Anděl

Current stage of the project is work in progress. It's not ready to use by any means.

Try editor sample app

Dev

• lein figwheel
• go to http://localhost:3449

Prod

• run lein cljsbuild once min && lein run
• go to http://localhost:3000

Dev recompiles and reloads live. Prod is slow to build but resulting code is much faster.

The goals of the project and priciples behind it are:

• Create a universal code editor component, which could be embedded in a web application
• Great performance
• No limitation for the document size (it should be able to fetch only parts of a document into memory as needed)
• Purely functional implementation. Which means no mutable state except single reference to an immutable model, ui is considered to be pure function of immutable state

Currently taken design decisions

• Document is stored in a rope-like data structure (tree branching factor is 32).
• Leafs in this rope are blocks of text of size 64 characters.
• Rope maintains a number of metrics. Such as number of linebreaks and characters. Some other associative metrics like brace matches, soft-wraps data and folding are to be stored there in a future.
• Background lexing. Currently tokens array is stored per line. We should get rid of the assumption of short lines in a nearest future. The probable solution is to store it for fixed-size blocks.
• Virtual scroll is performed by wheel handler and translate3d is used to adjust view position for a smooth scrolling.
• Despite reagent is used to render lines array, lines themselves are rendered by supplying a real DOM elements.
• At the moment editor uses standalone running CodeMirror modes to provide syntax highlighting. They are bundled in resource folder.
• No reads from DOM. It implies limitation of using monospaced fonts only, but we are choosing performance in this tradeoff. All needed measurements should be performed once and ahead of time.

Roadmap

• Repair caret movement and other basic editor stuff after the redesign
• Figure out the best way to store persistent range markers for non-trivial highlighting (they are very massive and should be preserved during the edits)
• Get rid of short lines assumptions in lexer part
• Implement soft-wraps and folding
• Make an extension points to extend editor with custom widgets, code completion, custom popups.

Credits

Thanks to:

• ClojureScript
• CodeMirror
• Xi-editor
• Reagent