skia2/site/user/api/SkPoint_Reference.md

SkPoint Reference

Point

Struct SkPoint

Typedef

SkPoint typedef define a data type.

Topic	Description

SkPoint holds two 32-bit floating point coordinates.

Overview

Topic	Description
Constructors	functions that construct SkPoint
Functions	global and class member functions
Members	member values
Operators	operator overloading methods
Related Functions	similar member functions grouped together

Related Function

SkPoint global, struct, and class related member functions share a topic.

Topic	Description
Offset	moves sides
Property	member values
Set	replaces all values
Vector	alias for Point

Member Function

SkPoint member functions read and modify the structure properties.

Topic	Description
CrossProduct	returns cross product
Distance	returns straight-line distance between points
DotProduct	returns dot product
Length	returns straight-line distance to origin
Make	constructs from SkScalar inputs
Normalize	sets length to one, and returns prior length
Offset	translates Point array
cross	returns cross product
distanceToOrigin	returns straight-line distance to origin
dot	returns dot product
equals	returns true if Points are equal
isFinite	returns true if no member is infinite or NaN
isZero	returns true if both members equal zero
iset	sets to integer input
length	returns straight-line distance to origin
negate	reverses the sign of both members
normalize	sets length to one, preserving direction
offset	translates Point
scale	multiplies Point by scale factor
set	sets to SkScalar input
setAbs	sets sign of both members to positive
setLength	sets straight-line distance to origin
setNormalize	sets length to one, in direction of (x, y)
x	returns fX
y	returns fY

Member

Members

Type	Name	Description
SkScalar	fX	x-axis value
SkScalar	fY	y-axis value

SkPoint members may be read and written directly without using a member function.

Topic	Description
fX	x-axis value
fY	y-axis value

Members

Constructor

SkPoint can be constructed or initialized by these functions, including C++ class constructors.

Type	Name	Description
SkScalar	fX	x-axis value used by both Point and Vector. May contain any value, including infinities and NaN.
SkScalar	fY	y-axis value used by both Point and Vector. May contain any value, including infinities and NaN.

Topic	Description
Make	constructs from SkScalar inputs

Make

static constexpr SkPoint Make(SkScalar x, SkScalar y)

Sets fX to x, fY to y. Used both to set Point and Vector.

Parameters

x	SkScalar x-axis value of constructed Point or Vector
y	SkScalar y-axis value of constructed Point or Vector

Return Value

Point (x, y)

Example

Example Output

all equal

See Also

set iset^[2] SkIPoint::Make

---

Property

Topic	Description
Distance	returns straight-line distance between points
Length	returns straight-line distance to origin
distanceToOrigin	returns straight-line distance to origin
isFinite	returns true if no member is infinite or NaN
isZero	returns true if both members equal zero
length	returns straight-line distance to origin
x	returns fX
y	returns fY

x

SkScalar x() const

Returns x-axis value of Point or Vector.

Return Value

fX

Example

Example Output

pt1.fX == pt1.x()

See Also

y SkIPoint::x()

---

y

SkScalar y() const

Returns y-axis value of Point or Vector.

Return Value

fY

Example

Example Output

pt1.fY == pt1.y()

See Also

x SkIPoint::y()

---

isZero

bool isZero() const

Returns true if fX and fY are both zero.

Return Value

true if fX is zero and fY is zero

Example

Example Output

pt.fX=+0 pt.fY=-0
pt.isZero() == true

See Also

isFinite SkIPoint::isZero

---

Set

Topic	Description
iset	sets to integer input
	iset(int32 t x, int32 t y)
	iset(const SkIPoint& p)
normalize	sets length to one, preserving direction
set	sets to SkScalar input
setAbs	sets sign of both members to positive
setLength	sets straight-line distance to origin
	setLength(SkScalar length)
	setLength(SkScalar x, SkScalar y, SkScalar length)
setNormalize	sets length to one, in direction of (x, y)

set

void set(SkScalar x, SkScalar y)

Sets fX to x and fY to y.

Parameters

x	new value for fX
y	new value for fY

Example

Example Output

pt1 == pt2

See Also

iset^[2] Make

---

iset

void iset(int32_t x, int32_t y)

Sets fX to x and fY to y, promoting integers to SkScalar values.

Assigning a large integer value directly to fX or fY may cause a compiler error, triggered by narrowing conversion of int to SkScalar. This safely casts x and y to avoid the error.

