gtk/gsk/gskcontour.c

/*
 * 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 "gskcontourprivate.h"

#include "gskcurveprivate.h"
#include "gskpathbuilder.h"
#include "gskpathprivate.h"
#include "gskpathpointprivate.h"
#include "gsksplineprivate.h"
#include "gskstrokeprivate.h"

typedef struct _GskContourClass GskContourClass;

struct _GskContour
{
  const GskContourClass *klass;
};

struct _GskContourClass
{
  gsize struct_size;
  const char *type_name;

  void                  (* copy)                (const GskContour       *contour,
                                                 GskContour             *dest);
  gsize                 (* get_size)            (const GskContour       *contour);
  GskPathFlags          (* get_flags)           (const GskContour       *contour);
  void                  (* print)               (const GskContour       *contour,
                                                 GString                *string);
  gboolean              (* get_bounds)          (const GskContour       *contour,
                                                 GskBoundingBox         *bounds);
  gboolean              (* get_stroke_bounds)   (const GskContour       *contour,
                                                 const GskStroke        *stroke,
                                                 GskBoundingBox         *bounds);
  void                  (* get_start_end)       (const GskContour       *self,
                                                 graphene_point_t       *start,
                                                 graphene_point_t       *end);
  gboolean              (* foreach)             (const GskContour       *contour,
                                                 float                   tolerance,
                                                 GskPathForeachFunc      func,
                                                 gpointer                user_data);
  GskContour *          (* reverse)             (const GskContour       *contour);
  int                   (* get_winding)         (const GskContour       *contour,
                                                 const graphene_point_t *point);
  gsize                 (* get_n_ops)           (const GskContour       *contour);
  gboolean              (* get_closest_point)   (const GskContour       *contour,
                                                 const graphene_point_t *point,
                                                 float                   threshold,
                                                 GskRealPathPoint       *result,
                                                 float                  *out_dist);
  void                  (* get_position)        (const GskContour       *contour,
                                                 GskRealPathPoint       *point,
                                                 graphene_point_t       *position);
  void                  (* get_tangent)         (const GskContour       *contour,
                                                 GskRealPathPoint       *point,
                                                 GskPathDirection        direction,
                                                 graphene_vec2_t        *tangent);
  float                 (* get_curvature)       (const GskContour       *contour,
                                                 GskRealPathPoint       *point,
                                                 graphene_point_t       *center);
  void                  (* add_segment)         (const GskContour       *contour,
                                                 GskPathBuilder         *builder,
                                                 gboolean                emit_move_to,
                                                 GskRealPathPoint       *start,
                                                 GskRealPathPoint       *end);
};

/* {{{ Utilities */

#define DEG_TO_RAD(x)          ((x) * (G_PI / 180.f))
#define RAD_TO_DEG(x)          ((x) / (G_PI / 180.f))

static void
_g_string_append_double (GString *string,
                         double   d)
{
  char buf[G_ASCII_DTOSTR_BUF_SIZE];

  g_ascii_dtostr (buf, G_ASCII_DTOSTR_BUF_SIZE, d);
  g_string_append (string, buf);
}

static void
_g_string_append_point (GString                *string,
                        const graphene_point_t *pt)
{
  _g_string_append_double (string, pt->x);
  g_string_append_c (string, ' ');
  _g_string_append_double (string, pt->y);
}


/* }}} */
/* {{{ Standard */

typedef struct _GskStandardContour GskStandardContour;
struct _GskStandardContour
{
  GskContour contour;

  GskPathFlags flags;

  GskBoundingBox bounds;

  gsize n_ops;
  gsize n_points;
  graphene_point_t *points;
  gskpathop ops[];
};

static gsize
gsk_standard_contour_compute_size (gsize n_ops,
                                   gsize n_points)
{
  gsize align = MAX (G_ALIGNOF (graphene_point_t),
                     MAX (G_ALIGNOF (gpointer),
                          G_ALIGNOF (GskStandardContour)));
  gsize s = sizeof (GskStandardContour)
          + sizeof (gskpathop) * n_ops
          + sizeof (graphene_point_t) * n_points;
  return s + (align - (s % align));
}

