| // Copyright 2013 The Flutter Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "impeller/tessellator/tessellator.h" |
| |
| #include "impeller/core/buffer_view.h" |
| #include "impeller/core/formats.h" |
| #include "impeller/core/vertex_buffer.h" |
| |
| namespace impeller { |
| |
| Tessellator::Tessellator() |
| : point_buffer_(std::make_unique<std::vector<Point>>()), |
| index_buffer_(std::make_unique<std::vector<uint16_t>>()) { |
| point_buffer_->reserve(2048); |
| index_buffer_->reserve(2048); |
| } |
| |
| Tessellator::~Tessellator() = default; |
| |
| Path::Polyline Tessellator::CreateTempPolyline(const Path& path, |
| Scalar tolerance) { |
| FML_DCHECK(point_buffer_); |
| point_buffer_->clear(); |
| auto polyline = |
| path.CreatePolyline(tolerance, std::move(point_buffer_), |
| [this](Path::Polyline::PointBufferPtr point_buffer) { |
| point_buffer_ = std::move(point_buffer); |
| }); |
| return polyline; |
| } |
| |
| VertexBuffer Tessellator::TessellateConvex(const Path& path, |
| HostBuffer& host_buffer, |
| Scalar tolerance, |
| std::optional<Matrix> uv_transform) { |
| FML_DCHECK(point_buffer_); |
| FML_DCHECK(index_buffer_); |
| TessellateConvexInternal(path, *point_buffer_, *index_buffer_, tolerance, |
| uv_transform); |
| |
| if (point_buffer_->empty()) { |
| return VertexBuffer{ |
| .vertex_buffer = {}, |
| .index_buffer = {}, |
| .vertex_count = 0u, |
| .index_type = IndexType::k16bit, |
| }; |
| } |
| |
| BufferView vertex_buffer = host_buffer.Emplace( |
| point_buffer_->data(), sizeof(Point) * point_buffer_->size(), |
| alignof(Point)); |
| |
| BufferView index_buffer = host_buffer.Emplace( |
| index_buffer_->data(), sizeof(uint16_t) * index_buffer_->size(), |
| alignof(uint16_t)); |
| |
| return VertexBuffer{ |
| .vertex_buffer = std::move(vertex_buffer), |
| .index_buffer = std::move(index_buffer), |
| .vertex_count = index_buffer_->size(), |
| .index_type = IndexType::k16bit, |
| }; |
| } |
| |
| void Tessellator::TessellateConvexInternal(const Path& path, |
| std::vector<Point>& point_buffer, |
| std::vector<uint16_t>& index_buffer, |
| Scalar tolerance, |
| std::optional<Matrix> uv_transform) { |
| index_buffer_->clear(); |
| point_buffer_->clear(); |
| |
| VertexWriter writer(point_buffer, index_buffer, uv_transform); |
| |
| path.WritePolyline(tolerance, writer); |
| writer.EndContour(); |
| } |
| |
| static constexpr int kPrecomputedDivisionCount = 1024; |
| static int kPrecomputedDivisions[kPrecomputedDivisionCount] = { |
| // clang-format off |
| 1, 2, 3, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, |
| 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, |
| 10, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 13, |
| 13, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, |
| 15, 15, 15, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 16, |
| 16, 16, 16, 16, 17, 17, 17, 17, 17, 17, 17, 17, 17, 17, 18, 18, |
| 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 19, |
| 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 20, 20, 20, 20, 20, |
| 20, 20, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, |
| 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, |
| 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 24, 24, 24, 24, |
| 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 25, 25, 25, 25, 25, |
| 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 26, 26, 26, 26, 26, |
| 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 27, 27, 27, 27, |
| 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 28, 28, 28, |
| 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 29, |
| 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, |
| 29, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, 30, |
| 30, 30, 30, 30, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, 31, |
| 31, 31, 31, 31, 31, 31, 31, 31, 32, 32, 32, 32, 32, 32, 32, 32, |
| 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 33, 33, 33, |
| 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, |
| 33, 33, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, |
