termenv

Advanced ANSI style & color support for your terminal applications

Programming language: Go

License: MIT License

Tags: Command Line     Advanced Console UIs    

README

termenv lets you safely use advanced styling options on the terminal. It gathers information about the terminal environment in terms of its ANSI & color support and offers you convenient methods to colorize and style your output, without you having to deal with all kinds of weird ANSI escape sequences and color conversions.

Features

• RGB/TrueColor support
• Detects the supported color range of your terminal
• Automatically converts colors to the best matching, available colors
• Terminal theme (light/dark) detection
• Chainable syntax
• Nested styles

Installation

go get github.com/muesli/termenv

Usage

output := termenv.NewOutput(os.Stdout)

termenv queries the terminal's capabilities it is running in, so you can safely use advanced features, like RGB colors or ANSI styles. output.Profile returns the supported profile:

• termenv.Ascii - no ANSI support detected, ASCII only
• termenv.ANSI - 16 color ANSI support
• termenv.ANSI256 - Extended 256 color ANSI support
• termenv.TrueColor - RGB/TrueColor support

Alternatively, you can use termenv.EnvColorProfile which evaluates the terminal like ColorProfile, but also respects the NO_COLOR and CLICOLOR_FORCE environment variables.

You can also query the terminal for its color scheme, so you know whether your app is running in a light- or dark-themed environment:

// Returns terminal's foreground color
color := output.ForegroundColor()

// Returns terminal's background color
color := output.BackgroundColor()

// Returns whether terminal uses a dark-ish background
darkTheme := output.HasDarkBackground()

Manual Profile Selection

If you don't want to rely on the automatic detection, you can manually select the profile you want to use:

output := termenv.NewOutput(os.Stdout, termenv.WithProfile(termenv.TrueColor))

Colors

termenv supports multiple color profiles: Ascii (black & white only), ANSI (16 colors), ANSI Extended (256 colors), and TrueColor (24-bit RGB). Colors will automatically be degraded to the best matching available color in the desired profile:

TrueColor => ANSI 256 Colors => ANSI 16 Colors => Ascii

s := output.String("Hello World")

// Supports hex values
// Will automatically degrade colors on terminals not supporting RGB
s.Foreground(output.Color("#abcdef"))
// but also supports ANSI colors (0-255)
s.Background(output.Color("69"))
// ...or the color.Color interface
s.Foreground(output.FromColor(color.RGBA{255, 128, 0, 255}))

// Combine fore- & background colors
s.Foreground(output.Color("#ffffff")).Background(output.Color("#0000ff"))

// Supports the fmt.Stringer interface
fmt.Println(s)

Styles

You can use a chainable syntax to compose your own styles:

s := output.String("foobar")

// Text styles
s.Bold()
s.Faint()
s.Italic()
s.CrossOut()
s.Underline()
s.Overline()

// Reverse swaps current fore- & background colors
s.Reverse()

// Blinking text
s.Blink()

// Combine multiple options
s.Bold().Underline()

Template Helpers

termenv provides a set of helper functions to style your Go templates:

// load template helpers
f := output.TemplateFuncs()
tpl := template.New("tpl").Funcs(f)

// apply bold style in a template
bold := `{{ Bold "Hello World" }}`

// examples for colorized templates
col := `{{ Color "#ff0000" "#0000ff" "Red on Blue" }}`
fg := `{{ Foreground "#ff0000" "Red Foreground" }}`
bg := `{{ Background "#0000ff" "Blue Background" }}`

// wrap styles
wrap := `{{ Bold (Underline "Hello World") }}`

// parse and render
tpl, err = tpl.Parse(bold)

var buf bytes.Buffer
tpl.Execute(&buf, nil)
fmt.Println(&buf)

Other available helper functions are: Faint, Italic, CrossOut, Underline, Overline, Reverse, and Blink.

Positioning

// Move the cursor to a given position
output.MoveCursor(row, column)

// Save the cursor position
output.SaveCursorPosition()

// Restore a saved cursor position
output.RestoreCursorPosition()

// Move the cursor up a given number of lines
output.CursorUp(n)

// Move the cursor down a given number of lines
output.CursorDown(n)

// Move the cursor up a given number of lines
output.CursorForward(n)

// Move the cursor backwards a given number of cells
output.CursorBack(n)

// Move the cursor down a given number of lines and place it at the beginning
// of the line
output.CursorNextLine(n)

// Move the cursor up a given number of lines and place it at the beginning of
// the line
output.CursorPrevLine(n)

Screen

// Reset the terminal to its default style, removing any active styles
output.Reset()

// RestoreScreen restores a previously saved screen state
output.RestoreScreen()

// SaveScreen saves the screen state
output.SaveScreen()

// Switch to the altscreen. The former view can be restored with ExitAltScreen()
output.AltScreen()

// Exit the altscreen and return to the former terminal view
output.ExitAltScreen()

// Clear the visible portion of the terminal
output.ClearScreen()

// Clear the current line
output.ClearLine()

// Clear a given number of lines
output.ClearLines(n)

// Set the scrolling region of the terminal
output.ChangeScrollingRegion(top, bottom)

// Insert the given number of lines at the top of the scrollable region, pushing
// lines below down
output.InsertLines(n)

// Delete the given number of lines, pulling any lines in the scrollable region
// below up
output.DeleteLines(n)

Session

// SetWindowTitle sets the terminal window title
output.SetWindowTitle(title)

// SetForegroundColor sets the default foreground color
output.SetForegroundColor(color)

// SetBackgroundColor sets the default background color
output.SetBackgroundColor(color)

