Update and modernize the flutter_markdown package (#9044)

We now use modern scrolling machinery and patterns. The API should also be
easier to maintain over time.

Fixes #6166
Fixes #2591
Fixes #3123

packages/flutter/lib/src/painting/text_span.dart

@@ -185,6 +185,8 @@ class TextSpan {
     final String indent = '$prefix  ';
     if (style != null)
       buffer.writeln(style.toString(indent));
+    if (recognizer != null)
+      buffer.writeln('${indent}recognizer: ${recognizer.runtimeType}');
     if (text != null)
       buffer.writeln('$indent"$text"');
     if (children != null) {

packages/flutter_markdown/lib/flutter_markdown.dart

@@ -5,5 +5,6 @@
 /// A library to render markdown formatted text.
 library flutter_markdown;
 
-export 'src/markdown.dart';
+export 'src/builder.dart';
-export 'src/markdown_style.dart';
+export 'src/style_sheet.dart';
+export 'src/widget.dart';

packages/flutter_markdown/lib/flutter_markdown_raw.dart

@@ -1,8 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-library flutter_markdown_raw;
-
-export 'src/markdown_raw.dart';
-export 'src/markdown_style_raw.dart';

packages/flutter_markdown/lib/src/builder.dart

@@ -0,0 +1,243 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/gestures.dart';
+import 'package:flutter/widgets.dart';
+import 'package:markdown/markdown.dart' as md;
+
+import 'style_sheet.dart';
+
+final Set<String> _kBlockTags = new Set<String>.from(<String>[
+  'p',
+  'h1',
+  'h2',
+  'h3',
+  'h4',
+  'h5',
+  'h6',
+  'li',
+  'blockquote',
+  'img',
+  'pre',
+  'ol',
+  'ul',
+]);
+
+const List<String> _kListTags = const <String>['ul', 'ol'];
+
+bool _isBlockTag(String tag) => _kBlockTags.contains(tag);
+bool _isListTag(String tag) => _kListTags.contains(tag);
+
+class _BlockElement {
+  _BlockElement(this.tag);
+
+  final String tag;
+  final List<Widget> children = <Widget>[];
+
+  int nextListIndex = 0;
+}
+
+class _InlineElement {
+  final List<TextSpan> children = <TextSpan>[];
+}
+
+/// A delegate used by [MarkdownBuilder] to control the widgets it creates.
+abstract class MarkdownBuilderDelegate {
+  /// Returns a gesture recognizer to use for an `a` element with the given
+  /// `href` attribute.
+  GestureRecognizer createLink(String href);
+
+  /// Returns formatted text to use to display the given contents of a `pre`
+  /// element.
+  ///
+  /// The `styleSheet` is the value of [MarkdownBuilder.styleSheet].
+  TextSpan formatText(MarkdownStyleSheet styleSheet, String code);
+}
+
+/// Builds a [Widget] tree from parsed Markdown.
+///
+/// See also:
+///
+///  * [Markdown], which is a widget that parses and displays Markdown.
+class MarkdownBuilder implements md.NodeVisitor {
+  /// Creates an object that builds a [Widget] tree from parsed Markdown.
+  MarkdownBuilder({ this.delegate, this.styleSheet });
+
+  /// A delegate that controls how link and `pre` elements behave.
+  final MarkdownBuilderDelegate delegate;
+
+  /// Defines which [TextStyle] objects to use for each type of element.
+  final MarkdownStyleSheet styleSheet;
+
+  final List<String> _listIndents = <String>[];
+  final List<_BlockElement> _blocks = <_BlockElement>[];
+  final List<_InlineElement> _inlines = <_InlineElement>[];
+
+  /// Returns widgets that display the given Markdown nodes.
+  ///
+  /// The returned widgets are typically used as children in a [ListView].
+  List<Widget> build(List<md.Node> nodes) {
+    _listIndents.clear();
+    _blocks.clear();
+    _inlines.clear();
+
+    _blocks.add(new _BlockElement(null));
+    _inlines.add(new _InlineElement());
+
+    for (md.Node node in nodes) {
+      assert(_blocks.length == 1);
+      node.accept(this);
+    }
+
+    assert(_inlines.single.children.isEmpty);
+    return _blocks.single.children;
+  }
+
+  @override
+  void visitText(md.Text text) {
+    if (_blocks.last.tag == null) // Don't allow text directly under the root.
+      return;
+    final TextSpan span = _blocks.last.tag == 'pre' ?
+      delegate.formatText(styleSheet, text.text) : new TextSpan(text: text.text);
+    _inlines.last.children.add(span);
+  }
+
+  @override
+  bool visitElementBefore(md.Element element) {
+    final String tag = element.tag;
+    if (_isBlockTag(tag)) {
+      _addAnonymousBlockIfNeeded(styleSheet.styles[tag]);
+      if (_isListTag(tag))
+        _listIndents.add(tag);
+      _blocks.add(new _BlockElement(tag));
+    } else {
+      _inlines.add(new _InlineElement());
+    }
+    return true;
+  }
+
+  @override
+  void visitElementAfter(md.Element element) {
+    final String tag = element.tag;
+
+    if (_isBlockTag(tag)) {
+      _addAnonymousBlockIfNeeded(styleSheet.styles[tag]);
+
+      final _BlockElement current = _blocks.removeLast();
+      Widget child;
+      if (tag == 'img') {
+        child = _buildImage(element.attributes['src']);
+      } else {
+        if (current.children.isNotEmpty) {
+          child = new Column(
+            crossAxisAlignment: CrossAxisAlignment.stretch,
+            children: current.children,
+          );
+        } else {
+          child = const SizedBox();
+        }
+
+        if (_isListTag(tag)) {
+          assert(_listIndents.isNotEmpty);
+          _listIndents.removeLast();
+        } else if (tag == 'li') {
+          if (_listIndents.isNotEmpty) {
+            child = new Row(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              children: <Widget>[
+                new SizedBox(
+                  width: styleSheet.listIndent,
+                  child: _buildBullet(_listIndents.last),
+                ),
+                new Expanded(child: child)
+              ],
+            );
+          }
+        } else if (tag == 'blockquote') {
+          child = new DecoratedBox(
+            decoration: styleSheet.blockquoteDecoration,
+            child: new Padding(
+              padding: new EdgeInsets.all(styleSheet.blockquotePadding),
+              child: child,
+            ),
+          );
+        } else if (tag == 'pre') {
+          child = new DecoratedBox(
+            decoration: styleSheet.codeblockDecoration,
+            child: new Padding(
+              padding: new EdgeInsets.all(styleSheet.codeblockPadding),
+              child: child,
+            ),
+          );
+        }
+      }
+
+      _addBlockChild(child);
+    } else {
+      final _InlineElement current = _inlines.removeLast();
+      final _InlineElement parent = _inlines.last;
+
+      if (current.children.isNotEmpty) {
+        GestureRecognizer recognizer;
+
+        if (tag == 'a')
+          recognizer = delegate.createLink(element.attributes['href']);
+
+        parent.children.add(new TextSpan(
+          style: styleSheet.styles[tag],
+          recognizer: recognizer,
+          children: current.children,
+        ));
+      }
+    }
+  }
+
+  Widget _buildImage(String src) {
+    final List<String> parts = src.split('#');
+    if (parts.isEmpty)
+      return const SizedBox();
+
+    final String path = parts.first;
+    double width;
+    double height;
+    if (parts.length == 2) {
+      final List<String> dimensions = parts.last.split('x');
+      if (dimensions.length == 2) {
+        width = double.parse(dimensions[0]);
+        height = double.parse(dimensions[1]);
+      }
+    }
+
+    return new Image.network(path, width: width, height: height);
+  }
+
+  Widget _buildBullet(String listTag) {
+    if (listTag == 'ul')
+      return new Text('•', textAlign: TextAlign.center);
+
+    final int index = _blocks.last.nextListIndex;
+    return new Padding(
+      padding: const EdgeInsets.only(right: 5.0),
+      child: new Text('${index + 1}.', textAlign: TextAlign.right),
+    );
+  }
+
+  void _addBlockChild(Widget child) {
+    final _BlockElement parent = _blocks.last;
+    if (parent.children.isNotEmpty)
+      parent.children.add(new SizedBox(height: styleSheet.blockSpacing));
+    parent.children.add(child);
+    parent.nextListIndex += 1;
+  }
+
+  void _addAnonymousBlockIfNeeded(TextStyle style) {
+    final _InlineElement inline = _inlines.single;
+    if (inline.children.isNotEmpty) {
+      final TextSpan span = new TextSpan(style: style, children: inline.children);
+      _addBlockChild(new RichText(text: span));
+      _inlines.clear();
+      _inlines.add(new _InlineElement());
+    }
+  }
+}

