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gtk/gsk/gskpathbuilder.c
Matthias Clasen 5777587e7a docs: Add details for GskPathBuilder 
Mention that GskPathBuilder will simplify
added Bézier curves.
2023-09-17 09:31:59 -04:00

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/*
* Copyright © 2020 Benjamin Otte
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
*
* Authors: Benjamin Otte <otte@gnome.org>
*/
#include "config.h"
#include <math.h>
#include "gskpathbuilder.h"
#include "gskpathprivate.h"
#include "gskcurveprivate.h"
#include "gskpathpointprivate.h"
#include "gskcontourprivate.h"
/**
* GskPathBuilder:
*
* `GskPathBuilder` is an auxiliary object for constructing
* `GskPath` objects.
*
* A path is constructed like this:
*
* |[<!-- language="C" -->
* GskPath *
* construct_path (void)
* {
* GskPathBuilder *builder;
*
* builder = gsk_path_builder_new ();
*
* // add contours to the path here
*
* return gsk_path_builder_free_to_path (builder);
* ]|
*
* Adding contours to the path can be done in two ways.
* The easiest option is to use the `gsk_path_builder_add_*` group
* of functions that add predefined contours to the current path,
* either common shapes like [method@Gsk.PathBuilder.add_circle]
* or by adding from other paths like [method@Gsk.PathBuilder.add_path].
*
* The `gsk_path_builder_add_*` methods always add complete contours,
* and do not use or modify the current point.
*
* The other option is to define each line and curve manually with
* the `gsk_path_builder_*_to` group of functions. You start with
* a call to [method@Gsk.PathBuilder.move_to] to set the starting point
* and then use multiple calls to any of the drawing functions to
* move the pen along the plane. Once you are done, you can call
* [method@Gsk.PathBuilder.close] to close the path by connecting it
* back with a line to the starting point.
*
* This is similar to how paths are drawn in Cairo.
*
* Note that `GskPathBuilder` will reduce the degree of added Bézier
* curves as much as possible, to simplify rendering.
*
* Since: 4.14
*/
struct _GskPathBuilder
{
int ref_count;
GSList *contours; /* (reverse) list of already recorded contours */
GskPathFlags flags; /* flags for the current path */
graphene_point_t current_point; /* the point all drawing ops start from */
GArray *ops; /* operations for current contour - size == 0 means no current contour */
GArray *points; /* points for the operations */
};
G_DEFINE_BOXED_TYPE (GskPathBuilder,
gsk_path_builder,
gsk_path_builder_ref,
gsk_path_builder_unref)
/**
* gsk_path_builder_new:
*
* Create a new `GskPathBuilder` object.
*
* The resulting builder would create an empty `GskPath`.
* Use addition functions to add types to it.
*
* Returns: a new `GskPathBuilder`
*
* Since: 4.14
*/
GskPathBuilder *
gsk_path_builder_new (void)
{
GskPathBuilder *self;
self = g_slice_new0 (GskPathBuilder);
self->ref_count = 1;
self->ops = g_array_new (FALSE, FALSE, sizeof (gskpathop));
self->points = g_array_new (FALSE, FALSE, sizeof (graphene_point_t));
/* Be explicit here */
self->current_point = GRAPHENE_POINT_INIT (0, 0);
return self;
}
/**
* gsk_path_builder_ref:
* @self: a `GskPathBuilder`
*
* Acquires a reference on the given builder.
*
* This function is intended primarily for language bindings.
* `GskPathBuilder` objects should not be kept around.
*
* Returns: (transfer none): the given `GskPathBuilder` with
* its reference count increased
*
* Since: 4.14
*/
GskPathBuilder *
gsk_path_builder_ref (GskPathBuilder *self)
{
g_return_val_if_fail (self != NULL, NULL);
g_return_val_if_fail (self->ref_count > 0, NULL);
self->ref_count += 1;
return self;
}
/* We're cheating here. Out pathops are relative to the NULL pointer,
* so that we can not care about the points GArray reallocating itself
* until we create the contour.
* This does however mean that we need to not use gsk_pathop_get_points()
* without offsetting the returned pointer.
*/
static inline gskpathop
gsk_pathop_encode_index (GskPathOperation op,
gsize index)
{
return gsk_pathop_encode (op, ((graphene_point_t *) NULL) + index);
}
static void
gsk_path_builder_ensure_current (GskPathBuilder *self)
{
if (self->ops->len != 0)
return;
self->flags = GSK_PATH_FLAT;
g_array_append_vals (self->ops, (gskpathop[1]) { gsk_pathop_encode_index (GSK_PATH_MOVE, 0) }, 1);
g_array_append_val (self->points, self->current_point);
}
static void
gsk_path_builder_append_current (GskPathBuilder *self,
GskPathOperation op,
gsize n_points,
const graphene_point_t *points)
{
gsk_path_builder_ensure_current (self);
g_array_append_vals (self->ops, (gskpathop[1]) { gsk_pathop_encode_index (op, self->points->len - 1) }, 1);
g_array_append_vals (self->points, points, n_points);
self->current_point = points[n_points - 1];
}
static void
gsk_path_builder_end_current (GskPathBuilder *self)
{
GskContour *contour;
if (self->ops->len == 0)
return;
contour = gsk_standard_contour_new (self->flags,
(graphene_point_t *) self->points->data,
self->points->len,
(gskpathop *) self->ops->data,
self->ops->len,
(graphene_point_t *) self->points->data - (graphene_point_t *) NULL);
g_array_set_size (self->ops, 0);
g_array_set_size (self->points, 0);
/* do this at the end to avoid inflooping when add_contour calls back here */
gsk_path_builder_add_contour (self, contour);
}
static void
gsk_path_builder_clear (GskPathBuilder *self)
{
gsk_path_builder_end_current (self);
g_slist_free_full (self->contours, g_free);
self->contours = NULL;
}
/**
* gsk_path_builder_unref:
* @self: a `GskPathBuilder`
*
* Releases a reference on the given builder.
