Change Vertices.indices to use a Uint16 list to more accurately reflect Skia's API (flutter/engine#8657)

Also throw if SkVertices::Builder reports an invalid configuration.

Fixes https://github.com/flutter/flutter/issues/31270

DEPS

@@ -130,7 +130,7 @@ deps = {
    # and not have to specific specific hashes.
 
   'src/third_party/tonic':
-   Var('fuchsia_git') + '/tonic' + '@' + '02f9d8dd18dd259e3c5efe1fbe713819a730b6e0',
+   Var('fuchsia_git') + '/tonic' + '@' + '2919ef4751621fabecb721c153ea9a3b72af995d',
 
   'src/third_party/benchmark':
    Var('fuchsia_git') + '/third_party/benchmark' + '@' + '21f1eb3fe269ea43eba862bf6b699cde46587ade',

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

@@ -2913,12 +2913,13 @@ class Vertices extends NativeFieldWrapperClass2 {
     final Int32List encodedColors = colors != null
       ? _encodeColorList(colors)
       : null;
-    final Int32List encodedIndices = indices != null
-      ? new Int32List.fromList(indices)
+    final Uint16List encodedIndices = indices != null
+      ? new Uint16List.fromList(indices)
       : null;
 
     _constructor();
-    _init(mode.index, encodedPositions, encodedTextureCoordinates, encodedColors, encodedIndices);
+    if (!_init(mode.index, encodedPositions, encodedTextureCoordinates, encodedColors, encodedIndices))
+      throw new ArgumentError('Invalid configuration for vertices.');
   }
 
   Vertices.raw(
@@ -2926,7 +2927,7 @@ class Vertices extends NativeFieldWrapperClass2 {
     Float32List positions, {
     Float32List textureCoordinates,
     Int32List colors,
-    Int32List indices,
+    Uint16List indices,
   }) : assert(mode != null),
        assert(positions != null) {
     if (textureCoordinates != null && textureCoordinates.length != positions.length)
@@ -2937,16 +2938,17 @@ class Vertices extends NativeFieldWrapperClass2 {
       throw new ArgumentError('"indices" values must be valid indices in the positions list.');
 
     _constructor();
-    _init(mode.index, positions, textureCoordinates, colors, indices);
+    if (!_init(mode.index, positions, textureCoordinates, colors, indices))
+      throw new ArgumentError('Invalid configuration for vertices.');
   }
 
   void _constructor() native 'Vertices_constructor';
 
-  void _init(int mode,
+  bool _init(int mode,
              Float32List positions,
              Float32List textureCoordinates,
              Int32List colors,
-             Int32List indices) native 'Vertices_init';
+             Uint16List indices) native 'Vertices_init';
 }
 
 /// Defines how a list of points is interpreted when drawing a set of points.

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

@@ -4,6 +4,8 @@
 
 #include "flutter/lib/ui/painting/vertices.h"
 
+#include <algorithm>
+
 #include "third_party/tonic/dart_binding_macros.h"
 #include "third_party/tonic/dart_library_natives.h"
 
@@ -47,11 +49,11 @@ fml::RefPtr<Vertices> Vertices::Create() {
   return fml::MakeRefCounted<Vertices>();
 }
 
-void Vertices::init(SkVertices::VertexMode vertex_mode,
+bool Vertices::init(SkVertices::VertexMode vertex_mode,
                     const tonic::Float32List& positions,
                     const tonic::Float32List& texture_coordinates,
                     const tonic::Int32List& colors,
-                    const tonic::Int32List& indices) {
+                    const tonic::Uint16List& indices) {
   uint32_t builderFlags = 0;
   if (texture_coordinates.data())
     builderFlags |= SkVertices::kHasTexCoords_BuilderFlag;
@@ -61,6 +63,9 @@ void Vertices::init(SkVertices::VertexMode vertex_mode,
   SkVertices::Builder builder(vertex_mode, positions.num_elements() / 2,
                               indices.num_elements(), builderFlags);
 
+  if (!builder.isValid())
+    return false;
+
   // positions are required for SkVertices::Builder
   FML_DCHECK(positions.data());
   if (positions.data())
@@ -77,10 +82,14 @@ void Vertices::init(SkVertices::VertexMode vertex_mode,
     DecodeInts<SkColor>(colors, builder.colors());
   }
 
-  if (indices.data())
-    DecodeInts<uint16_t>(indices, builder.indices());
+  if (indices.data()) {
+    std::copy(indices.data(), indices.data() + indices.num_elements(),
+              builder.indices());
+  }
 
   vertices_ = builder.detach();
+
+  return true;
 }
 
 }  // namespace flutter

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

@@ -9,6 +9,7 @@
 #include "third_party/skia/include/core/SkVertices.h"
 #include "third_party/tonic/typed_data/float32_list.h"
 #include "third_party/tonic/typed_data/int32_list.h"
+#include "third_party/tonic/typed_data/uint16_list.h"
 
 namespace tonic {
 class DartLibraryNatives;
@@ -27,11 +28,11 @@ class Vertices : public RefCountedDartWrappable<Vertices> {
 
   static fml::RefPtr<Vertices> Create();
 
-  void init(SkVertices::VertexMode vertex_mode,
+  bool init(SkVertices::VertexMode vertex_mode,
             const tonic::Float32List& positions,
             const tonic::Float32List& texture_coordinates,
             const tonic::Int32List& colors,
-            const tonic::Int32List& indices);
+            const tonic::Uint16List& indices);
 
   const sk_sp<SkVertices>& vertices() const { return vertices_; }