Fix Text decoration placements

@@ -10,6 +10,7 @@
 - Add PdfColor.shade
 - Uniformize examples
 - Fix context painting empty Table
+- Fix Text decoration placements
 
 ## 1.5.0
 

@@ -52,7 +52,9 @@ abstract class _Span {
 }
 
 class _TextDecoration {
-  _TextDecoration(this.style, this.annotation) : assert(style != null);
+  _TextDecoration(this.style, this.annotation, this.startSpan, this.endSpan)
+      : assert(startSpan <= endSpan),
+        assert(style != null);
 
   static const double _space = -0.15;
 
@@ -60,13 +62,44 @@ class _TextDecoration {
 
   final AnnotationBuilder annotation;
 
-  PdfRect box = PdfRect.zero;
+  final int startSpan;
+
+  final int endSpan;
+
+  PdfRect _box;
+
+  PdfRect _getBox(List<_Span> spans) {
+    if (_box != null) {
+      return _box;
+    }
+    final double x1 = spans[startSpan].offset.x + spans[startSpan].left;
+    final double x2 =
+        spans[endSpan].offset.x + spans[endSpan].left + spans[endSpan].width;
+    double y1 = spans[startSpan].offset.y + spans[startSpan].top;
+    double y2 = y1 + spans[startSpan].height;
+
+    for (int n = startSpan + 1; n <= endSpan; n++) {
+      final double ny1 = spans[n].offset.y + spans[n].top;
+      final double ny2 = ny1 + spans[n].height;
+      y1 = math.min(y1, ny1);
+      y2 = math.max(y2, ny2);
+    }
+
+    _box = PdfRect.fromLTRB(x1, y1, x2, y2);
+    return _box;
+  }
+
+  _TextDecoration copyWith({int endSpan}) =>
+      _TextDecoration(style, annotation, startSpan, endSpan ?? this.endSpan);
 
   void backgroundPaint(
     Context context,
     double textScaleFactor,
     PdfRect globalBox,
+    List<_Span> spans,
   ) {
+    final PdfRect box = _getBox(spans);
+
     if (annotation != null) {
       final PdfRect spanBox = PdfRect(
         globalBox.x + box.left,
@@ -93,78 +126,80 @@ class _TextDecoration {
     Context context,
     double textScaleFactor,
     PdfRect globalBox,
+    List<_Span> spans,
   ) {
-    if (style.decoration != null) {
-      final PdfFont font = style.font.getFont(context);
-      final double space =
-          _space * style.fontSize * textScaleFactor * style.decorationThickness;
-
-      context.canvas
-        ..setStrokeColor(style.decorationColor ?? style.color)
-        ..setLineWidth(style.decorationThickness *
-            style.fontSize *
-            textScaleFactor *
-            0.05);
-
-      if (style.decoration.contains(TextDecoration.underline)) {
-        final double base =
-            -font.descent * style.fontSize * textScaleFactor / 2;
+    if (style.decoration == null) {
+      return;
+    }
+
+    final PdfRect box = _getBox(spans);
+
+    final PdfFont font = style.font.getFont(context);
+    final double space =
+        _space * style.fontSize * textScaleFactor * style.decorationThickness;
+
+    context.canvas
+      ..setStrokeColor(style.decorationColor ?? style.color)
+      ..setLineWidth(
+          style.decorationThickness * style.fontSize * textScaleFactor * 0.05);
 
+    if (style.decoration.contains(TextDecoration.underline)) {
+      final double base = -font.descent * style.fontSize * textScaleFactor / 2;
+
+      context.canvas.drawLine(
+        globalBox.x + box.left,
+        globalBox.top + box.bottom + base,
+        globalBox.x + box.right,
+        globalBox.top + box.bottom + base,
+      );
+      if (style.decorationStyle == TextDecorationStyle.double) {
         context.canvas.drawLine(
           globalBox.x + box.left,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base + space,
           globalBox.x + box.right,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base + space,
         );
-        if (style.decorationStyle == TextDecorationStyle.double) {
-          context.canvas.drawLine(
-            globalBox.x + box.left,
-            globalBox.top + box.bottom + base + space,
-            globalBox.x + box.right,
-            globalBox.top + box.bottom + base + space,
-          );
-        }
-        context.canvas.strokePath();
       }
+      context.canvas.strokePath();
+    }
 
-      if (style.decoration.contains(TextDecoration.overline)) {
-        final double base = style.fontSize * textScaleFactor;
+    if (style.decoration.contains(TextDecoration.overline)) {
+      final double base = style.fontSize * textScaleFactor;
+      context.canvas.drawLine(
+        globalBox.x + box.left,
+        globalBox.top + box.bottom + base,
+        globalBox.x + box.right,
+        globalBox.top + box.bottom + base,
+      );
+      if (style.decorationStyle == TextDecorationStyle.double) {
         context.canvas.drawLine(
           globalBox.x + box.left,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base - space,
           globalBox.x + box.right,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base - space,
         );
-        if (style.decorationStyle == TextDecorationStyle.double) {
-          context.canvas.drawLine(
-            globalBox.x + box.left,
-            globalBox.top + box.bottom + base - space,
-            globalBox.x + box.right,
-            globalBox.top + box.bottom + base - space,
-          );
-        }
-        context.canvas.strokePath();
       }
+      context.canvas.strokePath();
+    }
 
