WM_DEADCHAR
chDeadKey = wParam; /* dead-key character */
dwKeyData = (DWORD) lParam; /* key data */The WM_DEADCHAR message is sent when a WM_KEYUP message and a WM_KEYDOWN message are translated. It specifies the character value of a dead key. A dead key is a key, such as the umlaut (double-dot) character, that is combined with other characters to form a composite character. For example, the umlaut-O character consists of the dead key, umlaut, and the O key.
chDeadKey
Value of wParam. Specifies the dead-key character value.
dwKeyData
Value of lParam. Specifies the repeat count, scan code, extended key, context code, previous key state, and key-transition state, as shown in the following table:
| Bit | Description |
| 0–15 | Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user holding down the key. |
| 16–23 | Specifies the scan code. The value depends on the original equipment manufacturer (OEM). |
| 24 | Specifies whether the key is an extended key, such as a function key or a key on the numeric keypad. The value is 1 if it is an extended key; otherwise, it is 0. |
| 25–26 | Not used. |
| 27–28 | Used internally by Windows. |
| 29 | Specifies 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 | Specifies 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 | Specifies the key-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.
An application typically uses the WM_DEADCHAR message to give the user feedback about each key pressed. For example, an application can display the accent in the current character position without moving the caret.
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 dwKeyData parameter is usually not useful to applications. The information in the high-order word applies only to the most recent WM_KEYUP or WM_KEYDOWN message that precedes the posting of the character message.
For IBM Enhanced 101- and 102-key keyboards, enhanced keys are the right ALT key and the right CTRL key 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 division (/) and ENTER keys on the numeric keypad. Some other keyboards may support the extended-key bit in the dwKeyData parameter.