Flutter Quill Delta from HTML

This is a Dart package that converts HTML input into Quill Delta format, which is used in the Quill Js package.

This package supports the conversion of a wide range of HTML tags and attributes into their corresponding Delta operations, ensuring that your HTML content is accurately represented in the Quill editor.

Supported tags

    <!--Text Formatting-->
        <b>, <strong>: Bold text 
        <i>, <em>: Italic text
        <u>, <ins>: Underlined text
        <s>, <del>: Strikethrough text
        <sup>: Superscript text
        <sub>: Subscript text

    <!--Headings-->
        <h1> to <h6>: Headings of various levels

    <!--Lists and nested ones-->
        <ul>: Unordered lists
        <ol>: Ordered lists
        <li>: List items
        <li data-checked="true">: Check lists 
        <input type="checkbox">: Another alternative to make a check lists

    <!--Links-->
        <a>: Hyperlinks with support for the href attribute

    <!--Images-->
        <img>: Images with support for the src, align, and styles

    <!--div-->
        <div>: HTML tag containers
        
    <!--Videos -->
        <video>: Videos with support for the src

    <!--Blockquotes-->
        <blockquote>: Block quotations

    <!--Code Blocks-->
        <pre>, <code>: Code blocks

    <!--Text Alignment, inline text align and direction-->
        <p style="text-align:left|center|right|justify">: Paragraph style alignment
        <p align="left|center|right|justify">: Paragraph alignment
        <p dir="rtl">: Paragraph direction 

    <!--Text attributes-->
        <p style="padding: 10px;line-height: 1.0px;font-size: 12px;font-family: Times New Roman;color:#ffffff">: Inline attributes
    
    <!--Custom Blocks-->
        <pullquote data-author="john">: Custom html

Getting Started

Add the dependency to your pubspec.yaml:

dependencies:
  flutter_quill_delta_from_html: <lastest_version>

Then, import the package and use it in your Flutter application:

import 'package:flutter_quill_delta_from_html/flutter_quill_delta_from_html.dart';

void main() {
  String htmlContent = "<p>Hello, <b>world</b>!</p>";
  var delta = HtmlToDelta().convert(htmlContent);
/*
   { "insert": "hello, " },
   { "insert": "world", "attributes": {"bold": true} },
   { "insert": "!" },
   { "insert": "\n" }
*/
}

Creating your own CustomHtmlPart (alternative to create CustomBlockEmbeds from custom html)

First you need to define your own CustomHtmlPart

import 'package:flutter_quill_delta_from_html/flutter_quill_delta_from_html.dart';
import 'package:html/dom.dart' as dom;

/// Custom block handler for <pullquote> elements.
class PullquoteBlock extends CustomHtmlPart {
  @override
  bool matches(dom.Element element) {
    //you can put here the validation that you want
    //
    // To detect a <p>, you just need to do something like: 
    // element.localName == 'p'
    return element.localName == 'pullquote';
  }

  @override
  List<Operation> convert(dom.Element element, {Map<String, dynamic>? currentAttributes}) {
    final Delta delta = Delta();
    final Map<String, dynamic> attributes = currentAttributes != null ? Map.from(currentAttributes) : {};

    // Extract custom attributes from the <pullquote> element
    // The attributes represents the data into a html tag
    // at this point, <pullquote> should have these attributes
    //
    // <pullquote data-author="John Doe" data-style="italic">
    // These attributes can be optional, so do you need to ensure to not use "!" 
    // to avoid any null conflict
    final author = element.attributes['data-author'];
    final style = element.attributes['data-style'];

    // Apply custom attributes to the Delta operations
    if (author != null) {
      delta.insert('Pullquote: "${element.text}" by $author', attributes);
    } else {
      delta.insert('Pullquote: "${element.text}"', attributes);
    }

    if (style != null && style.toLowerCase() == 'italic') {
      attributes['italic'] = true;
    }

    delta.insert('\n', attributes);

    return delta.toList();
  }
}

After, put your PullquoteBlock to HtmlToDelta using the param customBlocks

import 'package:flutter_quill_delta_from_html/flutter_quill_delta_from_html.dart';

void main() {
  // Example HTML snippet
  final htmlText = '''
    <html>
      <body>
        <p>Regular paragraph before the custom block</p>
        <pullquote data-author="John Doe" data-style="italic">This is a custom pullquote</pullquote>
        <p>Regular paragraph after the custom block</p>
      </body>
    </html>
  ''';

  // Registering the custom block
  final customBlocks = [PullquoteBlock()];

  // Initialize HtmlToDelta with the HTML text and custom blocks
  final converter = HtmlToDelta(customBlocks: customBlocks);

  // Convert HTML to Delta operations
  final delta = converter.convert(htmlText);
/*
This should be resulting delta
  {"insert": "Regular paragraph before the custom block"},
  {"insert": "Pullquote: \"This is a custom pullquote\" by John Doe", "attributes": {"italic": true}},
  {"insert": "\n"},
  {"insert": "Regular paragraph after the custom block\n"}
*/
}

HtmlOperations

The HtmlOperations class is designed to streamline the conversion process from HTML to Delta operations, accommodating a wide range of HTML structures and attributes commonly used in web content.

To utilize HtmlOperations, extend this class and implement the methods necessary to handle specific HTML elements. Each method corresponds to a different HTML tag or element type and converts it into Delta operations suitable for use with QuillJS.

abstract class HtmlOperations {
  /// custom blocks are passed internally by HtmlToDelta
  List<CustomHtmlPart>? customBlocks;

  // You don't need to override this method 
  // since it just call the other methods 
  // when detect the type of HTML tag
  List<Operation> resolveCurrentElement(dom.Element element, [int indentLevel = 0]);

  List<Operation> brToOp(dom.Element element);
  List<Operation> headerToOp(dom.Element element);
  List<Operation> listToOp(dom.Element element, [int indentLevel = 0]);
  List<Operation> paragraphToOp(dom.Element element);
  List<Operation> linkToOp(dom.Element element);
  List<Operation> spanToOp(dom.Element element);
  List<Operation> imgToOp(dom.Element element);
  List<Operation> videoToOp(dom.Element element);
  List<Operation> codeblockToOp(dom.Element element);
  List<Operation> blockquoteToOp(dom.Element element);
}

Contributions

If you find a bug or want to add a new feature, please open an issue or submit a pull request on the GitHub repository.

This project is licensed under the MIT License - see the LICENSE file for details.