The character code of the key.
The repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following 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.
An application should return zero if it processes this message.
The WM_CHAR message uses Unicode Transformation Format (UTF)-16.
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_CHAR 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.
The WM_UNICHAR message is the same as WM_CHAR, except it uses UTF-32. It is designed to send or post Unicode characters to ANSI windows, and it can handle Unicode Supplementary Plane characters.
Minimum supported client
|Windows 2000 Professional [desktop apps only]|
Minimum supported server
|Windows 2000 Server [desktop apps only]|