeyPressed;
+    }
+}
+void CoreWebView2Controller_UnhandledKeyPressed(object sender, CoreWebView2UnhandledKeyPressedEventArgs e)
+{
+    if ((e.KeyEventKind == CoreWebView2KeyEventKind.KeyDown) && (e.Modifiers & CoreWebView2KeyPressedFlagKind.CoreWebView2KeyEventFlagControlDown) != 0)
+    {
+        if (e.VirtualKey == 'z')
+        {
+            Debug.WriteLine($"Key combination Ctrl + Z unhandled by browser is triggered.");
+        }
+    }
+}
+```
+
+# API Details
+
+## Win32 C++
+```idl
+[uuid(053b9a5d-7033-4515-9898-912977d2fde8), object, pointer_default(unique)]
+interface ICoreWebView2Controller : IUnknown {
+  /// Adds an event handler for the `UnhandledKeyPressed` event.
+  /// `UnhandledKeyPressed` runs when an key is not handled in
+  /// the DOM.
+
+  HRESULT add_UnhandledKeyPressed(
+    [in] ICoreWebView2UnhandledKeyPressedEventHandler* eventHandler,
+    [out] EventRegistrationToken* token);
+
+  /// Removes an event handler previously added with
+  /// `add_UnhandledKeyPressed`.
+
+  HRESULT remove_UnhandledKeyPressed(
+    [in] EventRegistrationToken token);
+}
+
+[uuid(dc83113b-ce7a-47bb-9661-16b03ff8aac1), object, pointer_default(unique)]
+interface ICoreWebView2UnhandledKeyPressedEventHandler : IUnknown {
+
+  /// Provides the event args for the corresponding event.
+
+  HRESULT Invoke(
+      [in] ICoreWebView2Controller* sender,
+      [in] ICoreWebView2UnhandledKeyPressedEventArgs* args);
+}
+
+[uuid(dd30e20c-d1b3-4e51-9bb6-1be7aaa3ce90), object, pointer_default(unique)]
+interface ICoreWebView2UnhandledKeyPressedEventArgs : IUnknown {
+
+  /// The key event type that caused the event to run.
+
+  [propget] HRESULT KeyEventKind([out, retval] COREWEBVIEW2_KEY_EVENT_KIND* keyEventKind);
+
+  /// The Win32 virtual key code of the key that was pressed or released.  It
+  /// is one of the Win32 virtual key constants such as `VK_RETURN` or an
+  /// (uppercase) ASCII value such as `A`.
+  /// use ICoreWebView2UnhandledKeyPressedEventArgs::get_Modifiers()
+  /// instead of Win32 API ::GetKeyState() to verify whether Ctrl or Alt
+  /// is pressed.
+
+  [propget] HRESULT VirtualKey([out, retval] UINT* virtualKey);
+
+  /// The `LPARAM` value that accompanied the window message.  For more
+  /// information, navigate to [WM_KEYDOWN](/windows/win32/inputdev/wm-keydown)
+  /// and [WM_KEYUP](/windows/win32/inputdev/wm-keyup).
+  /// For visual hosting, only scan code and extended key (16-24bit) are provided.
+  /// For other bits, check out the origin message from ::GetMessage().
+
+  [propget] HRESULT KeyEventLParam([out, retval] INT* lParam);
+
+  /// A structure representing the information passed in the `LPARAM` of the
+  /// window message.
+
+  [propget] HRESULT PhysicalKeyStatus(
+      [out, retval] COREWEBVIEW2_PHYSICAL_KEY_STATUS* physicalKeyStatus);
+
+  /// The `Handled` property will not influence the future WebView
+  /// action. It can be used with other UnhandledKeyPressed
+  /// Event handlers.
+
+  [propget] HRESULT Handled([out, retval] BOOL* handled);
+
+  /// Sets the `Handled` property.
+
+  [propput] HRESULT Handled([in] BOOL handled);
+
+  /// Retrieves the status of the keyboard when the key event is triggered.
