impeller::PathBuilder Class Reference

#include <path_builder.h>

Classes
struct	RoundingRadii

Public Member Functions
	PathBuilder ()
	~PathBuilder ()
Path	CopyPath (FillType fill=FillType::kNonZero)
Path	TakePath (FillType fill=FillType::kNonZero)
void	Reserve (size_t point_size, size_t verb_size)
	Reserve [point_size] points and [verb_size] verbs in the underlying path buffer.
PathBuilder &	SetConvexity (Convexity value)
PathBuilder &	MoveTo (Point point, bool relative=false)
PathBuilder &	Close ()
PathBuilder &	LineTo (Point point, bool relative=false)
	Insert a line from the current position to point.
PathBuilder &	HorizontalLineTo (Scalar x, bool relative=false)
PathBuilder &	VerticalLineTo (Scalar y, bool relative=false)
PathBuilder &	QuadraticCurveTo (Point controlPoint, Point point, bool relative=false)
	Insert a quadradic curve from the current position to point using the control point controlPoint.
PathBuilder &	CubicCurveTo (Point controlPoint1, Point controlPoint2, Point point, bool relative=false)
	Insert a cubic curve from the curren position to point using the control points controlPoint1 and controlPoint2.
PathBuilder &	AddRect (Rect rect)
PathBuilder &	AddCircle (const Point &center, Scalar radius)
PathBuilder &	AddArc (const Rect &oval_bounds, Radians start, Radians sweep, bool use_center=false)
PathBuilder &	AddOval (const Rect &rect)
PathBuilder &	AddLine (const Point &p1, const Point &p2)
	Move to point p1, then insert a line from p1 to p2.
PathBuilder &	AddQuadraticCurve (Point p1, Point cp, Point p2)
	Move to point p1, then insert a quadradic curve from p1 to p2 with the control point cp.
PathBuilder &	AddCubicCurve (Point p1, Point cp1, Point cp2, Point p2)
	Move to point p1, then insert a cubic curve from p1 to p2 with control points cp1 and cp2.
PathBuilder &	Shift (Point offset)
	Transform the existing path segments and contours by the given offset.
PathBuilder &	SetBounds (Rect bounds)
	Set the bounding box that will be used by Path.GetBoundingBox in place of performing the computation.
PathBuilder &	AddRoundedRect (Rect rect, RoundingRadii radii)
PathBuilder &	AddRoundedRect (Rect rect, Size radii)
PathBuilder &	AddRoundedRect (Rect rect, Scalar radius)
PathBuilder &	AddPath (const Path &path)

Static Public Attributes
static constexpr const Scalar	kArcApproximationMagic = 0.551915024494f

Detailed Description

Definition at line 14 of file path_builder.h.

Constructor & Destructor Documentation

PathBuilder()

impeller::PathBuilder::PathBuilder

(

)

Definition at line 11 of file path_builder.cc.

                         {
  AddContourComponent({});
}

~PathBuilder()

impeller::PathBuilder::~PathBuilder ( )

default

Member Function Documentation

AddArc()

PathBuilder & impeller::PathBuilder::AddArc	(	const Rect &	oval_bounds,
		Radians	start,
		Radians	sweep,
		bool	use_center = false
	)

Definition at line 318 of file path_builder.cc.

                                                  {
  if (sweep.radians < 0) {
    start.radians += sweep.radians;
    sweep.radians *= -1;
  }
  sweep.radians = std::min(k2Pi, sweep.radians);
  start.radians = std::fmod(start.radians, k2Pi);
 
  const Point center = oval_bounds.GetCenter();
  const Point radius = center - oval_bounds.GetOrigin();
 
  Vector2 p1_unit(std::cos(start.radians), std::sin(start.radians));
 
  if (use_center) {
    MoveTo(center);
    LineTo(center + p1_unit * radius);
  } else {
    MoveTo(center + p1_unit * radius);
  }
 
  while (sweep.radians > 0) {
    Vector2 p2_unit;
    Scalar quadrant_angle;
    if (sweep.radians < kPiOver2) {
      quadrant_angle = sweep.radians;
      p2_unit = Vector2(std::cos(start.radians + quadrant_angle),
                        std::sin(start.radians + quadrant_angle));
    } else {
      quadrant_angle = kPiOver2;
      p2_unit = Vector2(-p1_unit.y, p1_unit.x);
    }
 
    Vector2 arc_cp_lengths =
        (quadrant_angle / kPiOver2) * kArcApproximationMagic * radius;
 
    Point p1 = center + p1_unit * radius;
    Point p2 = center + p2_unit * radius;
    Point cp1 = p1 + Vector2(-p1_unit.y, p1_unit.x) * arc_cp_lengths;
    Point cp2 = p2 + Vector2(p2_unit.y, -p2_unit.x) * arc_cp_lengths;
 
    AddCubicComponent(p1, cp1, cp2, p2);
    current_ = p2;
 
    start.radians += quadrant_angle;
    sweep.radians -= quadrant_angle;
    p1_unit = p2_unit;
  }
 
  if (use_center) {
    Close();
  }
 
  return *this;
}

AddCircle()

PathBuilder & impeller::PathBuilder::AddCircle	(	const Point &	center,
		Scalar	radius
	)

Definition at line 135 of file path_builder.cc.

