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