brick: A declarative terminal user interface library

brick is a Haskell terminal user interface (TUI) programming toolkit. To use it, you write a pure function that describes how your user interface should be drawn based on your current application state and you provide a state transformation function to handle events.

brick exposes a declarative API. Unlike most GUI toolkits which require you to write a long and tedious sequence of widget creations and layout setup, brick just requires you to describe your interface using a set of declarative layout combinators. Event-handling is done by pattern-matching on incoming events and updating your application state.

Under the hood, this library builds upon vty, so some knowledge of Vty will be necessary to use this library. Brick depends on vty-crossplatform, so Brick should work anywhere Vty works (Unix and Windows). Brick releases prior to 2.0 only support Unix-based systems.

Example

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

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

Result:

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

Featured Projects

To get an idea of what some people have done with brick, check out these projects. If you have made something and would like me to include it, get in touch!

These third-party packages also extend brick:

Getting Started

Check out the many demo programs to get a feel for different aspects of the library:

$ cabal new-build -f demos
$ find dist-newstyle -type f -name \*-demo

To get started, see the user guide.

Documentation

Documentation for brick comes in a variety of forms:

• The official brick user guide
• Haddock documentation
• Demo programs
• FAQ

Feature Overview

brick comes with a bunch of batteries included:

• Vertical and horizontal box layout widgets
• Basic single- and multi-line text editor widgets
• List and table widgets
• Progress bar widget
• Simple dialog box widget
• Border-drawing widgets (put borders around or in between things)
• Generic scrollable viewports and viewport scroll bars
• General-purpose layout control combinators
• Extensible widget-building API
• User-customizable attribute themes
• Type-safe, validated input form API (see the Brick.Forms module)
• A filesystem browser for file and directory selection
• Borders can be configured to automatically connect!

Brick Discussion

There are two forums for discussing brick-related things:

1. The Discussions page on the github repo, and
2. The brick-users Google Group / e-mail list. You can subscribe here.

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 might not be right for your application. Brick is not intended to be all things to all people; rather, I want it to provide a good foundation for building complex terminal interfaces in a declarative style to take away specific headaches of building, modifying, and working with such interfaces, all while seeing how far we can get with a pure function to specify the interface.

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!

A note on Windows support

Brick supports Windows implicitly by way of Vty's Windows support. While I don't (and can't) personally test Brick on Windows hosts, it should be possible to use Brick on Windows. If you have any trouble, report any issues here. If needed, we'll migrate them to the vty-windows repository if they need to be fixed there.

Reporting bugs

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

• Include the versions of relevant software packages: your terminal emulator, brick, ghc, vty, and Vty platform packages 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.
• Please ensure that commits are -Wall clean.
• Please ensure that each commit makes a single, logical, isolated change as much as possible.
• Please do not submit changes that your linter told you to make. I will probably decline them. Relatedly: please do not submit changes that change only style without changing functionality.
• Please do NOT include package version changes in your patches. Package version changes are only done at release time when the full scope of a release's changes can be evaluated to determine the appropriate version change.