[Impeller] geometry changes to support line/point style.

impeller/entity/entity_unittests.cc

@@ -14,6 +14,7 @@
 #include "gtest/gtest.h"
 #include "impeller/core/device_buffer.h"
 #include "impeller/core/formats.h"
+#include "impeller/core/host_buffer.h"
 #include "impeller/core/texture_descriptor.h"
 #include "impeller/entity/contents/clip_contents.h"
 #include "impeller/entity/contents/conical_gradient_contents.h"
@@ -2424,6 +2425,59 @@ TEST_P(EntityTest, GiantStrokePathAllocation) {
   EXPECT_NEAR(point.y, expected[4].y, 0.1);
 }
 
+TEST_P(EntityTest, GiantLineStripPathAllocation) {
+  PathBuilder builder{};
+  for (int i = 0; i < 10000; i++) {
+    builder.LineTo(Point(i, i));
+  }
+  Path path = builder.TakePath();
+
+  ContentContext content_context(GetContext(), /*typographer_context=*/nullptr);
+  Entity entity;
+
+  auto host_buffer = HostBuffer::Create(GetContext()->GetResourceAllocator(),
+                                        GetContext()->GetIdleWaiter());
+  auto tessellator = Tessellator();
+
+  auto vertex_buffer = tessellator.GenerateLineStrip(path, *host_buffer, 1.0);
+
+  // Validate the buffer data overflowed the small buffer
+  EXPECT_GT(vertex_buffer.vertex_count, kPointArenaSize);
+
+  // Validate that there are no uninitialized points near the gap.
+  Point* written_data = reinterpret_cast<Point*>(
+      (vertex_buffer.vertex_buffer.GetBuffer()->OnGetContents() +
+       vertex_buffer.vertex_buffer.GetRange().offset));
+
+  std::vector<Point> expected = {
+      Point(4093, 4093),  //
+      Point(4094, 4094),  //
+      Point(4095, 4095),  //
+      Point(4096, 4096),  //
+      Point(4097, 4097)   //
+  };
+
+  Point point = written_data[kPointArenaSize - 2];
+  EXPECT_NEAR(point.x, expected[0].x, 0.1);
+  EXPECT_NEAR(point.y, expected[0].y, 0.1);
+
+  point = written_data[kPointArenaSize - 1];
+  EXPECT_NEAR(point.x, expected[1].x, 0.1);
+  EXPECT_NEAR(point.y, expected[1].y, 0.1);
+
+  point = written_data[kPointArenaSize];
+  EXPECT_NEAR(point.x, expected[2].x, 0.1);
+  EXPECT_NEAR(point.y, expected[2].y, 0.1);
+
+  point = written_data[kPointArenaSize + 1];
+  EXPECT_NEAR(point.x, expected[3].x, 0.1);
+  EXPECT_NEAR(point.y, expected[3].y, 0.1);
+
+  point = written_data[kPointArenaSize + 2];
+  EXPECT_NEAR(point.x, expected[4].x, 0.1);
+  EXPECT_NEAR(point.y, expected[4].y, 0.1);
+}
+
 }  // namespace testing
 }  // namespace impeller
 

impeller/geometry/path.cc

@@ -59,6 +59,10 @@ bool Path::IsEmpty() const {
           data_->components[0] == ComponentType::kContour);
 }
 
+bool Path::IsSingleContour() const {
+  return data_->single_countour;
+}
+
 /// Determine required storage for points and indices.
 std::pair<size_t, size_t> Path::CountStorage(Scalar scale) const {
   size_t points = 0;

impeller/geometry/path.h

@@ -153,6 +153,9 @@ class Path {
 
   bool IsEmpty() const;
 
+  /// @brief Whether the line contains a single contour.
+  bool IsSingleContour() const;
+
   bool GetLinearComponentAtIndex(size_t index,
                                  LinearPathComponent& linear) const;
 
