Add GskPathMeasure

GskPathMeasure is the public API for path lengths.

gsk/gsk.h

@@ -22,6 +22,7 @@
 #include <gsk/gskenums.h>
 #include <gsk/gskpath.h>
 #include <gsk/gskpathbuilder.h>
+#include <gsk/gskpathmeasure.h>
 #include <gsk/gskpathpoint.h>
 #include <gsk/gskrenderer.h>
 #include <gsk/gskrendernode.h>

gsk/gskpathmeasure.c

@@ -0,0 +1,327 @@
+/*
+ * 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 "gskpathmeasure.h"
+
+#include "gskpathbuilder.h"
+#include "gskpathpointprivate.h"
+#include "gskpathprivate.h"
+
+/**
+ * GskPathMeasure:
+ *
+ * `GskPathMeasure` is an object that allows measurements
+ * on `GskPath`s such as determining the length of the path.
+ *
+ * Many measuring operations require sampling the path length
+ * at intermediate points. Therefore, a `GskPathMeasure` has
+ * a tolerance that determines what precision is required
+ * for such approximations.
+ *
+ * A `GskPathMeasure` struct is a reference counted struct
+ * and should be treated as opaque.
+ */
+
+typedef struct _GskContourMeasure GskContourMeasure;
+
+struct _GskContourMeasure
+{
+  float length;
+  gpointer contour_data;
+};
+
+struct _GskPathMeasure
+{
+  /*< private >*/
+  guint ref_count;
+
+  GskPath *path;
+  float tolerance;
+
+  float length;
+  gsize n_contours;
+  GskContourMeasure measures[];
+};
+
+G_DEFINE_BOXED_TYPE (GskPathMeasure, gsk_path_measure,
+                     gsk_path_measure_ref,
+                     gsk_path_measure_unref)
+
+/**
+ * gsk_path_measure_new:
+ * @path: the path to measure
+ *
+ * Creates a measure object for the given @path.
+ *
+ * Returns: a new `GskPathMeasure` representing @path
+ *
+ * Since: 4.14
+ */
+GskPathMeasure *
+gsk_path_measure_new (GskPath *path)
+{
+  return gsk_path_measure_new_with_tolerance (path, GSK_PATH_TOLERANCE_DEFAULT);
+}
+
+/**
+ * gsk_path_measure_new_with_tolerance:
+ * @path: the path to measure
+ * @tolerance: the tolerance for measuring operations
+ *
+ * Creates a measure object for the given @path and @tolerance.
+ *
+ * Returns: a new `GskPathMeasure` representing @path
+ *
+ * Since: 4.14
+ */
+GskPathMeasure *
+gsk_path_measure_new_with_tolerance (GskPath *path,
+                                     float    tolerance)
+{
+  GskPathMeasure *self;
+  gsize i, n_contours;
+
+  g_return_val_if_fail (path != NULL, NULL);
+  g_return_val_if_fail (tolerance > 0, NULL);
+
+  n_contours = gsk_path_get_n_contours (path);
+
+  self = g_malloc0 (sizeof (GskPathMeasure) + n_contours * sizeof (GskContourMeasure));
+
+  self->ref_count = 1;
+  self->path = gsk_path_ref (path);
+  self->tolerance = tolerance;
+  self->n_contours = n_contours;
+
+  for (i = 0; i < n_contours; i++)
+    {
+      self->measures[i].contour_data = gsk_contour_init_measure (gsk_path_get_contour (path, i),
+                                                                 self->tolerance,
+                                                                 &self->measures[i].length);
+      self->length += self->measures[i].length;
+    }
+
+  return self;
+}
+
+/**
+ * gsk_path_measure_ref:
+ * @self: a `GskPathMeasure`
+ *
+ * Increases the reference count of a `GskPathMeasure` by one.
+ *
+ * Returns: the passed in `GskPathMeasure`.
+ *
+ * Since: 4.14
+ */
+GskPathMeasure *
+gsk_path_measure_ref (GskPathMeasure *self)
+{
+  g_return_val_if_fail (self != NULL, NULL);
+
+  self->ref_count++;
+
+  return self;
+}
+
+/**
+ * gsk_path_measure_unref:
+ * @self: a `GskPathMeasure`
+ *
+ * Decreases the reference count of a `GskPathMeasure` by one.
+ *
+ * If the resulting reference count is zero, frees the object.
+ *
+ * Since: 4.14
+ */
+void
+gsk_path_measure_unref (GskPathMeasure *self)
+{
+  gsize i;
+
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (self->ref_count > 0);
+
+  self->ref_count--;
+  if (self->ref_count > 0)
+    return;
+
+  for (i = 0; i < self->n_contours; i++)
+    {