+  /// Use this instead of ::GetKeyState().
+  /// See COREWEBVIEW2_KEY_PRESSED_FLAG_KIND for details.
+  [propget] HRESULT Modifiers([out, retval] COREWEBVIEW2_KEY_PRESSED_FLAG_KIND* modifiers);
+}
+
+/// Flag bits representing the state of keyboard when a "UnhandledKeyPressed" Event happens.
+[v1_enum]
+typedef enum COREWEBVIEW2_KEY_PRESSED_FLAG_KIND {
+
+  /// No additional keys pressed.
+  COREWEBVIEW2_KEY_EVENT_FLAG_NONE = 0,
+
+  /// SHIFT is down, VK_SHIFT.
+  COREWEBVIEW2_KEY_EVENT_FLAG_SHIFT_DOWN = 1 << 1,
+
+  /// Control is down, VK_CONTROL.
+  COREWEBVIEW2_KEY_EVENT_FLAG_CONTROL_DOWN = 1 << 2,
+
+  /// ALT is down, VK_MENU. 
+  /// This bit is 0 when COREWEBVIEW2_KEY_EVENT_FLAG_ALTGR_DOWN bit is 1.
+  COREWEBVIEW2_KEY_EVENT_FLAG_ALT_DOWN = 1 << 3,
+
+  /// Windows key is down. VK_LWIN | VK_RWIN
+  COREWEBVIEW2_KEY_EVENT_FLAG_COMMAND_DOWN = 1 << 4,
+
+  /// Right ALT is down and AltGraph is enabled.
+  COREWEBVIEW2_KEY_EVENT_FLAG_ALTGR_DOWN = 1 << 6,
+
+  /// NUMLOCK is on. VK_NUMLOCK.
+  COREWEBVIEW2_KEY_EVENT_FLAG_NUM_LOCK_ON = 1 << 8,
+
+  /// CapsLock is on. VK_CAPITAL.
+  COREWEBVIEW2_KEY_EVENT_FLAG_CAPS_LOCK_ON = 1 << 9,
+
+  /// ScrollLock is On. VK_SCROLL.
+  COREWEBVIEW2_KEY_EVENT_FLAG_SCROLL_LOCK_ON = 1 << 10,
+} COREWEBVIEW2_KEY_PRESSED_FLAG_KIND;
+```
+
+## .NET and WinRT
+```c#
+namespace Microsoft.Web.WebView2.Core
+{
+    public class CoreWebView2Controller
+    {
+        event EventHandler<CoreWebView2UnhandledKeyPressedEventArgs> UnhandledKeyPressed;
+    }
+
+    /// Event args for the `CoreWebView2Controller.UnhandledKeyPressed` event.
+    runtimeclass CoreWebView2UnhandledKeyPressedEventArgs
+    {
+        CoreWebView2KeyEventKind KeyEventKind { get; };
+
+        uint VirtualKey { get; };
+
+        int KeyEventLParam { get; };
+
+        CoreWebView2PhysicalKeyStatus PhysicalKeyStatus { get; };
+
+        bool Handled { get; set; };
+
+        CoreWebView2KeyPressedFlagKind Modifiers { get; };
+    }
+
+    [Flags] enum CoreWebView2KeyPressedFlagKind
+    {
+        CoreWebView2KeyEventFlagNone = 0,
+        CoreWebView2KeyEventFlagShiftDown = 2,
+        CoreWebView2KeyEventFlagControlDown = 4,
+        CoreWebView2KeyEventFlagAltDown = 8,
+        CoreWebView2KeyEventFlagCommandDown = 16,
+        CoreWebView2KeyEventFlagAltgrDown = 64,
+        CoreWebView2KeyEventFlagNumLockOn = 256,
+        CoreWebView2KeyEventFlagCapsLockOn = 512,
+        CoreWebView2KeyEventFlagScrollLockOn = 1024,
+    }
+}
+```