flutter_markdown/lib/src/builder.dart - third_party/dart-pkg - Git at Google

 // 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 'dart:io';

 import 'package:flutter/gestures.dart';
 import 'package:flutter/widgets.dart';
 import 'package:markdown/markdown.dart' as md;
 import 'package:path/path.dart' as p;

 import 'style_sheet.dart';

 final Set<String> _kBlockTags = new Set<String>.from(<String>[
   'p',
   'h1',
   'h2',
   'h3',
   'h4',
   'h5',
   'h6',
   'li',
   'blockquote',
   'pre',
   'ol',
   'ul',
   'hr',
 ]);

 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;
 }

 /// A collection of widgets that should be placed adjacent to (inline with)
 /// other inline elements in the same parent block.
 ///
 /// Inline elements can be textual (a/em/strong) represented by [RichText]
 /// widgets or images (img) represented by [Image.network] widgets.
 ///
 /// Inline elements can be nested within other inline elements, inheriting their
 /// parent's style along with the style of the block they are in.
 ///
 /// When laying out inline widgets, first, any adjacent RichText widgets are
 /// merged, then, all inline widgets are enclosed in a parent [Wrap] widget.
 class _InlineElement {
   _InlineElement(this.tag, {this.style});

   final String tag;

   /// Created by merging the style defined for this element's [tag] in the
   /// delegate's [MarkdownStyleSheet] with the style of its parent.
   final TextStyle style;

   final List<Widget> children = <Widget>[];
 }

 /// 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, this.imageDirectory });

   /// 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;

   /// The base directory holding images referenced by Img tags with local file paths.
   final Directory imageDirectory;

   final List<String> _listIndents = <String>[];
   final List<_BlockElement> _blocks = <_BlockElement>[];
   final List<_InlineElement> _inlines = <_InlineElement>[];
   final List<GestureRecognizer> _linkHandlers = <GestureRecognizer>[];


   /// 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();
     _linkHandlers.clear();

     _blocks.add(new _BlockElement(null));

     for (md.Node node in nodes) {
       assert(_blocks.length == 1);
       node.accept(this);
     }

     assert(_inlines.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;

     _addParentInlineIfNeeded(_blocks.last.tag);

     final TextSpan span = _blocks.last.tag == 'pre'
       ? delegate.formatText(styleSheet, text.text)
       : new TextSpan(
           style: _inlines.last.style,
           text: text.text,
           recognizer: _linkHandlers.isNotEmpty ? _linkHandlers.last : null,
         );

     _inlines.last.children.add(new RichText(text: 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 {
       _addParentInlineIfNeeded(_blocks.last.tag);

       TextStyle parentStyle = _inlines.last.style;
       _inlines.add(new _InlineElement(
         tag,
         style: parentStyle.merge(styleSheet.styles[tag]),
       ));
     }

     if (tag == 'a') {
       _linkHandlers.add(delegate.createLink(element.attributes['href']));
     }

     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 (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,
           ),
         );
       } else if (tag == 'hr') {
         child = new DecoratedBox(
           decoration: styleSheet.horizontalRuleDecoration,
           child: child,
         );
       }

       _addBlockChild(child);
     } else {
       final _InlineElement current = _inlines.removeLast();
       final _InlineElement parent = _inlines.last;

       if (tag == 'img') {
         // create an image widget for this image
         current.children.add(_buildImage(element.attributes['src']));
       } else if (tag == 'a') {
         _linkHandlers.removeLast();
       }

       if (current.children.isNotEmpty) {
         parent.children.addAll(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]);
       }
     }

     Uri uri = Uri.parse(path);
     Widget child;
     if (uri.scheme == 'http' || uri.scheme == 'https') {
       child = new Image.network(uri.toString(), width: width, height: height);
     } else {
       String filePath = (imageDirectory == null
           ? uri.toFilePath()
           : p.join(imageDirectory.path, uri.toFilePath()));
       child = new Image.file(new File(filePath), width: width, height: height);
     }

     if (_linkHandlers.isNotEmpty) {
       TapGestureRecognizer recognizer = _linkHandlers.last;
       return new GestureDetector(child: child, onTap: recognizer.onTap);
     } else {
       return child;
     }
   }

   Widget _buildBullet(String listTag) {
     if (listTag == 'ul')
       return const 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 _addParentInlineIfNeeded(String tag) {
     if (_inlines.isEmpty) {
       _inlines.add(new _InlineElement(
         tag,
         style: styleSheet.styles[tag],
       ));
     }
   }

   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) {
     if (_inlines.isEmpty) {
       return;
     }

     final _InlineElement inline = _inlines.single;
     if (inline.children.isNotEmpty) {
       List<Widget> mergedInlines = _mergeInlineChildren(inline);
       final Wrap wrap = new Wrap(children: mergedInlines);
       _addBlockChild(wrap);
       _inlines.clear();
     }
   }

   /// Merges adjacent [TextSpan] children of the given [_InlineElement]
   List<Widget> _mergeInlineChildren(_InlineElement inline) {
     List<Widget> mergedTexts = <Widget>[];
     for (Widget child in inline.children) {
       if (mergedTexts.isNotEmpty && mergedTexts.last is RichText && child is RichText) {
         RichText previous = mergedTexts.removeLast();
         List<TextSpan> children = previous.text.children != null
           ? new List.from(previous.text.children)
           : [previous.text];
         children.add(child.text);
         TextSpan mergedSpan = new TextSpan(children: children);
         mergedTexts.add(new RichText(text: mergedSpan));
       } else {
         mergedTexts.add(child);
       }
     }
     return mergedTexts;
   }
 }
	// 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 'dart:io';

	import 'package:flutter/gestures.dart';
	import 'package:flutter/widgets.dart';
	import 'package:markdown/markdown.dart' as md;
	import 'package:path/path.dart' as p;

	import 'style_sheet.dart';

	final Set<String> _kBlockTags = new Set<String>.from(<String>[
	'p',
	'h1',
	'h2',
	'h3',
	'h4',
	'h5',
	'h6',
	'li',
	'blockquote',
	'pre',
	'ol',
	'ul',
	'hr',
	]);