| 34, 34, 34, 34, 34, 34, 34, 35, 35, 35, 35, 35, 35, 35, 35, 35, |
| 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 36, 36, |
| 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, |
| 36, 36, 36, 36, 36, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, |
| 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, |
| 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, 38, |
| 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, |
| 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 39, 40, 40, |
| 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, |
| 40, 40, 40, 40, 40, 40, 40, 41, 41, 41, 41, 41, 41, 41, 41, 41, |
| 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, |
| 41, 41, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, |
| 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 43, 43, 43, 43, |
| 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, |
| 43, 43, 43, 43, 43, 43, 43, 43, 44, 44, 44, 44, 44, 44, 44, 44, |
| 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, |
| 44, 44, 44, 44, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, |
| 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, |
| 45, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, |
| 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 47, |
| 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, |
| 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 48, 48, 48, |
| 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, |
| 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 49, 49, 49, 49, |
| 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, |
| 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 50, 50, 50, 50, 50, |
| 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, |
| 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 50, 51, 51, 51, 51, 51, |
| 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, |
| 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 51, 52, 52, 52, 52, |
| 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, |
| 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 52, 53, 53, 53, |
| 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, |
| 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 53, 54, |
| 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, |
| 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, 54, |
| 54, 54, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, |
| 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, 55, |
| 55, 55, 55, 55, 55, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, |
| 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, 56, |
| 56, 56, 56, 56, 56, 56, 56, 56, 56, 57, 57, 57, 57, 57, 57, 57, |
| // clang-format on |
| }; |
| |
| static size_t ComputeQuadrantDivisions(Scalar pixel_radius) { |
| if (pixel_radius <= 0.0) { |
| return 1; |
| } |
| int radius_index = ceil(pixel_radius); |
| if (radius_index < kPrecomputedDivisionCount) { |
| return kPrecomputedDivisions[radius_index]; |
| } |
| |
| // For a circle with N divisions per quadrant, the maximum deviation of |
| // the polgyon approximation from the true circle will be at the center |
| // of the base of each triangular pie slice. We can compute that distance |
| // by finding the midpoint of the line of the first slice and compare |
| // its distance from the center of the circle to the radius. We will aim |
| // to have the length of that bisector to be within |kCircleTolerance| |
| // from the radius in pixels. |
| // |
| // Each vertex will appear at an angle of: |
| // theta(i) = (kPi / 2) * (i / N) // for i in [0..N] |
| // with each point falling at: |
| // point(i) = r * (cos(theta), sin(theta)) |
| // If we consider the unit circle to simplify the calculations below then |
| // we need to scale the tolerance from its absolute quantity into a unit |
| // circle fraction: |
| // k = tolerance / radius |
| // Using this scaled tolerance below to avoid multiplying by the radius |
| // throughout all of the math, we have: |
| // first point = (1, 0) // theta(0) == 0 |
| // theta = kPi / 2 / N // theta(1) |
