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Support for multiline display bracket-wrapped formulas #11 #12

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71 changes: 56 additions & 15 deletions lib/src/latex_block_syntax.dart
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Original file line number Diff line number Diff line change
@@ -1,34 +1,76 @@
import 'package:markdown/markdown.dart';

class LatexBlockSyntax extends BlockSyntax {
static final RegExp _singleLineBracket = RegExp(r'^\s*\\\[(.*)\\\]\s*$');
static final RegExp _startBracket = RegExp(r'^\s*\\\[\s*$');
static final RegExp _endBracket = RegExp(r'^\s*\\\]\s*$');
static final RegExp _startDollar = RegExp(r'^\s*(\${1,2})\s*$');

@override
RegExp get pattern => RegExp(
r'^(?:(\${1,2})(?:\n|$))|(?:(?:\\\[(.+)\\\])(?:\n|$))',
multiLine: true,
);
RegExp get pattern => RegExp(r'^\s*(?:\${1,2}|\\\[)\s*$|^\s*\\\[(.*)\\\]\s*$');

LatexBlockSyntax() : super();

@override
bool canParse(BlockParser parser) {
final line = parser.current.content;
return _singleLineBracket.hasMatch(line) ||
_startBracket.hasMatch(line) ||
_startDollar.hasMatch(line);
}

@override
List<Line> parseChildLines(BlockParser parser) {
final m = pattern.firstMatch(parser.current.content);
if (m?[2] != null) {
final line = parser.current.content;

// Single-line bracket form: \[ ... \]
final single = _singleLineBracket.firstMatch(line);
if (single != null) {
parser.advance();
return [Line(m?[2] ?? '')];
return [Line(single.group(1) ?? '')];
}

// Multiline bracket form:
// \[
// ...
// \]
if (_startBracket.hasMatch(line)) {
final childLines = <Line>[];
parser.advance(); // consume \[
while (!parser.isDone) {
final current = parser.current.content;
if (_endBracket.hasMatch(current)) {
parser.advance(); // consume \]
break;
}
childLines.add(parser.current);
parser.advance();
}
return childLines;
}

// Multiline dollar form:
// $$
// ...
// $$
// or
// $
// ...
// $
final m = _startDollar.firstMatch(line);
final delimiter = m?.group(1);

final childLines = <Line>[];
parser.advance();
parser.advance(); // consume opening $ or $$

while (!parser.isDone) {
final match = pattern.hasMatch(parser.current.content);
if (!match) {
childLines.add(parser.current);
parser.advance();
} else {
parser.advance();
final current = parser.current.content.trim();
if (delimiter != null && current == delimiter) {
parser.advance(); // consume closing delimiter
break;
}
childLines.add(parser.current);
parser.advance();
}

return childLines;
Expand All @@ -40,7 +82,6 @@ class LatexBlockSyntax extends BlockSyntax {
final content = lines.map((e) => e.content).join('\n').trim();
final textElement = Element.text('latex', content);
textElement.attributes['MathStyle'] = 'display';

return Element('p', [textElement]);
}
}