lightweight variant (#1)

Reviewed-on: #1 Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>
2026-08-12 13:37:30 +00:00
parent a0d3098fe4
commit 55ac8e6556
147 changed files with 4055 additions and 2349 deletions
@@ -0,0 +1,85 @@
+using System.Runtime.InteropServices;
+
+namespace CursorLang.Core.Interop;
+
+/// <summary>
+/// Win32 API for reading the layout of the active application.
+/// </summary>
+internal static class KeyboardLayoutNative
+{
+    private const uint WmInputLangChangeRequest = 0x0050;
+
+    /// <summary>Take the next layout from the system list.</summary>
+    private static readonly IntPtr InputLangChangeForward = new(0x0002);
+
+    /// <summary>HKL_NEXT — the same request in the language of older Windows versions.</summary>
+    private static readonly IntPtr HklNext = new(1);
+
+    [DllImport("user32.dll")]
+    internal static extern IntPtr GetForegroundWindow();
+
+    [DllImport("user32.dll")]
+    private static extern uint GetWindowThreadProcessId(IntPtr hWnd, IntPtr lpdwProcessId);
+
+    [DllImport("user32.dll")]
+    private static extern IntPtr GetKeyboardLayout(uint idThread);
+
+    [DllImport("user32.dll")]
+    private static extern bool PostMessage(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
+
+    /// <summary>
+    /// The layout the user is currently typing with.
+    /// </summary>
+    internal static int GetActiveLocaleId() => GetLocaleIdOf(GetInputWindow());
+
+    /// <summary>
+    /// Asks the active application to switch to the next layout from the system list.
+    /// </summary>
+    /// <remarks>
+    /// Synthesizing a system shortcut such as Alt+Shift will not do: the user can
+    /// reassign it in the Windows settings or turn it off entirely. A request sent as
+    /// a message does not depend on those settings and works in another process.
+    /// </remarks>
+    internal static void RequestNextLayout()
+    {
+        IntPtr target = GetInputWindow();
+        if (target == IntPtr.Zero)
+        {
+            return;
+        }
+
+        // Both parameters mean the same thing: different Windows versions and different
+        // UI frameworks look either at the flag or at lParam
+        PostMessage(target, WmInputLangChangeRequest, InputLangChangeForward, HklNext);
+    }
+
+    /// <summary>
+    /// The window that owns keyboard input.
+    /// </summary>
+    /// <remarks>
+    /// We ask the window with keyboard focus rather than the foreground window: in
+    /// Windows 11 Notepad, the Start menu and other WinUI applications the input field
+    /// lives in a separate thread, and the layout changes only for that thread. For the
+    /// main window's thread it stays the same, and the switch goes unnoticed.
+    /// </remarks>
+    private static IntPtr GetInputWindow()
+    {
+        if (ForegroundInputNative.TryGetInfo(out ForegroundInputNative.GuiThreadInfo info) &&
+            info.hwndFocus != IntPtr.Zero)
+        {
+            return info.hwndFocus;
+        }
+
+        return GetForegroundWindow();
+    }
+
+    /// <summary>
+    /// The locale identifier for a window. In Windows the layout is bound to a thread,
+    /// so this reveals it for any application, not only for our own.
+    /// </summary>
+    internal static int GetLocaleIdOf(IntPtr hWnd)
+    {
+        uint threadId = GetWindowThreadProcessId(hWnd, IntPtr.Zero);
+        return (int)GetKeyboardLayout(threadId).ToInt64() & 0xFFFF;
+    }
+}