                                                            {
  return AddOval(Rect::MakeXYWH(c.x - r, c.y - r, 2.0f * r, 2.0f * r));
}

AddCubicCurve()

PathBuilder & impeller::PathBuilder::AddCubicCurve	(	Point	p1,
		Point	cp1,
		Point	cp2,
		Point	p2
	)

Move to point p1, then insert a cubic curve from p1 to p2 with control points cp1 and cp2.

Definition at line 108 of file path_builder.cc.

                                                  {
  MoveTo(p1);
  AddCubicComponent(p1, cp1, cp2, p2);
  return *this;
}

AddLine()

PathBuilder & impeller::PathBuilder::AddLine	(	const Point &	p1,
		const Point &	p2
	)

Move to point p1, then insert a line from p1 to p2.

Definition at line 424 of file path_builder.cc.

                                                                  {
  MoveTo(p1);
  AddLinearComponent(p1, p2);
  return *this;
}

AddOval()

PathBuilder & impeller::PathBuilder::AddOval

(

const Rect &

rect

)

Definition at line 376 of file path_builder.cc.

                                                       {
  const Point c = container.GetCenter();
  const Point r = c - container.GetOrigin();
  const Point m = r * kArcApproximationMagic;
 
  MoveTo({c.x, c.y - r.y});
 
  //----------------------------------------------------------------------------
  // Top right arc.
  //
  AddCubicComponent({c.x, c.y - r.y},        // p1
                    {c.x + m.x, c.y - r.y},  // cp1
                    {c.x + r.x, c.y - m.y},  // cp2
                    {c.x + r.x, c.y}         // p2
  );
 
  //----------------------------------------------------------------------------
  // Bottom right arc.
  //
  AddCubicComponent({c.x + r.x, c.y},        // p1
                    {c.x + r.x, c.y + m.y},  // cp1
                    {c.x + m.x, c.y + r.y},  // cp2
                    {c.x, c.y + r.y}         // p2
  );
 
  //----------------------------------------------------------------------------
  // Bottom left arc.
  //
  AddCubicComponent({c.x, c.y + r.y},        // p1
                    {c.x - m.x, c.y + r.y},  // cp1
                    {c.x - r.x, c.y + m.y},  // cp2
                    {c.x - r.x, c.y}         // p2
  );
 
  //----------------------------------------------------------------------------
  // Top left arc.
  //
  AddCubicComponent({c.x - r.x, c.y},        // p1
                    {c.x - r.x, c.y - m.y},  // cp1
                    {c.x - m.x, c.y - r.y},  // cp2
                    {c.x, c.y - r.y}         // p2
  );
 
  Close();
 
  return *this;
}

AddPath()

PathBuilder & impeller::PathBuilder::AddPath

(

const Path &

path

)

Definition at line 430 of file path_builder.cc.

                                                  {
  auto linear = [&](size_t index, const LinearPathComponent& l) {
    AddLinearComponent(l.p1, l.p2);
  };
  auto quadratic = [&](size_t index, const QuadraticPathComponent& q) {
    AddQuadraticComponent(q.p1, q.cp, q.p2);
  };
  auto cubic = [&](size_t index, const CubicPathComponent& c) {
    AddCubicComponent(c.p1, c.cp1, c.cp2, c.p2);
  };
  auto move = [&](size_t index, const ContourComponent& m) {
    AddContourComponent(m.destination);
  };
  path.EnumerateComponents(linear, quadratic, cubic, move);
  return *this;
}

AddQuadraticCurve()

PathBuilder & impeller::PathBuilder::AddQuadraticCurve	(	Point	p1,
		Point	cp,
		Point	p2
	)

Move to point p1, then insert a quadradic curve from p1 to p2 with the control point cp.

Definition at line 102 of file path_builder.cc.

                                                                        {
  MoveTo(p1);
  AddQuadraticComponent(p1, cp, p2);
  return *this;
}

AddRect()

PathBuilder & impeller::PathBuilder::AddRect

(

Rect

rect

)

Definition at line 117 of file path_builder.cc.