*
* Since: 4.14
*/
void
gsk_path_builder_unref (GskPathBuilder *self)
{
g_return_if_fail (self != NULL);
g_return_if_fail (self->ref_count > 0);
self->ref_count -= 1;
if (self->ref_count > 0)
return;
gsk_path_builder_clear (self);
g_array_unref (self->ops);
g_array_unref (self->points);
g_slice_free (GskPathBuilder, self);
}
/**
* gsk_path_builder_free_to_path: (skip)
* @self: a `GskPathBuilder`
*
* Creates a new `GskPath` from the current state of the
* given builder, and unrefs the @builder instance.
*
* Returns: (transfer full): the newly created `GskPath`
* with all the contours added to the builder
*
* Since: 4.14
*/
GskPath *
gsk_path_builder_free_to_path (GskPathBuilder *self)
{
GskPath *res;
g_return_val_if_fail (self != NULL, NULL);
res = gsk_path_builder_to_path (self);
gsk_path_builder_unref (self);
return res;
}
/**
* gsk_path_builder_to_path:
* @self: a `GskPathBuilder`
*
* Creates a new `GskPath` from the given builder.
*
* The given `GskPathBuilder` is reset once this function returns;
* you cannot call this function multiple times on the same builder
* instance.
*
* This function is intended primarily for language bindings.
* C code should use [method@Gsk.PathBuilder.free_to_path].
*
* Returns: (transfer full): the newly created `GskPath`
* with all the contours added to the builder
*
* Since: 4.14
*/
GskPath *
gsk_path_builder_to_path (GskPathBuilder *self)
{
GskPath *path;
g_return_val_if_fail (self != NULL, NULL);
gsk_path_builder_end_current (self);
self->contours = g_slist_reverse (self->contours);
path = gsk_path_new_from_contours (self->contours);
gsk_path_builder_clear (self);
return path;
}
void
gsk_path_builder_add_contour (GskPathBuilder *self,
GskContour *contour)
{
gsk_path_builder_end_current (self);
self->contours = g_slist_prepend (self->contours, contour);
}
/**
* gsk_path_builder_get_current_point:
* @self: a `GskPathBuilder`
*
* Gets the current point.
*
* The current point is used for relative drawing commands and
* updated after every operation.
*
* When the builder is created, the default current point is set
* to `0, 0`. Note that this is different from cairo, which starts
* out without a current point.
*
* Returns: (transfer none): The current point
*
* Since: 4.14
*/
const graphene_point_t *
gsk_path_builder_get_current_point (GskPathBuilder *self)
{
g_return_val_if_fail (self != NULL, NULL);
return &self->current_point;
}
/**
* gsk_path_builder_add_path:
* @self: a `GskPathBuilder`
* @path: (transfer none): the path to append
*
* Appends all of @path to the builder.
*
* Since: 4.14
*/
void
gsk_path_builder_add_path (GskPathBuilder *self,
GskPath *path)
{
g_return_if_fail (self != NULL);
g_return_if_fail (path != NULL);
for (gsize i = 0; i < gsk_path_get_n_contours (path); i++)
{
const GskContour *contour = gsk_path_get_contour (path, i);
gsk_path_builder_add_contour (self, gsk_contour_dup (contour));
}
}
/**
* gsk_path_builder_add_reverse_path:
* @self: a `GskPathBuilder`
* @path: (transfer none): the path to append
*
* Appends all of @path to the builder, in reverse order.
*
* Since: 4.14
*/
void
gsk_path_builder_add_reverse_path (GskPathBuilder *self,
GskPath *path)
{
g_return_if_fail (self != NULL);
g_return_if_fail (path != NULL);
for (gsize i = gsk_path_get_n_contours (path); i > 0; i--)
{
const GskContour *contour = gsk_path_get_contour (path, i - 1);
gsk_path_builder_add_contour (self, gsk_contour_reverse (contour));
}
}
/**
* gsk_path_builder_add_cairo_path:
* @self: a `GskPathBuilder`
*
* Adds a Cairo path to the builder.
*
* You can use cairo_copy_path() to access the path
* from a Cairo context.
*
* Since: 4.14
*/
void
gsk_path_builder_add_cairo_path (GskPathBuilder *self,
const cairo_path_t *path)
{
graphene_point_t current;
g_return_if_fail (self != NULL);
g_return_if_fail (path != NULL);
current = self->current_point;
for (gsize i = 0; i < path->num_data; i += path->data[i].header.length)
{
const cairo_path_data_t *data = &path->data[i];
switch (data->header.type)
{
case CAIRO_PATH_MOVE_TO:
gsk_path_builder_move_to (self, data[1].point.x, data[1].point.y);
break;
case CAIRO_PATH_LINE_TO:
gsk_path_builder_line_to (self, data[1].point.x, data[1].point.y);
break;
case CAIRO_PATH_CURVE_TO:
gsk_path_builder_cubic_to (self,
data[1].point.x, data[1].point.y,
data[2].point.x, data[2].point.y,
data[3].point.x, data[3].point.y);
break;
case CAIRO_PATH_CLOSE_PATH:
gsk_path_builder_close (self);
break;
default:
g_assert_not_reached ();
break;
}
}
gsk_path_builder_end_current (self);
self->current_point = current;
}
/**
* gsk_path_builder_add_rect:
* @self: A `GskPathBuilder`
* @rect: The rectangle to create a path for
*
* Adds @rect as a new contour to the path built by the builder.
