Dispose the things (flutter/engine#35730)

engine/src/flutter/lib/ui/dart_ui.cc

@@ -197,6 +197,7 @@ typedef CanvasPath Path;
   V(Paragraph, alphabeticBaseline, 1)                  \
   V(Paragraph, computeLineMetrics, 1)                  \
   V(Paragraph, didExceedMaxLines, 1)                   \
+  V(Paragraph, dispose, 1)                             \
   V(Paragraph, getLineBoundary, 2)                     \
   V(Paragraph, getPositionForOffset, 3)                \
   V(Paragraph, getRectsForPlaceholders, 1)             \
@@ -280,7 +281,8 @@ typedef CanvasPath Path;
   V(SemanticsUpdateBuilder, build, 2)                  \
   V(SemanticsUpdateBuilder, updateCustomAction, 5)     \
   V(SemanticsUpdateBuilder, updateNode, 36)            \
-  V(SemanticsUpdate, dispose, 1)
+  V(SemanticsUpdate, dispose, 1)                       \
+  V(Vertices, dispose, 1)
 
 #define FFI_FUNCTION_INSERT(FUNCTION, ARGS)     \
   g_function_dispatchers.insert(std::make_pair( \

engine/src/flutter/lib/ui/painting.dart

@@ -4417,6 +4417,36 @@ class Vertices extends NativeFieldWrapperClass1 {
                              Float32List? textureCoordinates,
                              Int32List? colors,
                              Uint16List? indices);
+
+  /// Release the resources used by this object. The object is no longer usable
+  /// after this method is called.
+  void dispose() {
+    assert(!_disposed);
+    assert(() {
+      _disposed = true;
+      return true;
+    }());
+    _dispose();
+  }
+
+  /// This can't be a leaf call because the native function calls Dart API
+  /// (Dart_SetNativeInstanceField).
+  @FfiNative<Void Function(Pointer<Void>)>('Vertices::dispose')
+  external void _dispose();
+
+  bool _disposed = false;
+  /// Whether this reference to the underlying picture is [dispose]d.
+  ///
+  /// This only returns a valid value if asserts are enabled, and must not be
+  /// used otherwise.
+  bool get debugDisposed {
+    bool? disposed;
+    assert(() {
+      disposed = _disposed;
+      return true;
+    }());
+    return disposed ?? (throw StateError('$runtimeType.debugDisposed is only available when asserts are enabled.'));
+  }
 }
 
 /// Defines how a list of points is interpreted when drawing a set of points.
@@ -5009,6 +5039,7 @@ class Canvas extends NativeFieldWrapperClass1 {
   /// given [Offset]. The image is composited into the canvas using the given [Paint].
   void drawImage(Image image, Offset offset, Paint paint) {
     assert(image != null); // image is checked on the engine side
+    assert(!image.debugDisposed);
     assert(_offsetIsValid(offset));
     assert(paint != null);
     final String? error = _drawImage(image._image, offset.dx, offset.dy, paint._objects, paint._data, paint.filterQuality.index);
@@ -5031,6 +5062,7 @@ class Canvas extends NativeFieldWrapperClass1 {
   /// performance.
   void drawImageRect(Image image, Rect src, Rect dst, Paint paint) {
     assert(image != null); // image is checked on the engine side
+    assert(!image.debugDisposed);
     assert(_rectIsValid(src));
     assert(_rectIsValid(dst));
     assert(paint != null);
@@ -5081,6 +5113,7 @@ class Canvas extends NativeFieldWrapperClass1 {
   /// positions.
   void drawImageNine(Image image, Rect center, Rect dst, Paint paint) {
     assert(image != null); // image is checked on the engine side
+    assert(!image.debugDisposed);
     assert(_rectIsValid(center));
     assert(_rectIsValid(dst));
     assert(paint != null);
@@ -5120,6 +5153,7 @@ class Canvas extends NativeFieldWrapperClass1 {
   /// [PictureRecorder].
   void drawPicture(Picture picture) {
     assert(picture != null); // picture is checked on the engine side
+    assert(!picture.debugDisposed);
     _drawPicture(picture);
   }
 
