[gtk/curve-ops: 26/29] Add gsk_curve_decompose_curve
- From: Matthias Clasen <matthiasc src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [gtk/curve-ops: 26/29] Add gsk_curve_decompose_curve
- Date: Sat, 12 Dec 2020 15:04:57 +0000 (UTC)
commit ef210f7d2467b4a37fdae93c61bc963b526212fb
Author: Matthias Clasen <mclasen redhat com>
Date: Wed Dec 9 17:46:31 2020 -0500
Add gsk_curve_decompose_curve
This is mainly useful for decomposing a conic into
cubics. The criterion here for terminating the
subdivision is very improvised.
gsk/gskcurve.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++++++
gsk/gskcurveprivate.h | 7 +++
2 files changed, 135 insertions(+)
---
diff --git a/gsk/gskcurve.c b/gsk/gskcurve.c
index e9aa622074..ea8446f987 100644
--- a/gsk/gskcurve.c
+++ b/gsk/gskcurve.c
@@ -52,6 +52,10 @@ struct _GskCurveClass
float tolerance,
GskCurveAddLineFunc add_line_func,
gpointer user_data);
+ gboolean (* decompose_curve) (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data);
gskpathop (* pathop) (const GskCurve *curve);
const graphene_point_t * (* get_start_point) (const GskCurve *curve);
const graphene_point_t * (* get_end_point) (const GskCurve *curve);
@@ -174,6 +178,23 @@ gsk_line_curve_decompose (const GskCurve *curve,
return add_line_func (&self->points[0], &self->points[1], 0.0f, 1.0f, user_data);
}
+static gboolean
+gsk_line_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data)
+{
+ const GskLineCurve *self = &curve->line;
+ graphene_point_t p[4];
+
+ p[0] = self->points[0];
+ p[3] = self->points[1];
+ graphene_point_interpolate (&p[0], &p[3], 1/3.0, &p[1]);
+ graphene_point_interpolate (&p[0], &p[3], 2/3.0, &p[2]);
+
+ return add_curve_func (p, user_data);
+}
+
static gskpathop
gsk_line_curve_pathop (const GskCurve *curve)
{
@@ -226,6 +247,7 @@ static const GskCurveClass GSK_LINE_CURVE_CLASS = {
gsk_line_curve_split,
gsk_line_curve_segment,
gsk_line_curve_decompose,
+ gsk_line_curve_decompose_curve,
gsk_line_curve_pathop,
gsk_line_curve_get_start_point,
gsk_line_curve_get_end_point,
@@ -406,6 +428,17 @@ gsk_curve_curve_decompose (const GskCurve *curve,
return gsk_curce_curve_decompose_step (curve, 0.0, 1.0, tolerance, add_line_func, user_data);
}
+static gboolean
+gsk_curve_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data)
+{
+ const GskCurveCurve *self = &curve->curve;
+
+ return add_curve_func (self->points, user_data);
+}
+
static gskpathop
gsk_curve_curve_pathop (const GskCurve *curve)
{
@@ -543,6 +576,7 @@ static const GskCurveClass GSK_CURVE_CURVE_CLASS = {
gsk_curve_curve_split,
gsk_curve_curve_segment,
gsk_curve_curve_decompose,
+ gsk_curve_curve_decompose_curve,
gsk_curve_curve_pathop,
gsk_curve_curve_get_start_point,
gsk_curve_curve_get_end_point,
@@ -910,6 +944,90 @@ gsk_conic_curve_decompose (const GskCurve *curve,
user_data);
}
+/* See Floater, M: An analysis of cubic approximation schemes
+ * for conic sections
+ */
+static void
+cubic_approximation (const GskCurve *curve,
+ GskCurve *cubic)
+{
+ const GskConicCurve *self = &curve->conic;
+ graphene_point_t p[4];
+ float w = self->points[2].x;
+ float w2 = w*w;
+ float lambda;
+
+ lambda = 2 * (6*w2 + 1 - sqrt (3*w2 + 1)) / (12*w2 + 3);
+
+ p[0] = self->points[0];
+ p[3] = self->points[3];
+ graphene_point_interpolate (&self->points[0], &self->points[1], lambda, &p[1]);
