WM_UNICHAR message

The WM_UNICHAR message can be used by an application to post input to other windows. This message contains the character code of the key that was pressed. (Test whether a target app can process WM_UNICHAR messages by sending the message with wParam set to UNICODE_NOCHAR.)

#define WM_UNICHAR                      0x0109

wParam

The character code of the key.

If wParam is UNICODE_NOCHAR and the application processes this message, then return TRUE. The DefWindowProc function will return FALSE (the default).

If wParam is not UNICODE_NOCHAR, return FALSE. The Unicode DefWindowProc posts a WM_CHAR message with the same parameters and the ANSI DefWindowProc function posts either one or two WM_CHAR messages with the corresponding ANSI character(s).

lParam

The repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following table.

Expand table

Bits	Meaning
0-15	The repeat count for the current message. The value is the number of times the keystroke is autorepeated as a result of the user holding down the key. If the keystroke is held long enough, multiple messages are sent. However, the repeat count is not cumulative.
16-23	The scan code. The value depends on the OEM.
24	Indicates whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0.
25-28	Reserved; do not use.
29	The context code. The value is 1 if the ALT key is held down while the key is pressed; otherwise, the value is 0.
30	The previous key state. The value is 1 if the key is down before the message is sent, or it is 0 if the key is up.
31	The transition state. The value is 1 if the key is being released, or it is 0 if the key is being pressed.

For more detail, see Keystroke Message Flags.

An application should return zero if it processes this message.

The WM_UNICHAR message is similar to WM_CHAR, but it uses Unicode Transformation Format (UTF)-32, whereas WM_CHAR uses UTF-16.

This message is designed to send or post Unicode characters to ANSI windows and can handle Unicode Supplementary Plane characters.

Because there is not necessarily a one-to-one correspondence between keys pressed and character messages generated, the information in the high-order word of the lParam parameter is generally not useful to applications. The information in the high-order word applies only to the most recent WM_KEYDOWN message that precedes the posting of the WM_UNICHAR message.

For enhanced 101- and 102-key keyboards, extended keys are the right ALT and the right CTRL keys on the main section of the keyboard; the INS, DEL, HOME, END, PAGE UP, PAGE DOWN and arrow keys in the clusters to the left of the numeric keypad; and the divide (/) and ENTER keys in the numeric keypad. Some other keyboards may support the extended-key bit in the lParam parameter.

• TranslateMessage
• WM_CHAR
• WM_KEYDOWN
• Keyboard Input
• About Keyboard Input