static void
gsk_standard_contour_init (GskContour             *contour,
                           GskPathFlags            flags,
                           const graphene_point_t *points,
                           gsize                   n_points,
                           const gskpathop        *ops,
                           gsize                   n_ops,
                           ptrdiff_t               offset);

static void
gsk_standard_contour_copy (const GskContour *contour,
                           GskContour       *dest)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;

  gsk_standard_contour_init (dest, self->flags, self->points, self->n_points, self->ops, self->n_ops, 0);
}

static gsize
gsk_standard_contour_get_size (const GskContour *contour)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;

  return gsk_standard_contour_compute_size (self->n_ops, self->n_points);
}

static gboolean
gsk_standard_contour_foreach (const GskContour   *contour,
                              float               tolerance,
                              GskPathForeachFunc  func,
                              gpointer            user_data)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;
  gsize i;

  for (i = 0; i < self->n_ops; i ++)
    {
      if (!gsk_pathop_foreach (self->ops[i], func, user_data))
        return FALSE;
    }

  return TRUE;
}

static gboolean
add_reverse (GskPathOperation        op,
             const graphene_point_t *pts,
             gsize                   n_pts,
             gpointer                user_data)
{
  GskPathBuilder *builder = user_data;
  GskCurve c, r;

  if (op == GSK_PATH_MOVE)
    return TRUE;

  if (op == GSK_PATH_CLOSE)
    op = GSK_PATH_LINE;

  gsk_curve_init_foreach (&c, op, pts, n_pts);
  gsk_curve_reverse (&c, &r);
  gsk_curve_builder_to (&r, builder);

  return TRUE;
}

static GskContour *
gsk_standard_contour_reverse (const GskContour *contour)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;
  GskPathBuilder *builder;
  GskPath *path;
  GskContour *res;

  builder = gsk_path_builder_new ();

  gsk_path_builder_move_to (builder, self->points[self->n_points - 1].x,
                                     self->points[self->n_points - 1].y);

  for (int i = self->n_ops - 1; i >= 0; i--)
    gsk_pathop_foreach (self->ops[i], add_reverse, builder);

  if (self->flags & GSK_PATH_CLOSED)
    gsk_path_builder_close (builder);

  path = gsk_path_builder_free_to_path (builder);

  g_assert (gsk_path_get_n_contours (path) == 1);

  res = gsk_contour_dup (gsk_path_get_contour (path, 0));

  gsk_path_unref (path);

  return res;
}

static GskPathFlags
gsk_standard_contour_get_flags (const GskContour *contour)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;

  return self->flags;
}

static void
gsk_standard_contour_print (const GskContour *contour,
                            GString          *string)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;
  gsize i;

  for (i = 0; i < self->n_ops; i ++)
    {
      const graphene_point_t *pt = gsk_pathop_points (self->ops[i]);

      switch (gsk_pathop_op (self->ops[i]))
        {
        case GSK_PATH_MOVE:
          g_string_append (string, "M ");
          _g_string_append_point (string, &pt[0]);
          break;

        case GSK_PATH_CLOSE:
          g_string_append (string, " Z");
          break;

        case GSK_PATH_LINE:
          g_string_append (string, " L ");
          _g_string_append_point (string, &pt[1]);
          break;

        case GSK_PATH_QUAD:
          g_string_append (string, " Q ");
          _g_string_append_point (string, &pt[1]);
          g_string_append (string, ", ");
          _g_string_append_point (string, &pt[2]);
          break;

        case GSK_PATH_CUBIC:
          g_string_append (string, " C ");
          _g_string_append_point (string, &pt[1]);
          g_string_append (string, ", ");
          _g_string_append_point (string, &pt[2]);
          g_string_append (string, ", ");
          _g_string_append_point (string, &pt[3]);
          break;

        case GSK_PATH_ARC:
          g_string_append (string, " E ");
          _g_string_append_point (string, &pt[1]);
          g_string_append (string, ", ");
          _g_string_append_point (string, &pt[2]);
          break;

        default:
          g_assert_not_reached();
          return;
        }
    }
}

static gboolean
gsk_standard_contour_get_bounds (const GskContour *contour,
                                 GskBoundingBox   *bounds)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;

  if (self->n_points == 0)
    return FALSE;