packages/flutter_markdown/lib/src/markdown.dart

@@ -1,95 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:flutter/material.dart';
-
-import 'markdown_raw.dart';
-import 'markdown_style.dart';
-
-/// A [Widget] that renders markdown formatted text. It supports all standard
-/// markdowns from the original markdown specification found here:
-/// https://daringfireball.net/projects/markdown/ The rendered markdown is
-/// placed in a padded scrolling view port. If you do not want the scrolling
-/// behaviour, use the [MarkdownBody] class instead.
-class Markdown extends MarkdownRaw {
-
-  /// Creates a new Markdown [Widget] that renders the markdown formatted string
-  /// passed in as [data]. By default the markdown will be rendered using the
-  /// styles from the current theme, but you can optionally pass in a custom
-  /// [markdownStyle] that specifies colors and fonts to use. Code blocks are
-  /// by default not using syntax highlighting, but it's possible to pass in
-  /// a custom [syntaxHighlighter].
-  ///
-  ///     new Markdown(data: "Hello _world_!");
-  Markdown({
-    String data,
-    SyntaxHighlighter syntaxHighlighter,
-    MarkdownStyle markdownStyle,
-    MarkdownLinkCallback onTapLink
-  }) : super(
-    data: data,
-    syntaxHighlighter: syntaxHighlighter,
-    markdownStyle: markdownStyle,
-    onTapLink: onTapLink
-  );
-
-  @override
-  MarkdownBody createMarkdownBody({
-    String data,
-    MarkdownStyle markdownStyle,
-    SyntaxHighlighter syntaxHighlighter,
-    MarkdownLinkCallback onTapLink
-  }) {
-    return new MarkdownBody(
-      data: data,
-      markdownStyle: markdownStyle,
-      syntaxHighlighter: syntaxHighlighter,
-      onTapLink: onTapLink
-    );
-  }
-}
-
-/// A [Widget] that renders markdown formatted text.
-///
-/// It supports all standard markdowns from the original markdown specification
-/// found here: <https://daringfireball.net/projects/markdown/>
-///
-/// This class doesn't implement any scrolling behavior, if you want scrolling
-/// either wrap the widget in a [SingleChildScrollView] or use the [Markdown]
-/// widget.
-class MarkdownBody extends MarkdownBodyRaw {
-
-  /// Creates a new Markdown [Widget] that renders the markdown formatted string
-  /// passed in as [data]. By default the markdown will be rendered using the
-  /// styles from the current theme, but you can optionally pass in a custom
-  /// [markdownStyle] that specifies colors and fonts to use. Code blocks are
-  /// by default not using syntax highlighting, but it's possible to pass in
-  /// a custom [syntaxHighlighter].
-  ///
-  /// Typically, you may want to wrap the [MarkdownBody] widget in a
-  /// [SingleChildScrollView], or use the [Markdown] class.
-  ///
-  /// ```dart
-  /// new SingleChildScrollView(
-  ///   padding: new EdgeInsets.all(16.0),
-  ///   child: new Markdown(data: markdownSource),
-  /// ),
-  /// ```
-  MarkdownBody({
-    String data,
-    SyntaxHighlighter syntaxHighlighter,
-    MarkdownStyle markdownStyle,
-    MarkdownLinkCallback onTapLink
-  }) : super(
-    data: data,
-    syntaxHighlighter: syntaxHighlighter,
-    markdownStyle: markdownStyle,
-    onTapLink: onTapLink
-  );
-
-  @override
-  MarkdownStyle createDefaultStyle(BuildContext context) {
-    return new MarkdownStyle.defaultFromTheme(Theme.of(context));
-  }
-}

