flutter_widget_from_html_core 0.15.2

Flutter package to render html as widgets that focuses on correctness and extensibility.

Flutter Widget from HTML (core)

Flutter package to render html as widgets that focuses on correctness and extensibility. Supports 70+ most popular tags.

Live demo

Getting Started

Add this to your app's pubspec.yaml file:

dependencies:
  flutter_widget_from_html_core: ^0.15.2

Usage

Then you have to import the package with:

import 'package:flutter_widget_from_html_core/flutter_widget_from_html_core.dart';

And use HtmlWidget where appropriate:

HtmlWidget(
  // the first parameter (`html`) is required
  '''
  <h3>Heading</h3>
  <p>
    A paragraph with <strong>strong</strong>, <em>emphasized</em>
    and <span style="color: red">colored</span> text.
  </p>
  ''',

  // all other parameters are optional, a few notable params:

  // specify custom styling for an element
  // see supported inline styling below
  customStylesBuilder: (element) {
    if (element.classes.contains('foo')) {
      return {'color': 'red'};
    }

    return null;
  },

  customWidgetBuilder: (element) {
    if (element.attributes['foo'] == 'bar') {
      // render a custom widget that takes the full width
      return FooBarWidget();
    }

    if (element.attributes['fizz'] == 'buzz') {
      // render a custom widget that inlines with surrounding text
      return InlineCustomWidget(
        child: FizzBuzzWidget(),
      )
    }

    return null;
  },

  // this callback will be triggered when user taps a link
  onTapUrl: (url) => print('tapped $url'),

  // select the render mode for HTML body
  // by default, a simple `Column` is rendered
  // consider using `ListView` or `SliverList` for better performance
  renderMode: RenderMode.column,

  // set the default styling for text
  textStyle: TextStyle(fontSize: 14),
),

Features

HTML tags

Below tags are the ones that have special meaning / styling, all other tags will be parsed as text. Compare between Flutter rendering and browser's.

• A: underline, theme accent color with scroll to anchor support
• H1/H2/H3/H4/H5/H6
• IMG with support for asset (asset://), data uri, local file (file://) and network image
• LI/OL/UL with support for:
  • Attributes: type, start, reversed
  • Inline style list-style-type values: lower-alpha, upper-alpha, lower-latin, upper-latin, circle, decimal, disc, lower-roman, upper-roman, square
• TABLE/CAPTION/THEAD/TBODY/TFOOT/TR/TD/TH with support for:
  • TABLE attributes border, cellpadding, cellspacing
  • TD/TH attributes colspan, rowspan, valign
  • Table is scrollable if columns are too wide
• ABBR, ACRONYM, ADDRESS, ARTICLE, ASIDE, B, BIG, BLOCKQUOTE, BR, CENTER, CITE, CODE, DD, DEL, DETAILS, DFN, DIV, DL, DT, EM, FIGCAPTION, FIGURE, FONT, FOOTER, HEADER, HR, I, INS, KBD, MAIN, MARK, NAV, NOSCRIPT, P, PRE, Q, RP, RT, RUBY, S, SAMP, SECTION, SMALL, STRIKE, STRONG, STYLE, SUB, SUMMARY, SUP, TT, U, VAR
• Everything with screenshot: https://demo.fwfh.dev/supported/tags.html
• Try with fwfh.dev

These tags requires flutter_widget_from_html:

• AUDIO
• IFRAME
• SVG
• VIDEO

These tags and their contents will be ignored:

• SCRIPT
• STYLE

Attributes

• align: center/end/justify/left/right/start/-moz-center/-webkit-center
• dir: auto/ltr/rtl

Inline stylings

• background: 1 value (color)
  • background-color: currentcolor, hex values, rgb(), hsl() or named colors
  • background-image: url() with support for asset (asset://), data uri, local file (file://) and network image
  • background-repeat: no-repeat/repeat/repeat-x/repeat-y
  • background-position: single or double instances of bottom/center/left/right/top (e.g. top left)
  • background-size: auto/contain/cover
• border: 3 values (width style color), 2 values (width style) or 1 value (width)
  • border-top, border-right, border-bottom, border-left
  • border-block-start, border-block-end
  • border-inline-start, border-inline-end
• border-radius: 4, 3, 2 or 1 value with slash support (e.g. 10px / 20px)
  • border-top-left-radius: 2 values or 1 value in em, pt and px
  • border-top-right-radius: 2 values or 1 value in em, pt and px
  • border-bottom-right-radius: 2 values or 1 value in em, pt and px
  • border-bottom-left-radius: 2 values or 1 value in em, pt and px
• color: hex values, rgb(), hsl() or named colors
• direction (similar to dir attribute)
• display: block/flex/inline/inline-block/none
  • In flex mode:
    • flex-direction: column/row
    • align-items: flex-start/flex-end/center/baseline/stretch
    • justify-content: flex-start/flex-end/center/space-between/space-around/space-evenly
• font-family
• font-size: absolute (e.g. xx-large), relative (larger, smaller) or values in em, %, pt and px
• font-style: italic/normal
• font-weight: bold/normal/100..900
• line-height: normal, number or values in em, %, pt and px
• margin: 4 values, 2 values or 1 value in em, pt and px
  • margin-top, margin-right, margin-bottom, margin-left
  • margin-block-start, margin-block-end
  • margin-inline-start, margin-inline-end
• padding: 4 values, 2 values or 1 value in em, pt and px
  • padding-top, padding-right, padding-bottom, padding-left
  • padding-block-start, padding-block-end
  • padding-inline-start, padding-inline-end
• vertical-align: baseline/top/bottom/middle/sub/super
• text-align (similar to align attribute)
• text-decoration
  • text-decoration-color: currentcolor, hex values, rgb(), hsl() or named colors
  • text-decoration-line: line-through/none/overline/underline
  • text-decoration-style: dotted/dashed/double/solid
  • text-decoration-thickness, text-decoration-width: values in % only
• text-overflow: clip/ellipsis. Note: text-overflow: ellipsis should be used in conjuntion with max-lines or -webkit-line-clamp for better result.
• text-shadow:
  • 4 values (color x y blur, color x y blur)
  • 3 values (x y color, color x y)
  • Or 2 values (x y)
  • Multiple shadows
• white-space: pre/normal/nowrap
• Sizing: auto or values in em, %, pt and px
  • width, max-width, min-width
  • height, max-height, min-height

Extensibility

This package implements widget building logic with high testing coverage to ensure correctness. It tries to render an optimal tree by using RichText with specific TextStyle, collapsing margins, proper whitespace handling, etc. The idea is to build a solid foundation for apps to customize.

The enhanced package uses a custom WidgetFactory with pre-built mixins for easy usage:

• fwfh_cached_network_image for optimized image rendering
• fwfh_chewie for VIDEO support
• fwfh_just_audio for AUDIO support
• fwfh_svg for SVG support
• fwfh_url_launcher to launch URLs
• fwfh_webview for IFRAME support

See the extensibility document for detailed information.