@@ -5148,6 +5182,7 @@ class Canvas extends NativeFieldWrapperClass1 {
   /// [Paragraph.layout], to the `offset` argument's [Offset.dx] coordinate.
   void drawParagraph(Paragraph paragraph, Offset offset) {
     assert(paragraph != null);
+    assert(!paragraph.debugDisposed);
     assert(_offsetIsValid(offset));
     assert(!paragraph._needsLayout);
     paragraph._paint(this, offset.dx, offset.dy);
@@ -5211,8 +5246,8 @@ class Canvas extends NativeFieldWrapperClass1 {
   ///     rather than unencoded lists.
   ///   * [paint], Image shaders can be used to draw images on a triangular mesh.
   void drawVertices(Vertices vertices, BlendMode blendMode, Paint paint) {
-
     assert(vertices != null); // vertices is checked on the engine side
+    assert(!vertices.debugDisposed);
     assert(paint != null);
     assert(blendMode != null);
     _drawVertices(vertices, blendMode.index, paint._objects, paint._data);
@@ -5360,6 +5395,7 @@ class Canvas extends NativeFieldWrapperClass1 {
                  Rect? cullRect,
                  Paint paint) {
     assert(atlas != null); // atlas is checked on the engine side
+    assert(!atlas.debugDisposed);
     assert(transforms != null);
     assert(rects != null);
     assert(colors == null || colors.isEmpty || blendMode != null);

engine/src/flutter/lib/ui/painting/vertices.cc

@@ -81,7 +81,15 @@ bool Vertices::init(Dart_Handle vertices_handle,
 }
 
 size_t Vertices::GetAllocationSize() const {
+  if (!vertices_) {
+    return sizeof(*this);
+  }
   return vertices_->size();
 }
 
+void Vertices::dispose() {
+  vertices_.reset();
+  ClearDartWrapper();
+}
+
 }  // namespace flutter

engine/src/flutter/lib/ui/painting/vertices.h

@@ -30,6 +30,8 @@ class Vertices : public RefCountedDartWrappable<Vertices> {
 
   size_t GetAllocationSize() const override;
 
+  void dispose();
+
  private:
   Vertices();
 

engine/src/flutter/lib/ui/semantics.dart

@@ -1017,6 +1017,8 @@ class SemanticsUpdateBuilder extends NativeFieldWrapperClass1 {
   ///
   /// The returned object can be passed to [PlatformDispatcher.updateSemantics]
   /// to actually update the semantics retained by the system.
+  ///
+  /// This object is unusable after calling build.
   SemanticsUpdate build() {
     final SemanticsUpdate semanticsUpdate = SemanticsUpdate._();
     _build(semanticsUpdate);

engine/src/flutter/lib/ui/semantics/semantics_update_builder.cc

@@ -131,6 +131,7 @@ void SemanticsUpdateBuilder::updateCustomAction(int id,
 void SemanticsUpdateBuilder::build(Dart_Handle semantics_update_handle) {
   SemanticsUpdate::create(semantics_update_handle, std::move(nodes_),
                           std::move(actions_));
+  ClearDartWrapper();
 }
 
 }  // namespace flutter

engine/src/flutter/lib/ui/text.dart

@@ -2907,6 +2907,36 @@ class Paragraph extends NativeFieldWrapperClass1 {
 
   @FfiNative<Handle Function(Pointer<Void>)>('Paragraph::computeLineMetrics')
   external Float64List _computeLineMetrics();
+
+  /// Release the resources used by this object. The object is no longer usable
+  /// after this method is called.
+  void dispose() {
+    assert(!_disposed);
+    assert(() {
+      _disposed = true;
+      return true;
+    }());
+    _dispose();
+  }
+
+  /// This can't be a leaf call because the native function calls Dart API
+  /// (Dart_SetNativeInstanceField).
+  @FfiNative<Void Function(Pointer<Void>)>('Paragraph::dispose')
+  external void _dispose();
+
+  bool _disposed = false;
+  /// Whether this reference to the underlying picture is [dispose]d.
+  ///
+  /// This only returns a valid value if asserts are enabled, and must not be
+  /// used otherwise.
+  bool get debugDisposed {
+    bool? disposed;
+    assert(() {
+      disposed = _disposed;
+      return true;
+    }());
+    return disposed ?? (throw StateError('$runtimeType.debugDisposed is only available when asserts are enabled.'));
+  }
 }
 
 /// Builds a [Paragraph] containing text with the given styling information.
@@ -3166,8 +3196,8 @@ class ParagraphBuilder extends NativeFieldWrapperClass1 {
     _placeholderScales.add(scale);
   }
 
-  @FfiNative<Handle Function(Pointer<Void>, Double, Double, Uint32, Double, Uint32)>('ParagraphBuilder::addPlaceholder')
-  external String? _addPlaceholder(double width, double height, int alignment, double baselineOffset, int baseline);
+  @FfiNative<Void Function(Pointer<Void>, Double, Double, Uint32, Double, Uint32)>('ParagraphBuilder::addPlaceholder')
+  external void _addPlaceholder(double width, double height, int alignment, double baselineOffset, int baseline);
 