*
* The path is going around the rectangle in clockwise direction.
*
* If the the width or height are 0, the path will be a closed
* horizontal or vertical line. If both are 0, it'll be a closed dot.
*
* Since: 4.14
*/
void
gsk_path_builder_add_rect (GskPathBuilder *self,
const graphene_rect_t *rect)
{
graphene_rect_t r;
g_return_if_fail (self != NULL);
g_return_if_fail (rect != NULL);
graphene_rect_normalize_r (rect, &r);
gsk_path_builder_add_contour (self, gsk_rect_contour_new (&r));
}
/**
* gsk_path_builder_add_rounded_rect:
* @self: a #GskPathBuilder
* @rect: the rounded rect
*
* Adds @rect as a new contour to the path built in @self.
*
* The path is going around the rectangle in clockwise direction.
*
* Since: 4.14
*/
void
gsk_path_builder_add_rounded_rect (GskPathBuilder *self,
const GskRoundedRect *rect)
{
g_return_if_fail (self != NULL);
g_return_if_fail (rect != NULL);
gsk_path_builder_add_contour (self, gsk_rounded_rect_contour_new (rect));
}
/**
* gsk_path_builder_add_circle:
* @self: a `GskPathBuilder`
* @center: the center of the circle
* @radius: the radius of the circle
*
* Adds a circle with the @center and @radius.
*
* The path is going around the circle in clockwise direction.
*
* If @radius is zero, the contour will be a closed point.
*
* Since: 4.14
*/
void
gsk_path_builder_add_circle (GskPathBuilder *self,
const graphene_point_t *center,
float radius)
{
g_return_if_fail (self != NULL);
g_return_if_fail (center != NULL);
g_return_if_fail (radius >= 0);
gsk_path_builder_add_contour (self, gsk_circle_contour_new (center, radius));
}
/**
* gsk_path_builder_move_to:
* @self: a `GskPathBuilder`
* @x: x coordinate
* @y: y coordinate
*
* Starts a new contour by placing the pen at @x, @y.
*
* If this function is called twice in succession, the first
* call will result in a contour made up of a single point.
* The second call will start a new contour.
*
* Since: 4.14
*/
void
gsk_path_builder_move_to (GskPathBuilder *self,
float x,
float y)
{
g_return_if_fail (self != NULL);
gsk_path_builder_end_current (self);
self->current_point = GRAPHENE_POINT_INIT(x, y);
gsk_path_builder_ensure_current (self);
}
/**
* gsk_path_builder_rel_move_to:
* @self: a `GskPathBuilder`
* @x: x offset
* @y: y offset
*
* Starts a new contour by placing the pen at @x, @y
* relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.move_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_move_to (GskPathBuilder *self,
float x,
float y)
{
g_return_if_fail (self != NULL);
gsk_path_builder_move_to (self,
self->current_point.x + x,
self->current_point.y + y);
}
/**
* gsk_path_builder_line_to:
* @self: a `GskPathBuilder`
* @x: x coordinate
* @y: y coordinate
*
* Draws a line from the current point to @x, @y and makes it
* the new current point.
*
* <picture>
* <source srcset="line-dark.png" media="(prefers-color-scheme: dark)">
* <img alt="Line To" src="line-light.png">
* </picture>
*
* Since: 4.14
*/
void
gsk_path_builder_line_to (GskPathBuilder *self,
float x,
float y)
{
g_return_if_fail (self != NULL);
/* skip the line if it goes to the same point */
if (graphene_point_equal (&self->current_point,
&GRAPHENE_POINT_INIT (x, y)))
return;
gsk_path_builder_append_current (self,
GSK_PATH_LINE,
1, (graphene_point_t[1]) {
GRAPHENE_POINT_INIT (x, y)
});
}
/**
* gsk_path_builder_rel_line_to:
* @self: a `GskPathBuilder`
* @x: x offset
* @y: y offset
*
* Draws a line from the current point to a point offset from it
* by @x, @y and makes it the new current point.
*
* This is the relative version of [method@Gsk.PathBuilder.line_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_line_to (GskPathBuilder *self,
float x,
float y)
{
g_return_if_fail (self != NULL);
gsk_path_builder_line_to (self,
self->current_point.x + x,
self->current_point.y + y);
}
static inline void
closest_point (const graphene_point_t *p,
const graphene_point_t *a,
const graphene_point_t *b,
graphene_point_t *q)
{
graphene_vec2_t n;
graphene_vec2_t ap;
float t;
graphene_vec2_init (&n, b->x - a->x, b->y - a->y);
graphene_vec2_init (&ap, p->x - a->x, p->y - a->y);
t = graphene_vec2_dot (&ap, &n) / graphene_vec2_dot (&n, &n);
q->x = a->x + t * (b->x - a->x);
q->y = a->y + t * (b->y - a->y);
}
static inline gboolean
collinear (const graphene_point_t *p,
const graphene_point_t *a,
const graphene_point_t *b)
{
graphene_point_t q;
if (graphene_point_equal (a, b))
return TRUE;
closest_point (p, a, b, &q);
return graphene_point_near (p, &q, 0.001);
}
/**
* gsk_path_builder_quad_to:
* @self: a #GskPathBuilder
* @x1: x coordinate of control point
* @y1: y coordinate of control point
* @x2: x coordinate of the end of the curve
* @y2: y coordinate of the end of the curve
*
* Adds a [quadratic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
* from the current point to @x2, @y2 with @x1, @y1 as the control point.
*
* After this, @x2, @y2 will be the new current point.
