cl-regis

ReGIS in Common Lisp

⚠️ work in progress 🚧

This is for now a prototype only inspired by https://github.com/feilipu/ReGIS.

Citing from the VT330/VT340 Graphics Programming Manual¹:

ReGIS is a graphics instruction set from Digital². ReGIS provides a set of commands you can use to draw images on the screen.

Of course, those terminals are hardly in use today, however, there still are some terminal emulations that support ReGIS graphics. Besides some commercial ones, we are only aware of good old XTerm, however, it must be compiled with --enable-regis-graphics contrary to Sixel³ support which is enabled by default. This is, however, no big deal (see below).

More info about ReGIS

• https://en.wikipedia.org/wiki/ReGIS
• http://www.sizecoding.org/wiki/ReGIS
• https://vt100.net/docs/vt3xx-gp/chapter1.html
• https://en.wikipedia.org/wiki/VT320

Compiling xterm with ReGIS support

Borrowed from https://github.com/feilipu/ReGIS:

$ sudo apt install -y libxaw7-dev libncurses-dev libxft-dev
$ wget https://invisible-island.net/datafiles/release/xterm.tar.gz
$ tar xf xterm.tar.gz
$ cd xterm-392
$ ./configure --enable-regis-graphics
$ make
$ sudo make install

Although ReGIS, short for Remote Graphic Instruction Set, we will not use an USART but rather print directly to the screen with (format ...).

Testing

We will try the following two examples:

The string from https://github.com/feilipu/ReGIS:

(defvar regis-ex1 (concatenate 'string
"S(E)W(I(M))P[600,200]V[][-200,+200]V[][400,100]W(I(G))P[700,100]"
"V(B)[+050,][,+050][-050,](E)V(W(S1))(B)[-100,][,-050][+100,](E)V(W(S1,E))"
"(B)[-050,][,-025][+050,](E)W(I(C))P[200,100]C(A-180)[+100]C(A+180)[+050]"
"W(I(B))P[200,300]C(W(S1))[+100]C(W(S1,E))[+050]W(I(W))T(S02)\"hello world\""))

and the sample from Wikipedia https://en.wikipedia.org/wiki/ReGIS:

(defvar regis-ex2 
"S(E)(C1)P[100,440]V(B),[+100,+0],[+0,-10],[-100,+0],(E)P[500,300],F(C[+100])")

Note that the begin and end control sequences were removed. Those have to be added, as can be seen from the following code that is used for the examples:

(defun rbeg () (format t "~C~C~C~C" #\Esc #\P #\1 #\p))
(defun rend () (format t "~C~C" #\Esc #\\))

(defun ex1 ()
  (progn (rbeg)(format t "~A" regis-ex1)(rend)))

(defun ex2 ()
  (progn (rbeg)(format t "~A" regis-ex2)(rend)))

Running (ex1):

Running (ex2):

Goals

Mapping the instruction set in a KISS manner to CL and likely to interface with some great libraries like VECTO⁴, CL-VECTORS⁵ and so on.

📅

Footnotes

1. http://bitsavers.trailing-edge.com/pdf/dec/terminal/vt340/EK-VT3XX-GP-001_VT330_VT340_Graphics_Programming_Mar87.pdf ↩

2. https://en.wikipedia.org/wiki/Digital_Equipment_Corporation ↩

3. https://github.com/nilqed/cl-sixel ↩

4. https://www.xach.com/lisp/vecto/ ↩

5. https://projects.tuxee.net/cl-vectors/ ↩