Parameters

x	new value for fX
y	new value for fY

Example

See Also

set Make SkIPoint::set

---

void iset(const SkIPoint& p)

Sets fX to p.fX and fY to p.fY, promoting integers to SkScalar values.

Assigning an IPoint containing a large integer value directly to fX or fY may cause a compiler error, triggered by narrowing conversion of int to SkScalar. This safely casts p.fX and p.fY to avoid the error.

Parameters

p	IPoint members promoted to SkScalar

Example

Example Output

iPt: -2147483647, 2147483647
fPt: -2.14748e+09, 2.14748e+09

See Also

set Make SkIPoint::set

---

setAbs

void setAbs(const SkPoint& pt)

Sets fX to absolute value of pt.fX; and fY to absolute value of pt.fY.

Parameters

pt	members providing magnitude for fX and fY

Example

Example Output

pt: 0, -0  abs: 0, 0
pt: -1, -2  abs: 1, 2
pt: inf, -inf  abs: inf, inf
pt: nan, -nan  abs: nan, nan

See Also

set Make negate

---

Offset

Topic	Description
Normalize	sets length to one, and returns prior length
Offset	translates Point array
	Offset(SkPoint points[], int count, const SkVector& offset)
	Offset(SkPoint points[], int count, SkScalar dx, SkScalar dy)
offset	translates Point
scale	multiplies Point by scale factor
	scale(SkScalar scale, SkPoint* dst) const
	scale(SkScalar value)

Offset

static void Offset(SkPoint points[], int count, const SkVector& offset)

Adds offset to each Point in points array with count entries.

Parameters

points	Point array
count	entries in array
offset	Vector added to points

Example

See Also

offset operator+=(const SkVector& v)

---

static void Offset(SkPoint points[], int count, SkScalar dx, SkScalar dy)

Adds offset (dx, dy) to each Point in points array of length count.

Parameters

points	Point array
count	entries in array
dx	added to fX in points
dy	added to fY in points

Example

See Also

offset operator+=(const SkVector& v)

---

offset

void offset(SkScalar dx, SkScalar dy)

Adds offset (dx, dy) to Point.

Parameters

dx	added to fX
dy	added to fY

Example

See Also

Offset^[2] operator+=(const SkVector& v)

---

length

SkScalar length() const

Returns the Euclidean Distance from origin, computed as:

sqrt(fX * fX + fY * fY)

.

Return Value

straight-line distance to origin

Example

See Also

distanceToOrigin Length setLength^[2] Distance

---

distanceToOrigin

SkScalar distanceToOrigin() const

Returns the Euclidean Distance from origin, computed as:

sqrt(fX * fX + fY * fY)

.

Return Value

straight-line distance to origin

Example

See Also

length Length setLength^[2] Distance

---

normalize

bool normalize()

Scales (fX, fY) so that length returns one, while preserving ratio of fX to fY, if possible. If prior length is nearly zero, sets Vector to (0, 0) and returns false; otherwise returns true.

Return Value

true if former length is not zero or nearly zero

Example

See Also

Normalize setLength^[2] length Length

---

setNormalize

bool setNormalize(SkScalar x, SkScalar y)

Sets Vector to (x, y) scaled so length returns one, and so that (fX, fY) is proportional to (x, y). If (x, y) length is nearly zero, sets Vector to (0, 0) and returns false; otherwise returns true.

Parameters

x	proportional value for fX
y	proportional value for fY

Return Value

true if (x, y) length is not zero or nearly zero

Example

See Also

normalize setLength^[2]

---

setLength

bool setLength(SkScalar length)

Scales Vector so that distanceToOrigin returns length, if possible. If former length is nearly zero, sets Vector to (0, 0) and return false; otherwise returns true.

Parameters

length

straight-line distance to origin

Return Value

true if former length is not zero or nearly zero

Example

See Also

length Length setNormalize setAbs

---

bool setLength(SkScalar x, SkScalar y, SkScalar length)

Sets Vector to (x, y) scaled to length, if possible. If former length is nearly zero, sets Vector to (0, 0) and return false; otherwise returns true.

Parameters

x	proportional value for fX
y	proportional value for fY
length	straight-line distance to origin

Return Value

true if (x, y) length is not zero or nearly zero

Example

See Also

length Length setNormalize setAbs

---

Operator

SkPoint operators inline class member functions with arithmetic equivalents.