   /// Applies the given paragraph style and returns a [Paragraph] containing the
   /// added text and associated styling.

engine/src/flutter/lib/ui/text/paragraph.cc

@@ -66,6 +66,11 @@ void Paragraph::layout(double width) {
 }
 
 void Paragraph::paint(Canvas* canvas, double x, double y) {
+  if (!m_paragraph || !canvas) {
+    // disposed.
+    return;
+  }
+
   SkCanvas* sk_canvas = canvas->canvas();
   if (!sk_canvas) {
     return;
@@ -168,4 +173,9 @@ tonic::Float64List Paragraph::computeLineMetrics() {
   return result;
 }
 
+void Paragraph::dispose() {
+  m_paragraph.reset();
+  ClearDartWrapper();
+}
+
 }  // namespace flutter

engine/src/flutter/lib/ui/text/paragraph.h

@@ -51,6 +51,8 @@ class Paragraph : public RefCountedDartWrappable<Paragraph> {
 
   size_t GetAllocationSize() const override;
 
+  void dispose();
+
  private:
   std::unique_ptr<txt::Paragraph> m_paragraph;
 

engine/src/flutter/lib/ui/text/paragraph_builder.cc

@@ -528,22 +528,22 @@ Dart_Handle ParagraphBuilder::addText(const std::u16string& text) {
   return Dart_Null();
 }
 
-Dart_Handle ParagraphBuilder::addPlaceholder(double width,
-                                             double height,
-                                             unsigned alignment,
-                                             double baseline_offset,
-                                             unsigned baseline) {
+void ParagraphBuilder::addPlaceholder(double width,
+                                      double height,
+                                      unsigned alignment,
+                                      double baseline_offset,
+                                      unsigned baseline) {
   txt::PlaceholderRun placeholder_run(
       width, height, static_cast<txt::PlaceholderAlignment>(alignment),
       static_cast<txt::TextBaseline>(baseline), baseline_offset);
 
   m_paragraphBuilder->AddPlaceholder(placeholder_run);
-
-  return Dart_Null();
 }
 
 void ParagraphBuilder::build(Dart_Handle paragraph_handle) {
   Paragraph::Create(paragraph_handle, m_paragraphBuilder->Build());
+  m_paragraphBuilder.reset();
+  ClearDartWrapper();
 }
 
 }  // namespace flutter

engine/src/flutter/lib/ui/text/paragraph_builder.h

@@ -60,11 +60,11 @@ class ParagraphBuilder : public RefCountedDartWrappable<ParagraphBuilder> {
   // Internally, this method adds a single object replacement character (0xFFFC)
   // and emplaces a new PlaceholderRun instance to the vector of inline
   // placeholders.
-  Dart_Handle addPlaceholder(double width,
-                             double height,
-                             unsigned alignment,
-                             double baseline_offset,
-                             unsigned baseline);
+  void addPlaceholder(double width,
+                      double height,
+                      unsigned alignment,
+                      double baseline_offset,
+                      unsigned baseline);
 
   void build(Dart_Handle paragraph_handle);
 

engine/src/flutter/lib/web_ui/lib/canvas.dart

@@ -21,7 +21,7 @@ enum VertexMode {
   triangleFan,
 }
 
-class Vertices {
+abstract class Vertices {
   factory Vertices(
     VertexMode mode,
     List<Offset> positions, {
@@ -48,6 +48,9 @@ class Vertices {
       colors: colors,
       indices: indices);
   }
+
+  void dispose();
+  bool get debugDisposed;
 }
 
 abstract class PictureRecorder {

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/text.dart

@@ -797,6 +797,23 @@ class CkParagraph extends SkiaObject<SkParagraph> implements ui.Paragraph {
     }
     return result;
   }
+
+  bool _disposed = false;
+
+  @override
+  void dispose() {
+    delete();
+    didDelete();
+    _disposed = true;
+  }
+
+  @override
+  bool get debugDisposed {
+    if (assertionsEnabled) {
+      return _disposed;
+    }
+    throw StateError('Paragraph.debugDisposed is only available when asserts are enabled.');
+  }
 }
 
 class CkLineMetrics implements ui.LineMetrics {

engine/src/flutter/lib/web_ui/lib/src/engine/canvaskit/vertices.dart

@@ -6,6 +6,7 @@ import 'dart:typed_data';
 
 import 'package:ui/ui.dart' as ui;
 
+import '../util.dart';
 import 'canvaskit_api.dart';
 import 'skia_object_cache.dart';
 
