ToAscii function (winuser.h)
Translates the specified virtual-key code and keyboard state to the corresponding character or characters. The function translates the code using the input language and physical keyboard layout identified by the keyboard layout handle.
To specify a handle to the keyboard layout to use to translate the specified code, use the ToAsciiEx function.
Note
This method may not work properly with some keyboard layouts that may produce multiple characters (i.e. ligatures) and/or supplementary Unicode characters on a single key press. It is highly recommended to use the ToUnicode or ToUnicodeEx methods that handles such cases properly.
Syntax
int ToAscii(
[in] UINT uVirtKey,
[in] UINT uScanCode,
[in, optional] const BYTE *lpKeyState,
[out] LPWORD lpChar,
[in] UINT uFlags
);
Parameters
[in] uVirtKey
Type: UINT
The virtual-key code to be translated. See Virtual-Key Codes.
[in] uScanCode
Type: UINT
The hardware scan code of the key to be translated. The high-order bit of this value is set if the key is up (not pressed).
[in, optional] lpKeyState
Type: const BYTE*
A pointer to a 256-byte array that contains the current keyboard state. Each element (byte) in the array contains the state of one key. If the high-order bit of a byte is set, the key is down (pressed).
The low bit, if set, indicates that the key is toggled on. In this function, only the toggle bit of the CAPS LOCK key is relevant. The toggle state of the NUM LOCK and SCROLL LOCK keys is ignored.
[out] lpChar
Type: LPWORD
A pointer to the buffer that receives the translated character (or two characters packed into a single WORD value, where the low-order byte contains the first character and the high-order byte contains the second character).
[in] uFlags
Type: UINT
This parameter must be 1 if a menu is active, or 0 otherwise.
Return value
Type: int
The return value is one of the following values.
| Return value | Description |
|---|---|
|
The specified virtual key has no translation for the current state of the keyboard. |
|
One character was copied to the buffer. |
|
Two characters were copied to the buffer. This usually happens when a dead-key character (accent or diacritic) stored in the keyboard layout cannot be composed with the specified virtual key to form a single character. |
Remarks
The parameters supplied to the ToAscii function might not be sufficient to translate the virtual-key code, because a previous dead key is stored in the keyboard layout.
Typically, ToAscii performs the translation based on the virtual-key code. In some cases, however, bit 15 of the uScanCode parameter may be used to distinguish between a key press and a key release. The scan code is used for translating ALT+ number key combinations.
Although NUM LOCK is a toggle key that affects keyboard behavior, ToAscii ignores the toggle setting (the low bit) of lpKeyState (VK_NUMLOCK) because the uVirtKey parameter alone is sufficient to distinguish the cursor movement keys (VK_HOME, VK_INSERT, and so on) from the numeric keys (VK_DECIMAL, VK_NUMPAD0 - VK_NUMPAD9).
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 2000 Professional [desktop apps only] |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Target Platform | Windows |
| Header | winuser.h (include Windows.h) |
| Library | User32.lib |
| DLL | User32.dll |
See also
Conceptual
Reference