packages/flutter_markdown/lib/src/markdown_raw.dart

@@ -1,545 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:markdown/markdown.dart' as md;
-import 'package:flutter/widgets.dart';
-import 'package:flutter/gestures.dart';
-
-import 'markdown_style_raw.dart';
-
-typedef void MarkdownLinkCallback(String href);
-
-
-/// A [Widget] that renders markdown formatted text. It supports all standard
-/// markdowns from the original markdown specification found here:
-/// https://daringfireball.net/projects/markdown/ The rendered markdown is
-/// placed in a padded scrolling view port. If you do not want the scrolling
-/// behaviour, use the [MarkdownBodyRaw] class instead.
-class MarkdownRaw extends StatelessWidget {
-
-  /// Creates a new Markdown [Widget] that renders the markdown formatted string
-  /// passed in as [data]. By default the markdown will be rendered using the
-  /// styles from the current theme, but you can optionally pass in a custom
-  /// [markdownStyle] that specifies colors and fonts to use. Code blocks are
-  /// by default not using syntax highlighting, but it's possible to pass in
-  /// a custom [syntaxHighlighter].
-  ///
-  ///     new MarkdownRaw(data: "Hello _world_!", markdownStyle: myStyle);
-  MarkdownRaw({
-    this.data,
-    this.markdownStyle,
-    this.syntaxHighlighter,
-    this.padding: const EdgeInsets.all(16.0),
-    this.onTapLink
-  });
-
-  /// Markdown styled text
-  final String data;
-
-  /// Style used for rendering the markdown
-  final MarkdownStyleRaw markdownStyle;
-
-  /// The syntax highlighter used to color text in code blocks
-  final SyntaxHighlighter syntaxHighlighter;
-
-  /// Padding used
-  final EdgeInsets padding;
-
-  /// Callback when a link is tapped
-  final MarkdownLinkCallback onTapLink;
-
-  @override
-  Widget build(BuildContext context) {
-    // TODO(abarth): We should use a ListView here and lazily build the widgets
-    // from the markdown.
-    return new SingleChildScrollView(
-      padding: padding,
-      child: createMarkdownBody(
-        data: data,
-        markdownStyle: markdownStyle,
-        syntaxHighlighter: syntaxHighlighter,
-        onTapLink: onTapLink,
-      ),
-    );
-  }
-
-  MarkdownBodyRaw createMarkdownBody({
-    String data,
-    covariant MarkdownStyleRaw markdownStyle,
-    SyntaxHighlighter syntaxHighlighter,
-    MarkdownLinkCallback onTapLink
-  }) {
-    return new MarkdownBodyRaw(
-      data: data,
-      markdownStyle: markdownStyle,
-      syntaxHighlighter: syntaxHighlighter,
-      onTapLink: onTapLink
-    );
-  }
-}
-
-/// A [Widget] that renders markdown formatted text.
-///
-/// It supports all standard markdowns from the original markdown specification
-/// found here: <https://daringfireball.net/projects/markdown/>.
-///
-/// This class doesn't implement any scrolling behavior, if you want scrolling
-/// either wrap the widget in a [SingleChildScrollView] or use the [MarkdownRaw]
-/// widget.
-class MarkdownBodyRaw extends StatefulWidget {
-
-  /// Creates a new Markdown [Widget] that renders the markdown formatted string
-  /// passed in as [data]. You need to pass in a [markdownStyle] that defines
-  /// how the code is rendered. Code blocks are by default not using syntax
-  /// highlighting, but it's possible to pass in a custom [syntaxHighlighter].
-  ///
-  /// Typically, you may want to wrap the [MarkdownBodyRaw] widget in a
-  /// a [SingleChildScrollView], or use the [Markdown class].
-  ///
-  /// ```dart
-  /// new SingleChildScrollView(
-  ///   padding: new EdgeInsets.all(16.0),
-  ///   child: new MarkdownBodyRaw(
-  ///     data: markdownSource,
-  ///     markdownStyle: myStyle,
-  ///   ),
-  /// ),
-  /// ```
-  MarkdownBodyRaw({
-    this.data,
-    this.markdownStyle,
-    this.syntaxHighlighter,
-    this.onTapLink
-  });
-
-  /// Markdown styled text
-  final String data;
-
-  /// Style used for rendering the markdown
-  final MarkdownStyleRaw markdownStyle;
-
-  /// The syntax highlighter used to color text in code blocks
-  final SyntaxHighlighter syntaxHighlighter;
-
-  /// Callback when a link is tapped
-  final MarkdownLinkCallback onTapLink;
-
-  @override
-  _MarkdownBodyRawState createState() => new _MarkdownBodyRawState();
-
-  MarkdownStyleRaw createDefaultStyle(BuildContext context) => null;
-}
-
-class _MarkdownBodyRawState extends State<MarkdownBodyRaw> {
-
-  @override
-  void didChangeDependencies() {
-    _buildMarkdownCache();
-    super.didChangeDependencies();
-  }
-
-  @override
-  void dispose() {
-    _linkHandler.dispose();
-    super.dispose();
-  }
-
-  @override
-  void didUpdateConfig(MarkdownBodyRaw oldConfig) {
-    super.didUpdateConfig(oldConfig);
-
-    if (oldConfig.data != config.data ||
-        oldConfig.markdownStyle != config.markdownStyle ||
-        oldConfig.syntaxHighlighter != config.syntaxHighlighter ||
-        oldConfig.onTapLink != config.onTapLink)
-      _buildMarkdownCache();
-  }
-
-  void _buildMarkdownCache() {
-    final MarkdownStyleRaw markdownStyle = config.markdownStyle ?? config.createDefaultStyle(context);
-    final SyntaxHighlighter syntaxHighlighter = config.syntaxHighlighter ?? new _DefaultSyntaxHighlighter(markdownStyle.code);
-
-    _linkHandler?.dispose();
-    _linkHandler = new _LinkHandler(config.onTapLink);
-
-    // TODO: This can be optimized by doing the split and removing \r at the same time
-    final List<String> lines = config.data.replaceAll('\r\n', '\n').split('\n');
-    final md.Document document = new md.Document();
-
-    final _Renderer renderer = new _Renderer();
-    _cachedBlocks = renderer.render(document.parseLines(lines), markdownStyle, syntaxHighlighter, _linkHandler);
-  }
-
-  List<_Block> _cachedBlocks;
-  _LinkHandler _linkHandler;
-
-  @override
-  Widget build(BuildContext context) {
-    final List<Widget> blocks = <Widget>[];
-    for (_Block block in _cachedBlocks) {
-      blocks.add(block.build(context));
-    }
-
-    return new Column(
-      crossAxisAlignment: CrossAxisAlignment.stretch,
-      children: blocks
-    );
-  }
-
-  @override
-  void debugFillDescription(List<String> description) {
-    super.debugFillDescription(description);
-    description.add('cached blocks identity: ${_cachedBlocks.hashCode}');
-  }
-}
-
-class _Renderer implements md.NodeVisitor {
-  List<_Block> render(List<md.Node> nodes, MarkdownStyleRaw markdownStyle, SyntaxHighlighter syntaxHighlighter, _LinkHandler linkHandler) {
-    assert(markdownStyle != null);
-
-    _blocks = <_Block>[];
-    _listIndents = <String>[];
-    _markdownStyle = markdownStyle;
-    _syntaxHighlighter = syntaxHighlighter;
-    _linkHandler = linkHandler;
-
-    for (final md.Node node in nodes) {
-      node.accept(this);
-    }
-
-    return _blocks;
-  }
-
-  List<_Block> _blocks;
-  List<String> _listIndents;
-  MarkdownStyleRaw _markdownStyle;
-  SyntaxHighlighter _syntaxHighlighter;
-  _LinkHandler _linkHandler;
-
-  @override
-  void visitText(md.Text text) {
-    if (_currentBlock != null) { // ignore if no corresponding block
-      final _MarkdownNodeList topList = _currentBlock.stack.last;
-      final List<_MarkdownNode> top = topList.list;
-
-      if (_currentBlock.tag == 'pre')
-        top.add(
-            new _MarkdownNodeTextSpan(_syntaxHighlighter.format(text.text)));
-      else
-        top.add(new _MarkdownNodeString(text.text));
-    }
-  }
-
-  @override
-  bool visitElementBefore(md.Element element) {
-    if (_isListTag(element.tag))
-      _listIndents.add(element.tag);
-
-    if (_isBlockTag(element.tag)) {
-      List<_Block> blockList;
-      if (_currentBlock == null)
-        blockList = _blocks;
-      else
-        blockList = _currentBlock.subBlocks;
-
-      final _Block newBlock = new _Block(element.tag, element.attributes, _markdownStyle, new List<String>.from(_listIndents), blockList.length);
-      blockList.add(newBlock);
-    } else {
-      _LinkInfo linkInfo;
-      if (element.tag == 'a') {
-        linkInfo = _linkHandler.createLinkInfo(element.attributes['href']);
-      }
-
-      final TextStyle style = _markdownStyle.styles[element.tag] ?? const TextStyle();
