Diving Into Linux Terminal Architecture pt. 1

Diving into Linux terminal architecture #

One of my current fixations is watching Togglebit’s Twitch stream where he works on his project Anathema. Anathema is a TUI graphics library, but it got me thinking of what actually goes on under the covers of a terminal. I dove into the rabbit hole that is the linux terminal and came out with even more questions. How does the operating system support terminals? Terminals are actually devices? There are terminals and pseudoterminals, how do they provide almost identical functionality?

As I go through cataloguing my information, I think the best way to catalogue knowledge is to do a actually implement a new TUI library. So here is my proposed design, admittedly overambitious.

Designing a new tui library in C #

Current Goals #

From most important to least important for me

NCurses/Curses independence #

• Perform screen manipulation without utilizing ncurses or curses
• Take advantage of some of the more modern rendering and display modes available on modern terminal emulators

Multiple Operation Modes #

• CLI mode: be able to embed graphics in a live scrolling application
• TUI mode: perform full non scrolling takeover the terminal UI, think of VIM, EMACS, tmux

Terminal Evaluation #

• Be able to analyze terminal features e.g.
  • color modes
  • cursor modes
  • screen size columns/rows
  • character set -> maybe through localization features
  • glyph support -> maybe through localization features

Multi Threading #

Be able to have multiple threads safely working within the same application. Likely the best way is to implement multi region

Primary targets #

Debian’s GNOME terminal, this is the default terminal that came with my Debian installation on

Later Targets #

In order from most likely to least likely

• Linux Virtual Consoles
• Kitty
• Other Linux Terminal Emulators at large
• Windows’ Linux style terminal emulator implementations
• Mac terminal emulator implementations, for lack of access to a Mac dev environment

Functional Goals #

• Provide a modern approach

Purpose #

The primary reason for this project is just for learning the inner workings of terminals in Linux. How virtual terminals and terminal emulators are related. The goal of this project will never be to become primetime contender to ncurses, there is already the awesome library by Nick Black notcurses

Secondary goals: #

• More learning of C: My main work currently consists of Java, Bash, some Go, and some other sysadmin-y tasks. I think being able to work on something that doesn’t feel like work is a bit liberating.

• Being able to excercise max control over a project. With deadlines and priorities ever changing in my current job I feel like a lot of compromises have to be made for the sake of meeting deadlines and accomadating client wants, regardless of impact to efficiency or complexity. With this project I hope to be able to exercise my decision making skills and take a less-compromises driven approach.

• Playing with the creation of a templating language for creating simple user interfaces

Inspirations #

anathema - the initial inspiration for this project, after going down the terminal rendering rabbit hole. notcurses - the primary contender as a C based replacement for ncurses

I promise I won’t cheat too much on these projects.