fix(code-field): align line numbers with wrapped text lines

lib/src/code_field/code_field.dart

@@ -132,6 +132,10 @@ class _CodeFieldState extends State<CodeField> {
   FocusNode? _focusNode;
   String? lines;
   String longestLine = '';
+  // Track the available width of the code column in order to compute
+  // visual line wrapping for line-numbers.
+  double _codeColumnWidth = 0;
+  var _currentTextStyle = const TextStyle();
 
   @override
   void initState() {
@@ -186,8 +190,34 @@ class _CodeFieldState extends State<CodeField> {
     final str = widget.controller.text.split('\n');
     final buf = <String>[];
 
-    for (var k = 0; k < str.length; k++) {
-      buf.add((k + 1).toString());
+    if (widget.wrap && _codeColumnWidth > 0) {
+      // When wrapping is enabled we need to account for visual lines that
+      // are created by the soft wrap. We measure each logical line using a
+      // TextPainter and add blank placeholders so the scrolling offset of
+      // the linked controllers stays in sync.
+      for (var k = 0; k < str.length; k++) {
+        final logicalLine = str[k];
+
+        // Compute how many visual lines this logical line occupies.
+        final tp = TextPainter(
+          text: TextSpan(text: logicalLine, style: _currentTextStyle),
+          textDirection: TextDirection.ltr,
+        )..layout(maxWidth: _codeColumnWidth);
+        final visualLines = tp.computeLineMetrics().length;
+
+        // First visual line gets the real line number.
+        buf.add((k + 1).toString());
+
+        // Remaining visual lines get an empty placeholder so that the
+        // total number of lines matches the code field.
+        for (int v = 1; v < visualLines; v++) {
+          buf.add('');
+        }
+      }
+    } else {
+      for (var k = 0; k < str.length; k++) {
+        buf.add((k + 1).toString());
+      }
     }
 
     _numberController?.text = buf.join('\n');
@@ -370,7 +400,28 @@ class _CodeFieldState extends State<CodeField> {
         textSelectionTheme: widget.textSelectionTheme,
       ),
       child: LayoutBuilder(
-        builder: (BuildContext context, BoxConstraints constraints) {
+        builder: (context, constraints) {
+          // Save the textStyle and available width so _onTextChanged can
+          // accurately compute the amount of visual lines when wrapping.
+          _currentTextStyle = textStyle;
+          // Subtract left padding that will be applied inside the
+          // SingleChildScrollView when horizontal scrolling is disabled.
+          var availableWidth = constraints.maxWidth;
+          if (widget.lineNumbers) {
+            availableWidth -= widget.lineNumberStyle.width;
+          }
+
+          if ((availableWidth - _codeColumnWidth).abs() > 0.5) {
+            _codeColumnWidth = max(0, availableWidth);
+            // Recalculate the line numbers because wrapping may have
+            // changed due to a width change.
+            WidgetsBinding.instance.addPostFrameCallback((_) {
+              if (mounted) {
+                _onTextChanged();
+              }
+            });
+          }
+
           // Control horizontal scrolling
           return widget.wrap
               ? codeField

lib/src/line_numbers/line_number_controller.dart

@@ -18,14 +18,19 @@ class LineNumberController extends TextEditingController {
 
     for (int k = 0; k < list.length; k++) {
       final el = list[k];
-      final number = int.parse(el);
-      var textSpan = TextSpan(text: el, style: style);
-
-      if (lineNumberBuilder != null) {
-        textSpan = lineNumberBuilder!(number, style);
+      // Blank lines are placeholders inserted to align with wrapped
+      // visual lines. They should render as empty text spans to
+      // preserve vertical spacing.
+      if (el.trim().isEmpty) {
+        children.add(TextSpan(text: '', style: style));
+      } else {
+        final number = int.tryParse(el) ?? 0;
+        var textSpan = TextSpan(text: el, style: style);
+        if (lineNumberBuilder != null && number != 0) {
+          textSpan = lineNumberBuilder!(number, style);
+        }
+        children.add(textSpan);
       }
-
-      children.add(textSpan);
       if (k < list.length - 1) {
         children.add(const TextSpan(text: '\n'));
       }