288 lines
8.4 KiB
C
288 lines
8.4 KiB
C
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/*
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* Copyright © 2023 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see <http://www.gnu.org/licenses/>.
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*
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* Authors: Matthias Clasen <mclasen@redhat.com>
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*/
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#include "config.h"
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#include <math.h>
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#include "gskpathpointprivate.h"
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#include "gskcontourprivate.h"
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#include "gdk/gdkprivate.h"
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#define RAD_TO_DEG(x) ((x) / (G_PI / 180.f))
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/**
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* GskPathPoint:
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*
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* `GskPathPoint` is an opaque type representing a point on a path.
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*
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* It can be queried for properties of the path at that point, such as
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* its tangent or its curvature.
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*
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* To obtain a `GskPathPoint`, use [method@Gsk.Path.get_closest_point],
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* [method@Gsk.Path.get_start_point], [method@Gsk.Path.get_end_point]
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* or [method@Gsk.PathMeasure.get_point].
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*
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* Note that `GskPathPoint` structs are meant to be stack-allocated,
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* and don't hold a reference to the path object they are obtained from.
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* It is the callers responsibility to keep a reference to the path
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* as long as the `GskPathPoint` is used.
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*
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* Since: 4.14
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*/
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G_DEFINE_BOXED_TYPE (GskPathPoint, gsk_path_point,
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gsk_path_point_copy,
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gsk_path_point_free)
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GskPathPoint *
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gsk_path_point_copy (GskPathPoint *point)
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{
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GskPathPoint *copy;
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copy = g_new0 (GskPathPoint, 1);
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memcpy (copy, point, sizeof (GskPathPoint));
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return copy;
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}
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void
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gsk_path_point_free (GskPathPoint *point)
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{
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g_free (point);
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}
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/**
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* gsk_path_point_equal:
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* @point1: a `GskPathPoint`
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* @point2: another `GskPathPoint`
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*
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* Returns whether the two path points refer to the same
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* location on all paths.
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*
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* Note that the start- and endpoint of a closed contour
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* will compare nonequal according to this definition.
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* Use [method@Gsk.Path.is_closed] to find out if the
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* start- and endpoint of a concrete path refer to the
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* same location.
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*
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* Return: `TRUE` if @point1 and @point2 are equal
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*
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* Since: 4.14
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*/
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gboolean
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gsk_path_point_equal (const GskPathPoint *point1,
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const GskPathPoint *point2)
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{
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if (point1->contour == point2->contour)
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{
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if ((point1->idx == point2->idx && point1->t == point2->t) ||
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(point1->idx + 1 == point2->idx && point1->t == 1 && point2->t == 0) ||
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(point1->idx == point2->idx + 1 && point1->t == 0 && point2->t == 1))
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return TRUE;
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}
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return FALSE;
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}
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/**
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* gsk_path_point_compare:
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* @point1: a `GskPathPoint`
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* @point2: another `GskPathPoint`
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*
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* Returns whether @point1 is before or after @point2.
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*
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* Returns: -1 if @point1 is before @point2,
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* 1 if @point1 is after @point2,
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* 0 if they are equal
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*
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* Since: 4.14
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*/
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int
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gsk_path_point_compare (const GskPathPoint *point1,
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const GskPathPoint *point2)
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{
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if (gsk_path_point_equal (point1, point2))
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return 0;
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if (point1->contour < point2->contour)
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return -1;
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else if (point1->contour > point2->contour)
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return 1;
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else if (point1->idx < point2->idx)
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return -1;
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else if (point1->idx > point2->idx)
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return 1;
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else if (point1->t < point2->t)
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return -1;
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else if (point1->t > point2->t)
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return 1;
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return 0;
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}
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/**
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* gsk_path_point_get_position:
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* @point: a `GskPathPoint`
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* @path: the path that @point is on
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* @position: (out caller-allocates): Return location for
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* the coordinates of the point
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*
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* Gets the position of the point.