| // second point = (cos(theta), sin(theta)) = (c, s) |
| // midpoint = (first + second) * 0.5 = ((1 + c)/2, s/2) |
| // |midpoint| = sqrt((1 + c)*(1 + c)/4 + s*s/4) |
| // = sqrt((1 + c + c + c*c + s*s) / 4) |
| // = sqrt((1 + 2c + 1) / 4) |
| // = sqrt((2 + 2c) / 4) |
| // = sqrt((1 + c) / 2) |
| // = cos(theta / 2) // using half-angle cosine formula |
| // error = 1 - |midpoint| = 1 - cos(theta / 2) |
| // cos(theta/2) = 1 - error |
| // theta/2 = acos(1 - error) |
| // kPi / 2 / N / 2 = acos(1 - error) |
| // kPi / 4 / acos(1 - error) = N |
| // Since we need error <= k, we want divisions >= N, so we use: |
| // N = ceil(kPi / 4 / acos(1 - k)) |
| // |
| // Math is confirmed in https://math.stackexchange.com/a/4132095 |
| // (keeping in mind that we are computing quarter circle divisions here) |
| // which also points out a performance optimization that is accurate |
| // to within an over-estimation of 1 division would be: |
| // N = ceil(kPi / 4 / sqrt(2 * k)) |
| // Since we have precomputed the divisions for radii up to 1024, we can |
| // afford to be more accurate using the acos formula here for larger radii. |
| double k = Tessellator::kCircleTolerance / pixel_radius; |
| return ceil(kPiOver4 / std::acos(1 - k)); |
| } |
| |
| void Tessellator::Trigs::init(size_t divisions) { |
| if (!trigs_.empty()) { |
| return; |
| } |
| |
| // Either not cached yet, or we are using the temp storage... |
| trigs_.reserve(divisions + 1); |
| |
| double angle_scale = kPiOver2 / divisions; |
| |
| trigs_.emplace_back(1.0, 0.0); |
| for (size_t i = 1; i < divisions; i++) { |
| trigs_.emplace_back(Radians(i * angle_scale)); |
| } |
| trigs_.emplace_back(0.0, 1.0); |
| } |
| |
| Tessellator::Trigs Tessellator::GetTrigsForDivisions(size_t divisions) { |
| return divisions < Tessellator::kCachedTrigCount |
| ? Trigs(precomputed_trigs_[divisions], divisions) |
| : Trigs(divisions); |
| } |
| |
| using TessellatedVertexProc = Tessellator::TessellatedVertexProc; |
| using EllipticalVertexGenerator = Tessellator::EllipticalVertexGenerator; |
| |
| EllipticalVertexGenerator::EllipticalVertexGenerator( |
| EllipticalVertexGenerator::GeneratorProc& generator, |
| Trigs&& trigs, |
| PrimitiveType triangle_type, |
| size_t vertices_per_trig, |
| Data&& data) |
| : impl_(generator), |
| trigs_(std::move(trigs)), |
| data_(data), |
| vertices_per_trig_(vertices_per_trig) {} |
| |
| EllipticalVertexGenerator Tessellator::FilledCircle( |
| const Matrix& view_transform, |
| const Point& center, |
| Scalar radius) { |
| auto divisions = |
| ComputeQuadrantDivisions(view_transform.GetMaxBasisLength() * radius); |
| return EllipticalVertexGenerator(Tessellator::GenerateFilledCircle, |
| GetTrigsForDivisions(divisions), |
| PrimitiveType::kTriangleStrip, 4, |
| { |
| .reference_centers = {center, center}, |
| .radii = {radius, radius}, |
| .half_width = -1.0f, |
| }); |
| } |
| |
| EllipticalVertexGenerator Tessellator::StrokedCircle( |
| const Matrix& view_transform, |
| const Point& center, |
| Scalar radius, |
| Scalar half_width) { |
| if (half_width > 0) { |
| auto divisions = ComputeQuadrantDivisions( |
| view_transform.GetMaxBasisLength() * radius + half_width); |
| return EllipticalVertexGenerator(Tessellator::GenerateStrokedCircle, |
| GetTrigsForDivisions(divisions), |
| PrimitiveType::kTriangleStrip, 8, |
| { |
| .reference_centers = {center, center}, |
| .radii = {radius, radius}, |
| .half_width = half_width, |
| }); |
| } else { |
| return FilledCircle(view_transform, center, radius); |
| } |
| } |
| |
| EllipticalVertexGenerator Tessellator::RoundCapLine( |
| const Matrix& view_transform, |
| const Point& p0, |
| const Point& p1, |
| Scalar radius) { |
| auto along = p1 - p0; |
| auto length = along.GetLength(); |
| if (length > kEhCloseEnough) { |
| auto divisions = |
| ComputeQuadrantDivisions(view_transform.GetMaxBasisLength() * radius); |
| return EllipticalVertexGenerator(Tessellator::GenerateRoundCapLine, |
| GetTrigsForDivisions(divisions), |
| PrimitiveType::kTriangleStrip, 4, |
| { |
| .reference_centers = {p0, p1}, |
| .radii = {radius, radius}, |
