impeller/geometry/path_component.h

// 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.

#pragma once

#include <vector>

#include "impeller/geometry/point.h"
#include "impeller/geometry/rect.h"
#include "impeller/geometry/scalar.h"

namespace impeller {

/// Information about how to approximate points on a curved path segment.
///
/// In particular, the values in this object control how many vertices to
/// generate when approximating curves, and what tolerances to use when
/// calculating the sharpness of curves.
struct SmoothingApproximation {
  /// The scaling coefficient to use when translating to screen coordinates.
  ///
  /// Values approaching 0.0 will generate smoother looking curves with a
  /// greater number of vertices, and will be more expensive to calculate.
  Scalar scale;

  /// The tolerance value in radians for calculating sharp angles.
  ///
  /// Values approaching 0.0 will provide more accurate approximation of sharp
  /// turns. A 0.0 value means angle conditions are not considered at all.
  Scalar angle_tolerance;

  /// An angle in radians at which to introduce bevel cuts.
  ///
  /// Values greater than zero will restirct the sharpness of bevel cuts on
  /// turns.
  Scalar cusp_limit;

  /// Used to more quickly detect colinear cases.
  Scalar distance_tolerance_square;

  SmoothingApproximation(/* default */)
      : SmoothingApproximation(1.0 /* scale */,
                               0.0 /* angle tolerance */,
                               0.0 /* cusp limit */) {}

  SmoothingApproximation(Scalar p_scale,
                         Scalar p_angle_tolerance,
                         Scalar p_cusp_limit)
      : scale(p_scale),
        angle_tolerance(p_angle_tolerance),
        cusp_limit(p_cusp_limit),
        distance_tolerance_square(0.5 * p_scale * 0.5 * p_scale) {}
};

struct LinearPathComponent {
  Point p1;
  Point p2;

  LinearPathComponent() {}

  LinearPathComponent(Point ap1, Point ap2) : p1(ap1), p2(ap2) {}

  Point Solve(Scalar time) const;

  std::vector<Point> CreatePolyline() const;

  std::vector<Point> Extrema() const;

  bool operator==(const LinearPathComponent& other) const {
    return p1 == other.p1 && p2 == other.p2;
  }
};

struct QuadraticPathComponent {
  Point p1;
  Point cp;
  Point p2;

  QuadraticPathComponent() {}

  QuadraticPathComponent(Point ap1, Point acp, Point ap2)
      : p1(ap1), cp(acp), p2(ap2) {}

  Point Solve(Scalar time) const;

  Point SolveDerivative(Scalar time) const;

  std::vector<Point> CreatePolyline(
      const SmoothingApproximation& approximation) const;

  std::vector<Point> Extrema() const;

  bool operator==(const QuadraticPathComponent& other) const {
    return p1 == other.p1 && cp == other.cp && p2 == other.p2;
  }
};

struct CubicPathComponent {
  Point p1;
  Point cp1;
  Point cp2;
  Point p2;

  CubicPathComponent() {}

  CubicPathComponent(const QuadraticPathComponent& q)
      : p1(q.p1),
        cp1(q.p1 + (q.cp - q.p1) * (2.0 / 3.0)),
        cp2(q.p2 + (q.cp - q.p2) * (2.0 / 3.0)),
        p2(q.p2) {}

  CubicPathComponent(Point ap1, Point acp1, Point acp2, Point ap2)
      : p1(ap1), cp1(acp1), cp2(acp2), p2(ap2) {}

  Point Solve(Scalar time) const;

  Point SolveDerivative(Scalar time) const;

  std::vector<Point> CreatePolyline(
      const SmoothingApproximation& approximation) const;

  std::vector<Point> Extrema() const;

  bool operator==(const CubicPathComponent& other) const {
    return p1 == other.p1 && cp1 == other.cp1 && cp2 == other.cp2 &&
           p2 == other.p2;
  }
};

struct ContourComponent {
  Point destination;
  bool is_closed = false;

  ContourComponent() {}

  ContourComponent(Point p, bool is_closed = false)
      : destination(p), is_closed(is_closed) {}

  bool operator==(const ContourComponent& other) const {
    return destination == other.destination && is_closed == other.is_closed;
  }
};

}  // namespace impeller