+      gsk_contour_free_measure (gsk_path_get_contour (self->path, i),
+                                self->measures[i].contour_data);
+    }
+
+  gsk_path_unref (self->path);
+  g_free (self);
+}
+
+/**
+ * gsk_path_measure_get_path:
+ * @self: a `GskPathMeasure`
+ *
+ * Returns the path that the measure was created for.
+ *
+ * Returns: (transfer none): the path of @self
+ *
+ * Since: 4.14
+ */
+GskPath *
+gsk_path_measure_get_path (GskPathMeasure *self)
+{
+  return self->path;
+}
+
+/**
+ * gsk_path_measure_get_tolerance:
+ * @self: a `GskPathMeasure`
+ *
+ * Returns the tolerance that the measure was created with.
+ *
+ * Returns: the tolerance of @self
+ *
+ * Since: 4.14
+ */
+float
+gsk_path_measure_get_tolerance (GskPathMeasure *self)
+{
+  return self->tolerance;
+}
+
+/**
+ * gsk_path_measure_get_length:
+ * @self: a `GskPathMeasure`
+ *
+ * Gets the length of the path being measured.
+ *
+ * The length is cached, so this function does not do any work.
+ *
+ * Returns: The length of the path measured by @self
+ *
+ * Since: 4.14
+ */
+float
+gsk_path_measure_get_length (GskPathMeasure *self)
+{
+  g_return_val_if_fail (self != NULL, 0);
+
+  return self->length;
+}
+
+static float
+gsk_path_measure_clamp_distance (GskPathMeasure *self,
+                                 float           distance)
+{
+  if (isnan (distance))
+    return 0;
+
+  return CLAMP (distance, 0, self->length);
+}
+
+/**
+ * gsk_path_measure_get_point:
+ * @self: a `GskPathMeasure`
+ * @distance: the distance
+ * @result: (out caller-allocates): return location for the result
+ *
+ * Sets @result to the point at the given distance into the path.
+ *
+ * An empty path has no points, so `FALSE` is returned in that case.
+ *
+ * Returns: `TRUE` if @result was set
+ *
+ * Since: 4.14
+ */
+gboolean
+gsk_path_measure_get_point (GskPathMeasure *self,
+                            float           distance,
+                            GskPathPoint   *result)
+{
+  GskRealPathPoint *res = (GskRealPathPoint *) result;
+  gsize i;
+  const GskContour *contour;
+
+  g_return_val_if_fail (self != NULL, FALSE);
+  g_return_val_if_fail (result != NULL, FALSE);
+
+  if (self->n_contours == 0)
+    return FALSE;
+
+  distance = gsk_path_measure_clamp_distance (self, distance);
+
+  for (i = 0; i < self->n_contours - 1; i++)
+    {
+      if (distance < self->measures[i].length)
+        break;
+
+      distance -= self->measures[i].length;
+    }
+
+  g_assert (0 <= i && i < self->n_contours);
+
+  distance = CLAMP (distance, 0, self->measures[i].length);
+
+  contour = gsk_path_get_contour (self->path, i);
+
+  gsk_contour_get_point (contour, self->measures[i].contour_data, distance, res);
+  res->contour = i;
+
+  return TRUE;
+}
+
+/**
+ * gsk_path_point_get_distance:
+ * @point: a `GskPathPoint on the path
+ * @measure: a `GskPathMeasure` for the path
+ *
+ * Returns the distance from the beginning of the path
+ * to @point.
+ *
+ * Returns: the distance of @point
+ *
+ * Since: 4.14
+ */
+float
+gsk_path_point_get_distance (const GskPathPoint *point,
+                             GskPathMeasure     *measure)
+{
+  GskRealPathPoint *p = (GskRealPathPoint *)point;
+  const GskContour *contour;
+  float contour_offset = 0;
+
+  g_return_val_if_fail (point != NULL, 0);
+  g_return_val_if_fail (measure != NULL, 0);
+  g_return_val_if_fail (p->contour < measure->n_contours, 0);
+
+  contour = gsk_path_get_contour (measure->path, p->contour);
+
+  for (gsize i = 0; i < measure->n_contours; i++)
+    {
+      if (contour == gsk_path_get_contour (measure->path, i))
+        return contour_offset + gsk_contour_get_distance (contour,
+                                                          p,
+                                                          measure->measures[i].contour_data);
+
+      contour_offset += measure->measures[i].length;
+    }
+
+  g_return_val_if_reached (0);
+}

