[Feature]: Support the Kitty image protocol to show images

[stevenxxiu]

Feature description

Support the Kitty image protocol.

#2973 implements the Sixel image protocol, but this is a rather legacy protocol. Many programs now only support the Kitty image protocol to show images. Terminal emulators too, like Ghostty.

Additional information

Per https://sw.kovidgoyal.net/kitty/graphics-protocol/, terminal emulators with support include:

• Ghostty
• Konsole
• st (with a patch)
• Warp
• wayst
• WezTerm
• iTerm2
• xterm.js

[robertkirkman]

I agree that since iTerm2, Kitty and Konsole all support the Kitty image protocol, having Kitty image protocol in Termux would be ok, but if any any image support is merged, I believe that Sixel image protocol should be merged first, with Kitty image protocol as a possibility for the future, and not something that should be merged first. I will explain my reasoning for holding that opinion.

Kitty is a high performance image protocol optimized for modern terminals. It is performant enough that it supports animated video playback and even real time framebuffer rendering in the terminal at a high framerate, and a nice demo of that is this project, glkitty https://github.com/larkmjc/glkitty which is a port of the glxgears program to the kitty image protocol.

Kitty has an opinionated lead developer who makes sure to focus on making Kitty not just a good terminal, but a leading terminal that pushes the terminal ecosystem into the future. For that reason,

• [RFC] Sixel support kovidgoyal/kitty#2511

the lead developer has explicitly chosen to implement only the Kitty image protocol and not Sixel in Kitty specifically because the Kitty image protocol is more performant and better-architected than Sixel. however, despite Kitty being my favorite and most used X11 terminal emulator (including on Termux within X11), I do not believe that Termux should follow Kitty's example of abandoning Sixel and prioritizing the Kitty protocol, and I will explain why.

Termux is not in the same role in the terminal ecosystem as Kitty. Kitty is competing directly with many other terminal emulators on desktop linux that are all moving forward at the same rate, and anyone who needs to use Sixel on desktop linux can simply open one of the dozen or more terminal emulators on desktop linux that do support Sixel, and get a near-identical usability experience with the addition of Sixel compatibility. Termux, on the other hand, is the only viable and popular native terminal emulator on Android, and anyone who wants to use a native terminal on Android and also have sixel basically has only a very limited range of options currently:

• Use a termux custom build that has Sixel support
• Use a terminal emulator that has a highly portable nested GUI with Sixel support nested inside of Termux and a GUI translation layer like
  • a web app (ttyd, code-server)
  • or an X11 server (VNC, Termux:X11)

many people avoid using X11 in Termux since they don't like it and find the interface clunky and the buttons tiny (I like X11, but I can definitely completely understand that, some people only use the default Termux terminal activity because they need an efficient, responsive touchscreen interface), and web apps are not optimal either, since I find that sometimes even just opening a web browser at the same time as termux on slow devices can slow things down, since web browsers are so heavy. (I believe that a simple WebView running in a standalone app rather than a full browser app GUI might be faster, but even if so, that's still a whole separate app to keep track of)

The main goal of Termux, the way I see it, is to bring as many legacy OS features and software that originated with desktop and server linux and unix to Android as possible that disappeared from the handheld computer platform when Android became the leading UNIX-like operating system in the world, where "legacy" means almost anything and everything that involves the use of a text terminal since that is what disappeared from the base system with Android, and this is a significantly broader and heavier responsibility than the responsibility of a project like Kitty. I believe personally that Sixel has significance for the fulfillment of Termux's responsibility to bring legacy features and software from Desktop Linux to Android, and that this significance outweighs, in this particular case, the downsides of adding code that introduces poorly-architected legacy systems and suffers from poor performance.

From a certain perspective, the entire Termux App is comprised of re-added bloat that was previously intentionally never added to Android to optimize it and clean up the codebase of userspace for Linux, and I believe that any perspective that Sixel should be kept out of Termux on similar grounds is probably dangerously close to that perspective.

[robertkirkman]

I know that nobody said that Sixel should not be added, so I am not accusing anyone of saying that, I just wanted to explain that I have a position that Sixel should probably be prioritized over Kitty in Termux, and explain my reason for believing that because I realize it might sound like a bad opinion so I wanted to justify it