// Note: Sometimes single VKCode represents multiple chars, thus string.
// E.g. typing "^1" (notice that when pressing 1 the both characters appear,
// because of this behavior, "^" is called dead key)
/// <summary>
/// Convert VKCode to Unicode.
/// <remarks>isKeyDown is required for because of keyboard state inconsistencies!</remarks>
/// </summary>
/// <param name="vkCode">VKCode</param>
/// <param name="isKeyDown">Is the key down event?</param>
/// <returns>String representing single unicode character.</returns>
internal static string VkCodeToString(uint vkCode, bool isKeyDown)
{
// ToUnicodeEx needs StringBuilder, it populates that during execution.
var sbString = new StringBuilder(5);
var bKeyState = new byte[255];
bool bKeyStateStatus;
bool isDead = false;
// Gets the current windows window handle, threadID, processID
IntPtr currentHWnd = (IntPtr)DllUser32.GetForegroundWindow();//may be bag
uint currentWindowThreadId = DllUser32.GetWindowThreadProcessId(currentHWnd, out _);
// This programs Thread ID
uint thisProgramThreadId = DllUser32.GetCurrentThreadId();
// Attach to active thread so we can get that keyboard state
if (DllUser32.AttachThreadInput(thisProgramThreadId, currentWindowThreadId, true))
{
// Current state of the modifiers in keyboard
bKeyStateStatus = DllUser32.GetKeyboardState(bKeyState);
// Detach
DllUser32.AttachThreadInput(thisProgramThreadId, currentWindowThreadId, false);
}
else
{
// Could not attach, perhaps it is this process?
bKeyStateStatus = DllUser32.GetKeyboardState(bKeyState);
}
// On failure we return empty string.
if (!bKeyStateStatus)
{
return("");
}
// Gets the layout of keyboard
var hkl = DllUser32.GetKeyboardLayout(currentWindowThreadId);
// Maps the virtual keycode
uint lScanCode = DllUser32.MapVirtualKeyEx(vkCode, 0, hkl);
// Keyboard state goes inconsistent if this is not in place. In other words, we need to call above commands in UP events also.
if (!isKeyDown)
{
return("");
}
// Converts the VKCode to unicode
int relevantKeyCountInBuffer =
DllUser32.ToUnicodeEx(vkCode, lScanCode, bKeyState, sbString, sbString.Capacity, 0, hkl);
string ret = string.Empty;
switch (relevantKeyCountInBuffer)
{
// Dead keys (^,`...)
case -1:
isDead = true;
// We must clear the buffer because ToUnicodeEx messed it up, see below.
ClearKeyboardBuffer(vkCode, lScanCode, hkl);
break;
case 0:
break;
// Single character in buffer
case 1:
ret = sbString[0].ToString();
break;
// Two or more (only two of them is relevant)
default:
ret = sbString.ToString().Substring(0, 2);
break;
}
// We inject the last dead key back, since ToUnicodeEx removed it.
// More about this peculiar behavior see e.g:
// http://www.experts-exchange.com/Programming/System/Windows__Programming/Q_23453780.html
// http://blogs.msdn.com/michkap/archive/2005/01/19/355870.aspx
// http://blogs.msdn.com/michkap/archive/2007/10/27/5717859.aspx
if (_lastVkCode != 0 && _lastIsDead)
{
var sbTemp = new StringBuilder(5);
DllUser32.ToUnicodeEx(_lastVkCode, _lastScanCode, _lastKeyState, sbTemp, sbTemp.Capacity, 0, hkl);
_lastVkCode = 0;
return(ret);
}
// Save these
_lastScanCode = lScanCode;
_lastVkCode = vkCode;
_lastIsDead = isDead;
_lastKeyState = (byte[])bKeyState.Clone();
return(ret);
}