| .half_width = -1.0f, |
| }); |
| } else { |
| return FilledCircle(view_transform, p0, radius); |
| } |
| } |
| |
| EllipticalVertexGenerator Tessellator::FilledEllipse( |
| const Matrix& view_transform, |
| const Rect& bounds) { |
| if (bounds.IsSquare()) { |
| return FilledCircle(view_transform, bounds.GetCenter(), |
| bounds.GetWidth() * 0.5f); |
| } |
| auto max_radius = bounds.GetSize().MaxDimension(); |
| auto divisions = |
| ComputeQuadrantDivisions(view_transform.GetMaxBasisLength() * max_radius); |
| auto center = bounds.GetCenter(); |
| return EllipticalVertexGenerator(Tessellator::GenerateFilledEllipse, |
| GetTrigsForDivisions(divisions), |
| PrimitiveType::kTriangleStrip, 4, |
| { |
| .reference_centers = {center, center}, |
| .radii = bounds.GetSize() * 0.5f, |
| .half_width = -1.0f, |
| }); |
| } |
| |
| EllipticalVertexGenerator Tessellator::FilledRoundRect( |
| const Matrix& view_transform, |
| const Rect& bounds, |
| const Size& radii) { |
| if (radii.width * 2 < bounds.GetWidth() || |
| radii.height * 2 < bounds.GetHeight()) { |
| auto max_radius = radii.MaxDimension(); |
| auto divisions = ComputeQuadrantDivisions( |
| view_transform.GetMaxBasisLength() * max_radius); |
| auto upper_left = bounds.GetLeftTop() + radii; |
| auto lower_right = bounds.GetRightBottom() - radii; |
| return EllipticalVertexGenerator(Tessellator::GenerateFilledRoundRect, |
| GetTrigsForDivisions(divisions), |
| PrimitiveType::kTriangleStrip, 4, |
| { |
| .reference_centers = |
| { |
| upper_left, |
| lower_right, |
| }, |
| .radii = radii, |
| .half_width = -1.0f, |
| }); |
| } else { |
| return FilledEllipse(view_transform, bounds); |
| } |
| } |
| |
| void Tessellator::GenerateFilledCircle( |
| const Trigs& trigs, |
| const EllipticalVertexGenerator::Data& data, |
| const TessellatedVertexProc& proc) { |
| auto center = data.reference_centers[0]; |
| auto radius = data.radii.width; |
| |
| FML_DCHECK(center == data.reference_centers[1]); |
| FML_DCHECK(radius == data.radii.height); |
| FML_DCHECK(data.half_width < 0); |
| |
| // Quadrant 1 connecting with Quadrant 4: |
| for (auto& trig : trigs) { |
| auto offset = trig * radius; |
| proc({center.x - offset.x, center.y + offset.y}); |
| proc({center.x - offset.x, center.y - offset.y}); |
| } |
| |
| // The second half of the circle should be iterated in reverse, but |
| // we can instead iterate forward and swap the x/y values of the |
| // offset as the angles should be symmetric and thus should generate |
| // symmetrically reversed trig vectors. |
| // Quadrant 2 connecting with Quadrant 2: |
| for (auto& trig : trigs) { |
| auto offset = trig * radius; |
| proc({center.x + offset.y, center.y + offset.x}); |
| proc({center.x + offset.y, center.y - offset.x}); |
| } |
| } |
| |
| void Tessellator::GenerateStrokedCircle( |
| const Trigs& trigs, |
| const EllipticalVertexGenerator::Data& data, |
| const TessellatedVertexProc& proc) { |
| auto center = data.reference_centers[0]; |
| |
| FML_DCHECK(center == data.reference_centers[1]); |
| FML_DCHECK(data.radii.IsSquare()); |
| FML_DCHECK(data.half_width > 0 && data.half_width < data.radii.width); |
| |
| auto outer_radius = data.radii.width + data.half_width; |
| auto inner_radius = data.radii.width - data.half_width; |
| |
| // Zig-zag back and forth between points on the outer circle and the |
| // inner circle. Both circles are evaluated at the same number of |
| // quadrant divisions so the points for a given division should match |
| // 1 for 1 other than their applied radius. |
| |
| // Quadrant 1: |
| for (auto& trig : trigs) { |
| auto outer = trig * outer_radius; |
| auto inner = trig * inner_radius; |
| proc({center.x - outer.x, center.y - outer.y}); |
| proc({center.x - inner.x, center.y - inner.y}); |
| } |
| |
| // The even quadrants of the circle should be iterated in reverse, but |
| // we can instead iterate forward and swap the x/y values of the |
| // offset as the angles should be symmetric and thus should generate |
| // symmetrically reversed trig vectors. |
| // Quadrant 2: |
| for (auto& trig : trigs) { |