+ graphene_point_interpolate (&self->points[3], &self->points[1], lambda, &p[2]);
+
+ gsk_curve_init (cubic, gsk_pathop_encode (GSK_PATH_CURVE, p));
+}
+
+static gboolean
+gsk_conic_is_close_to_cubic (const GskCurve *conic,
+ const GskCurve *cubic,
+ float tolerance)
+{
+ float t[] = { 0.1, 0.5, 0.9 };
+ graphene_point_t p0, p1;
+
+ for (int i = 0; i < G_N_ELEMENTS (t); i++)
+ {
+ gsk_curve_get_point (conic, t[i], &p0);
+ gsk_curve_get_point (cubic, t[i], &p1);
+ if (graphene_point_distance (&p0, &p1, NULL, NULL) > tolerance)
+ return FALSE;
+ }
+
+ return TRUE;
+}
+
+static gboolean gsk_conic_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data);
+
+static gboolean
+gsk_conic_curve_decompose_or_add (const GskCurve *curve,
+ const GskCurve *cubic,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data)
+{
+ if (gsk_conic_is_close_to_cubic (curve, cubic, tolerance))
+ return add_curve_func (cubic->curve.points, user_data);
+ else
+ {
+ GskCurve c1, c2;
+ GskCurve cc1, cc2;
+
+ gsk_conic_curve_split (curve, 0.5, &c1, &c2);
+
+ cubic_approximation (&c1, &cc1);
+ cubic_approximation (&c2, &cc2);
+
+ return gsk_conic_curve_decompose_or_add (&c1, &cc1, tolerance, add_curve_func, user_data) &&
+ gsk_conic_curve_decompose_or_add (&c2, &cc2, tolerance, add_curve_func, user_data);
+ }
+}
+
+static gboolean
+gsk_conic_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data)
+{
+ GskCurve c;
+
+ cubic_approximation (curve, &c);
+
+ return gsk_conic_curve_decompose_or_add (curve, &c, tolerance, add_curve_func, user_data);
+}
+
static gskpathop
gsk_conic_curve_pathop (const GskCurve *curve)
{
@@ -1038,6 +1156,7 @@ static const GskCurveClass GSK_CONIC_CURVE_CLASS = {
gsk_conic_curve_split,
gsk_conic_curve_segment,
gsk_conic_curve_decompose,
+ gsk_conic_curve_decompose_curve,
gsk_conic_curve_pathop,
gsk_conic_curve_get_start_point,
gsk_conic_curve_get_end_point,
@@ -1130,6 +1249,15 @@ gsk_curve_decompose (const GskCurve *curve,
return get_class (curve->op)->decompose (curve, tolerance, add_line_func, user_data);
}
+gboolean
+gsk_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data)
+{
+ return get_class (curve->op)->decompose_curve (curve, tolerance, add_curve_func, user_data);
+}
+
gskpathop
gsk_curve_pathop (const GskCurve *curve)
{
diff --git a/gsk/gskcurveprivate.h b/gsk/gskcurveprivate.h
index 74320323ef..1ae20e9e44 100644
--- a/gsk/gskcurveprivate.h
+++ b/gsk/gskcurveprivate.h
@@ -79,6 +79,9 @@ typedef gboolean (* GskCurveAddLineFunc) (const graphene_point_t *from,
float to_progress,
gpointer user_data);
+typedef gboolean (* GskCurveAddCurveFunc) (const graphene_point_t points[4],
+ gpointer user_data);
+
void gsk_curve_init (GskCurve *curve,
gskpathop op);
void gsk_curve_init_foreach (GskCurve *curve,
@@ -105,6 +108,10 @@ gboolean gsk_curve_decompose (const GskCurve
float tolerance,
GskCurveAddLineFunc add_line_func,
gpointer user_data);
+gboolean gsk_curve_decompose_curve (const GskCurve *curve,
+ float tolerance,
+ GskCurveAddCurveFunc add_curve_func,
+ gpointer user_data);
gskpathop gsk_curve_pathop (const GskCurve *curve);
#define gsk_curve_builder_to(curve, builder) gsk_path_builder_pathop_to ((builder), gsk_curve_pathop (curve))
const graphene_point_t *gsk_curve_get_start_point (const GskCurve *curve);
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