@@ -219,6 +222,7 @@ class Path {
 
     FillType fill = FillType::kNonZero;
     Convexity convexity = Convexity::kUnknown;
+    bool single_countour = true;
     std::optional<Rect> bounds;
     std::vector<Point> points;
     std::vector<ComponentType> components;

impeller/geometry/path_builder.cc

@@ -18,13 +18,22 @@ PathBuilder::~PathBuilder() = default;
 
 Path PathBuilder::CopyPath(FillType fill) {
   prototype_.fill = fill;
+  prototype_.single_countour =
+      current_contour_location_ == 0u ||
+      (contour_count_ == 2 &&
+       prototype_.components.back() == Path::ComponentType::kContour);
   return Path(prototype_);
 }
 
 Path PathBuilder::TakePath(FillType fill) {
   prototype_.fill = fill;
   UpdateBounds();
+  prototype_.single_countour =
+      current_contour_location_ == 0u ||
+      (contour_count_ == 2 &&
+       prototype_.components.back() == Path::ComponentType::kContour);
   current_contour_location_ = 0u;
+  contour_count_ = 1;
   return Path(std::move(prototype_));
 }
 
@@ -276,6 +285,7 @@ void PathBuilder::AddContourComponent(const Point& destination,
     points.push_back(destination);
     points.push_back(closed);
     components.push_back(Path::ComponentType::kContour);
+    contour_count_ += 1;
   }
   prototype_.bounds.reset();
 }
@@ -450,6 +460,7 @@ PathBuilder& PathBuilder::AddPath(const Path& path) {
   for (auto component : path.data_->components) {
     if (component == Path::ComponentType::kContour) {
       current_contour_location_ = source_offset;
+      contour_count_ += 1;
     }
     source_offset += Path::VerbToOffset(component);
   }

impeller/geometry/path_builder.h

@@ -111,6 +111,7 @@ class PathBuilder {
   Point subpath_start_;
   Point current_;
   size_t current_contour_location_ = 0u;
+  size_t contour_count_ = 0u;
   Path::Data prototype_;
 
   PathBuilder& AddRoundedRectTopLeft(Rect rect, RoundingRadii radii);

impeller/geometry/path_component.cc

@@ -5,6 +5,7 @@
 #include "path_component.h"
 
 #include <cmath>
+#include <utility>
 
 #include "impeller/geometry/scalar.h"
 #include "impeller/geometry/wangs_formula.h"
@@ -77,6 +78,29 @@ void StripVertexWriter::Write(Point point) {
   point_buffer_[count_++] = point;
 }
 
+/////////// LineStripVertexWriter ////////
+
+LineStripVertexWriter::LineStripVertexWriter(std::vector<Point>& points)
+    : points_(points) {}
+
+void LineStripVertexWriter::EndContour() {}
+
+void LineStripVertexWriter::Write(Point point) {
+  if (offset_ >= points_.size()) {
+    overflow_.push_back(point);
+  } else {
+    points_[offset_++] = point;
+  }
+}
+
+const std::vector<Point>& LineStripVertexWriter::GetOveriszedBuffer() const {
+  return overflow_;
+}
+
+std::pair<size_t, size_t> LineStripVertexWriter::GetVertexCount() const {
+  return std::make_pair(offset_, overflow_.size());
+}
+
 /////////// GLESVertexWriter ///////////
 
 GLESVertexWriter::GLESVertexWriter(std::vector<Point>& points,

impeller/geometry/path_component.h

@@ -67,6 +67,27 @@ class StripVertexWriter : public VertexWriter {
   uint16_t* index_buffer_ = nullptr;
 };
 
