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Jonah Williams
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[Impeller] add support for superellipse. (#54562)
This is an entity testing only implementation of a superellipse. rectellipse is a special case where degree = 4. Part of flutter/flutter#139321
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‎ci/licenses_golden/licenses_flutter‎

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@@ -42862,6 +42862,8 @@ ORIGIN: ../../../flutter/impeller/entity/geometry/round_rect_geometry.cc + ../..
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ORIGIN: ../../../flutter/impeller/entity/geometry/round_rect_geometry.h + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/stroke_path_geometry.cc + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/stroke_path_geometry.h + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/superellipse_geometry.cc + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/superellipse_geometry.h + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/vertices_geometry.cc + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/geometry/vertices_geometry.h + ../../../flutter/LICENSE
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ORIGIN: ../../../flutter/impeller/entity/inline_pass_context.cc + ../../../flutter/LICENSE
@@ -45739,6 +45741,8 @@ FILE: ../../../flutter/impeller/entity/geometry/round_rect_geometry.cc
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FILE: ../../../flutter/impeller/entity/geometry/round_rect_geometry.h
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FILE: ../../../flutter/impeller/entity/geometry/stroke_path_geometry.cc
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FILE: ../../../flutter/impeller/entity/geometry/stroke_path_geometry.h
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FILE: ../../../flutter/impeller/entity/geometry/superellipse_geometry.cc
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FILE: ../../../flutter/impeller/entity/geometry/superellipse_geometry.h
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FILE: ../../../flutter/impeller/entity/geometry/vertices_geometry.cc
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FILE: ../../../flutter/impeller/entity/geometry/vertices_geometry.h
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FILE: ../../../flutter/impeller/entity/inline_pass_context.cc

‎impeller/aiks/canvas.cc‎

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#include "impeller/entity/contents/texture_contents.h"
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#include "impeller/entity/contents/vertices_contents.h"
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#include "impeller/entity/geometry/geometry.h"
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#include "impeller/entity/geometry/superellipse_geometry.h"
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#include "impeller/geometry/color.h"
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#include "impeller/geometry/constants.h"
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#include "impeller/geometry/path_builder.h"

‎impeller/entity/BUILD.gn‎

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@@ -196,6 +196,8 @@ impeller_component("entity") {
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"geometry/round_rect_geometry.h",
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"geometry/stroke_path_geometry.cc",
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"geometry/stroke_path_geometry.h",
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"geometry/superellipse_geometry.cc",
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"geometry/superellipse_geometry.h",
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"geometry/vertices_geometry.cc",
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"geometry/vertices_geometry.h",
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"inline_pass_context.cc",

‎impeller/entity/entity_unittests.cc‎

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#include "impeller/entity/geometry/geometry.h"
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#include "impeller/entity/geometry/point_field_geometry.h"
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#include "impeller/entity/geometry/stroke_path_geometry.h"
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#include "impeller/entity/geometry/superellipse_geometry.h"
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#include "impeller/entity/render_target_cache.h"
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#include "impeller/geometry/color.h"
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#include "impeller/geometry/geometry_asserts.h"
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ASSERT_TRUE(OpenPlaygroundHere(std::move(entity)));
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}
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TEST_P(EntityTest, DrawSuperEllipse) {
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auto callback = [&](ContentContext& context, RenderPass& pass) -> bool {
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// UI state.
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static float alpha = 10;
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static float beta = 10;
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static float radius = 40;
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static int degree = 4;
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static Color color = Color::Red();
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ImGui::Begin("Controls", nullptr, ImGuiWindowFlags_AlwaysAutoResize);
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ImGui::SliderFloat("Alpha", &alpha, 0, 100);
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ImGui::SliderFloat("Beta", &beta, 0, 100);
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ImGui::SliderInt("Degreee", &degree, 1, 20);
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ImGui::SliderFloat("Radius", &radius, 0, 400);
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ImGui::ColorEdit4("Color", reinterpret_cast<float*>(&color));
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ImGui::End();
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auto contents = std::make_shared<SolidColorContents>();
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contents->SetColor(color);
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contents->SetGeometry(std::make_shared<SuperellipseGeometry>(
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Point{400, 400}, radius, degree, alpha, beta));
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Entity entity;
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entity.SetContents(contents);
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return entity.Render(context, pass);
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};
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ASSERT_TRUE(OpenPlaygroundHere(callback));
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}
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} // namespace testing
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} // namespace impeller
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‎impeller/entity/geometry/superellipse_geometry.cc‎