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*
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* Since: 4.14
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*/
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void
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gsk_path_point_get_position (const GskPathPoint *point,
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GskPath *path,
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graphene_point_t *position)
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{
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const GskContour *contour;
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g_return_if_fail (path != NULL);
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g_return_if_fail (gsk_path_point_valid (point, path));
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g_return_if_fail (position != NULL);
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contour = gsk_path_get_contour (path, point->contour),
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gsk_contour_get_position (contour, point, position);
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}
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/**
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* gsk_path_point_get_tangent:
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* @point: a `GskPathPoint`
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* @path: the path that @point is on
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* @direction: the direction for which to return the tangent
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* @tangent: (out caller-allocates): Return location for
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* the tangent at the point
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*
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* Gets the tangent of the path at the point.
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*
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* Note that certain points on a path may not have a single
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* tangent, such as sharp turns. At such points, there are
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* two tangents -- the direction of the path going into the
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* point, and the direction coming out of it. The @direction
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* argument lets you choose which one to get.
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*
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* If the path is just a single point (e.g. a circle with
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* radius zero), then @tangent is set to `0, 0`.
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*
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* If you want to orient something in the direction of the
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* path, [method@Gsk.PathPoint.get_rotation] may be more
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* convenient to use.
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*
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* Since: 4.14
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*/
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void
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gsk_path_point_get_tangent (const GskPathPoint *point,
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GskPath *path,
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GskPathDirection direction,
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graphene_vec2_t *tangent)
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{
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const GskContour *contour;
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g_return_if_fail (path != NULL);
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g_return_if_fail (gsk_path_point_valid (point, path));
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g_return_if_fail (tangent != NULL);
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contour = gsk_path_get_contour (path, point->contour),
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gsk_contour_get_tangent (contour, point, direction, tangent);
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}
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/**
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* gsk_path_point_get_rotation:
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* @point: a `GskPathPoint`
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* @path: the path that @point is on
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* @direction: the direction for which to return the rotation
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*
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* Gets the direction of the tangent at a given point.
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*
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* This is a convenience variant of [method@Gsk.PathPoint.get_tangent]
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* that returns the angle between the tangent and the X axis. The angle
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* can e.g. be used in
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* [gtk_snapshot_rotate()](../gtk4/method.Snapshot.rotate.html).
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*
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* Returns: the angle between the tangent and the X axis, in degrees
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*
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* Since: 4.14
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*/
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float
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gsk_path_point_get_rotation (const GskPathPoint *point,
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GskPath *path,
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GskPathDirection direction)
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{
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graphene_vec2_t tangent;
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g_return_val_if_fail (path != NULL, 0);
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g_return_val_if_fail (gsk_path_point_valid (point, path), 0);
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gsk_path_point_get_tangent (point, path, direction, &tangent);
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return RAD_TO_DEG (atan2f (graphene_vec2_get_y (&tangent),
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graphene_vec2_get_x (&tangent)));
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}
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/**
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* gsk_path_point_get_curvature:
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* @point: a `GskPathPoint`
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* @path: the path that @point is on
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* @direction: the direction for which to return the curvature
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* @center: (out caller-allocates) (nullable): Return location for
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* the center of the osculating circle
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*
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* Calculates the curvature of the path at the point.
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*
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* Optionally, returns the center of the osculating circle as well.
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* The curvature is the inverse of the radius of the osculating circle.
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*
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* Lines have a curvature of zero (indicating an osculating circle of
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* infinite radius. In this case, the @center is not modified.
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*
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* Circles with a radius of zero have `INFINITY` as curvature
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*
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* Note that certain points on a path may not have a single curvature,
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* such as sharp turns. At such points, there are two curvatures --
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* the (limit of) the curvature of the path going into the point,
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* and the (limit of) the curvature of the path coming out of it.
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* The @direction argument lets you choose which one to get.
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*
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* <picture>
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* <source srcset="curvature-dark.png" media="(prefers-color-scheme: dark)">
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* <img alt="Osculating circle" src="curvature-light.png">
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* </picture>
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* Returns: The curvature of the path at the given point
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*
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* Since: 4.14
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*/
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float
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gsk_path_point_get_curvature (const GskPathPoint *point,
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GskPath *path,
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GskPathDirection direction,
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graphene_point_t *center)
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{
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const GskContour *contour;
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g_return_val_if_fail (path != NULL, 0);
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g_return_val_if_fail (gsk_path_point_valid (point, path), 0);
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contour = gsk_path_get_contour (path, point->contour);
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return gsk_contour_get_curvature (contour, point, direction, center);
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}
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