Keypress and what will happen then?

[deepzero]

or grabbed directly from the window's callback.

[|roe]

In K&R (ANSI) C you find an explanation about this in the following (adapted by me a bit) form:

Originally Posted by K&R

Before offering CR (Carriage Return) to the Operating System all your keystrokes will be stored in a buffer. Since each key is mapped in ASCII to a hexadecimal code, these values will be stored in the specified buffer before. The reason why it is easy to compare plain values to keystrokes (here it was about buffer['character'-0]). After hitting Enter (Carriage Return), the syscall will be triggered and the OS's kernel will perform it's task on the buffer, fetching the data and executing on it.

Something like that :-) So I guess for a keylogger, it will sit in between the Kernel and the Keyboard, grabbing data detected, or at least, hooking up to some specific functions/API that provide keypress data to it. The rest, is left to your imagination to do with this knowledge.

More (Linux topic):
[1] Keyboard generalities - http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-2.html
[2] Interrupt Handlers (Kernel specific) - http://www.tldp.org/LDP/lkmpg/2.4/html/x1210.html