This function is called before the OnKeyUp member function and after the OnKeyDown member function are called. OnChar contains the value of the keyboard key being pressed or released.
Because there is not necessarily a one-to-one correspondence between keys pressed and OnChar calls generated, the information in nFlags is generally not useful to applications. The information in nFlags applies only to the most recent call to the OnKeyUp member function or the OnKeyDown member function that precedes the call to OnChar.
For IBM Enhanced 101- and 102-key keyboards, enhanced 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 slash (/) and ENTER keys in the numeric keypad. Some other keyboards may support the extended-key bit in nFlags.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.