+/// @brief A vertex writer that generates a line strip topology.
+class LineStripVertexWriter : public VertexWriter {
+ public:
+  explicit LineStripVertexWriter(std::vector<Point>& points);
+
+  ~LineStripVertexWriter() = default;
+
+  void EndContour() override;
+
+  void Write(Point point) override;
+
+  std::pair<size_t, size_t> GetVertexCount() const;
+
+  const std::vector<Point>& GetOveriszedBuffer() const;
+
+ private:
+  size_t offset_ = 0u;
+  std::vector<Point>& points_;
+  std::vector<Point> overflow_;
+};
+
 /// @brief A vertex writer that has no hardware requirements.
 class GLESVertexWriter : public VertexWriter {
  public:

impeller/geometry/path_unittests.cc

@@ -50,6 +50,142 @@ TEST(PathTest, PathCreatePolyLineDoesNotDuplicatePoints) {
   ASSERT_EQ(polyline.GetPoint(4).x, 50);
 }
 
+TEST(PathTest, PathSingleContour) {
+  // Closed shapes.
+  {
+    Path path = PathBuilder{}.AddCircle({100, 100}, 50).TakePath();
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  {
+    Path path =
+        PathBuilder{}.AddOval(Rect::MakeXYWH(100, 100, 100, 100)).TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  {
+    Path path =
+        PathBuilder{}.AddRect(Rect::MakeXYWH(100, 100, 100, 100)).TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddRoundRect(RoundRect::MakeRectRadius(
+                        Rect::MakeXYWH(100, 100, 100, 100), 10))
+                    .TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  // Open shapes.
+  {
+    Point p(100, 100);
+    Path path = PathBuilder{}.AddLine(p, {200, 100}).TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  {
+    Path path =
+        PathBuilder{}
+            .AddCubicCurve({100, 100}, {100, 50}, {100, 150}, {200, 100})
+            .TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddQuadraticCurve({100, 100}, {100, 50}, {200, 100})
+                    .TakePath();
+
+    EXPECT_TRUE(path.IsSingleContour());
+  }
+}
+
+TEST(PathTest, PathSingleContourDoubleShapes) {
+  // Closed shapes.
+  {
+    Path path = PathBuilder{}
+                    .AddCircle({100, 100}, 50)
+                    .AddCircle({100, 100}, 50)
+                    .TakePath();
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddOval(Rect::MakeXYWH(100, 100, 100, 100))
+                    .AddOval(Rect::MakeXYWH(100, 100, 100, 100))
+                    .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddRect(Rect::MakeXYWH(100, 100, 100, 100))
+                    .AddRect(Rect::MakeXYWH(100, 100, 100, 100))
+                    .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddRoundRect(RoundRect::MakeRectRadius(
+                        Rect::MakeXYWH(100, 100, 100, 100), 10))
+                    .AddRoundRect(RoundRect::MakeRectRadius(
+                        Rect::MakeXYWH(100, 100, 100, 100), 10))
+                    .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddRoundRect(RoundRect::MakeRectXY(
+                        Rect::MakeXYWH(100, 100, 100, 100), Size(10, 20)))
+                    .AddRoundRect(RoundRect::MakeRectXY(
+                        Rect::MakeXYWH(100, 100, 100, 100), Size(10, 20)))
+                    .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  // Open shapes.
+  {
+    Point p(100, 100);
+    Path path =
+        PathBuilder{}.AddLine(p, {200, 100}).AddLine(p, {200, 100}).TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path =
+        PathBuilder{}
+            .AddCubicCurve({100, 100}, {100, 50}, {100, 150}, {200, 100})
+            .AddCubicCurve({100, 100}, {100, 50}, {100, 150}, {200, 100})
+            .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+
+  {
+    Path path = PathBuilder{}
+                    .AddQuadraticCurve({100, 100}, {100, 50}, {200, 100})
+                    .Close()
+                    .AddQuadraticCurve({100, 100}, {100, 50}, {200, 100})
+                    .TakePath();
+
+    EXPECT_FALSE(path.IsSingleContour());
+  }
+}
+
 TEST(PathTest, PathBuilderSetsCorrectContourPropertiesForAddCommands) {
   // Closed shapes.
   {