[vector_graphics_compiler] Fix tspan transform applied twice

packages/vector_graphics_compiler/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.3.2
+
+* Fixes a `tspan` without its own position being drawn with its parent group
+  transform applied twice.
+
 ## 1.3.1
 
 * Adds support for SVG alpha masks (`mask-type="alpha"`).

packages/vector_graphics_compiler/lib/src/svg/node.dart

@@ -236,7 +236,9 @@ class TextPositionNode extends ParentNode {
   final bool reset;
 
   /// Computes a [TextPosition] to encode for this node.
-  TextPosition computeTextPosition(Rect bounds, AffineMatrix transform) {
+  ///
+  /// [parent] is the [TextPosition] of the enclosing text or tspan, if any.
+  TextPosition computeTextPosition(Rect bounds, AffineMatrix transform, {TextPosition? parent}) {
     final AffineMatrix computedTransform = concatTransform(transform);
 
     double? x = attributes.x?.calculate(bounds.width);
@@ -246,6 +248,16 @@ class TextPositionNode extends ParentNode {
 
     final bool hasXY = x != null && y != null;
     final bool hasDxDy = dx != null && dy != null;
+    // A tspan without its own position continues from the parent's position.
+    // If the parent already applied the transform to its position (its
+    // `transform` is null), the transform must not be applied again.
+    final bool inheritsConsumedTransform =
+        parent != null &&
+        parent.transform == null &&
+        x == null &&
+        y == null &&
+        dx == null &&
+        dy == null;
     final bool consumeTransform =
         computedTransform == AffineMatrix.identity ||
         (computedTransform.encodableInRect && (hasXY || hasDxDy));
@@ -272,7 +284,7 @@ class TextPositionNode extends ParentNode {
       dx: dx,
       dy: dy,
       reset: reset,
-      transform: consumeTransform ? null : computedTransform,
+      transform: (inheritsConsumedTransform || consumeTransform) ? null : computedTransform,
     );
   }
 

packages/vector_graphics_compiler/lib/src/svg/resolver.dart

@@ -25,6 +25,9 @@ class ResolvingVisitor extends Visitor<Node, AffineMatrix> {
   final Set<String> _activePatterns = <String>{};
   int _deferredExpansionCount = 0;
 
+  /// The position of the text or tspan currently being resolved, if any.
+  TextPosition? _currentTextPosition;
+
   @override
   Node visitClipNode(ClipNode clipNode, AffineMatrix data) {
     final AffineMatrix childTransform = clipNode.concatTransform(data);
@@ -137,11 +140,22 @@ class ResolvingVisitor extends Visitor<Node, AffineMatrix> {
   @override
   Node visitTextPositionNode(TextPositionNode textPositionNode, AffineMatrix data) {
     final AffineMatrix nextTransform = textPositionNode.concatTransform(data);
+    final TextPosition? parentTextPosition = _currentTextPosition;
+    final TextPosition textPosition = textPositionNode.computeTextPosition(
+      _bounds,
+      data,
+      parent: parentTextPosition,
+    );
 
-    return ResolvedTextPositionNode(textPositionNode.computeTextPosition(_bounds, data), <Node>[
-      for (final Node child in textPositionNode.children)
-        child.applyAttributes(textPositionNode.attributes).accept(this, nextTransform),
-    ]);
+    _currentTextPosition = textPosition;
+    try {
+      return ResolvedTextPositionNode(textPosition, <Node>[
+        for (final Node child in textPositionNode.children)
+          child.applyAttributes(textPositionNode.attributes).accept(this, nextTransform),
+      ]);
+    } finally {
+      _currentTextPosition = parentTextPosition;
+    }
   }
 
   @override

packages/vector_graphics_compiler/pubspec.yaml

@@ -2,7 +2,7 @@ name: vector_graphics_compiler
 description: A compiler to convert SVGs to the binary format used by `package:vector_graphics`.
 repository: https://github.com/flutter/packages/tree/main/packages/vector_graphics_compiler
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+vector_graphics%22
-version: 1.3.1
+version: 1.3.2
 
 executables:
   vector_graphics_compiler:

packages/vector_graphics_compiler/test/parser_test.dart

@@ -414,6 +414,25 @@ ${[for (var i = 2; i <= 30; i++) '    <pattern id="lvl$i" width="10" height="10"
     ]);
   });
 
+  test('tspan without position does not apply the group transform twice', () {
+    final VectorInstructions instructions = parseWithoutOptimizers('''
+<svg width="400" height="100" xmlns="http://www.w3.org/2000/svg">
+  <g transform="translate(10,10)">
+    <g transform="translate(10,10)">
+      <text x="15" y="25">bare text</text>
+      <text x="15" y="50"><tspan>text in tspan</tspan></text>
+    </g>
+  </g>
+</svg>
+''');
+
+    expect(instructions.textPositions, const <TextPosition>[
+      TextPosition(x: 35, y: 45, reset: true),
+      TextPosition(x: 35, y: 70, reset: true),
+      TextPosition(),
+    ]);
+  });
+
   test('Non-standard root font-weight="regular" uses initial weight', () {
     final VectorInstructions instructions = parseWithoutOptimizers('''
 <svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">