akvelon/code_field

A customizable code text field supporting syntax highlighting

CodeField

A customizable code text field supporting syntax highlighting

Live demo

A live demo showcasing a few language / themes combinaisons

Showcase

The experimental VM dlox uses CodeField in its online editor

Features

• Code highlight for 189 built-in languages with 90 themes thanks to flutter_highlight
• Easy language highlight customization through the use of theme maps
• Fully customizable code field style through a TextField like API
• Handles horizontal/vertical scrolling and vertical expansion
• Supports code modifiers
• Works on Android, iOS, and Web

Code modifiers help manage indents automatically

The editor is wrapped in a horizontal scrollable container to handle long lines

Installing

In the pubspec.yaml of your flutter project, add the following dependency:

dependencies:
  ...
  code_text_field: <latest_version>

latest version

In your library add the following import:

import 'package:code_text_field/code_field.dart';

Simple example

A CodeField widget works with a CodeController which dynamically parses the text input according to a language and renders it with a theme map

import 'package:flutter/material.dart';
import 'package:code_text_field/code_field.dart';
// Import the language & theme
import 'package:highlight/languages/dart.dart';
import 'package:flutter_highlight/themes/monokai-sublime.dart';

class CodeEditor extends StatefulWidget {
  @override
  _CodeEditorState createState() => _CodeEditorState();
}

class _CodeEditorState extends State<CodeEditor> {
  CodeController? _codeController;

  @override
  void initState() {
    super.initState();
    final source = "void main() {\n    print(\"Hello, world!\");\n}";
    // Instantiate the CodeController
    _codeController = CodeController(
      text: source,
      language: dart,
      theme: monokaiSublimeTheme,
    );
  }

  @override
  void dispose() {
    _codeController?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return CodeField(
      controller: _codeController!,
      textStyle: TextStyle(fontFamily: 'SourceCode'),
    );
  }
}

Here, the monospace font Source Code Pro has been added to the assets folder and to the pubspec.yaml file

Parser options

On top of a language definition, world-wise styling can be specified in the stringMap field

_codeController = CodeController(
  //...
  stringMap: {
    "Hello": TextStyle(fontWeight: FontWeight.bold, color: Colors.red),
    "world": TextStyle(fontStyle: FontStyle.italic, color: Colors.green),
  },
);

More complex regexes may also be used with the patternMap. When a language is used though, its regexes patterns take precedence over patternMap and stringMap.

_codeController = CodeController(
  //...
  patternMap: {
    r"\B#[a-zA-Z0-9]+\b":
        TextStyle(fontWeight: FontWeight.bold, color: Colors.purpleAccent),
  },
);

Both patternMap and stringMap can be used without specifying a language

_codeController = CodeController(
  text: source,
  patternMap: {
    r'".*"': TextStyle(color: Colors.yellow),
    r'[a-zA-Z0-9]+\(.*\)': TextStyle(color: Colors.green),
  },
  stringMap: {
    "void": TextStyle(fontWeight: FontWeight.bold, color: Colors.red),
    "print": TextStyle(fontWeight: FontWeight.bold, color: Colors.blue),
  },
);

Code Modifiers

Code modifiers can be created to react to special keystrokes. The default modifiers handle tab to space & automatic indentation. Here's the implementation of the default TabModifier

class TabModifier extends CodeModifier {
  const TabModifier() : super('\t');

  @override
  TextEditingValue? updateString(
      String text, TextSelection sel, EditorParams params) {
    final tmp = replace(text, sel.start, sel.end, " " * params.tabSpaces);
    return tmp;
  }
}

API

CodeField

CodeField({
Key? key,
  required this.controller,
  this.minLines,
  this.maxLines,
  this.expands = false,
  this.wrap = false,
  this.background,
  this.decoration,
  this.textStyle,
  this.padding = const EdgeInsets.symmetric(),
  this.lineNumberStyle = const LineNumberStyle(),
  this.enabled,
  this.cursorColor,
  this.textSelectionTheme,
  this.lineNumberBuilder,
  this.focusNode,
})

LineNumberStyle({
  this.width = 42.0,
  this.textAlign = TextAlign.right,
  this.margin = 10.0,
  this.textStyle,
  this.background,
})

CodeController

CodeController({
  String? text,
  this.language,
  this.theme,
  this.patternMap,
  this.stringMap,
  this.params = const EditorParams(),
  this.modifiers = const <CodeModifier>[
    const IntendModifier(),
    const CloseBlockModifier(),
    const TabModifier(),
  ],
  this.onChange,
})

Limitations

• Autocomplete disabling on android doesn't work yet
• The TextField cursor doesn't seem to be handling space inputs properly on the web platform. Pending issue resolution. The flag webSpaceFix fixes it by swapping spaces with transparent middle points.

Notes

A breaking change to the TextEditingController was introduced in flutter beta, dev & master channels. The branch beta should comply with those changes.