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// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include <vector>
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#include "flutter/impeller/entity/geometry/superellipse_geometry.h"
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#include "impeller/geometry/constants.h"
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namespace impeller {
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SuperellipseGeometry::SuperellipseGeometry(const Point& center,
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Scalar radius,
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Scalar degree,
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Scalar alpha,
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Scalar beta)
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: center_(center),
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degree_(degree),
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radius_(radius),
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alpha_(alpha),
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beta_(beta) {}
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GeometryResult SuperellipseGeometry::GetPositionBuffer(
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const ContentContext& renderer,
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const Entity& entity,
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RenderPass& pass) const {
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// https://math.stackexchange.com/questions/2573746/superellipse-parametric-equation
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Scalar a = alpha_;
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Scalar b = beta_;
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Scalar n = degree_;
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// TODO(jonahwilliams): determine parameter values based on scaling factor.
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Scalar step = kPi / 80;
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// Generate the points for the top left quadrant, and then mirror to the other
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// quadrants.
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std::vector<Point> points;
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points.reserve(41);
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for (int i = 0; i <= 40; i++) {
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Scalar t = i * step;
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Scalar x = a * pow(abs(cos(t)), 2 / n);
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Scalar y = b * pow(abs(sin(t)), 2 / n);
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points.emplace_back(x * radius_, y * radius_);
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}
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static constexpr Point reflection[4] = {{1, 1}, {-1, 1}, {-1, -1}, {1, -1}};
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// Reflect into the 4 quadrants and generate the tessellated mesh. The
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// iteration order is reversed so that the trianges are continuous from
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// quadrant to quadrant.
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std::vector<Point> geometry;
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geometry.reserve(1 + 4 * points.size());
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geometry.push_back(center_);
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for (auto i = 0u; i < points.size(); i++) {
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geometry.push_back(center_ + (reflection[0] * points[i]));
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}
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for (auto i = 0u; i < points.size(); i++) {
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geometry.push_back(center_ +
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(reflection[1] * points[points.size() - i - 1]));
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}
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for (auto i = 0u; i < points.size(); i++) {
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geometry.push_back(center_ + (reflection[2] * points[i]));
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}
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for (auto i = 0u; i < points.size(); i++) {
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geometry.push_back(center_ +
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(reflection[3] * points[points.size() - i - 1]));
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}
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std::vector<uint16_t> indices;
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indices.reserve(geometry.size() * 3);
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for (auto i = 2u; i < geometry.size(); i++) {
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indices.push_back(0);
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indices.push_back(i - 1);
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indices.push_back(i);
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}
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auto& host_buffer = renderer.GetTransientsBuffer();
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return GeometryResult{
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.type = PrimitiveType::kTriangle,
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.vertex_buffer =
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{
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.vertex_buffer = host_buffer.Emplace(
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geometry.data(), geometry.size() * sizeof(Point),
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alignof(Point)),
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.index_buffer = host_buffer.Emplace(
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indices.data(), indices.size() * sizeof(uint16_t),
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alignof(uint16_t)),
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.vertex_count = indices.size(),
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.index_type = IndexType::k16bit,
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},
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.transform = entity.GetShaderTransform(pass),
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};
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}
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std::optional<Rect> SuperellipseGeometry::GetCoverage(
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const Matrix& transform) const {
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return Rect::MakeOriginSize(center_ - Point(radius_, radius_),
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Size(radius_ * 2, radius_ * 2));
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}
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bool SuperellipseGeometry::CoversArea(const Matrix& transform,
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const Rect& rect) const {
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return false;
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}
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bool SuperellipseGeometry::IsAxisAlignedRect() const {
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return false;
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}
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} // namespace impeller

‎impeller/entity/geometry/superellipse_geometry.h‎

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// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_
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#define FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_
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#include "impeller/entity/geometry/geometry.h"
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namespace impeller {
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/// Geometry class that can generate vertices for a superellipse.
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///
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/// A Superellipse is an ellipse-like shape that is defined by the parameters N,
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/// alpha, and beta:
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///
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/// 1 = |x / b| ^n + |y / a| ^n
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///
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/// The radius and center apply a uniform scaling and offset that is separate
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/// from alpha or beta. When n = 4, the shape is referred to as a rectellipse.
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///
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/// See also: https://en.wikipedia.org/wiki/Superellipse
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class SuperellipseGeometry final : public Geometry {
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public:
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explicit SuperellipseGeometry(const Point& center,
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Scalar radius,
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Scalar degree,
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Scalar alpha,
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Scalar beta);
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~SuperellipseGeometry() = default;
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// |Geometry|
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bool CoversArea(const Matrix& transform, const Rect& rect) const override;
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// |Geometry|
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bool IsAxisAlignedRect() const override;
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private:
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// |Geometry|
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GeometryResult GetPositionBuffer(const ContentContext& renderer,
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const Entity& entity,
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RenderPass& pass) const override;
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// |Geometry|
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std::optional<Rect> GetCoverage(const Matrix& transform) const override;
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Point center_;
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// 4 is a rectellipse
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Scalar degree_;
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Scalar radius_;
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Scalar alpha_;
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Scalar beta_;
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SuperellipseGeometry(const SuperellipseGeometry&) = delete;
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SuperellipseGeometry& operator=(const SuperellipseGeometry&) = delete;
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};
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} // namespace impeller
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#endif // FLUTTER_IMPELLER_ENTITY_GEOMETRY_SUPERELLIPSE_GEOMETRY_H_

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