Which command handles keys used to edit text in a buffer?

Question

I have just (yesterday) installed emacs and am in the process of learning the very basics of its usage (I have never used emacs before, but I am maybe on the way to switch from SciTE and lua to emacs and elisp).

In between I mean to have already gained some basic understanding how emacs works under the hood and if I got it right there must be a lisp function there which is taking all keystrokes from user in order to dispatch them to other functions if the keystrokes are representing a keyboard shortcut or to the buffer if not, but was not able to find any information which one it is yet.

Is my understanding of how emacs handles user input the right one?

Or are the user input events (keystrokes, mouse action) sent by the OS to the emacs window dispatched by the emacs binary to the commands after being in a first stage internally evaluated by the binary, so there is no elisp script there which receives them all?

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UPDATE responding to comment by Drew:

I have started to read the recommended documentation https://www.gnu.org/software/emacs/manual/html_node/elisp/Command-Overview.html but if I understand it right there should be somewhere an elisp function read-key-sequence so I should be able to find it using:

~ $ locate read-key-sequence

or if this fails

~ $ grep "defun read-key-sequence" $(locate -b *.el)

but both of the above commands fail to find something.

Is this a hint that the read-key-sequence is hard coded in the emacs binary and not available as elisp code which with appropriate modification would be able to trigger an own elisp script receiving all the user input as it comes in?

Answer 1

You really should just ask a single question at a time, and not modify that question over time, but I want to address this part:

… but both of the above commands fail to find something.

Is this a hint that the read-key-sequence is hard coded in the emacs binary and not available as elisp code …

To find more information about a function that someone tells you about, use C-h f. It will prompt you for a function name, with autocompletion. If you put in read-key-sequence you will get a help buffer that says “read-key-sequence is a function defined in keyboard.c.”, and then goes on to describe the arguments it takes and to quote the documentation for it.

Note that the filename is always a link that you can click on to jump directly to the source code for the function; in this case it is a Lisp function which is defined directly in C. The C source code is not generally installed, so very likely this will prompt you again for the location of the source code. Just point it to a copy of the source code that you have downloaded or checked out from git.

To get back to your original question, the low–level keyboard handling is done in C, with different code for when Emacs is using a GUI toolkit like GTK or is inside of a terminal. There is a middle layer made of Lisp functions mostly written in C, like read-key-sequence and read-char, plus some Lisp variables like unread-command-events. There is a layer of Lisp code on top of that which implements Emacs’s built in Input Method Editors.