Package org.gnome.gsk

Class PathPoint

java.lang.Object

io.github.jwharm.javagi.base.ProxyInstance

org.gnome.gsk.PathPoint

All Implemented Interfaces:

Proxy

@Generated("io.github.jwharm.JavaGI")
public class PathPoint
extends ProxyInstance

GskPathPoint is an opaque type representing a point on a path.

It can be queried for properties of the path at that point, such as its tangent or its curvature.

To obtain a GskPathPoint, use Path.getClosestPoint(org.gnome.graphene.Point, float, org.gnome.gsk.PathPoint, io.github.jwharm.javagi.base.Out<java.lang.Float>), Path.getStartPoint(org.gnome.gsk.PathPoint), Path.getEndPoint(org.gnome.gsk.PathPoint) or PathMeasure.getPoint(float, org.gnome.gsk.PathPoint).

Note that GskPathPoint structs are meant to be stack-allocated, and don't hold a reference to the path object they are obtained from. It is the callers responsibility to keep a reference to the path as long as the GskPathPoint is used.

Constructor Summary

Constructors

Constructor	Description
PathPoint()	Allocate a new PathPoint.
PathPoint(Arena arena)	Allocate a new PathPoint.
PathPoint(MemorySegment address)	Create a PathPoint proxy instance for the provided memory address.

Method Summary

Modifier and Type	Method	Description
int	compare(PathPoint point2)	Returns whether this PathPoint is before or after point2.
PathPoint	copy()	Copies a path point.
boolean	equal(PathPoint point2)	Returns whether the two path points refer to the same location on all paths.
void	free()	Frees a path point copied by copy().
float	getCurvature(Path path, PathDirection direction, @Nullable Point center)	Calculates the curvature of the path at the point.
float	getDistance(PathMeasure measure)	Returns the distance from the beginning of the path to this PathPoint.
static MemoryLayout	getMemoryLayout()	The memory layout of the native struct.
void	getPosition(Path path, Point position)	Gets the position of the point.
float	getRotation(Path path, PathDirection direction)	Gets the direction of the tangent at a given point.
void	getTangent(Path path, PathDirection direction, Vec2 tangent)	Gets the tangent of the path at the point.
static Type	getType()	Get the GType of the PathPoint class
Vec4	readAlignment()	Read the value of the field alignment.
void	writeAlignment(Vec4 alignment)	Write a value in the field alignment.

Methods inherited from class io.github.jwharm.javagi.base.ProxyInstance

equals, handle, hashCode

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Details

PathPoint

public PathPoint(MemorySegment address)

Create a PathPoint proxy instance for the provided memory address.

Parameters:

address - the memory address of the native object

PathPoint

public PathPoint(Arena arena)

Allocate a new PathPoint.

Parameters:

arena - to control the memory allocation scope

PathPoint

public PathPoint()

Allocate a new PathPoint. The memory is allocated with Arena.ofAuto().

Method Details

getType

public static Type getType()

Get the GType of the PathPoint class

Returns:

the GType

getMemoryLayout

public static MemoryLayout getMemoryLayout()

The memory layout of the native struct.

Returns:

the memory layout

readAlignment

public Vec4 readAlignment()

Read the value of the field alignment.

Returns:

The value of the field alignment

writeAlignment

public void writeAlignment(Vec4 alignment)

Write a value in the field alignment.

Parameters:

alignment - The new value for the field alignment

compare

public int compare(PathPoint point2)

Returns whether this PathPoint is before or after point2.

Parameters:

point2 - another GskPathPoint

Returns:

-1 if this PathPoint is before point2, 1 if this PathPoint is after point2, 0 if they are equal

copy

public PathPoint copy()

Copies a path point.

Returns:

the copied point

equal

public boolean equal(PathPoint point2)

Returns whether the two path points refer to the same location on all paths.

Note that the start- and endpoint of a closed contour will compare nonequal according to this definition. Use Path.isClosed() to find out if the start- and endpoint of a concrete path refer to the same location.

Parameters:

point2 - another GskPathPoint

Returns:

TRUE if this PathPoint and point2 are equal

free

public void free()

Frees a path point copied by copy().

getCurvature

public float getCurvature(Path path,
 PathDirection direction,
 @Nullable
 @Nullable Point center)

Calculates the curvature of the path at the point.

Optionally, returns the center of the osculating circle as well. The curvature is the inverse of the radius of the osculating circle.

Lines have a curvature of zero (indicating an osculating circle of infinite radius. In this case, the center is not modified.

Circles with a radius of zero have INFINITY as curvature

Note that certain points on a path may not have a single curvature, such as sharp turns. At such points, there are two curvatures -- the (limit of) the curvature of the path going into the point, and the (limit of) the curvature of the path coming out of it. The direction argument lets you choose which one to get.

<picture> <source srcset="curvature-dark.png" media="(prefers-color-scheme: dark)"> <img alt="Osculating circle" src="curvature-light.png"> </picture>

Parameters:

path - the path that this PathPoint is on

direction - the direction for which to return the curvature

center - Return location for the center of the osculating circle

Returns:

The curvature of the path at the given point

getDistance

public float getDistance(PathMeasure measure)

Returns the distance from the beginning of the path to this PathPoint.

Parameters:

measure - a GskPathMeasure for the path

Returns:

the distance of this PathPoint

getPosition

public void getPosition(Path path,
 Point position)

Gets the position of the point.

Parameters:

path - the path that this PathPoint is on

position - Return location for the coordinates of the point

getRotation

public float getRotation(Path path,
 PathDirection direction)

Gets the direction of the tangent at a given point.

This is a convenience variant of getTangent(org.gnome.gsk.Path, org.gnome.gsk.PathDirection, org.gnome.graphene.Vec2) that returns the angle between the tangent and the X axis. The angle can e.g. be used in gtk_snapshot_rotate().

Parameters:

path - the path that this PathPoint is on

direction - the direction for which to return the rotation

Returns:

the angle between the tangent and the X axis, in degrees

getTangent

public void getTangent(Path path,
 PathDirection direction,
 Vec2 tangent)

Gets the tangent of the path at the point.

Note that certain points on a path may not have a single tangent, such as sharp turns. At such points, there are two tangents -- the direction of the path going into the point, and the direction coming out of it. The direction argument lets you choose which one to get.

If the path is just a single point (e.g. a circle with radius zero), then tangent is set to 0, 0.

If you want to orient something in the direction of the path, getRotation(org.gnome.gsk.Path, org.gnome.gsk.PathDirection) may be more convenient to use.

Parameters:

path - the path that this PathPoint is on

direction - the direction for which to return the tangent

tangent - Return location for the tangent at the point