Topic	Description
CrossProduct	returns cross product
DotProduct	returns dot product
cross	returns cross product
dot	returns dot product
equals	returns true if Points are equal
negate	reverses the sign of both members
operator!=(const SkPoint& a, const SkPoint& b)	returns true if Point are unequal
operator*(SkScalar scale) const	returns Point multiplied by scale
operator*=(SkScalar scale)	multiplies Point by scale factor
operator+(const SkPoint& a, const SkVector& b)	returns Point offset by Vector
operator+=(const SkVector& v)	adds Vector to Point
operator-() const	reverses sign of Point
operator-(const SkPoint& a, const SkPoint& b)	returns Vector between Points
operator-=(const SkVector& v)	subtracts Vector from Point
operator==(const SkPoint& a, const SkPoint& b)	returns true if Point are equal

scale

void scale(SkScalar scale, SkPoint* dst) const

Sets dst to Point times scale. dst may be Point to modify Point in place.

Parameters

scale	factor to multiply Point by
dst	storage for scaled Point

Example

See Also

operator*(SkScalar scale) const operator*=(SkScalar scale) setLength^[2]

---

void scale(SkScalar value)

Scales Point in place by scale.

Parameters

value

factor to multiply Point by

Example

See Also

operator*(SkScalar scale) const operator*=(SkScalar scale) setLength^[2]

---

negate

void negate()

Changes the sign of fX and fY.

Example

Example Output

pt: 0, -0  negate: -0, 0
pt: -1, -2  negate: 1, 2
pt: inf, -inf  negate: -inf, inf
pt: nan, -nan  negate: -nan, nan

See Also

operator-() const setAbs

---

operator-

SkPoint operator-() _const

Returns Point changing the signs of fX and fY.

Return Value

Point as (-fX, -fY)

Example

Example Output

pt: 0, -0  negate: -0, 0
pt: -1, -2  negate: 1, 2
pt: inf, -inf  negate: -inf, inf
pt: nan, -nan  negate: -nan, nan

See Also

negate operator-(const SkPoint& a, const SkPoint& b) operator-=(const SkVector& v) SkIPoint::operator-() const

---

operator+=

void operator+=(const SkVector& v)

Adds Vector v to Point. Sets Point to: (fX + v.fX, fY + v.fY) .

Parameters

v	Vector to add

Example

See Also

offset operator+(const SkPoint& a, const SkVector& b) SkIPoint::operator+=(const SkIVector& v)

---

operator-=

void operator-=(const SkVector& v)

Subtracts Vector v from Point. Sets Point to: (fX - v.fX, fY - v.fY) .

Parameters

v	Vector to subtract

Example

See Also

offset operator-(const SkPoint& a, const SkPoint& b) SkIPoint::operator-=(const SkIVector& v)

---

operator*

SkPoint operator*(SkScalar scale) _const

Returns Point multiplied by scale.

Parameters

scale

Scalar to multiply by

Return Value

Point as (fX * scale, fY * scale)

Example

See Also

operator*=(SkScalar scale) scale^[2] setLength^[2] setNormalize

---

operator*=

SkPoint& operator*=(SkScalar scale)

Multiplies Point by scale. Sets Point to: (fX * scale, fY * scale)

Parameters

scale

Scalar to multiply by

Return Value

reference to Point

Example

See Also

operator*(SkScalar scale) const scale^[2] setLength^[2] setNormalize

---

isFinite

bool isFinite() const

Returns true if both fX and fY are measurable values.

Return Value

true for values other than infinities and NaN

Example

Example Output

pt: 0, -0  finite: true
pt: -1, -2  finite: true
pt: inf, 1  finite: false
pt: nan, -1  finite: false

See Also

SkRect::isFinite SkPath::isFinite

---

equals

bool equals(SkScalar x, SkScalar y) const

Returns true if Point is equivalent to Point constructed from (x, y).

Parameters

x	value compared with fX
y	value compared with fY

Return Value

true if Point equals (x, y)

Example

Example Output

pt: 0, -0  == pt
pt: -1, -2  == pt
pt: inf, 1  == pt
pt: nan, -1  != pt

See Also

operator==(const SkPoint& a, const SkPoint& b)

---

operator==

bool operator==(const SkPoint& a, const SkPoint& b)

Returns true if a is equivalent to b.