-      final List<_MarkdownNode> styleElement = <_MarkdownNode>[new _MarkdownNodeTextStyle(style, linkInfo)];
-      _currentBlock.stack.add(new _MarkdownNodeList(styleElement));
-    }
-    return true;
-  }
-
-  @override
-  void visitElementAfter(md.Element element) {
-    if (_isListTag(element.tag))
-      _listIndents.removeLast();
-
-    if (_isBlockTag(element.tag)) {
-      if (_currentBlock.stack.isNotEmpty) {
-        final _MarkdownNodeList stackList = _currentBlock.stack.first;
-        _currentBlock.stack = stackList.list;
-        _currentBlock.open = false;
-      } else {
-        _currentBlock.stack = <_MarkdownNode>[new _MarkdownNodeString('')];
-      }
-    } else {
-      if (_currentBlock.stack.length > 1) {
-        final _MarkdownNodeList poppedList = _currentBlock.stack.last;
-        final List<_MarkdownNode> popped = poppedList.list;
-        _currentBlock.stack.removeLast();
-
-        final _MarkdownNodeList topList = _currentBlock.stack.last;
-        final List<_MarkdownNode> top = topList.list;
-        top.add(new _MarkdownNodeList(popped));
-      }
-    }
-  }
-
-  static const List<String> _kBlockTags = const <String>['p', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'li', 'blockquote', 'img', 'pre', 'ol', 'ul'];
-  static const List<String> _kListTags = const <String>['ul', 'ol'];
-
-  bool _isBlockTag(String tag) {
-    return _kBlockTags.contains(tag);
-  }
-
-  bool _isListTag(String tag) {
-    return _kListTags.contains(tag);
-  }
-
-  _Block get _currentBlock => _currentBlockInList(_blocks);
-
-  _Block _currentBlockInList(List<_Block> blocks) {
-    if (blocks.isEmpty)
-      return null;
-
-    if (!blocks.last.open)
-      return null;
-
-    final _Block childBlock = _currentBlockInList(blocks.last.subBlocks);
-    if (childBlock != null)
-      return childBlock;
-
-    return blocks.last;
-  }
-}
-
-abstract class _MarkdownNode {
-}
-
-class _MarkdownNodeList extends _MarkdownNode {
-  _MarkdownNodeList(this.list);
-  List<_MarkdownNode> list;
-}
-
-class _MarkdownNodeTextStyle extends _MarkdownNode {
-  _MarkdownNodeTextStyle(this.style, [this.linkInfo = null]);
-  TextStyle style;
-  _LinkInfo linkInfo;
-}
-
-class _MarkdownNodeString extends _MarkdownNode {
-  _MarkdownNodeString(this.string);
-  String string;
-}
-
-class _MarkdownNodeTextSpan extends _MarkdownNode {
-  _MarkdownNodeTextSpan(this.textSpan);
-  TextSpan textSpan;
-}
-
-class _Block {
-  _Block(this.tag, this.attributes, this.markdownStyle, this.listIndents, this.blockPosition) {
-    TextStyle style = markdownStyle.styles[tag];
-    if (style == null)
-      style = const TextStyle(color: const Color(0xffff0000));
-
-    stack = <_MarkdownNode>[new _MarkdownNodeList(<_MarkdownNode>[new _MarkdownNodeTextStyle(style)])];
-    subBlocks = <_Block>[];
-  }
-
-  final String tag;
-  final Map<String, String> attributes;
-  final MarkdownStyleRaw markdownStyle;
-  final List<String> listIndents;
-  final int blockPosition;
-
-  List<_MarkdownNode> stack;
-  List<_Block> subBlocks;
-
-  bool get open => _open;
-  set open(bool value) {
-    _open = value;
-    if (!value && subBlocks.isNotEmpty)
-      subBlocks.last.isLast = true;
-  }
-
-  bool _open = true;
-  bool isLast = false;
-
-  Widget build(BuildContext context) {
-
-    if (tag == 'img') {
-      return _buildImage(context, attributes['src']);
-    }
-
-    double spacing = markdownStyle.blockSpacing;
-    if (isLast) spacing = 0.0;
-
-    Widget contents;
-
-    if (subBlocks.isNotEmpty) {
-      final List<Widget> subWidgets = <Widget>[];
-      for (_Block subBlock in subBlocks) {
-        subWidgets.add(subBlock.build(context));
-      }
-
-      contents = new Column(
-        crossAxisAlignment: CrossAxisAlignment.stretch,
-        children: subWidgets
-      );
-    } else {
-      final TextSpan span = _stackToTextSpan(new _MarkdownNodeList(stack));
-      contents = new RichText(text: span);
-
-      if (listIndents.isNotEmpty) {
-        Widget bullet;
-        if (listIndents.last == 'ul') {
-          bullet = new Text(
-            '•',
-            textAlign: TextAlign.center
-          );
-        }
-        else {
-          bullet = new Padding(
-            padding: const EdgeInsets.only(right: 5.0),
-            child: new Text(
-              "${blockPosition + 1}.",
-              textAlign: TextAlign.right
-            )
-          );
-        }
-
-        contents = new Row(
-          crossAxisAlignment: CrossAxisAlignment.start,
-          children: <Widget>[
-            new SizedBox(
-              width: listIndents.length * markdownStyle.listIndent,
-              child: bullet
-            ),
-            new Expanded(child: contents)
-          ]
-        );
-      }
-    }
-
-    BoxDecoration decoration;
-    EdgeInsets padding;
-
-    if (tag == 'blockquote') {
-      decoration = markdownStyle.blockquoteDecoration;
-      padding = new EdgeInsets.all(markdownStyle.blockquotePadding);
-    } else if (tag == 'pre') {
-      decoration = markdownStyle.codeblockDecoration;
-      padding = new EdgeInsets.all(markdownStyle.codeblockPadding);
-    }
-
-    return new Container(
-      padding: padding,
-      margin: new EdgeInsets.only(bottom: spacing),
-      child: contents,
-      decoration: decoration
-    );
-  }
-
-  TextSpan _stackToTextSpan(_MarkdownNode stack) {
-    if (stack is _MarkdownNodeTextSpan)
-      return stack.textSpan;
-
-    if (stack is _MarkdownNodeList) {
-      final List<_MarkdownNode> list = stack.list;
-      final _MarkdownNodeTextStyle styleNode = list[0];
-      final _LinkInfo linkInfo = styleNode.linkInfo;
-      final TextStyle style = styleNode.style;
-
-      List<TextSpan> children = <TextSpan>[];
-      for (int i = 1; i < list.length; i++) {
-        children.add(_stackToTextSpan(list[i]));
-      }
-
-      String text;
-      if (children.length == 1 && _isPlainText(children[0])) {
-        text = children[0].text;
-        children = null;
-      }
-
-      final TapGestureRecognizer recognizer = linkInfo?.recognizer;
-
-      return new TextSpan(style: style, children: children, recognizer: recognizer, text: text);
-    }
-
-    if (stack is _MarkdownNodeString) {
-      return new TextSpan(text: stack.string);
-    }
-
-    return null;
-  }
-
-  bool _isPlainText(TextSpan span) {
-    return (span.text != null && span.style == null && span.recognizer == null && span.children == null);
-  }
-
-  Widget _buildImage(BuildContext context, String src) {
-    final List<String> parts = src.split('#');
-    if (parts.isEmpty) return new Container();
-
-    final String path = parts.first;
-    double width;
-    double height;
-    if (parts.length == 2) {
-      final List<String> dimensions = parts.last.split('x');
-      if (dimensions.length == 2) {
-        width = double.parse(dimensions[0]);
-        height = double.parse(dimensions[1]);
-      }
-    }
-
-    return new Image.network(path, width: width, height: height);
-  }
-}
-
-class _LinkInfo {
-  _LinkInfo(this.href, this.recognizer);
-
-  final String href;
-  final TapGestureRecognizer recognizer;
-}
-
-class _LinkHandler {
-  _LinkHandler(this.onTapLink);
-
-  List<_LinkInfo> links = <_LinkInfo>[];
-  MarkdownLinkCallback onTapLink;
-
-  _LinkInfo createLinkInfo(String href) {
-    final TapGestureRecognizer recognizer = new TapGestureRecognizer();
-    recognizer.onTap = () {
-      if (onTapLink != null)
-        onTapLink(href);
-    };
-
-    final _LinkInfo linkInfo = new _LinkInfo(href, recognizer);
-    links.add(linkInfo);
-
-    return linkInfo;
-  }
-
-  void dispose() {
-    for (_LinkInfo linkInfo in links) {
-      linkInfo.recognizer.dispose();
-    }
-  }
-}
-
-abstract class SyntaxHighlighter { // ignore: one_member_abstracts
-  TextSpan format(String source);
-}
-
-class _DefaultSyntaxHighlighter extends SyntaxHighlighter{
-  _DefaultSyntaxHighlighter(this.style);
-
-  final TextStyle style;
-
-  @override
-  TextSpan format(String source) {
-    return new TextSpan(style: style, children: <TextSpan>[new TextSpan(text: source)]);
-  }
-}

