ToAscii

The ToAscii function translates the specified virtual-key code and keyboard state to the corresponding Windows character or characters. The function translates the code using the input language and physical keyboard layout identified by the given keyboard layout handle.

int ToAscii(

UINT uVirtKey,	// virtual-key code
UINT uScanCode,	// scan code
PBYTE lpKeyState,	// address of key-state array
LPWORD lpChar,	// buffer for translated key
UINT uFlags	// active-menu flag
);

Parameters

uVirtKey

Specifies the virtual-key code to be translated.

uScanCode

Specifies 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).

lpKeyState

Points 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.

lpChar

Points to the buffer that will receive the translated Windows character or characters.

uFlags

Specifies whether a menu is active. This parameter must be 1 if a menu is active, or 0 otherwise.

Return Values

If the specified key is a dead key, the return value is negative. Otherwise, it is one of the following values:

Value	Meaning
0	The specified virtual key has no translation for the current state of the keyboard.
	One Windows 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).

See Also

OemKeyScan, ToUnicode, VkKeyScan

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