                                           {
  auto origin = rect.GetOrigin();
  auto size = rect.GetSize();
 
  auto tl = origin;
  auto bl = origin + Point{0.0, size.height};
  auto br = origin + size;
  auto tr = origin + Point{size.width, 0.0};
 
  MoveTo(tl);
  LineTo(tr);
  LineTo(br);
  LineTo(bl);
  Close();
 
  return *this;
}

AddRoundedRect() [1/3]

PathBuilder & impeller::PathBuilder::AddRoundedRect	(	Rect	rect,
		RoundingRadii	radii
	)

Definition at line 150 of file path_builder.cc.

                                                                       {
  if (radii.AreAllZero()) {
    return AddRect(rect);
  }
 
  auto rect_origin = rect.GetOrigin();
  auto rect_size = rect.GetSize();
 
  current_ = rect_origin + Point{radii.top_left.x, 0.0};
 
  MoveTo({rect_origin.x + radii.top_left.x, rect_origin.y});
 
  //----------------------------------------------------------------------------
  // Top line.
  //
  AddLinearComponent(
      {rect_origin.x + radii.top_left.x, rect_origin.y},
      {rect_origin.x + rect_size.width - radii.top_right.x, rect_origin.y});
 
  //----------------------------------------------------------------------------
  // Top right arc.
  //
  AddRoundedRectTopRight(rect, radii);
 
  //----------------------------------------------------------------------------
  // Right line.
  //
  AddLinearComponent(
      {rect_origin.x + rect_size.width, rect_origin.y + radii.top_right.y},
      {rect_origin.x + rect_size.width,
       rect_origin.y + rect_size.height - radii.bottom_right.y});
 
  //----------------------------------------------------------------------------
  // Bottom right arc.
  //
  AddRoundedRectBottomRight(rect, radii);
 
  //----------------------------------------------------------------------------
  // Bottom line.
  //
  AddLinearComponent(
      {rect_origin.x + rect_size.width - radii.bottom_right.x,
       rect_origin.y + rect_size.height},
      {rect_origin.x + radii.bottom_left.x, rect_origin.y + rect_size.height});
 
  //----------------------------------------------------------------------------
  // Bottom left arc.
  //
  AddRoundedRectBottomLeft(rect, radii);
 
  //----------------------------------------------------------------------------
  // Left line.
  //
  AddLinearComponent(
      {rect_origin.x, rect_origin.y + rect_size.height - radii.bottom_left.y},
      {rect_origin.x, rect_origin.y + radii.top_left.y});
 
  //----------------------------------------------------------------------------
  // Top left arc.
  //
  AddRoundedRectTopLeft(rect, radii);
 
  Close();
 
  return *this;
}

AddRoundedRect() [2/3]

PathBuilder & impeller::PathBuilder::AddRoundedRect	(	Rect	rect,
		Scalar	radius
	)

Definition at line 139 of file path_builder.cc.

                                                                 {
  return radius <= 0.0 ? AddRect(rect)
                       : AddRoundedRect(rect, RoundingRadii(radius));
}

AddRoundedRect() [3/3]

PathBuilder & impeller::PathBuilder::AddRoundedRect	(	Rect	rect,
		Size	radii
	)

Definition at line 144 of file path_builder.cc.

                                                              {
  return radii.width <= 0 || radii.height <= 0
             ? AddRect(rect)
             : AddRoundedRect(rect, RoundingRadii(radii));
}

Close()

PathBuilder & impeller::PathBuilder::Close

(

)

Definition at line 40 of file path_builder.cc.

                                {
  // If the subpath start is the same as the current position, this
  // is an empty contour and inserting a line segment will just
  // confuse the tessellator.
  if (subpath_start_ != current_) {
    LineTo(subpath_start_);
  }
  SetContourClosed(true);
  AddContourComponent(current_);
  return *this;
}

CopyPath()

Path impeller::PathBuilder::CopyPath

(

FillType

fill = FillType::kNonZero

)

Definition at line 17 of file path_builder.cc.

                                        {
  prototype_.fill = fill;
  return Path(prototype_);
}

CubicCurveTo()

PathBuilder & impeller::PathBuilder::CubicCurveTo	(	Point	controlPoint1,
		Point	controlPoint2,
		Point	point,
		bool	relative = false
	)

Insert a cubic curve from the curren position to point using the control points controlPoint1 and controlPoint2.

If relative is true the point, controlPoint1, and controlPoint2 are relative to current location.

Definition at line 90 of file path_builder.cc.

