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Update InputLanguage.cs #13925

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ef6d40f
Update InputLanguage.cs
DJm00n Oct 2, 2025
b0a78b1
Update InputLanguage.cs
DJm00n Oct 2, 2025
ad3f9bb
Update InputLanguage.cs
DJm00n Oct 2, 2025
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70 changes: 28 additions & 42 deletions src/System.Windows.Forms/System/Windows/Forms/Input/InputLanguage.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,24 @@ public string LayoutName
}
}

private static int FindKeyboardLayout(int specialId)
{
using RegistryKey? layouts = Registry.LocalMachine.OpenSubKey(KeyboardLayoutsRegistryPath);
if (layouts is null) return specialId;

foreach (string keyName in layouts.GetSubKeyNames())
{
using RegistryKey? subKey = layouts.OpenSubKey(keyName);
if (subKey?.GetValue("Layout Id") is string layoutId && Convert.ToInt32(layoutId, 16) == specialId)
{
Debug.Assert(keyName.Length == 8, $"unexpected key length in registry: {subKey.Name}");
return Convert.ToInt32(keyName, 16);
}
}

return specialId;
}

/// <summary>
/// Returns the
/// <see href="https://learn.microsoft.com/windows/win32/api/winuser/nf-winuser-getkeyboardlayoutnamew">
Expand All @@ -128,52 +146,20 @@ internal string LayoutId
{
// There is no good way to do this in Windows. GetKeyboardLayoutName does what we want, but only for the
// current input language; setting and resetting the current input language would generate spurious
// InputLanguageChanged events. Try to extract needed information manually.
// InputLanguageChanged events. Try to extract needed information manually from HKL.
int langId = PARAM.LOWORD(_handle);

// High word of HKL contains a device handle to the physical layout of the keyboard but exact format of this
// handle is not documented. For older keyboard layouts device handle seems contains keyboard layout
// identifier.
int device = PARAM.HIWORD(_handle);

// But for newer keyboard layouts device handle contains special layout id if its high nibble is 0xF. This
// id may be used to search for keyboard layout under registry.
//
// NOTE: this logic may break in future versions of Windows since it is not documented.
if ((device & 0xF000) == 0xF000)
{
// Extract special layout id from the device handle
int layoutId = device & 0x0FFF;
// handle is not documented. For older keyboard layouts device handle contains keyboard layout identifier.
// But for newer keyboard layouts device handle contains special layout identifier if its high nibble is 0xF.
// This identifier may be used to search for keyboard layout under registry.
int deviceId = PARAM.HIWORD(_handle);

using RegistryKey? key = Registry.LocalMachine.OpenSubKey(KeyboardLayoutsRegistryPath);
if (key is not null)
{
// Match keyboard layout by layout id
foreach (string subKeyName in key.GetSubKeyNames())
{
using RegistryKey? subKey = key.OpenSubKey(subKeyName);
if (subKey is not null
&& subKey.GetValue("Layout Id") is string subKeyLayoutId
&& Convert.ToInt32(subKeyLayoutId, 16) == layoutId)
{
Debug.Assert(subKeyName.Length == 8, $"unexpected key length in registry: {subKey.Name}");
return subKeyName.ToUpperInvariant();
}
}
}
}
else
{
// Use input language only if keyboard layout language is not available. This is crucial in cases when
// keyboard is installed more than once or under different languages. For example when French keyboard
// is installed under US input language we need to return French keyboard identifier.
if (device == 0)
{
// According to the GetKeyboardLayout API function docs low word of HKL contains input language.
device = PARAM.LOWORD(_handle);
}
}
int layoutId = (deviceId & 0xF000) == 0xF000
? FindKeyboardLayout(deviceId & 0x0FFF)
: (deviceId != 0 ? deviceId : langId);

return device.ToString("X8");
return layoutId.ToString("X8");
}
}

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