*
* <picture>
* <source srcset="quad-dark.png" media="(prefers-color-scheme: dark)">
* <img alt="Quad To" src="quad-light.png">
* </picture>
*
* Since: 4.14
*/
void
gsk_path_builder_quad_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2)
{
graphene_point_t p0 = self->current_point;
graphene_point_t p1 = GRAPHENE_POINT_INIT (x1, y1);
graphene_point_t p2 = GRAPHENE_POINT_INIT (x2, y2);
g_return_if_fail (self != NULL);
if (collinear (&p0, &p1, &p2))
{
GskBoundingBox bb;
/* We simplify degenerate quads to one or two lines */
if (!gsk_bounding_box_contains_point (gsk_bounding_box_init (&bb, &p0, &p2), &p1))
{
GskCurve c;
gsk_curve_init_foreach (&c, GSK_PATH_QUAD,
(const graphene_point_t []) { p0, p1, p2 },
3, 0.f);
gsk_curve_get_tight_bounds (&c, &bb);
for (int i = 0; i < 4; i++)
{
graphene_point_t q;
gsk_bounding_box_get_corner (&bb, i, &q);
if (graphene_point_equal (&p0, &q) ||
graphene_point_equal (&p2, &q))
{
gsk_bounding_box_get_corner (&bb, (i + 2) % 4, &q);
gsk_path_builder_line_to (self, q.x, q.y);
break;
}
}
}
gsk_path_builder_line_to (self, x2, y2);
return;
}
self->flags &= ~GSK_PATH_FLAT;
gsk_path_builder_append_current (self,
GSK_PATH_QUAD,
2, (graphene_point_t[2]) { p1, p2 });
}
/**
* gsk_path_builder_rel_quad_to:
* @self: a `GskPathBuilder`
* @x1: x offset of control point
* @y1: y offset of control point
* @x2: x offset of the end of the curve
* @y2: y offset of the end of the curve
*
* Adds a [quadratic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
* from the current point to @x2, @y2 with @x1, @y1 the control point.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.quad_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_quad_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2)
{
g_return_if_fail (self != NULL);
gsk_path_builder_quad_to (self,
self->current_point.x + x1,
self->current_point.y + y1,
self->current_point.x + x2,
self->current_point.y + y2);
}
static gboolean
point_is_between (const graphene_point_t *q,
const graphene_point_t *p0,
const graphene_point_t *p1)
{
return collinear (p0, p1, q) &&
fabsf (graphene_point_distance (p0, q, NULL, NULL) + graphene_point_distance (p1, q, NULL, NULL) - graphene_point_distance (p0, p1, NULL, NULL)) < 0.001;
}
static gboolean
bounding_box_corner_between (const GskBoundingBox *bb,
const graphene_point_t *p0,
const graphene_point_t *p1,
graphene_point_t *p)
{
for (int i = 0; i < 4; i++)
{
graphene_point_t q;
gsk_bounding_box_get_corner (bb, i, &q);
if (point_is_between (&q, p0, p1))
{
*p = q;
return TRUE;
}
}
return FALSE;
}
/**
* gsk_path_builder_cubic_to:
* @self: a `GskPathBuilder`
* @x1: x coordinate of first control point
* @y1: y coordinate of first control point
* @x2: x coordinate of second control point
* @y2: y coordinate of second control point
* @x3: x coordinate of the end of the curve
* @y3: y coordinate of the end of the curve
*
* Adds a [cubic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
* from the current point to @x3, @y3 with @x1, @y1 and @x2, @y2 as the control
* points.
*
* After this, @x3, @y3 will be the new current point.
*
* <picture>
* <source srcset="cubic-dark.png" media="(prefers-color-scheme: dark)">
* <img alt="Cubic To" src="cubic-light.png">
* </picture>
*
* Since: 4.14
*/
void
gsk_path_builder_cubic_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float x3,
float y3)
{
graphene_point_t p0 = self->current_point;
graphene_point_t p1 = GRAPHENE_POINT_INIT (x1, y1);
graphene_point_t p2 = GRAPHENE_POINT_INIT (x2, y2);
graphene_point_t p3 = GRAPHENE_POINT_INIT (x3, y3);
graphene_point_t p, q;
gboolean p01, p12, p23;
g_return_if_fail (self != NULL);
p01 = graphene_point_equal (&p0, &p1);
p12 = graphene_point_equal (&p1, &p2);
p23 = graphene_point_equal (&p2, &p3);
if (p01 && p12 && p23)
return;
if ((p01 && p23) || (p12 && (p01 || p23)))
{
gsk_path_builder_line_to (self, x3, y3);
return;
}
if (collinear (&p0, &p1, &p2) &&
collinear (&p1, &p2, &p3) &&
(!p12 || collinear (&p0, &p1, &p3)))
{
GskBoundingBox bb;
gboolean p1in, p2in;
gsk_bounding_box_init (&bb, &p0, &p3);
p1in = gsk_bounding_box_contains_point (&bb, &p1);
p2in = gsk_bounding_box_contains_point (&bb, &p2);
if (p1in && p2in)
{
gsk_path_builder_line_to (self, x3, y3);
}
else
{
GskCurve c;
gsk_curve_init_foreach (&c,
GSK_PATH_CUBIC,
(const graphene_point_t[]) { p0, p1, p2, p3 },
4,
0.f);
gsk_curve_get_tight_bounds (&c, &bb);
if (!p1in)
{
/* Find the intersection of bb with p0 - p1.