                                                      {
  controlPoint1 = relative ? current_ + controlPoint1 : controlPoint1;
  controlPoint2 = relative ? current_ + controlPoint2 : controlPoint2;
  point = relative ? current_ + point : point;
  AddCubicComponent(current_, controlPoint1, controlPoint2, point);
  current_ = point;
  return *this;
}

HorizontalLineTo()

PathBuilder & impeller::PathBuilder::HorizontalLineTo	(	Scalar	x,
		bool	relative = false
	)

Definition at line 59 of file path_builder.cc.

                                                                  {
  Point endpoint =
      relative ? Point{current_.x + x, current_.y} : Point{x, current_.y};
  AddLinearComponent(current_, endpoint);
  current_ = endpoint;
  return *this;
}

LineTo()

PathBuilder & impeller::PathBuilder::LineTo	(	Point	point,
		bool	relative = false
	)

Insert a line from the current position to point.

If relative is true, then point is relative to the current location.

Definition at line 52 of file path_builder.cc.

                                                           {
  point = relative ? current_ + point : point;
  AddLinearComponent(current_, point);
  current_ = point;
  return *this;
}

MoveTo()

PathBuilder & impeller::PathBuilder::MoveTo	(	Point	point,
		bool	relative = false
	)

Definition at line 33 of file path_builder.cc.

                                                           {
  current_ = relative ? current_ + point : point;
  subpath_start_ = current_;
  AddContourComponent(current_);
  return *this;
}

QuadraticCurveTo()

PathBuilder & impeller::PathBuilder::QuadraticCurveTo	(	Point	controlPoint,
		Point	point,
		bool	relative = false
	)

Insert a quadradic curve from the current position to point using the control point controlPoint.

If relative is true the point and controlPoint are relative to current location.

Definition at line 75 of file path_builder.cc.

                                                          {
  point = relative ? current_ + point : point;
  controlPoint = relative ? current_ + controlPoint : controlPoint;
  AddQuadraticComponent(current_, controlPoint, point);
  current_ = point;
  return *this;
}

Reserve()

void impeller::PathBuilder::Reserve	(	size_t	point_size,
		size_t	verb_size
	)

Reserve [point_size] points and [verb_size] verbs in the underlying path buffer.

Definition at line 28 of file path_builder.cc.

                                                             {
  prototype_.points.reserve(point_size);
  prototype_.components.reserve(verb_size);
}

SetBounds()

PathBuilder & impeller::PathBuilder::SetBounds

(

Rect

bounds

)

Set the bounding box that will be used by Path.GetBoundingBox in place of performing the computation.

   When Impeller recieves Skia Path objects, many of these already
   have computed bounds. This method is used to avoid needlessly
   recomputing these bounds. 

Definition at line 458 of file path_builder.cc.

                                               {
  prototype_.bounds = bounds;
  return *this;
}

SetConvexity()

PathBuilder & impeller::PathBuilder::SetConvexity

(

Convexity

value

)

Definition at line 85 of file path_builder.cc.

                                                      {
  prototype_.convexity = value;
  return *this;
}

Shift()

PathBuilder & impeller::PathBuilder::Shift

(

Point

offset

)

Transform the existing path segments and contours by the given offset.

Definition at line 447 of file path_builder.cc.

                                            {
  for (auto& point : prototype_.points) {
    point += offset;
  }
  for (auto& contour : prototype_.contours) {
    contour.destination += offset;
  }
  prototype_.bounds.reset();
  return *this;
}

TakePath()

Path impeller::PathBuilder::TakePath

(

FillType

fill = FillType::kNonZero

)

Definition at line 22 of file path_builder.cc.

                                        {
  prototype_.fill = fill;
  UpdateBounds();
  return Path(std::move(prototype_));
}

VerticalLineTo()

PathBuilder & impeller::PathBuilder::VerticalLineTo	(	Scalar	y,
		bool	relative = false
	)

Definition at line 67 of file path_builder.cc.

                                                                {
  Point endpoint =
      relative ? Point{current_.x, current_.y + y} : Point{current_.x, y};
  AddLinearComponent(current_, endpoint);
  current_ = endpoint;
  return *this;
}

Member Data Documentation

kArcApproximationMagic

constexpr const Scalar impeller::PathBuilder::kArcApproximationMagic = 0.551915024494f

staticconstexpr

Used for approximating quarter circle arcs with cubic curves. This is the control point distance which results in the smallest possible unit circle integration for a right angle arc. It can be used to approximate arcs less than 90 degrees to great effect by simply reducing it proportionally to the angle. However, accuracy rapidly diminishes if magnified for obtuse angle arcs, and so multiple cubic curves should be used when approximating arcs greater than 90 degrees.

Definition at line 23 of file path_builder.h.

---

The documentation for this class was generated from the following files:

• impeller/geometry/path_builder.h
• impeller/geometry/path_builder.cc