gsk/gskpathmeasure.h

@@ -0,0 +1,62 @@
+/*
+ * 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>
+ */
+
+#pragma once
+
+#if !defined (__GSK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gsk/gsk.h> can be included directly."
+#endif
+
+
+#include <gsk/gskpath.h>
+#include <gsk/gskpathpoint.h>
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_PATH_MEASURE (gsk_path_measure_get_type ())
+
+GDK_AVAILABLE_IN_4_14
+GType                   gsk_path_measure_get_type               (void) G_GNUC_CONST;
+GDK_AVAILABLE_IN_4_14
+GskPathMeasure *        gsk_path_measure_new                    (GskPath                *path);
+GDK_AVAILABLE_IN_4_14
+GskPathMeasure *        gsk_path_measure_new_with_tolerance     (GskPath                *path,
+                                                                 float                   tolerance);
+
+GDK_AVAILABLE_IN_4_14
+GskPathMeasure *        gsk_path_measure_ref                    (GskPathMeasure         *self);
+GDK_AVAILABLE_IN_4_14
+void                    gsk_path_measure_unref                  (GskPathMeasure         *self);
+
+GDK_AVAILABLE_IN_4_14
+GskPath *               gsk_path_measure_get_path               (GskPathMeasure         *self) G_GNUC_PURE;
+GDK_AVAILABLE_IN_4_14
+float                   gsk_path_measure_get_tolerance          (GskPathMeasure         *self) G_GNUC_PURE;
+
+GDK_AVAILABLE_IN_4_14
+float                   gsk_path_measure_get_length             (GskPathMeasure         *self);
+
+GDK_AVAILABLE_IN_4_14
+gboolean                gsk_path_measure_get_point              (GskPathMeasure         *self,
+                                                                 float                   distance,
+                                                                 GskPathPoint           *result);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GskPathMeasure, gsk_path_measure_unref)
+
+G_END_DECLS

gsk/gskpathpoint.h

@@ -78,5 +78,8 @@ float                   gsk_path_point_get_curvature   (const GskPathPoint *poin
                                                         GskPathDirection    direction,
                                                         graphene_point_t   *center);
 
+GDK_AVAILABLE_IN_4_14
+float                   gsk_path_point_get_distance    (const GskPathPoint *point,
+                                                        GskPathMeasure     *measure);
 
 G_END_DECLS

gsk/gsktypes.h

@@ -27,6 +27,7 @@
 
 typedef struct _GskPath                 GskPath;
 typedef struct _GskPathBuilder          GskPathBuilder;
+typedef struct _GskPathMeasure          GskPathMeasure;
 typedef struct _GskPathPoint            GskPathPoint;
 typedef struct _GskRenderer             GskRenderer;
 typedef struct _GskRenderNode           GskRenderNode;

gsk/meson.build

@@ -28,6 +28,7 @@ gsk_public_sources = files([
   'gskglshader.c',
   'gskpath.c',
   'gskpathbuilder.c',
+  'gskpathmeasure.c',
   'gskpathpoint.c',
   'gskrenderer.c',
   'gskrendernode.c',
@@ -75,6 +76,7 @@ gsk_public_headers = files([
   'gskglshader.h',
   'gskpath.h',
   'gskpathbuilder.h',
+  'gskpathmeasure.h',
   'gskpathpoint.h',
   'gskrenderer.h',
   'gskrendernode.h',