* It must be a corner
*/
bounding_box_corner_between (&bb, &p0, &p1, &p);
gsk_path_builder_line_to (self, p.x, p.y);
}
if (!p2in)
{
/* Find the intersection of bb with p2 - p3. */
bounding_box_corner_between (&bb, &p3, &p2, &p);
gsk_path_builder_line_to (self, p.x, p.y);
}
gsk_path_builder_line_to (self, x3, y3);
}
return;
}
/* reduce to a quadratic if possible */
graphene_point_interpolate (&p0, &p1, 1.5, &p);
graphene_point_interpolate (&p3, &p2, 1.5, &q);
if (graphene_point_near (&p, &q, 0.001))
{
gsk_path_builder_quad_to (self, p.x, p.y, x3, y3);
return;
}
self->flags &= ~GSK_PATH_FLAT;
/* At this point, we are dealing with a cubic that can't be reduced to
* lines or quadratics. Check for cusps.
*/
{
GskCurve c, c1, c2, c3, c4;
float t[2];
int n;
gsk_curve_init_foreach (&c,
GSK_PATH_CUBIC,
(const graphene_point_t[]) { p0, p1, p2, p3 },
4,
0.f);
n = gsk_curve_get_cusps (&c, t);
if (n == 1)
{
gsk_curve_split (&c, t[0], &c1, &c2);
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, &c1.cubic.points[1]);
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, &c2.cubic.points[1]);
return;
}
else if (n == 2)
{
if (t[1] < t[0])
{
float s = t[0];
t[0] = t[1];
t[1] = s;
}
gsk_curve_split (&c, t[0], &c1, &c2);
gsk_curve_split (&c2, (t[1] - t[0]) / (1 - t[0]), &c3, &c4);
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, &c1.cubic.points[1]);
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, &c3.cubic.points[1]);
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, &c4.cubic.points[1]);
return;
}
}
gsk_path_builder_append_current (self,
GSK_PATH_CUBIC,
3, (graphene_point_t[3]) { p1, p2, p3 });
}
/**
* gsk_path_builder_rel_cubic_to:
* @self: a `GskPathBuilder`
* @x1: x offset of first control point
* @y1: y offset of first control point
* @x2: x offset of second control point
* @y2: y offset of second control point
* @x3: x offset of the end of the curve
* @y3: y offset of the end of the curve
*
* Adds a [cubic Bézier curve](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)
* from the current point to @x3, @y3 with @x1, @y1 and @x2, @y2 as the control
* points.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.cubic_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_cubic_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float x3,
float y3)
{
g_return_if_fail (self != NULL);
gsk_path_builder_cubic_to (self,
self->current_point.x + x1,
self->current_point.y + y1,
self->current_point.x + x2,
self->current_point.y + y2,
self->current_point.x + x3,
self->current_point.y + y3);
}
/**
* gsk_path_builder_conic_to:
* @self: a `GskPathBuilder`
* @x1: x coordinate of control point
* @y1: y coordinate of control point
* @x2: x coordinate of the end of the curve
* @y2: y coordinate of the end of the curve
* @weight: weight of the control point, must be greater than zero
*
* Adds a [conic curve](https://en.wikipedia.org/wiki/Non-uniform_rational_B-spline)
* from the current point to @x2, @y2 with the given @weight and @x1, @y1 as the
* control point.
*
* The weight determines how strongly the curve is pulled towards the control point.
* A conic with weight 1 is identical to a quadratic Bézier curve with the same points.
*
* Conic curves can be used to draw ellipses and circles. They are also known as
* rational quadratic Bézier curves.
*
* After this, @x2, @y2 will be the new current point.
*
* <picture>
* <source srcset="conic-dark.png" media="(prefers-color-scheme: dark)">
* <img alt="Conic To" src="conic-light.png">
* </picture>
*
* Since: 4.14
*/
void
gsk_path_builder_conic_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float weight)
{
graphene_point_t p0 = self->current_point;
graphene_point_t p1 = GRAPHENE_POINT_INIT (x1, y1);
graphene_point_t p2 = GRAPHENE_POINT_INIT (x2, y2);
g_return_if_fail (self != NULL);
g_return_if_fail (weight > 0);
if (weight == 1)
{
gsk_path_builder_quad_to (self, x1, y1, x2, y2);
return;
}
if (collinear (&p0, &p1, &p2))
{
GskBoundingBox bb;
/* We simplify degenerate quads to one or two lines
* (two lines are needed if there's a cusp).
*/
if (!gsk_bounding_box_contains_point (gsk_bounding_box_init (&bb, &p0, &p2), &p1))
{
GskCurve c;
gsk_curve_init_foreach (&c, GSK_PATH_CONIC,
(const graphene_point_t []) { p0, p1, p2 },
3, weight);
gsk_curve_get_tight_bounds (&c, &bb);
for (int i = 0; i < 4; i++)
{
graphene_point_t q;
gsk_bounding_box_get_corner (&bb, i, &q);
if (graphene_point_equal (&p0, &q) ||
graphene_point_equal (&p2, &q))
{
gsk_bounding_box_get_corner (&bb, (i + 2) % 4, &q);
gsk_path_builder_line_to (self, q.x, q.y);
break;
}
}
}
gsk_path_builder_line_to (self, x2, y2);
return;
}
self->flags &= ~GSK_PATH_FLAT;
gsk_path_builder_append_current (self,
GSK_PATH_CONIC,
3, (graphene_point_t[3]) {
GRAPHENE_POINT_INIT (x1, y1),
GRAPHENE_POINT_INIT (weight, 0),
GRAPHENE_POINT_INIT (x2, y2)
});
}
/**
* gsk_path_builder_rel_conic_to:
* @self: a `GskPathBuilder`
* @x1: x offset of control point
* @y1: y offset of control point
* @x2: x offset of the end of the curve
* @y2: y offset of the end of the curve
* @weight: weight of the curve, must be greater than zero
*
* Adds a [conic curve](https://en.wikipedia.org/wiki/Non-uniform_rational_B-spline)
* from the current point to @x2, @y2 with the given @weight and @x1, @y1 as the
* control point.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.conic_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_conic_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float weight)
{
g_return_if_fail (self != NULL);
g_return_if_fail (weight > 0);
gsk_path_builder_conic_to (self,
self->current_point.x + x1,
self->current_point.y + y1,
self->current_point.x + x2,
self->current_point.y + y2,
weight);
}
/**
* gsk_path_builder_arc_to:
* @self: a `GskPathBuilder`
* @x1: x coordinate of first control point
* @y1: y coordinate of first control point
* @x2: x coordinate of second control point
* @y2: y coordinate of second control point
*
* Adds an elliptical arc from the current point to @x3, @y3
* with @x1, @y1 determining the tangent directions.