packages/flutter_markdown/lib/src/markdown_style.dart

@@ -1,78 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:flutter/material.dart';
-import 'markdown.dart';
-import 'markdown_style_raw.dart';
-
-/// Style used for rendering markdown formatted text using the [MarkdownBody]
-/// widget.
-class MarkdownStyle extends MarkdownStyleRaw{
-
-  /// Creates a [MarkdownStyle] from the [TextStyle]s in the provided [theme].
-  MarkdownStyle.defaultFromTheme(ThemeData theme) : super(
-    a: new TextStyle(color: Colors.blue),
-    p: theme.textTheme.body1,
-    code: new TextStyle(
-      color: Colors.grey.shade700,
-      fontFamily: "monospace",
-      fontSize: theme.textTheme.body1.fontSize * 0.85
-    ),
-    h1: theme.textTheme.headline,
-    h2: theme.textTheme.title,
-    h3: theme.textTheme.subhead,
-    h4: theme.textTheme.body2,
-    h5: theme.textTheme.body2,
-    h6: theme.textTheme.body2,
-    em: const TextStyle(fontStyle: FontStyle.italic),
-    strong: const TextStyle(fontWeight: FontWeight.bold),
-    blockquote: theme.textTheme.body1,
-    blockSpacing: 8.0,
-    listIndent: 32.0,
-    blockquotePadding: 8.0,
-    blockquoteDecoration: new BoxDecoration(
-      backgroundColor: Colors.blue.shade100,
-      borderRadius: new BorderRadius.circular(2.0)
-    ),
-    codeblockPadding: 8.0,
-    codeblockDecoration: new BoxDecoration(
-      backgroundColor: Colors.grey.shade100,
-      borderRadius: new BorderRadius.circular(2.0)
-    )
-  );
-
-  /// Creates a [MarkdownStyle] from the [TextStyle]s in the provided [theme].
-  /// This style uses larger fonts for the headings than in
-  /// [MarkdownStyle.defaultFromTheme].
-  MarkdownStyle.largeFromTheme(ThemeData theme) : super (
-    a: new TextStyle(color: Colors.blue),
-    p: theme.textTheme.body1,
-    code: new TextStyle(
-      color: Colors.grey.shade700,
-      fontFamily: "monospace",
-      fontSize: theme.textTheme.body1.fontSize * 0.85
-    ),
-    h1: theme.textTheme.display3,
-    h2: theme.textTheme.display2,
-    h3: theme.textTheme.display1,
-    h4: theme.textTheme.headline,
-    h5: theme.textTheme.title,
-    h6: theme.textTheme.subhead,
-    em: const TextStyle(fontStyle: FontStyle.italic),
-    strong: const TextStyle(fontWeight: FontWeight.bold),
-    blockquote: theme.textTheme.body1,
-    blockSpacing: 8.0,
-    listIndent: 32.0,
-    blockquotePadding: 8.0,
-    blockquoteDecoration: new BoxDecoration(
-      backgroundColor: Colors.blue.shade100,
-      borderRadius: new BorderRadius.circular(2.0)
-    ),
-    codeblockPadding: 8.0,
-    codeblockDecoration: new BoxDecoration(
-      backgroundColor: Colors.grey.shade100,
-      borderRadius: new BorderRadius.circular(2.0)
-    )
-  );
-}

packages/flutter_markdown/lib/src/markdown_style_raw.dart

@@ -1,121 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:flutter/widgets.dart';
-import 'markdown.dart';
-
-/// Style used for rendering markdown formatted text using the [MarkdownBody]
-/// widget.
-class MarkdownStyleRaw {
-
-  /// Creates a new [MarkdownStyleRaw]
-  MarkdownStyleRaw({
-    this.a,
-    this.p,
-    this.code,
-    this.h1,
-    this.h2,
-    this.h3,
-    this.h4,
-    this.h5,
-    this.h6,
-    this.em,
-    this.strong,
-    this.blockquote,
-    this.blockSpacing,
-    this.listIndent,
-    this.blockquotePadding,
-    this.blockquoteDecoration,
-    this.codeblockPadding,
-    this.codeblockDecoration
-  }) {
-    _init();
-  }
-
-  /// Creates a new [MarkdownStyleRaw] based on the current style, with the
-  /// provided parameters overridden.
-  MarkdownStyleRaw copyWith({
-    TextStyle a,
-    TextStyle p,
-    TextStyle code,
-    TextStyle h1,
-    TextStyle h2,
-    TextStyle h3,
-    TextStyle h4,
-    TextStyle h5,
-    TextStyle h6,
-    TextStyle em,
-    TextStyle strong,
-    TextStyle blockquote,
-    double blockSpacing,
-    double listIndent,
-    double blockquotePadding,
-    BoxDecoration blockquoteDecoration,
-    double codeblockPadding,
-    BoxDecoration codeblockDecoration
-  }) {
-    return new MarkdownStyleRaw(
-      a: a != null ? a : this.a,
-      p: p != null ? p : this.p,
-      code: code != null ? code : this.code,
-      h1: h1 != null ? h1 : this.h1,
-      h2: h2 != null ? h2 : this.h2,
-      h3: h3 != null ? h3 : this.h3,
-      h4: h4 != null ? h4 : this.h4,
-      h5: h5 != null ? h5 : this.h5,
-      h6: h6 != null ? h6 : this.h6,
-      em: em != null ? em : this.em,
-      strong: strong != null ? strong : this.strong,
-      blockquote: blockquote != null ? blockquote : this.blockquote,
-      blockSpacing: blockSpacing != null ? blockSpacing : this.blockSpacing,
-      listIndent: listIndent != null ? listIndent : this.listIndent,
-      blockquotePadding: blockquotePadding != null ? blockquotePadding : this.blockquotePadding,
-      blockquoteDecoration: blockquoteDecoration != null ? blockquoteDecoration : this.blockquoteDecoration,
-      codeblockPadding: codeblockPadding != null ? codeblockPadding : this.codeblockPadding,
-      codeblockDecoration: codeblockDecoration != null ? codeblockDecoration : this.codeblockDecoration
-    );
-  }
-
-  final TextStyle a;
-  final TextStyle p;
-  final TextStyle code;
-  final TextStyle h1;
-  final TextStyle h2;
-  final TextStyle h3;
-  final TextStyle h4;
-  final TextStyle h5;
-  final TextStyle h6;
-  final TextStyle em;
-  final TextStyle strong;
-  final TextStyle blockquote;
-  final double blockSpacing;
-  final double listIndent;
-  final double blockquotePadding;
-  final BoxDecoration blockquoteDecoration;
-  final double codeblockPadding;
-  final BoxDecoration codeblockDecoration;
-
-  Map<String, TextStyle> _styles;
-
-  Map<String, TextStyle> get styles => _styles;
-
-  void _init() {
-    _styles = <String, TextStyle>{
-      'a': a,
-      'p': p,
-      'li': p,
-      'code': code,
-      'pre': p,
-      'h1': h1,
-      'h2': h2,
-      'h3': h3,
-      'h4': h4,
-      'h5': h5,
-      'h6': h6,
-      'em': em,
-      'strong': strong,
-      'blockquote': blockquote
-    };
-  }
-}