  *bounds = self->bounds;

  return bounds->max.x > bounds->min.x && bounds->max.y > bounds->min.y;
}

static gboolean
gsk_standard_contour_get_stroke_bounds (const GskContour *contour,
                                        const GskStroke  *stroke,
                                        GskBoundingBox   *bounds)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  float extra;

  if (self->n_points == 0)
    return FALSE;

  extra = MAX (stroke->line_width, gsk_stroke_get_join_width (stroke));

  gsk_bounding_box_init (bounds, &GRAPHENE_POINT_INIT (self->bounds.min.x - extra,
                                                       self->bounds.min.y - extra),
                                 &GRAPHENE_POINT_INIT (self->bounds.max.x + extra,
                                                       self->bounds.max.y + extra));

  return TRUE;
}

static void
gsk_standard_contour_get_start_end (const GskContour *contour,
                                    graphene_point_t *start,
                                    graphene_point_t *end)
{
  const GskStandardContour *self = (const GskStandardContour *) contour;

  if (start)
    *start = self->points[0];

  if (end)
    *end = self->points[self->n_points - 1];
}

static int
gsk_standard_contour_get_winding (const GskContour       *contour,
                                  const graphene_point_t *point)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  int winding = 0;

  if (!gsk_bounding_box_contains_point (&self->bounds, point))
    return 0;

  for (gsize i = 0; i < self->n_ops; i ++)
    {
      GskCurve c;

      if (gsk_pathop_op (self->ops[i]) == GSK_PATH_MOVE)
        continue;

      gsk_curve_init (&c, self->ops[i]);
      winding += gsk_curve_get_crossing (&c, point);
    }

  if ((self->flags & GSK_PATH_CLOSED) == 0)
    {
      GskCurve c;

      gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CLOSE,
                                             (const graphene_point_t[]) { self->points[self->n_points - 1],
                                                                          self->points[0] }));

      winding += gsk_curve_get_crossing (&c, point);
    }

  return winding;
}

static gsize
gsk_standard_contour_get_n_ops (const GskContour *contour)
{
  GskStandardContour *self = (GskStandardContour *) contour;

  return self->n_ops;
}

static gboolean
gsk_standard_contour_get_closest_point (const GskContour       *contour,
                                        const graphene_point_t *point,
                                        float                   threshold,
                                        GskRealPathPoint       *result,
                                        float                  *out_dist)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  unsigned int best_idx = G_MAXUINT;
  float best_t = 0;

  g_assert (gsk_pathop_op (self->ops[0]) == GSK_PATH_MOVE);

  if (self->n_ops == 1)
    {
      float dist;

      dist = graphene_point_distance (point, &self->points[0], NULL, NULL);
      if (dist <= threshold)
        {
          *out_dist = dist;
          result->idx = 0;
          result->t = 0;
          return TRUE;
        }

      return FALSE;
    }

  for (gsize i = 0; i < self->n_ops; i ++)
    {
      GskCurve c;
      float distance, t;

      if (gsk_pathop_op (self->ops[i]) == GSK_PATH_MOVE)
        continue;

      gsk_curve_init (&c, self->ops[i]);
      if (gsk_curve_get_closest_point (&c, point, threshold, &distance, &t) &&
          distance < threshold)
        {
          best_idx = i;
          best_t = t;
          threshold = distance;
        }
    }

  if (best_idx != G_MAXUINT)
    {
      *out_dist = threshold;
      result->idx = best_idx;
      result->t = best_t;
      return TRUE;
    }

  return FALSE;
}

static void
gsk_standard_contour_get_position (const GskContour *contour,
                                   GskRealPathPoint *point,
                                   graphene_point_t *position)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  GskCurve curve;

  if (G_UNLIKELY (point->idx == 0))
    {
      *position = self->points[0];
      return;
    }

  gsk_curve_init (&curve, self->ops[point->idx]);
  gsk_curve_get_point (&curve, point->t, position);
}

