brick: A declarative terminal user interface library

module Main where

import Brick

ui :: Widget ()
ui = str "Hello, world!"

main :: IO ()
main = simpleMain ui

brick

brick is a Haskell terminal user interface programming library in the style of gloss. This means you write a function that describes how your user interface should look, but the library takes care of a lot of the book-keeping that so commonly goes into writing such programs.

brick exposes a declarative API. Unlike most GUI toolkits which require you to write a long and tedious sequence of "create a widget, now bind an event handler", brick just requires you to describe your interface using a set of declarative combinators. Then you provide a function to transform your application state when input or other kinds of events arrive.

Under the hood, this library builds upon vty, so some knowledge of Vty will be helpful in using this library.

This library deprecates vty-ui.

Example

Here's an example interface (see programs/ReadmeDemo.hs):

withBorderStyle unicode $
borderWithLabel (str "Hello!") $
(center (str "Left") <+> vBorder <+> center (str "Right"))

Result:

┌─────────Hello!─────────┐
│           │            │
│           │            │
│   Left    │   Right    │
│           │            │
│           │            │
└────────────────────────┘

Featured Projects

To give you an idea of what some people have done with brick, take a look at these projects:

• tetris: https://github.com/SamTay/tetris
• gotta-go-fast, a typing tutor: https://github.com/hot-leaf-juice/gotta-go-fast
• haskell-player, an afplay frontend: https://github.com/potomak/haskell-player
• mushu, an MPD client: https://github.com/elaye/mushu
• matterhorn, a client for Mattermost: https://github.com/matterhorn-chat/matterhorn
• viewprof, a GHC profile viewer: https://github.com/maoe/viewprof
• tart, a mouse-driven ASCII art drawing program: https://github.com/jtdaugherty/tart

Getting Started

TLDR:

$ cabal sandbox init
$ cabal install -j -f demos
$ .cabal-sandbox/bin/brick-???-demo

To get started, see the user guide.

Documentation

Documentation for brick comes in a variety of forms:

• The brick user guide
• Samuel Tay's brick tutorial
• Haddock (all modules)
• Demo programs
• FAQ

Feature Overview

brick comes with a bunch of widget types to get you started:

• Vertical and horizontal box layout widgets
• Basic single- and multi-line text editor widgets
• List widget
• Progress bar widget
• Simple dialog box widget
• Border-drawing widgets (put borders around or in between things)
• Generic scrollable viewports
• Extensible widget-building API
• (And many more general-purpose layout control combinators)

In addition, some of brick's more powerful features may not be obvious right away:

• All widgets can be arranged in predictable layouts so you don't have to worry about terminal resizes.
• Attribute management is flexible and can be customized at runtime on a per-widget basis.

Brick-Users Discussion

The brick-users Google Group / e-mail list is a place to discuss library changes, give feedback, and ask questions. You can subscribe at:

https://groups.google.com/group/brick-users

Status

There are some places were I have deliberately chosen to worry about performance later for the sake of spending more time on the design (and to wait on performance issues to arise first). brick is also something of an experimental project of mine and some aspects of the design involve trade-offs that may are not entirely settled. In addition you can expect this library to follow a principle of fearless improvement: new versions will make (sometimes substantial) API changes if those changes really do make the library better. I will place more importance on getting the API right than on maintaining backwards compatibility.

brick exports an extension API that makes it possible to make your own packages and widgets. If you use that, you'll also be helping to test whether the exported interface is usable and complete!

Reporting bugs

Please file bug reports as GitHub issues. For best results:

• Include the versions of relevant software packages: your terminal emulator, brick, ghc, and vty will be the most important ones.

• Clearly describe the behavior you expected ...

• ... and include a minimal demonstration program that exhibits the behavior you actually observed.

Contributing

If you decide to contribute, that's great! Here are some guidelines you should consider to make submitting patches easier for all concerned:

• If you want to take on big things, talk to me first; let's have a design/vision discussion before you start coding. Create a GitHub issue and we can use that as the place to hash things out.
• Please make changes consistent with the conventions I've used in the codebase.
• Please adjust or provide Haddock and/or user guide documentation relevant to any changes you make.