packages/flutter_markdown/lib/src/style_sheet.dart

@@ -0,0 +1,269 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+
+/// Defines which [TextStyle] objects to use for which Markdown elements.
+class MarkdownStyleSheet {
+  /// Creates an explicit mapping of [TextStyle] objects to Markdown elements.
+  MarkdownStyleSheet({
+    this.a,
+    this.p,
+    this.code,
+    this.h1,
+    this.h2,
+    this.h3,
+    this.h4,
+    this.h5,
+    this.h6,
+    this.em,
+    this.strong,
+    this.blockquote,
+    this.blockSpacing,
+    this.listIndent,
+    this.blockquotePadding,
+    this.blockquoteDecoration,
+    this.codeblockPadding,
+    this.codeblockDecoration
+  }) : _styles = <String, TextStyle>{
+    'a': a,
+    'p': p,
+    'li': p,
+    'code': code,
+    'pre': p,
+    'h1': h1,
+    'h2': h2,
+    'h3': h3,
+    'h4': h4,
+    'h5': h5,
+    'h6': h6,
+    'em': em,
+    'strong': strong,
+    'blockquote': blockquote
+  };
+
+  /// Creates a [MarkdownStyleSheet] from the [TextStyle]s in the provided [ThemeData].
+  factory MarkdownStyleSheet.fromTheme(ThemeData theme) {
+    return new MarkdownStyleSheet(
+      a: new TextStyle(color: Colors.blue),
+      p: theme.textTheme.body1,
+      code: new TextStyle(
+        color: Colors.grey.shade700,
+        fontFamily: "monospace",
+        fontSize: theme.textTheme.body1.fontSize * 0.85
+      ),
+      h1: theme.textTheme.headline,
+      h2: theme.textTheme.title,
+      h3: theme.textTheme.subhead,
+      h4: theme.textTheme.body2,
+      h5: theme.textTheme.body2,
+      h6: theme.textTheme.body2,
+      em: const TextStyle(fontStyle: FontStyle.italic),
+      strong: const TextStyle(fontWeight: FontWeight.bold),
+      blockquote: theme.textTheme.body1,
+      blockSpacing: 8.0,
+      listIndent: 32.0,
+      blockquotePadding: 8.0,
+      blockquoteDecoration: new BoxDecoration(
+        backgroundColor: Colors.blue.shade100,
+        borderRadius: new BorderRadius.circular(2.0)
+      ),
+      codeblockPadding: 8.0,
+      codeblockDecoration: new BoxDecoration(
+        backgroundColor: Colors.grey.shade100,
+        borderRadius: new BorderRadius.circular(2.0)
+      )
+    );
+  }
+
+  /// Creates a [MarkdownStyle] from the [TextStyle]s in the provided [ThemeData].
+  ///
+  /// This constructor uses larger fonts for the headings than in
+  /// [MarkdownStyle.fromTheme].
+  factory MarkdownStyleSheet.largeFromTheme(ThemeData theme) {
+    return new MarkdownStyleSheet(
+      a: new TextStyle(color: Colors.blue),
+      p: theme.textTheme.body1,
+      code: new TextStyle(
+        color: Colors.grey.shade700,
+        fontFamily: "monospace",
+        fontSize: theme.textTheme.body1.fontSize * 0.85
+      ),
+      h1: theme.textTheme.display3,
+      h2: theme.textTheme.display2,
+      h3: theme.textTheme.display1,
+      h4: theme.textTheme.headline,
+      h5: theme.textTheme.title,
+      h6: theme.textTheme.subhead,
+      em: const TextStyle(fontStyle: FontStyle.italic),
+      strong: const TextStyle(fontWeight: FontWeight.bold),
+      blockquote: theme.textTheme.body1,
+      blockSpacing: 8.0,
+      listIndent: 32.0,
+      blockquotePadding: 8.0,
+      blockquoteDecoration: new BoxDecoration(
+        backgroundColor: Colors.blue.shade100,
+        borderRadius: new BorderRadius.circular(2.0)
+      ),
+      codeblockPadding: 8.0,
+      codeblockDecoration: new BoxDecoration(
+        backgroundColor: Colors.grey.shade100,
+        borderRadius: new BorderRadius.circular(2.0)
+      )
+    );
+  }
+
+  /// Creates a new [MarkdownStyleSheet] based on the current style, with the
+  /// provided parameters overridden.
+  MarkdownStyleSheet copyWith({
+    TextStyle a,
+    TextStyle p,
+    TextStyle code,
+    TextStyle h1,
+    TextStyle h2,
+    TextStyle h3,
+    TextStyle h4,
+    TextStyle h5,
+    TextStyle h6,
+    TextStyle em,
+    TextStyle strong,
+    TextStyle blockquote,
+    double blockSpacing,
+    double listIndent,
+    double blockquotePadding,
+    Decoration blockquoteDecoration,
+    double codeblockPadding,
+    Decoration codeblockDecoration
+  }) {
+    return new MarkdownStyleSheet(
+      a: a != null ? a : this.a,
+      p: p != null ? p : this.p,
+      code: code != null ? code : this.code,
+      h1: h1 != null ? h1 : this.h1,
+      h2: h2 != null ? h2 : this.h2,
+      h3: h3 != null ? h3 : this.h3,
+      h4: h4 != null ? h4 : this.h4,
+      h5: h5 != null ? h5 : this.h5,
+      h6: h6 != null ? h6 : this.h6,
+      em: em != null ? em : this.em,
+      strong: strong != null ? strong : this.strong,
+      blockquote: blockquote != null ? blockquote : this.blockquote,
+      blockSpacing: blockSpacing != null ? blockSpacing : this.blockSpacing,
+      listIndent: listIndent != null ? listIndent : this.listIndent,
+      blockquotePadding: blockquotePadding != null ? blockquotePadding : this.blockquotePadding,
+      blockquoteDecoration: blockquoteDecoration != null ? blockquoteDecoration : this.blockquoteDecoration,
+      codeblockPadding: codeblockPadding != null ? codeblockPadding : this.codeblockPadding,
+      codeblockDecoration: codeblockDecoration != null ? codeblockDecoration : this.codeblockDecoration
+    );
+  }
+
+  /// The [TextStyle] to use for `a` elements.
+  final TextStyle a;
+
+  /// The [TextStyle] to use for `p` elements.
+  final TextStyle p;
+
+  /// The [TextStyle] to use for `code` elements.
+  final TextStyle code;
+
+  /// The [TextStyle] to use for `h1` elements.
+  final TextStyle h1;
+
+  /// The [TextStyle] to use for `h2` elements.
+  final TextStyle h2;
+
+  /// The [TextStyle] to use for `h3` elements.
+  final TextStyle h3;
+
+  /// The [TextStyle] to use for `h4` elements.
+  final TextStyle h4;
+
+  /// The [TextStyle] to use for `h5` elements.
+  final TextStyle h5;
+
+  /// The [TextStyle] to use for `h6` elements.
+  final TextStyle h6;
+
+  /// The [TextStyle] to use for `em` elements.
+  final TextStyle em;
+
+  /// The [TextStyle] to use for `strong` elements.
+  final TextStyle strong;
+
+  /// The [TextStyle] to use for `blockquote` elements.
+  final TextStyle blockquote;
+
+  /// The amount of vertical space to use between block-level elements.
+  final double blockSpacing;
+
+  /// The amount of horizontal space to indent list items.
+  final double listIndent;
+
+  /// The padding to use for `blockquote` elements.
+  final double blockquotePadding;
+
+  /// The decoration to use behind `blockquote` elements.
+  final Decoration blockquoteDecoration;
+
+  /// The padding to use for `pre` elements.
+  final double codeblockPadding;
+
+  /// The decoration to use behind for `pre` elements.
+  final Decoration codeblockDecoration;
+
+  /// A [Map] from element name to the cooresponding [TextStyle] object.
+  Map<String, TextStyle> get styles => _styles;
+  Map<String, TextStyle> _styles;
+
+  @override
+  bool operator ==(dynamic other) {
+    if (identical(this, other))
+      return true;
+    if (other.runtimeType != MarkdownStyleSheet)
+      return false;
+    final MarkdownStyleSheet typedOther = other;
+    return typedOther.a == a
+        && typedOther.p == p
+        && typedOther.code == code
+        && typedOther.h1 == h1
+        && typedOther.h2 == h2
+        && typedOther.h3 == h3
+        && typedOther.h4 == h4
+        && typedOther.h5 == h5
+        && typedOther.h6 == h6
+        && typedOther.em == em
+        && typedOther.strong == strong
+        && typedOther.blockquote == blockquote
+        && typedOther.blockSpacing == blockSpacing
+        && typedOther.listIndent == listIndent
+        && typedOther.blockquotePadding == blockquotePadding
+        && typedOther.blockquoteDecoration == blockquoteDecoration
+        && typedOther.codeblockPadding == codeblockPadding
+        && typedOther.codeblockDecoration == codeblockDecoration;
+  }
+
+  @override
+  int get hashCode {
+    return hashValues(
+      a,
+      p,
+      code,
+      h1,
+      h2,
+      h3,
+      h4,
+      h5,
+      h6,
+      em,
+      strong,
+      blockquote,
+      blockSpacing,
+      listIndent,
+      blockquotePadding,
+      blockquoteDecoration,
+      codeblockPadding,
+      codeblockDecoration,
+    );
+  }
+}