static void
gsk_standard_contour_get_tangent (const GskContour *contour,
                                  GskRealPathPoint *point,
                                  GskPathDirection  direction,
                                  graphene_vec2_t  *tangent)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  GskCurve curve;
  gsize idx;
  float t;

  if (G_UNLIKELY (point->idx == 0))
    {
      graphene_vec2_init (tangent, 1, 0);
      return;
    }

  idx = point->idx;
  t = point->t;

  if (t == 0 && (direction == GSK_PATH_FROM_START ||
                 direction == GSK_PATH_TO_START))
    {
      /* Look at the previous segment */
      if (idx > 1)
        {
          idx--;
          t = 1;
        }
      else if (self->flags & GSK_PATH_CLOSED)
        {
          idx = self->n_ops - 1;
          t = 1;
        }
    }
  else if (t == 1 && (direction == GSK_PATH_TO_END ||
                      direction == GSK_PATH_FROM_END))
    {
      /* Look at the next segment */
      if (idx < self->n_ops - 1)
        {
          idx++;
          t = 0;
        }
      else if (self->flags & GSK_PATH_CLOSED)
        {
          idx = 1;
          t = 0;
        }
    }

  gsk_curve_init (&curve, self->ops[idx]);
  gsk_curve_get_tangent (&curve, t, tangent);

  if (direction == GSK_PATH_TO_START || direction == GSK_PATH_FROM_END)
    graphene_vec2_negate (tangent, tangent);
}

static float
gsk_standard_contour_get_curvature (const GskContour *contour,
                                    GskRealPathPoint *point,
                                    graphene_point_t *center)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  GskCurve curve;

  if (G_UNLIKELY (point->idx == 0))
    return 0;

  gsk_curve_init (&curve, self->ops[point->idx]);
  return gsk_curve_get_curvature (&curve, point->t, center);
}

static void
add_curve (GskCurve       *curve,
           GskPathBuilder *builder,
           gboolean       *emit_move_to)
{
  if (*emit_move_to)
    {
      const graphene_point_t *s;

      s = gsk_curve_get_start_point (curve);
      gsk_path_builder_move_to (builder, s->x, s->y);
      *emit_move_to = FALSE;
    }
  gsk_curve_builder_to (curve, builder);
}

static void
gsk_standard_contour_add_segment (const GskContour *contour,
                                  GskPathBuilder   *builder,
                                  gboolean          emit_move_to,
                                  GskRealPathPoint *start,
                                  GskRealPathPoint *end)
{
  GskStandardContour *self = (GskStandardContour *) contour;
  GskCurve c, c1, c2;

  g_assert (start->idx < self->n_ops);

  gsk_curve_init (&c, self->ops[start->idx]);

  if (start->idx == end->idx)
    {
      gsk_curve_segment (&c, start->t, end->t, &c1);
      add_curve (&c1, builder, &emit_move_to);
      return;
    }
  if (start->t == 0)
    {
      add_curve (&c, builder, &emit_move_to);
    }
  else if (start->t < 1)
    {
      gsk_curve_split (&c, start->t, &c1, &c2);
      add_curve (&c2, builder, &emit_move_to);
    }

  for (gsize i = start->idx + 1; i < end->idx; i++)
    {
      gsk_curve_init (&c, self->ops[i]);
      add_curve (&c, builder, &emit_move_to);
    }

  gsk_curve_init (&c, self->ops[end->idx]);
  if (c.op == GSK_PATH_CLOSE)
    c.op = GSK_PATH_LINE;

  if (end->t == 1)
    {
      add_curve (&c, builder, &emit_move_to);
    }
  else if (end->t > 0)
    {
      gsk_curve_split (&c, end->t, &c1, &c2);
      add_curve (&c1, builder, &emit_move_to);
    }
}

static const GskContourClass GSK_STANDARD_CONTOUR_CLASS =
{
  sizeof (GskStandardContour),
  "GskStandardContour",
  gsk_standard_contour_copy,
  gsk_standard_contour_get_size,
  gsk_standard_contour_get_flags,
  gsk_standard_contour_print,
  gsk_standard_contour_get_bounds,
  gsk_standard_contour_get_stroke_bounds,
  gsk_standard_contour_get_start_end,
  gsk_standard_contour_foreach,
  gsk_standard_contour_reverse,
  gsk_standard_contour_get_winding,
  gsk_standard_contour_get_n_ops,
  gsk_standard_contour_get_closest_point,
  gsk_standard_contour_get_position,
  gsk_standard_contour_get_tangent,
  gsk_standard_contour_get_curvature,
  gsk_standard_contour_add_segment,
};

