CodeField

A customizable code text field supporting syntax highlighting

Live demo

A live demo showcasing a few language / theme combinations

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

const CodeField({
    Key? key,
    required this.controller,
    this.minLines,
    this.maxLines,
    this.expands = false,
    this.wrap = false,
    this.background,
    this.decoration,
    this.textStyle,
    this.padding = EdgeInsets.zero,
    this.lineNumberStyle = const LineNumberStyle(),
    this.enabled,
    this.onTap,
    this.readOnly = false,
    this.cursorColor,
    this.textSelectionTheme,
    this.lineNumberBuilder,
    this.focusNode,
    this.onChanged,
    this.isDense = false,
    this.smartQuotesType,
    this.keyboardType,
    this.lineNumbers = true,
    this.horizontalScroll = true,
    this.selectionControls,
  })

LineNumberStyle

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

CodeController

CodeController({
    String? text,
    Mode? language,
    this.patternMap,
    this.stringMap,
    this.params = const EditorParams(),
    this.modifiers = const [
      IndentModifier(),
      CloseBlockModifier(),
      TabModifier(),
    ],
  }) 

Limitations

• Autocomplete disabling on android doesn't work yet

Notes

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