*
* After this, @x3, @y3 will be the new current point.
*
* Note: Two points and their tangents do not determine
* a unique ellipse, so GSK just picks one. If you need more
* precise control, use [method@Gsk.PathBuilder.conic_to]
* or [method@Gsk.PathBuilder.svg_arc_to].
*
* <picture>
* <source srcset="arc-dark.png" media="(prefers-color-scheme: dark)">
* <img alt="Arc To" src="arc-light.png">
* </picture>
*
* Since: 4.14
*/
void
gsk_path_builder_arc_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2)
{
g_return_if_fail (self != NULL);
gsk_path_builder_conic_to (self, x1, y1, x2, y2, M_SQRT1_2);
}
/**
* gsk_path_builder_rel_arc_to:
* @self: a `GskPathBuilder`
* @x1: x coordinate of first control point
* @y1: y coordinate of first control point
* @x2: x coordinate of second control point
* @y2: y coordinate of second control point
*
* Adds an elliptical arc from the current point to @x3, @y3
* with @x1, @y1 determining the tangent directions.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.arc_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_arc_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2)
{
g_return_if_fail (self != NULL);
gsk_path_builder_arc_to (self,
self->current_point.x + x1,
self->current_point.y + y1,
self->current_point.x + x2,
self->current_point.y + y2);
}
/**
* gsk_path_builder_close:
* @self: a `GskPathBuilder`
*
* Ends the current contour with a line back to the start point.
*
* Note that this is different from calling [method@Gsk.PathBuilder.line_to]
* with the start point in that the contour will be closed. A closed
* contour behaves differently from an open one. When stroking, its
* start and end point are considered connected, so they will be
* joined via the line join, and not ended with line caps.
*
* Since: 4.14
*/
void
gsk_path_builder_close (GskPathBuilder *self)
{
g_return_if_fail (self != NULL);
if (self->ops->len == 0)
return;
self->flags |= GSK_PATH_CLOSED;
gsk_path_builder_append_current (self,
GSK_PATH_CLOSE,
1, (graphene_point_t[1]) {
g_array_index (self->points, graphene_point_t, 0)
});
gsk_path_builder_end_current (self);
}
static void
arc_segment (GskPathBuilder *self,
double cx,
double cy,
double rx,
double ry,
double sin_phi,
double cos_phi,
double sin_th0,
double cos_th0,
double sin_th1,
double cos_th1,
double t)
{
double x1, y1, x2, y2, x3, y3;
x1 = rx * (cos_th0 - t * sin_th0);
y1 = ry * (sin_th0 + t * cos_th0);
x3 = rx * cos_th1;
y3 = ry * sin_th1;
x2 = x3 + rx * (t * sin_th1);
y2 = y3 + ry * (-t * cos_th1);
gsk_path_builder_cubic_to (self,
cx + cos_phi * x1 - sin_phi * y1,
cy + sin_phi * x1 + cos_phi * y1,
cx + cos_phi * x2 - sin_phi * y2,
cy + sin_phi * x2 + cos_phi * y2,
cx + cos_phi * x3 - sin_phi * y3,
cy + sin_phi * x3 + cos_phi * y3);
}
static inline void
_sincos (double angle,
double *y,
double *x)
{
#ifdef HAVE_SINCOS
sincos (angle, y, x);
#else
*x = cos (angle);
*y = sin (angle);
#endif
}
/**
* gsk_path_builder_svg_arc_to:
* @self: a `GskPathBuilder`
* @rx: X radius
* @ry: Y radius
* @x_axis_rotation: the rotation of the ellipsis
* @large_arc: whether to add the large arc
* @positive_sweep: whether to sweep in the positive direction
* @x: the X coordinate of the endpoint
* @y: the Y coordinate of the endpoint
*
* Implements arc-to according to the SVG spec.
*
* A convenience function that implements the
* [SVG arc_to](https://www.w3.org/TR/SVG11/paths.html#PathDataEllipticalArcCommands)
* functionality.
*
* After this, @x, @y will be the new current point.