	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;
	}

	/// A collection of widgets that should be placed adjacent to (inline with)
	/// other inline elements in the same parent block.
	///
	/// Inline elements can be textual (a/em/strong) represented by [RichText]
	/// widgets or images (img) represented by [Image.network] widgets.
	///
	/// Inline elements can be nested within other inline elements, inheriting their
	/// parent's style along with the style of the block they are in.
	///
	/// When laying out inline widgets, first, any adjacent RichText widgets are
	/// merged, then, all inline widgets are enclosed in a parent [Wrap] widget.
	class _InlineElement {
	_InlineElement(this.tag, {this.style});

	final String tag;

	/// Created by merging the style defined for this element's [tag] in the
	/// delegate's [MarkdownStyleSheet] with the style of its parent.
	final TextStyle style;

	final List<Widget> children = <Widget>[];
	}

	/// 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, this.imageDirectory });

	/// 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;

	/// The base directory holding images referenced by Img tags with local file paths.
	final Directory imageDirectory;

	final List<String> _listIndents = <String>[];
	final List<_BlockElement> _blocks = <_BlockElement>[];
	final List<_InlineElement> _inlines = <_InlineElement>[];
	final List<GestureRecognizer> _linkHandlers = <GestureRecognizer>[];


	/// 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();
	_linkHandlers.clear();

	_blocks.add(new _BlockElement(null));

	for (md.Node node in nodes) {
	assert(_blocks.length == 1);
	node.accept(this);
	}

	assert(_inlines.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;

	_addParentInlineIfNeeded(_blocks.last.tag);

	final TextSpan span = _blocks.last.tag == 'pre'
	? delegate.formatText(styleSheet, text.text)
	: new TextSpan(
	style: _inlines.last.style,
	text: text.text,
	recognizer: _linkHandlers.isNotEmpty ? _linkHandlers.last : null,
	);

	_inlines.last.children.add(new RichText(text: 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 {
	_addParentInlineIfNeeded(_blocks.last.tag);

	TextStyle parentStyle = _inlines.last.style;
	_inlines.add(new _InlineElement(
	tag,
	style: parentStyle.merge(styleSheet.styles[tag]),
	));
	}

	if (tag == 'a') {
	_linkHandlers.add(delegate.createLink(element.attributes['href']));
	}

	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 (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,
	),
	);
	} else if (tag == 'hr') {
	child = new DecoratedBox(
	decoration: styleSheet.horizontalRuleDecoration,
	child: child,
	);
	}

	_addBlockChild(child);
	} else {
	final _InlineElement current = _inlines.removeLast();
	final _InlineElement parent = _inlines.last;

	if (tag == 'img') {
	// create an image widget for this image
	current.children.add(_buildImage(element.attributes['src']));
	} else if (tag == 'a') {
	_linkHandlers.removeLast();
	}

	if (current.children.isNotEmpty) {
	parent.children.addAll(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]);
	}
	}

	Uri uri = Uri.parse(path);
	Widget child;
	if (uri.scheme == 'http' \|\| uri.scheme == 'https') {
	child = new Image.network(uri.toString(), width: width, height: height);
	} else {
	String filePath = (imageDirectory == null
	? uri.toFilePath()
	: p.join(imageDirectory.path, uri.toFilePath()));
	child = new Image.file(new File(filePath), width: width, height: height);
	}

	if (_linkHandlers.isNotEmpty) {
	TapGestureRecognizer recognizer = _linkHandlers.last;
	return new GestureDetector(child: child, onTap: recognizer.onTap);
	} else {
	return child;
	}
	}

	Widget _buildBullet(String listTag) {
	if (listTag == 'ul')
	return const 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 _addParentInlineIfNeeded(String tag) {
	if (_inlines.isEmpty) {
	_inlines.add(new _InlineElement(
	tag,
	style: styleSheet.styles[tag],
	));
	}
	}

	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) {
	if (_inlines.isEmpty) {
	return;
	}

	final _InlineElement inline = _inlines.single;
	if (inline.children.isNotEmpty) {
	List<Widget> mergedInlines = _mergeInlineChildren(inline);
	final Wrap wrap = new Wrap(children: mergedInlines);
	_addBlockChild(wrap);
	_inlines.clear();
	}
	}

	/// Merges adjacent [TextSpan] children of the given [_InlineElement]
	List<Widget> _mergeInlineChildren(_InlineElement inline) {
	List<Widget> mergedTexts = <Widget>[];
	for (Widget child in inline.children) {
	if (mergedTexts.isNotEmpty && mergedTexts.last is RichText && child is RichText) {
	RichText previous = mergedTexts.removeLast();
	List<TextSpan> children = previous.text.children != null
	? new List.from(previous.text.children)
	: [previous.text];
	children.add(child.text);
	TextSpan mergedSpan = new TextSpan(children: children);
	mergedTexts.add(new RichText(text: mergedSpan));
	} else {
	mergedTexts.add(child);
	}
	}
	return mergedTexts;
	}
	}