Applications decode WM_CHAR messages by examining individual bits in the flag word contained in the first message parameter (mp1) that the system passes with every WM_CHAR message. The type of flag word indicates the nature of the message. The system can set the bits in the flag word in various combinations. For example, a WM_CHAR message can have the KC_CHAR, KC_SCANCODE, and KC_SHIFT attribute bits all set at the same time. An application can use the following list of flag values to test the flag word and determine the nature of a WM_CHAR message:
旼컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿑lag Name 쿏escription � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_ALT 쿔ndicates that the Alt key was down when the � � 쿺essage was generated. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_CHAR 쿔ndicates that the message contains a valid � � 쿬haracter code for a key, typically an ASCII � � 쿬haracter code. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_COMPOSITE 쿔n combination with the KC_CHAR flag, this � � 쿯lag indicates that the character code is a � � 쿬ombination of the key that was pressed and � � 퀃he previous dead key. This flag is used to � � 쿬reate characters with diacritical marks. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_CTRL 쿔ndicates that the Ctrl key was down when the� � 쿺essage was generated. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_DEADKEY 쿔n combination with the KC_CHAR flag, this � � 쿯lag indicates that the character code � � 퀁epresents a dead-key glyph (such as an � � 쿪ccent). An application displays the � � 쿭ead-key glyph and does not advance the � � 쿬ursor. Typically, the next WM_CHAR message � � 쿶s a KC_COMPOSITE message, containing the � � 쿲lyph associated with the dead key. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_INVALIDCHAR 쿔ndicates that the character is not valid for� � 퀃he current translation tables. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_INVALIDCOMP 쿔ndicates that the character code is not � � 퀆alid in combination with the previous dead � � 쿸ey. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_KEYUP 쿔ndicates that the message was generated when� � 퀃he user released the key. If this flag is � � 쿬lear, the message was generated when the � � 퀅ser pressed the key. An application can use� � 퀃his flag to determine key-down and key-up � � 쿮vents. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_LONEKEY 쿔n combination with the KC_KEYUP flag, this � � 쿯lag indicates that the user pressed no other� � 쿸ey while this key was down. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_PREVDOWN 쿔n combination with the KC_VIRTUALKEY flag, � � 퀃his flag indicates that the virtual key was � � 쿾ressed previously. If this flag is clear, � � 퀃he virtual key was not previously pressed. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_SCANCODE 쿔ndicates that the message contains a valid � � 퀂can code generated by the keyboard when the � � 퀅ser pressed the key. The system uses the � � 퀂can code to identify the character code in � � 퀃he current code page; therefore, most � � 쿪pplications do not need the scan code unless� � 퀃hey cannot identify the key that the user � � 쿾ressed. WM_CHAR messages generated by user � � 쿸eyboard input generally have a valid scan � � 쿬ode, but WM_CHAR messages posted to the � � 쿿ueue by other applications might not contain� � 쿪 scan code. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_SHIFT 쿔ndicates that the Shift key was down when � � 퀃he message was generated. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_TOGGLE 쿟oggles on and off every time the user � � 쿾resses a specified key. This is important � � 쿯or keys like NumLock, which have an on or � � 쿽ff state. � 쳐컴컴컴컴컴컴컴탠컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿖C_VIRTUALKEY 쿔ndicates that the message contains a valid � � 퀆irtual-key code for a key. Virtual keys � � 퀃ypically correspond to function keys. � � 쿑or those using hooks, when this bit is set, � � 쿖C_SCANCODE should usually be set as well. � 읕컴컴컴컴컴컴컴좔컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
The mp1 and mp2 parameters of the WM_CHAR message contain information describing the nature of a keyboard input event, as follows:
An application window procedure should return TRUE if it processes a particular WM_CHAR message or FALSE if it does not. Typically, applications respond to key-down events and ignore key-up events.
The following sections describe the different types of WM_CHAR messages. Generally, an application decodes these messages by creating layers of conditional statements that discriminate among the different combinations of flag and code attributes that can occur in a keyboard message.