It begins with them, but ends with me. Their son, Vaxis

Vaxis is a Terminal User Interface (TUI) library for go. Vaxis supports modern terminal features, such as styled underlines and graphics. A widgets package is provided with some useful widgets.

Vaxis is blazingly fast at rendering. It might not be as fast or efficient as notcurses, but significant profiling has been done to reduce all render bottlenecks while still maintaining the feature-set.

All input parsing is done using a real terminal parser, based on the excellent state machine by Paul Flo Williams. Some modifications have been made to allow for proper SGR parsing (':' separated sub-parameters)

Vaxis does not use terminfo. Support for features is detected through terminal queries. Vaxis assumes xterm-style escape codes everywhere else.

Contributions are welcome.

package main

import "go.rockorager.dev/vaxis"

func main() {
	vx, err := vaxis.New(vaxis.Options{})
	if err != nil {
		panic(err)
	}
	defer vx.Close()
	for ev := range vx.Events() {
		switch ev := ev.(type) {
		case vaxis.Key:
			switch ev.String() {
			case "Ctrl+c":
				return
			}
		}
		win := vx.Window()
		win.Clear()
		win.Print(vaxis.Segment{Text: "Hello, World!"})
		vx.Render()
	}
}

By default Vaxis enters the alternate screen. For applications that should leave output in the shell scrollback, create Vaxis with PrimaryScreen. In this mode Window is the live region, and Append, AppendString, or AppendWriter queue output to be written before that live region on the next Render.

vx, err := vaxis.New(vaxis.Options{
	PrimaryScreen: &vaxis.PrimaryScreenOptions{RegionHeight: 1},
})
if err != nil {
	panic(err)
}
defer vx.Close()

vx.AppendString("command output\n")
win := vx.Window()
win.Clear()
win.Print(vaxis.Segment{Text: "status: running"})
vx.Render()

The primary screen is owned by the terminal, so existing shell scrollback may reflow on resize. Vaxis repaints the live region after resize, but appended content remains normal terminal output.

The ui package can use the same mode. WithDynamicPrimaryScreen measures the root widget and resizes the live region to the widget's preferred height each frame:

err := ui.Run(root, ui.WithDynamicPrimaryScreen())

EventContext.AppendText and AppendTextLn append styled inline TextSpan values without doing widget layout, so the terminal can still wrap and reflow the text naturally. EventContext.AppendWidget can append a one-time rendered widget snapshot. It is useful for tables, status records, and other fixed layouts, but wrapped text is converted to hard line breaks at the current terminal width. Use AppendString, AppendWriter, AppendText, or AppendTextLn for prose or logs that should reflow naturally in terminal scrollback.

Questions are welcome in #vaxis on libera.chat, or on the mailing list.

Issues can be reported on the tracker.