*
* Since: 4.14
*/
void
gsk_path_builder_svg_arc_to (GskPathBuilder *self,
float rx,
float ry,
float x_axis_rotation,
gboolean large_arc,
gboolean positive_sweep,
float x,
float y)
{
graphene_point_t *current;
double x1, y1, x2, y2;
double phi, sin_phi, cos_phi;
double mid_x, mid_y;
double lambda;
double d;
double k;
double x1_, y1_;
double cx_, cy_;
double cx, cy;
double ux, uy, u_len;
double cos_theta1, theta1;
double vx, vy, v_len;
double dp_uv;
double cos_delta_theta, delta_theta;
int i, n_segs;
double d_theta, theta;
double sin_th0, cos_th0;
double sin_th1, cos_th1;
double th_half;
double t;
g_return_if_fail (self != NULL);
if (self->points->len > 0)
{
current = &g_array_index (self->points, graphene_point_t, self->points->len - 1);
x1 = current->x;
y1 = current->y;
}
else
{
x1 = 0;
y1 = 0;
}
x2 = x;
y2 = y;
phi = x_axis_rotation * M_PI / 180.0;
_sincos (phi, &sin_phi, &cos_phi);
rx = fabs (rx);
ry = fabs (ry);
mid_x = (x1 - x2) / 2;
mid_y = (y1 - y2) / 2;
x1_ = cos_phi * mid_x + sin_phi * mid_y;
y1_ = - sin_phi * mid_x + cos_phi * mid_y;
lambda = (x1_ / rx) * (x1_ / rx) + (y1_ / ry) * (y1_ / ry);
if (lambda > 1)
{
lambda = sqrt (lambda);
rx *= lambda;
ry *= lambda;
}
d = (rx * y1_) * (rx * y1_) + (ry * x1_) * (ry * x1_);
if (d == 0)
return;
k = sqrt (fabs ((rx * ry) * (rx * ry) / d - 1.0));
if (positive_sweep == large_arc)
k = -k;
cx_ = k * rx * y1_ / ry;
cy_ = -k * ry * x1_ / rx;
cx = cos_phi * cx_ - sin_phi * cy_ + (x1 + x2) / 2;
cy = sin_phi * cx_ + cos_phi * cy_ + (y1 + y2) / 2;
ux = (x1_ - cx_) / rx;
uy = (y1_ - cy_) / ry;
u_len = sqrt (ux * ux + uy * uy);
if (u_len == 0)
return;
cos_theta1 = CLAMP (ux / u_len, -1, 1);
theta1 = acos (cos_theta1);
if (uy < 0)
theta1 = - theta1;
vx = (- x1_ - cx_) / rx;
vy = (- y1_ - cy_) / ry;
v_len = sqrt (vx * vx + vy * vy);
if (v_len == 0)
return;
dp_uv = ux * vx + uy * vy;
cos_delta_theta = CLAMP (dp_uv / (u_len * v_len), -1, 1);
delta_theta = acos (cos_delta_theta);
if (ux * vy - uy * vx < 0)
delta_theta = - delta_theta;
if (positive_sweep && delta_theta < 0)
delta_theta += 2 * M_PI;
else if (!positive_sweep && delta_theta > 0)
delta_theta -= 2 * M_PI;
n_segs = ceil (fabs (delta_theta / (M_PI_2 + 0.001)));
d_theta = delta_theta / n_segs;
theta = theta1;
_sincos (theta1, &sin_th1, &cos_th1);
th_half = d_theta / 2;
t = (8.0 / 3.0) * sin (th_half / 2) * sin (th_half / 2) / sin (th_half);
for (i = 0; i < n_segs; i++)
{
theta = theta1;
theta1 = theta + d_theta;
sin_th0 = sin_th1;
cos_th0 = cos_th1;
_sincos (theta1, &sin_th1, &cos_th1);
arc_segment (self,
cx, cy, rx, ry,
sin_phi, cos_phi,
sin_th0, cos_th0,
sin_th1, cos_th1,
t);
}
}
/**
* gsk_path_builder_rel_svg_arc_to:
* @self: a `GskPathBuilder`
* @rx: X radius
* @ry: Y radius
* @x_axis_rotation: the rotation of the ellipsis
* @large_arc: whether to add the large arc
* @positive_sweep: whether to sweep in the positive direction
* @x: the X coordinate of the endpoint
* @y: the Y coordinate of the endpoint
*
* Implements arc-to according to the SVG spec.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.svg_arc_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_svg_arc_to (GskPathBuilder *self,
float rx,
float ry,
float x_axis_rotation,
gboolean large_arc,
gboolean positive_sweep,
float x,
float y)
{
gsk_path_builder_svg_arc_to (self,
rx, ry,
x_axis_rotation,
large_arc,
positive_sweep,
self->current_point.x + x,
self->current_point.y + y);
}
/* Return the angle between t1 and t2 in radians, such that
* 0 means straight continuation
* < 0 means right turn
* > 0 means left turn
*/
static float
angle_between (const graphene_vec2_t *t1,
const graphene_vec2_t *t2)
{
float angle = atan2 (graphene_vec2_get_y (t2), graphene_vec2_get_x (t2))
- atan2 (graphene_vec2_get_y (t1), graphene_vec2_get_x (t1));
if (angle > M_PI)
angle -= 2 * M_PI;
if (angle < - M_PI)
angle += 2 * M_PI;
return angle;
}
#define RAD_TO_DEG(r) ((r)*180.f/M_PI)
#define DEG_TO_RAD(d) ((d)*M_PI/180.f)
static float
angle_between_points (const graphene_point_t *c,
const graphene_point_t *a,
const graphene_point_t *b)
{
graphene_vec2_t t1, t2;
graphene_vec2_init (&t1, a->x - c->x, a->y - c->y);
graphene_vec2_init (&t2, b->x - c->x, b->y - c->y);
return (float) RAD_TO_DEG (angle_between (&t1, &t2));
}
/**
* gsk_path_builder_html_arc_to:
* @self: a `GskPathBuilder`
* @x1: X coordinate of first control point
* @y1: Y coordinate of first control point
* @x2: X coordinate of second control point
* @y2: Y coordinate of second control point
* @radius: Radius of the circle
*
* Implements arc-to according to the HTML Canvas spec.
*
* A convenience function that implements the
* [HTML arc_to](https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-arcto-dev)
* functionality.