| auto outer = trig * outer_radius; |
| auto inner = trig * inner_radius; |
| proc({center.x + outer.y, center.y - outer.x}); |
| proc({center.x + inner.y, center.y - inner.x}); |
| } |
| |
| // Quadrant 3: |
| for (auto& trig : trigs) { |
| auto outer = trig * outer_radius; |
| auto inner = trig * inner_radius; |
| proc({center.x + outer.x, center.y + outer.y}); |
| proc({center.x + inner.x, center.y + inner.y}); |
| } |
| |
| // Quadrant 4: |
| for (auto& trig : trigs) { |
| auto outer = trig * outer_radius; |
| auto inner = trig * inner_radius; |
| proc({center.x - outer.y, center.y + outer.x}); |
| proc({center.x - inner.y, center.y + inner.x}); |
| } |
| } |
| |
| void Tessellator::GenerateRoundCapLine( |
| const Trigs& trigs, |
| const EllipticalVertexGenerator::Data& data, |
| const TessellatedVertexProc& proc) { |
| auto p0 = data.reference_centers[0]; |
| auto p1 = data.reference_centers[1]; |
| auto radius = data.radii.width; |
| |
| FML_DCHECK(radius == data.radii.height); |
| FML_DCHECK(data.half_width < 0); |
| |
| auto along = p1 - p0; |
| along *= radius / along.GetLength(); |
| auto across = Point(-along.y, along.x); |
| |
| for (auto& trig : trigs) { |
| auto relative_along = along * trig.cos; |
| auto relative_across = across * trig.sin; |
| proc(p0 - relative_along + relative_across); |
| proc(p0 - relative_along - relative_across); |
| } |
| |
| // The second half of the round caps should be iterated in reverse, but |
| // we can instead iterate forward and swap the sin/cos values as they |
| // should be symmetric. |
| for (auto& trig : trigs) { |
| auto relative_along = along * trig.sin; |
| auto relative_across = across * trig.cos; |
| proc(p1 + relative_along + relative_across); |
| proc(p1 + relative_along - relative_across); |
| } |
| } |
| |
| void Tessellator::GenerateFilledEllipse( |
| const Trigs& trigs, |
| const EllipticalVertexGenerator::Data& data, |
| const TessellatedVertexProc& proc) { |
| auto center = data.reference_centers[0]; |
| auto radii = data.radii; |
| |
| FML_DCHECK(center == data.reference_centers[1]); |
| FML_DCHECK(data.half_width < 0); |
| |
| // Quadrant 1 connecting with Quadrant 4: |
| for (auto& trig : trigs) { |
| auto offset = trig * radii; |
| proc({center.x - offset.x, center.y + offset.y}); |
| proc({center.x - offset.x, center.y - offset.y}); |
| } |
| |
| // The second half of the circle should be iterated in reverse, but |
| // we can instead iterate forward and swap the x/y values of the |
| // offset as the angles should be symmetric and thus should generate |
| // symmetrically reversed trig vectors. |
| // Quadrant 2 connecting with Quadrant 2: |
| for (auto& trig : trigs) { |
| auto offset = Point(trig.sin * radii.width, trig.cos * radii.height); |
| proc({center.x + offset.x, center.y + offset.y}); |
| proc({center.x + offset.x, center.y - offset.y}); |
| } |
| } |
| |
| void Tessellator::GenerateFilledRoundRect( |
| const Trigs& trigs, |
| const EllipticalVertexGenerator::Data& data, |
| const TessellatedVertexProc& proc) { |
| Scalar left = data.reference_centers[0].x; |
| Scalar top = data.reference_centers[0].y; |
| Scalar right = data.reference_centers[1].x; |
| Scalar bottom = data.reference_centers[1].y; |
| auto radii = data.radii; |
| |
| FML_DCHECK(data.half_width < 0); |
| |
| // Quadrant 1 connecting with Quadrant 4: |
| for (auto& trig : trigs) { |
| auto offset = trig * radii; |
| proc({left - offset.x, bottom + offset.y}); |
| proc({left - offset.x, top - offset.y}); |
| } |
| |
| // The second half of the round rect should be iterated in reverse, but |
| // we can instead iterate forward and swap the x/y values of the |
| // offset as the angles should be symmetric and thus should generate |
| // symmetrically reversed trig vectors. |
| // Quadrant 2 connecting with Quadrant 2: |
| for (auto& trig : trigs) { |
| auto offset = Point(trig.sin * radii.width, trig.cos * radii.height); |
| proc({right + offset.x, bottom + offset.y}); |
| proc({right + offset.x, top - offset.y}); |
| } |
| } |
| |
| } // namespace impeller |