packages/flutter_markdown/lib/src/widget.dart

@@ -0,0 +1,211 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/gestures.dart';
+import 'package:flutter/material.dart';
+import 'package:markdown/markdown.dart' as md;
+import 'package:meta/meta.dart';
+
+import 'builder.dart';
+import 'style_sheet.dart';
+
+/// Signature for callbacks used by [MarkdownWidget] when the user taps a link.
+///
+/// Used by [MarkdownWidget.onTapLink].
+typedef void MarkdownTapLinkCallback(String href);
+
+/// Creates a format [TextSpan] given a string.
+///
+/// Used by [MarkdownWidget] to highlight the contents of `pre` elements.
+abstract class SyntaxHighlighter { // ignore: one_member_abstracts
+  /// Returns the formated [TextSpan] for the given string.
+  TextSpan format(String source);
+}
+
+/// A base class for widgets that parse and display Markdown.
+///
+/// Supports all standard Markdown from the original
+/// [Markdown specification](https://daringfireball.net/projects/markdown/).
+///
+/// See also:
+///
+///  * [Markdown], which is a scrolling container of Markdown.
+///  * [MarkdownBody], which is a non-scrolling container of Markdown.
+///  * <https://daringfireball.net/projects/markdown/>
+abstract class MarkdownWidget extends StatefulWidget {
+  /// Creates a widget that parses and displays Markdown.
+  ///
+  /// The [data] argument must not be null.
+  MarkdownWidget({
+    Key key,
+    @required this.data,
+    this.styleSheet,
+    this.syntaxHighlighter,
+    this.onTapLink,
+  }) : super(key: key) {
+    assert(data != null);
+  }
+
+  /// The Markdown to display.
+  final String data;
+
+  /// The styles to use when displaying the Markdown.
+  ///
+  /// If null, the styles are infered from the current [Theme].
+  final MarkdownStyleSheet styleSheet;
+
+  /// The syntax highlighter used to color text in `pre` elements.
+  ///
+  /// If null, the [MarkdownStyleSheet.code] style is used for `pre` elements.
+  final SyntaxHighlighter syntaxHighlighter;
+
+  /// Called when the user taps a link.
+  final MarkdownTapLinkCallback onTapLink;
+
+  /// Subclasses should override this function to display the given children,
+  /// which are the parsed representation of [data].
+  @protected
+  Widget build(BuildContext context, List<Widget> children);
+
+  @override
+  _MarkdownWidgetState createState() => new _MarkdownWidgetState();
+}
+
+class _MarkdownWidgetState extends State<MarkdownWidget> implements MarkdownBuilderDelegate {
+  List<Widget> _children;
+  final List<GestureRecognizer> _recognizers = <GestureRecognizer>[];
+
+  @override
+  void didChangeDependencies() {
+    _parseMarkdown();
+    super.didChangeDependencies();
+  }
+
+  @override
+  void didUpdateConfig(MarkdownWidget oldConfig) {
+    super.didUpdateConfig(oldConfig);
+    if (config.data != oldConfig.data
+        || config.styleSheet != oldConfig.styleSheet)
+      _parseMarkdown();
+  }
+
+  @override
+  void dispose() {
+    _disposeRecognizers();
+    super.dispose();
+  }
+
+  void _parseMarkdown() {
+    final MarkdownStyleSheet styleSheet = config.styleSheet ?? new MarkdownStyleSheet.fromTheme(Theme.of(context));
+
+    _disposeRecognizers();
+
+    // TODO: This can be optimized by doing the split and removing \r at the same time
+    final List<String> lines = config.data.replaceAll('\r\n', '\n').split('\n');
+    final md.Document document = new md.Document();
+    final MarkdownBuilder builder = new MarkdownBuilder(delegate: this, styleSheet: styleSheet);
+    _children = builder.build(document.parseLines(lines));
+  }
+
+  void _disposeRecognizers() {
+    if (_recognizers.isEmpty)
+      return;
+    final List<GestureRecognizer> localRecognizers = new List<GestureRecognizer>.from(_recognizers);
+    _recognizers.clear();
+    for (GestureRecognizer recognizer in localRecognizers)
+      recognizer.dispose();
+  }
+
+  @override
+  GestureRecognizer createLink(String href) {
+    final TapGestureRecognizer recognizer = new TapGestureRecognizer()
+      ..onTap = () {
+      if (config.onTapLink != null)
+        config.onTapLink(href);
+    };
+    _recognizers.add(recognizer);
+    return recognizer;
+  }
+
+  @override
+  TextSpan formatText(MarkdownStyleSheet styleSheet, String code) {
+    if (config.syntaxHighlighter != null)
+      return config.syntaxHighlighter.format(code);
+    return new TextSpan(style: styleSheet.code, text: code);
+  }
+
+  @override
+  Widget build(BuildContext context) => config.build(context, _children);
+}
+
+/// A non-scrolling widget that parses and displays Markdown.
+///
+/// Supports all standard Markdown from the original
+/// [Markdown specification](https://daringfireball.net/projects/markdown/).
+///
+/// See also:
+///
+///  * [Markdown], which is a scrolling container of Markdown.
+///  * <https://daringfireball.net/projects/markdown/>
+class MarkdownBody extends MarkdownWidget {
+  /// Creates a non-scrolling widget that parses and displays Markdown.
+  MarkdownBody({
+    Key key,
+    String data,
+    MarkdownStyleSheet styleSheet,
+    SyntaxHighlighter syntaxHighlighter,
+    MarkdownTapLinkCallback onTapLink,
+  }) : super(
+    key: key,
+    data: data,
+    styleSheet: styleSheet,
+    syntaxHighlighter: syntaxHighlighter,
+    onTapLink: onTapLink,
+  );
+
+  @override
+  Widget build(BuildContext context, List<Widget> children) {
+    if (children.length == 1)
+      return children.single;
+    return new Column(
+      crossAxisAlignment: CrossAxisAlignment.stretch,
+      children: children,
+    );
+  }
+}
+
+/// A scrolling widget that parses and displays Markdown.
+///
+/// Supports all standard Markdown from the original
+/// [Markdown specification](https://daringfireball.net/projects/markdown/).
+///
+/// See also:
+///
+///  * [MarkdownBody], which is a non-scrolling container of Markdown.
+///  * <https://daringfireball.net/projects/markdown/>
+class Markdown extends MarkdownWidget {
+  /// Creates a scrolling widget that parses and displays Markdown.
+  Markdown({
+    Key key,
+    String data,
+    MarkdownStyleSheet styleSheet,
+    SyntaxHighlighter syntaxHighlighter,
+    MarkdownTapLinkCallback onTapLink,
+    this.padding: const EdgeInsets.all(16.0),
+  }) : super(
+    key: key,
+    data: data,
+    styleSheet: styleSheet,
+    syntaxHighlighter: syntaxHighlighter,
+    onTapLink: onTapLink,
+  );
+
+  /// The amount of space by which to inset the children.
+  final EdgeInsets padding;
+
+  @override
+  Widget build(BuildContext context, List<Widget> children) {
+    return new ListView(padding: padding, children: children);
+  }
+}

