Some characters cause weird behaviours during input and rendering

[Bios-Marcel]

I just had someone sent ™ in an app using tview. Every tview is displayed as a two-cell character, even though the actual TM is in one cell. Sometimes the second cell is a different color than the rest of the TextView and sometimes it copies the character above it.

I can't figure out when which situation occurs, but here are two screenshots:

The latter can be reproduced with:

package main

import "github.com/rivo/tview"

func main() {
	text := tview.NewTextView()
	text.SetText("Terminals are lovely\nAren't ™ they?")

	app := tview.NewApplication()
	app.SetRoot(text, true)
	app.Run()
}

I Also saw this happen with some other characters sometimes. And I tried this on multiple terminals, those being iTerm2(mac OS), termite(vte-based on linux) and alacritity(linux).

The same also happens when for example inputting into an InputField.

[rivo]

Please check out #278. This is very likely a problem with the mattn/go-runewidth package.

package main

import (
	"fmt"

	runewidth "github.com/mattn/go-runewidth"
)

func main() {
	fmt.Println(runewidth.RuneWidth('™')) // Prints "2".
}

tcell also depends on this package so there there will probably artifacts as long as this is not fixed there. You could open an issue over at go-runewidth.

I'm thinking about implementing my own version of go-runewidth (there are multiple issues with it) but haven't gotten around to it yet.