-      if (style.decoration.contains(TextDecoration.lineThrough)) {
-        final double base =
-            (1 - font.descent) * style.fontSize * textScaleFactor / 2;
+    if (style.decoration.contains(TextDecoration.lineThrough)) {
+      final double base =
+          (1 - font.descent) * style.fontSize * textScaleFactor / 2;
+      context.canvas.drawLine(
+        globalBox.x + box.left,
+        globalBox.top + box.bottom + base,
+        globalBox.x + box.right,
+        globalBox.top + box.bottom + base,
+      );
+      if (style.decorationStyle == TextDecorationStyle.double) {
         context.canvas.drawLine(
           globalBox.x + box.left,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base + space,
           globalBox.x + box.right,
-          globalBox.top + box.bottom + base,
+          globalBox.top + box.bottom + base + space,
         );
-        if (style.decorationStyle == TextDecorationStyle.double) {
-          context.canvas.drawLine(
-            globalBox.x + box.left,
-            globalBox.top + box.bottom + base + space,
-            globalBox.x + box.right,
-            globalBox.top + box.bottom + base + space,
-          );
-        }
-        context.canvas.strokePath();
       }
+      context.canvas.strokePath();
     }
   }
 
@@ -172,7 +207,10 @@ class _TextDecoration {
     Context context,
     double textScaleFactor,
     PdfRect globalBox,
+    List<_Span> spans,
   ) {
+    final PdfRect box = _getBox(spans);
+
     context.canvas
       ..setLineWidth(.5)
       ..drawRect(
@@ -197,13 +235,13 @@ class _Word extends _Span {
   double get left => metrics.left;
 
   @override
-  double get top => metrics.top;
+  double get top => metrics.descent;
 
   @override
   double get width => metrics.width;
 
   @override
-  double get height => metrics.height;
+  double get height => metrics.maxHeight;
 
   @override
   String toString() {
@@ -464,14 +502,20 @@ class RichText extends Widget {
       span.offset = span.offset.translate(delta, -baseline);
     }
 
-    for (_TextDecoration decoration in decorations) {
-      decoration.box = PdfRect.fromPoints(
-        decoration.box.offset.translate(delta, -baseline),
-        decoration.box.size,
-      );
+    return totalWidth;
+  }
+
+  void _appendDecoration(bool append, _TextDecoration td) {
+    if (append && _decorations.isNotEmpty) {
+      final _TextDecoration last = _decorations.last;
+      if (last.style == td.style && last.annotation == td.annotation) {
+        _decorations[_decorations.length - 1] =
+            last.copyWith(endSpan: td.endSpan);
+        return;
+      }
     }
 
-    return totalWidth;
+    _decorations.add(td);
   }
 
   @override
@@ -568,16 +612,15 @@ class RichText extends Widget {
             _spans.add(wd);
             spanCount++;
 
-            final _TextDecoration td = _TextDecoration(
-              style,
-              span.annotation,
+            _appendDecoration(
+              spanCount > 1,
+              _TextDecoration(
+                style,
+                span.annotation,
+                _spans.length - 1,
+                _spans.length - 1,
+              ),
             );
-            td.box = PdfRect(
-                offsetX,
-                -offsetY + metrics.descent + baseline,
-                metrics.maxWidth + space.advanceWidth * style.wordSpacing,
-                metrics.maxHeight);
-            _decorations.add(td);
 
             offsetX +=
                 metrics.advanceWidth + space.advanceWidth * style.wordSpacing;
@@ -598,15 +641,6 @@ class RichText extends Widget {
             spanStart += spanCount;
             decorationStart = _decorations.length;
 
-            if (_decorations.isNotEmpty) {
-              // remove the last space
-              _decorations.last.box = PdfRect.fromPoints(
-                _decorations.last.box.offset,
-                _decorations.last.box.size
-                    .translate(-space.advanceWidth * style.wordSpacing, 0),
-              );
-            }
-
             lines++;
             if (maxLines != null && lines > maxLines) {
               break;
@@ -683,12 +717,15 @@ class RichText extends Widget {
         _spans.add(ws);
         spanCount++;
 
-        final _TextDecoration td = _TextDecoration(
-          style,
-          span.annotation,
+        _appendDecoration(
+          spanCount > 1,
+          _TextDecoration(
+            style,
+            span.annotation,
+            _spans.length - 1,
+            _spans.length - 1,
+          ),
         );
-        td.box = PdfRect(offsetX, -offsetY + baseline, ws.width, ws.height);
-        _decorations.add(td);
 
         offsetX += ws.left + ws.width;
       }
@@ -732,7 +769,7 @@ class RichText extends Widget {
     for (_TextDecoration decoration in _decorations) {
       assert(() {
         if (Document.debug && RichText.debug) {
-          decoration.debugPaint(context, textScaleFactor, box);
+          decoration.debugPaint(context, textScaleFactor, box, _spans);
         }
         return true;
       }());
@@ -741,6 +778,7 @@ class RichText extends Widget {
         context,
         textScaleFactor,
         box,
+        _spans,
       );
     }
 
@@ -773,6 +811,7 @@ class RichText extends Widget {
         context,
         textScaleFactor,
         box,
+        _spans,
       );
     }
   }