// SetCursorColor sets the cursor color
output.SetCursorColor(color)

// Hide the cursor
output.HideCursor()

// Show the cursor
output.ShowCursor()

// Copy to clipboard
output.Copy(message)

// Trigger notification
output.Notify(title, body)

Mouse

// Enable X10 mouse mode, only button press events are sent
output.EnableMousePress()

// Disable X10 mouse mode
output.DisableMousePress()

// Enable Mouse Tracking mode
output.EnableMouse()

// Disable Mouse Tracking mode
output.DisableMouse()

// Enable Hilite Mouse Tracking mode
output.EnableMouseHilite()

// Disable Hilite Mouse Tracking mode
output.DisableMouseHilite()

// Enable Cell Motion Mouse Tracking mode
output.EnableMouseCellMotion()

// Disable Cell Motion Mouse Tracking mode
output.DisableMouseCellMotion()

// Enable All Motion Mouse mode
output.EnableMouseAllMotion()

// Disable All Motion Mouse mode
output.DisableMouseAllMotion()

Bracketed Paste

// Enables bracketed paste mode
termenv.EnableBracketedPaste()

// Disables bracketed paste mode
termenv.DisableBracketedPaste()

Terminal Feature Support

Color Support

• 24-bit (RGB): alacritty, foot, iTerm, kitty, Konsole, st, tmux, vte-based, wezterm, Windows Terminal
• 8-bit (256): rxvt, screen, xterm, Apple Terminal
• 4-bit (16): Linux Console

Control Sequences

Click to show feature matrix

Terminal	Query Color Scheme	Query Cursor Position	Set Window Title	Change Cursor Color	Change Default Foreground Setting	Change Default Background Setting	Bracketed Paste
alacritty	✅	✅	✅	✅	✅	✅	✅
foot	✅	✅	✅	✅	✅	✅	✅
kitty	✅	✅	✅	✅	✅	✅	✅
Konsole	✅	✅	✅	❌	✅	✅	✅
rxvt	❌	✅	✅	✅	✅	✅	✅
urxvt	❌	✅	✅	✅	✅	✅	✅
screen	⛔1	✅	✅	❌	❌	✅	❌
st	✅	✅	✅	✅	✅	✅	✅
tmux	⛔1	✅	✅	✅	✅	✅	✅
vte-based2	✅	✅	✅	✅	✅	❌	✅
wezterm	✅	✅	✅	✅	✅	✅	✅
xterm	✅	✅	✅	❌	❌	❌	✅
Linux Console	❌	✅	⛔	❌	❌	❌	❌
Apple Terminal	✅	✅	✅	❌	✅	✅	✅
iTerm	✅	✅	✅	❌	❌	❌	✅
Windows cmd	❌	✅	✅	✅	✅	✅	❌
Windows Terminal	❌	✅	✅	✅	✅	✅	✅

You can help improve this list! Check out [how to](ansi_compat.md) and open an issue or pull request.

System Commands

Click to show feature matrix

Terminal	Copy to Clipboard (OSC52)	Hyperlinks (OSC8)	Notifications (OSC777)
alacritty	✅	❌3	❌
foot	✅	✅	✅
kitty	✅	✅	✅
Konsole	❌4	✅	❌
rxvt	❌	❌	❌
urxvt	✅5	❌	✅
screen	✅	❌6	❌
st	✅	❌	❌
tmux	✅	❌7	❌
vte-based2	❌2	✅	❌
wezterm	✅	✅	❌
xterm	✅	❌	❌
Linux Console	⛔	⛔	❌
Apple Terminal	✅8	❌	❌
iTerm	✅	✅	❌
Windows cmd	❌	❌	❌
Windows Terminal	✅	✅	❌

Platform Support

termenv works on Unix systems (like Linux, macOS, or BSD) and Windows. While terminal applications on Unix support ANSI styling out-of-the-box, on Windows you need to enable ANSI processing in your application first:

    restoreConsole, err := termenv.EnableVirtualTerminalProcessing(termenv.DefaultOutput())
    if err != nil {
        panic(err)
    }
    defer restoreConsole()

The above code is safe to include on non-Windows systems or when os.Stdout does not refer to a terminal (e.g. in tests).

Color Chart

You can find the source code used to create this chart in termenv's examples.

Related Projects

• reflow - ANSI-aware text operations
• Lip Gloss - style definitions for nice terminal layouts 👄
• ansi - ANSI sequence helpers

termenv in the Wild

Need some inspiration or just want to see how others are using termenv? Check out these projects:

• Bubble Tea - a powerful little TUI framework 🏗
• Glamour - stylesheet-based markdown rendering for your CLI apps 💇🏻‍♀️
• Glow - a markdown renderer for the command-line 💅🏻
• duf - Disk Usage/Free Utility - a better 'df' alternative
• gitty - contextual information about your git projects
• slides - terminal-based presentation tool

Feedback

Got some feedback or suggestions? Please open an issue or drop me a note!

• Twitter
• The Fediverse

License

MIT

---

1. Unavailable as multiplexers (like tmux or screen) can be connected to multiple terminals (with different color settings) at the same time. ↩

2. This covers all vte-based terminals, including Gnome Terminal, guake, Pantheon Terminal, Terminator, Tilix, XFCE Terminal. ↩

3. OSC8 is not supported, for more info see issue#922. ↩

4. OSC52 is not supported, for more info see bug#372116. ↩

5. Workaround for urxvt not supporting OSC52. See this for more information. ↩

6. OSC8 is not supported, for more info see bug#50952. ↩

7. OSC8 is not supported, for more info see issue#911. ↩

8. OSC52 works with a workaround. ↩