Devlin Ihmacs

Devlin Ihmacs is an Emacs-like text editor implemented in Python 3. It aims to reproduce the look and feel of Emacs by implementing an editing model based on buffers and modes.

Check out the source code for the project here.

Features

• A curses based interface

• Multiple text buffers

• Familiar Emacs keybindings (if you’re familiar with Emacs keybindings)

• Select regions via point and mark (although the region is not highlighted)

• Markov chain based text generation (I couldn’t resist)

• Around 900 source lines of code of Python 3

Demonstrations

Video Presentation

General Demo

Markov Chain Text Generation

Installation

Dependencies

Devlin Ihmacs has no dependencies other than Python 3 (3.9 or later) and ncurses. All functionality is implemented through the Python curses bindings and regular expressions, both of which are included in the Python standard library. Most Linux and Unix distributions should have everything installed. If you are on Windows with WSL, Devlin Ihmacs should run.

If you are on native Windows, sorry, Python does not include the curses module. It might be possible to run with slight modifications using UniCurses, although this has not been tested.

Installation

1. Download an archive of the source or clone this repository. git clone https://github.com/olincollege/devlin-ihmacs.git

2. Change directory to the project root.

3. Run python ihmacs.py. You will be placed into a scratch buffer. You can exit by typing C-x C-c.

Usage

Keybindings

For those not familiar with Emacs style keybindings and notation, here’s a brief rundown.

A single keystroke looks something like this: C-x. The C- means the CONTROL key is being held down. M- means the META key is held down (a historical term, ALT is bound to META). So C-M-x means CONTROL, ALT, and x were pressed at the same time.

Editing commands have bindings to “keychords.” A keychord is a sequence of keystrokes. For example, the keychord C-x C-c binds do the command kill_ihmacs.

A brief note: the program you call a “terminal” is actually a “terminal emulator,” this is because it is emulating a piece of hardware made over 50 years ago. Because of this and the way the ncurses library handles input, there are some limitations on the keystrokes that are allowed. For example, RET, C-j, and C-m all send the same signal. C-i and TAB also send the same signal. Pressing ESC is a sort of “sticky-keys” version of meta. This is because M- combinations are indicated by sending an escape character.

And with that out of the way, here are the keybindings implemented in Devlin Ihmacs.

Keychord	Command	Description
Alphanumeric keys	self_insert_command	Insert the typed character
C-j/RET/C-m	newline	Insert a newline
DEL (backspace)	backwards_delete_char	Delete character before point
KEY_DC (delete)	delete_char	Delete character after point
C-d	delete_char	^
C-f	forward_char	More point (cursor) forward 1 char
KEY_RIGHT	forward_char	^
M-f	forward_word	Move point forward 1 word
C-b	backward_char	Move point backward 1 char
M-b	backward_word	Move point backward 1 word
C-n	next_line	Move point down 1 line
KEY_DOWN	next_line	^
C-p	previous_line	Move point up one line
KEY_UP	previous_line	^
C-a	move_beginning_of_line	Move point to start of line
KEY_HOME	move_beginning_of_line	^
C-e	move_end_of_line	Move point to end of line
KEY_END	move_end_of_line	^
C-v	scroll_up	Scroll text on screen up
KEY_NPAGE	scroll_up	^
M-v	scroll_down	Scroll text on screen down
KEY_PPAGE	scroll_down	^
C-k	kill_line	Kill (cut) text from point to end of line
C-y	yank	Yank (paste) latest entry in kill ring
C-SPC	set_mark_command	Set mark to location of point
C-x C-x	exchange_point_and_mark	Swap locations of point and mark
C-w	kill_region	Kill text between point and mark
M-w	kill_ring_save	Copy text between point and mark
M-DEL (backspace)	backward_kill_word	Kill from point to start of word
M-d	forward_kill_word	Kill from point to end of word
M-<	beginning_of_buffer	Move point to start of buffer
M->	end_of_buffer	Move point to end of buffer
C-c C-j	generate_sentence_from_buffer	Generate random sentence based on buffer text
C-x C-f	create_buffer	Create a new virtual buffer
C-x b	next_buffer	Switch to next virtual buffer
C-x C-b	previous_buffer	Switch to previous virtual buffer
C-x k	kill_buffer	Close active buffer
C-x C-c	kill_ihmacs	Close the editor

About Me

I am Devlin Ih. “Ih” is pronounced like the letter “E.” Thus, “Ihmacs” is pronounced exactly like “Emacs.”

I’m a student (CO 2025) at Olin College of Engineering in Needham Massachusetts.

Devlin Ihmacs was created as my final project for Software Design in Spring 2022.

Good talk.