@@ -108,4 +109,20 @@ class CkVertices extends ManagedSkiaObject<SkVertices> implements ui.Vertices {
   void delete() {
     rawSkiaObject?.delete();
   }
+
+  bool _disposed = false;
+
+  @override
+  void dispose() {
+    delete();
+    _disposed = true;
+  }
+
+  @override
+  bool get debugDisposed {
+    if (assertionsEnabled) {
+      return _disposed;
+    }
+    throw StateError('Vertices.debugDisposed is only avialalbe when asserts are enabled.');
+  }
 }

engine/src/flutter/lib/web_ui/lib/src/engine/html/render_vertices.dart

@@ -57,6 +57,21 @@ class SurfaceVertices implements ui.Vertices {
     }
     return list;
   }
+
+  bool _disposed = false;
+
+  @override
+  void dispose() {
+    _disposed = true;
+  }
+
+  @override
+  bool get debugDisposed {
+    if (assertionsEnabled) {
+      return _disposed;
+    }
+    throw StateError('Vertices.debugDisposed is only avialalbe when asserts are enabled.');
+  }
 }
 
 /// Lazily initializes web gl.

engine/src/flutter/lib/web_ui/lib/src/engine/text/canvas_paragraph.dart

@@ -8,6 +8,7 @@ import '../dom.dart';
 import '../embedder.dart';
 import '../html/bitmap_canvas.dart';
 import '../profiler.dart';
+import '../util.dart';
 import 'layout_service.dart';
 import 'paint_service.dart';
 import 'paragraph.dart';
@@ -40,7 +41,7 @@ class CanvasParagraph implements ui.Paragraph {
   final EngineParagraphStyle paragraphStyle;
 
   /// The full textual content of the paragraph.
-  final String plainText;
+  late String plainText;
 
   /// The number of placeholders in this paragraph.
   final int placeholderCount;
@@ -254,6 +255,23 @@ class CanvasParagraph implements ui.Paragraph {
   List<EngineLineMetrics> computeLineMetrics() {
     return lines.map((ParagraphLine line) => line.lineMetrics).toList();
   }
+
+  bool _disposed = false;
+
+  @override
+  void dispose() {
+    spans.clear();
+    plainText = '';
+    _disposed = true;
+  }
+
+  @override
+  bool get debugDisposed {
+    if (assertionsEnabled) {
+      return _disposed;
+    }
+    throw StateError('Vertices.debugDisposed is only avialalbe when asserts are enabled.');
+  }
 }
 
 void _positionSpanElement(DomElement element, ParagraphLine line, RangeBox box) {

engine/src/flutter/lib/web_ui/lib/text.dart

@@ -670,6 +670,8 @@ abstract class Paragraph {
   TextRange getLineBoundary(TextPosition position);
   List<TextBox> getBoxesForPlaceholders();
   List<LineMetrics> computeLineMetrics();
+  void dispose();
+  bool get debugDisposed;
 }
 
 abstract class ParagraphBuilder {

engine/src/flutter/testing/dart/canvas_test.dart

@@ -109,6 +109,7 @@ void testNoCrashes() {
     testCanvas((Canvas canvas) => canvas.translate(double.nan, double.nan));
     testCanvas((Canvas canvas) => canvas.drawVertices(Vertices(VertexMode.triangles, <Offset>[],
                                                                indices: <int>[]), BlendMode.screen, paint));
+    testCanvas((Canvas canvas) => canvas.drawVertices(Vertices(VertexMode.triangles, <Offset>[])..dispose(), BlendMode.screen, paint));
   });
 }
 

engine/src/flutter/testing/dart/paragraph_builder_test.dart

@@ -25,7 +25,7 @@ void main() {
     final ParagraphBuilder paragraphBuilder =
         ParagraphBuilder(ParagraphStyle());
     paragraphBuilder.build();
-    paragraphBuilder.pushStyle(TextStyle());
+    expect(() { paragraphBuilder.pushStyle(TextStyle()); }, throwsStateError);
   });
 
   test('GetRectsForRange smoke test', () {

engine/src/flutter/testing/dart/paragraph_test.dart

@@ -197,4 +197,19 @@ void main() {
     expect(line.start, 6);
     expect(line.end, 10);
   });
+
+  test('painting a disposed paragraph does not crash', () {
+    final Paragraph paragraph = ParagraphBuilder(ParagraphStyle()).build();
+    paragraph.dispose();
+
+    final PictureRecorder recorder = PictureRecorder();
+    final Canvas canvas = Canvas(recorder);
+
+    void callback() { canvas.drawParagraph(paragraph, Offset.zero); }
+    if (assertStatementsEnabled) {
+      expectAssertion(callback);
+    } else {
+      expect(callback, throwsStateError);
+    }
+  });
 }