Parameters

a	Point to compare
b	Point to compare

Return Value

true if a.fX == b.fX and a.fY == b.fY

Example

Example Output

pt: 0, -0  == pt
pt: -1, -2  == pt
pt: inf, 1  == pt
pt: nan, -1  != pt

See Also

equals operator!=(const SkPoint& a, const SkPoint& b)

---

operator!=

bool operator!=(const SkPoint& a, const SkPoint& b)

Returns true if a is not equivalent to b.

Parameters

a	Point to compare
b	Point to compare

Return Value

true if a.fX != b.fX or a.fY != b.fY

Example

Example Output

pt: 0, -0  == pt
pt: -1, -2  == pt
pt: inf, 1  == pt
pt: nan, -1  != pt

See Also

operator==(const SkPoint& a, const SkPoint& b) equals

---

operator-

SkVector operator-(const SkPoint& a, const SkPoint& b)

Returns Vector from b to a, computed as(a.fX - b.fX, a.fY - b.fY) .

Can also be used to subtract Vector from Point, returning Point. Can also be used to subtract Vector from Vector, returning Vector.

Parameters

a	Point to subtract from
b	Point to subtract

Return Value

Vector from b to a

Example

See Also

operator-=(const SkVector& v) offset

---

operator+

SkPoint operator+(const SkPoint& a, const SkVector& b)

Returns Point resulting from Point a offset by Vector b, computed as: (a.fX + b.fX, a.fY + b.fY) .

Can also be used to offset Point b by Vector a, returning Point. Can also be used to add Vector to Vector, returning Vector.

Parameters

a	Point or Vector to add to
b	Point or Vector to add

Return Value

Point equal to a offset by b

Example

See Also

operator+=(const SkVector& v) offset

---

Length

static SkScalar Length(SkScalar x, SkScalar y)

Returns the Euclidean Distance from origin, computed as:

sqrt(x * x + y * y)

.

Parameters

x	component of length
y	component of length

Return Value

straight-line distance to origin

Example

See Also

length Distance setLength^[2]

---

Normalize

static SkScalar Normalize(SkVector* vec)

Scales (vec->fX, vec->fY) so that length returns one, while preserving ratio of vec->fX to vec->fY, if possible. If original length is nearly zero, sets vec to (0, 0) and returns zero; otherwise, returns length of vec before vec is scaled.

Returned prior length may be SK ScalarInfinity if it can not be represented by SkScalar.

Note that normalize is faster if prior length is not required.

Parameters

vec	normalized to unit length

Return Value

original vec length

Example

See Also

normalize setLength^[2] Length

---

Distance

static SkScalar Distance(const SkPoint& a, const SkPoint& b)

Returns the Euclidean Distance between a and b.

Parameters

a	line end point
b	line end point

Return Value

straight-line distance from a to b

Example

See Also

length setLength^[2]

---

DotProduct

static SkScalar DotProduct(const SkVector& a, const SkVector& b)

Returns the dot product of Vector a and Vector b.

Parameters

a	left side of dot product
b	right side of dot product

Return Value

product of input magnitudes and cosine of the angle between them

Example

See Also

dot CrossProduct

---

CrossProduct

static SkScalar CrossProduct(const SkVector& a, const SkVector& b)

Returns the cross product of Vector a and Vector b.

a and b form three-dimensional vectors with z-axis value equal to zero. The cross product is a three-dimensional vector with x-axis and y-axis values equal to zero. The cross product z-axis component is returned.

Parameters

a	left side of cross product
b	right side of cross product

Return Value

area spanned by Vectors signed by angle direction

Example

See Also

cross DotProduct

---

cross

SkScalar cross(const SkVector& vec) const

Returns the cross product of Vector and vec.

Vector and vec form three-dimensional vectors with z-axis value equal to zero. The cross product is a three-dimensional vector with x-axis and y-axis values equal to zero. The cross product z-axis component is returned.

Parameters

vec	right side of cross product

Return Value

area spanned by Vectors signed by angle direction

Example

See Also

CrossProduct dot

---

dot

SkScalar dot(const SkVector& vec) const

Returns the dot product of Vector and Vector vec.

Parameters

vec	right side of dot product

Return Value

product of input magnitudes and cosine of the angle between them

Example

See Also

DotProduct cross

---

Vector

Typedef SkVector

    typedef SkPoint SkVector;

SkVector provides an alternative name for SkPoint. SkVector and SkPoint can be used interchangeably for all purposes.