brick: A declarative terminal user interface library

brick

brick is a terminal user interface programming library written in Haskell, 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 -- even the bits that are stateful -- using a set of declarative combinators. Then you provide a function to transform your own application state when input (or other kinds of) events arrive.

Under the hood, this library builds upon vty.

This library deprecates vty-ui.

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.
• Most widgets can be made scrollable for free.
• Attribute management is flexible and can be customized at runtime on a per-widget basis.

brick exports lens and non-lens interfaces for most things, so you can get the full power of lens if you want it or use plain Haskell if you don't. If a brick library function named thing has a lens version, the lens version is named thingL.

Getting Started

TLDR:

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

To get started, see the first few sections of the brick user guide.

Documentation

Your documentation options, in recommended order, are:

• FAQ
• The brick user guide
• Haddock (all modules)
• Demo programs

Status

brick is young and may be missing some essential features. 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 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!

The development of this library has revealed some bugs in vty, and I've tried to report those as I go. If they haven't been resolved, you'll see them arise when using brick.

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. Even better, the output of cabal freeze would probably be helpful in making the problem reproducible.

• 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.
• If you make changes, try to make them consistent with the syntactic conventions I've used in the codebase.
• Please provide Haddock and/or user guide documentation for any changes you make.