C / C++ / MFC

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WM_CHAR<br />
The WM_CHAR message is posted to the window with the keyboard focus when a WM_KEYDOWN message is translated by the TranslateMessage function. The WM_CHAR message contains the character code of the key that was pressed. <br />
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A window receives this message through its WindowProc function. <br />
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LRESULT CALLBACK WindowProc(<br />
  HWND hwnd,       // handle to window<br />
  UINT uMsg,       // WM_CHAR<br />
  WPARAM wParam,   // character code (TCHAR)<br />
  LPARAM lParam    // key data<br />
);<br />
Parameters<br />
wParam <br />
Specifies the character code of the key. <br />
lParam <br />
Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following table. Value Description <br />
0–15 Specifies 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. <br />
16–23 Specifies the scan code. The value depends on the original equipment manufacturer (OEM). <br />
24 Specifies 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. <br />
25–28 Reserved; do not use. <br />
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. <br />
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. <br />
31 Specifies the transition state. The value is 1 if the key is being released, or it is 0 if the key is being pressed. <br />
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Return Values<br />
An application should return zero if it processes this message. <br />
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Remarks<br />
The WM_CHAR message uses UTF-16. <br />
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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. <br />
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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<br />
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