packages/flutter_markdown/test/flutter_markdown_test.dart

@@ -13,7 +13,7 @@ void main() {
     await tester.pumpWidget(new MarkdownBody(data: 'Hello'));
 
     final Iterable<Widget> widgets = tester.allWidgets;
-      _expectWidgetTypes(widgets, <Type>[MarkdownBody, Column, Container, Padding, RichText]);
+    _expectWidgetTypes(widgets, <Type>[MarkdownBody, Column, RichText]);
     _expectTextStrings(widgets, <String>['Hello']);
   });
 
@@ -21,7 +21,7 @@ void main() {
     await tester.pumpWidget(new MarkdownBody(data: '# Header'));
 
     final Iterable<Widget> widgets = tester.allWidgets;
-      _expectWidgetTypes(widgets, <Type>[MarkdownBody, Column, Container, Padding, RichText]);
+    _expectWidgetTypes(widgets, <Type>[MarkdownBody, Column, RichText]);
     _expectTextStrings(widgets, <String>['Header']);
   });
 
@@ -42,8 +42,8 @@ void main() {
       '2.',
       'Item 2',
       '3.',
-        'Item 3']
+      'Item 3',
-      );
+    ]);
   });
 
   testWidgets('Unordered list', (WidgetTester tester) async {
@@ -56,8 +56,8 @@ void main() {
       '•',
       'Item 2',
       '•',
-        'Item 3']
+      'Item 3',
-      );
+    ]);
   });
 
   testWidgets('Scrollable wrapping', (WidgetTester tester) async {
@@ -66,12 +66,11 @@ void main() {
     final List<Widget> widgets = tester.allWidgets.toList();
     _expectWidgetTypes(widgets.take(2), <Type>[
       Markdown,
-        SingleChildScrollView,
+      ListView,
     ]);
-      _expectWidgetTypes(widgets.reversed.take(3).toList().reversed, <Type>[
+    _expectWidgetTypes(widgets.reversed.take(2).toList().reversed, <Type>[
-        Padding,
+      SliverPadding,
-        MarkdownBody,
+      SliverList,
-        Column
     ]);
   });
 
@@ -110,9 +109,9 @@ void main() {
     await tester.pumpWidget(new Markdown(data: 'Data1'));
     _expectTextStrings(tester.allWidgets, <String>['Data1']);
 
-      final String stateBefore = WidgetsBinding.instance.renderViewElement.toStringDeep();
+    final String stateBefore = _dumpRenderView();
     await tester.pumpWidget(new Markdown(data: 'Data1'));
-      final String stateAfter = WidgetsBinding.instance.renderViewElement.toStringDeep();
+    final String stateAfter = _dumpRenderView();
     expect(stateBefore, equals(stateAfter));
 
     await tester.pumpWidget(new Markdown(data: 'Data2'));
@@ -122,15 +121,25 @@ void main() {
   testWidgets('Changing config - style', (WidgetTester tester) async {
     final ThemeData theme = new ThemeData.light();
 
-      final MarkdownStyle style1 = new MarkdownStyle.defaultFromTheme(theme);
+    final MarkdownStyleSheet style1 = new MarkdownStyleSheet.fromTheme(theme);
-      final MarkdownStyle style2 = new MarkdownStyle.largeFromTheme(theme);
+    final MarkdownStyleSheet style2 = new MarkdownStyleSheet.largeFromTheme(theme);
+    expect(style1, isNot(style2));
 
-      await tester.pumpWidget(new Markdown(data: 'Test', markdownStyle: style1));
+    await tester.pumpWidget(new Markdown(data: '# Test', styleSheet: style1));
+    final RichText text1 = tester.widget(find.byType(RichText));
+    await tester.pumpWidget(new Markdown(data: '# Test', styleSheet: style2));
+    final RichText text2 = tester.widget(find.byType(RichText));
 
-      final String stateBefore = WidgetsBinding.instance.renderViewElement.toStringDeep();
+    expect(text1.text, isNot(text2.text));
-      await tester.pumpWidget(new Markdown(data: 'Test', markdownStyle: style2));
+  });
-      final String stateAfter = WidgetsBinding.instance.renderViewElement.toStringDeep();
+
-      expect(stateBefore, isNot(stateAfter));
+  testWidgets('Style equality', (WidgetTester tester) async {
+    final ThemeData theme = new ThemeData.light();
+
+    final MarkdownStyleSheet style1 = new MarkdownStyleSheet.fromTheme(theme);
+    final MarkdownStyleSheet style2 = new MarkdownStyleSheet.fromTheme(theme);
+    expect(style1, equals(style2));
+    expect(style1.hashCode, equals(style2.hashCode));
   });
 }
 
@@ -160,3 +169,9 @@ String _extractTextFromTextSpan(TextSpan span) {
   }
   return text;
 }
+
+String _dumpRenderView() {
+  return WidgetsBinding.instance.renderViewElement.toStringDeep().replaceAll(
+    new RegExp(r'SliverChildListDelegate#\d+', multiLine: true), 'SliverChildListDelegate'
+  );
+}