*
* After this, the current point will be the point where
* the circle with the given radius touches the line from
* @x1, @y1 to @x2, @y2.
*
* Since: 4.14
*/
void
gsk_path_builder_html_arc_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float radius)
{
float angle, b;
graphene_vec2_t t;
graphene_point_t p, q;
g_return_if_fail (self != NULL);
g_return_if_fail (radius > 0);
angle = angle_between_points (&GRAPHENE_POINT_INIT (x1, y1),
&self->current_point,
&GRAPHENE_POINT_INIT (x2, y2));
if (fabsf (angle) < 3)
{
gsk_path_builder_line_to (self, x2, y2);
return;
}
b = radius / tanf (fabsf ((float) DEG_TO_RAD (angle / 2)));
graphene_vec2_init (&t, self->current_point.x - x1, self->current_point.y - y1);
graphene_vec2_normalize (&t, &t);
p.x = x1 + b * graphene_vec2_get_x (&t);
p.y = y1 + b * graphene_vec2_get_y (&t);
graphene_vec2_init (&t, x2 - x1, y2 - y1);
graphene_vec2_normalize (&t, &t);
q.x = x1 + b * graphene_vec2_get_x (&t);
q.y = y1 + b * graphene_vec2_get_y (&t);
gsk_path_builder_line_to (self, p.x, p.y);
gsk_path_builder_svg_arc_to (self, radius, radius, 0, FALSE, angle < 0, q.x, q.y);
}
/**
* gsk_path_builder_rel_html_arc_to:
* @self: a `GskPathBuilder`
* @x1: X coordinate of first control point
* @y1: Y coordinate of first control point
* @x2: X coordinate of second control point
* @y2: Y coordinate of second control point
* @radius: Radius of the circle
*
* Implements arc-to according to the HTML Canvas spec.
*
* All coordinates are given relative to the current point.
*
* This is the relative version of [method@Gsk.PathBuilder.html_arc_to].
*
* Since: 4.14
*/
void
gsk_path_builder_rel_html_arc_to (GskPathBuilder *self,
float x1,
float y1,
float x2,
float y2,
float radius)
{
gsk_path_builder_html_arc_to (self,
self->current_point.x + x1,
self->current_point.y + y1,
self->current_point.x + x2,
self->current_point.y + y2,
radius);
}
/**
* gsk_path_builder_add_layout:
* @self: a #GskPathBuilder
* @layout: the pango layout to add
*
* Adds the outlines for the glyphs in @layout to the builder.
*
* Since: 4.14
*/
void
gsk_path_builder_add_layout (GskPathBuilder *self,
PangoLayout *layout)
{
cairo_surface_t *surface;
cairo_t *cr;
cairo_path_t *cairo_path;
surface = cairo_recording_surface_create (CAIRO_CONTENT_COLOR_ALPHA, NULL);
cr = cairo_create (surface);
pango_cairo_layout_path (cr, layout);
cairo_path = cairo_copy_path (cr);
gsk_path_builder_add_cairo_path (self, cairo_path);
cairo_path_destroy (cairo_path);
cairo_destroy (cr);
cairo_surface_destroy (surface);
}
/**
* gsk_path_builder_add_segment:
* @self: a `GskPathBuilder`
* @path: the `GskPath` to take the segment to
* @start: the point on @path to start at
* @end: the point on @path to end at
*
* Adds to @self the segment of @path from @start to @end.
*
* If @start is equal to or after @end, the path will first add the
* segment from @start to the end of the path, and then add the segment
* from the beginning to @end. If the path is closed, these segments
* will be connected.
*
* Note that this method always adds a path with the given start point
* and end point. To add a closed path, use [method@Gsk.PathBuilder.add_path].
*
* Since: 4.14
*/
void
gsk_path_builder_add_segment (GskPathBuilder *self,
GskPath *path,
const GskPathPoint *start,
const GskPathPoint *end)
{
const GskContour *contour;
gsize n_contours = gsk_path_get_n_contours (path);
graphene_point_t current;
gsize n_ops;
g_return_if_fail (self != NULL);
g_return_if_fail (path != NULL);
g_return_if_fail (gsk_path_point_valid (start, path));
g_return_if_fail (gsk_path_point_valid (end, path));
current = self->current_point;
contour = gsk_path_get_contour (path, start->contour);
n_ops = gsk_contour_get_n_ops (contour);
if (start->contour == end->contour)
{
if (gsk_path_point_compare (start, end) < 0)
{
gsk_contour_add_segment (contour, self, TRUE, start, end);
goto out;
}
else if (n_contours == 1)
{
if (n_ops > 1)
gsk_contour_add_segment (contour, self, TRUE,
start,
&GSK_PATH_POINT_INIT (start->contour, n_ops - 1, 1.f));
gsk_contour_add_segment (contour, self, n_ops <= 1,
&GSK_PATH_POINT_INIT (start->contour, 1, 0.f),
end);
goto out;
}
}
if (n_ops > 1)
gsk_contour_add_segment (contour, self, TRUE,
start,
&GSK_PATH_POINT_INIT (start->contour, n_ops - 1, 1.f));
for (gsize i = (start->contour + 1) % n_contours; i != end->contour; i = (i + 1) % n_contours)
gsk_path_builder_add_contour (self, gsk_contour_dup (gsk_path_get_contour (path, i)));
contour = gsk_path_get_contour (path, end->contour);
n_ops = gsk_contour_get_n_ops (contour);
if (n_ops > 1)
gsk_contour_add_segment (contour, self, TRUE,
&GSK_PATH_POINT_INIT (end->contour, 1, 0.f),
end);
out:
gsk_path_builder_end_current (self);
self->current_point = current;
}
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