/* You must ensure the contour has enough size allocated,
 * see gsk_standard_contour_compute_size()
 */
static void
gsk_standard_contour_init (GskContour             *contour,
                           GskPathFlags            flags,
                           const graphene_point_t *points,
                           gsize                   n_points,
                           const gskpathop        *ops,
                           gsize                   n_ops,
                           gssize                  offset)

{
  GskStandardContour *self = (GskStandardContour *) contour;

  self->contour.klass = &GSK_STANDARD_CONTOUR_CLASS;

  self->flags = flags;
  self->n_ops = n_ops;
  self->n_points = n_points;
  self->points = (graphene_point_t *) &self->ops[n_ops];
  memcpy (self->points, points, sizeof (graphene_point_t) * n_points);

  offset += self->points - points;
  for (gsize i = 0; i < n_ops; i++)
    self->ops[i] = gsk_pathop_encode (gsk_pathop_op (ops[i]),
                                      gsk_pathop_points (ops[i]) + offset);

  gsk_bounding_box_init (&self->bounds,  &self->points[0], &self->points[0]);
  for (gsize i = 1; i < self->n_points; i ++)
    gsk_bounding_box_expand (&self->bounds, &self->points[i]);
}

GskContour *
gsk_standard_contour_new (GskPathFlags            flags,
                          const graphene_point_t *points,
                          gsize                   n_points,
                          const gskpathop        *ops,
                          gsize                   n_ops,
                          gssize                  offset)
{
  GskContour *contour;

  contour = g_malloc0 (gsk_standard_contour_compute_size (n_ops, n_points));

  gsk_standard_contour_init (contour, flags, points, n_points, ops, n_ops, offset);

  return contour;
}

/* }}} */
/* {{{ API */

gsize
gsk_contour_get_size (const GskContour *self)
{
  return self->klass->get_size (self);
}

void
gsk_contour_copy (GskContour       *dest,
                  const GskContour *src)
{
  src->klass->copy (src, dest);
}

GskContour *
gsk_contour_dup (const GskContour *src)
{
  GskContour *copy;

  copy = g_malloc0 (gsk_contour_get_size (src));
  gsk_contour_copy (copy, src);

  return copy;
}

GskContour *
gsk_contour_reverse (const GskContour *src)
{
  return src->klass->reverse (src);
}

GskPathFlags
gsk_contour_get_flags (const GskContour *self)
{
  return self->klass->get_flags (self);
}

void
gsk_contour_print (const GskContour *self,
                   GString          *string)
{
  self->klass->print (self, string);
}

gboolean
gsk_contour_get_bounds (const GskContour *self,
                        GskBoundingBox   *bounds)
{
  return self->klass->get_bounds (self, bounds);
}

gboolean
gsk_contour_get_stroke_bounds (const GskContour *self,
                               const GskStroke  *stroke,
                               GskBoundingBox   *bounds)
{
  return self->klass->get_stroke_bounds (self, stroke, bounds);
}

gboolean
gsk_contour_foreach (const GskContour   *self,
                     float               tolerance,
                     GskPathForeachFunc  func,
                     gpointer            user_data)
{
  return self->klass->foreach (self, tolerance, func, user_data);
}

void
gsk_contour_get_start_end (const GskContour *self,
                           graphene_point_t *start,
                           graphene_point_t *end)
{
  self->klass->get_start_end (self, start, end);
}

int
gsk_contour_get_winding (const GskContour       *self,
                         const graphene_point_t *point)
{
  return self->klass->get_winding (self, point);
}

gboolean
gsk_contour_get_closest_point (const GskContour       *self,
                               const graphene_point_t *point,
                               float                   threshold,
                               GskRealPathPoint       *result,
                               float                  *out_dist)
{
  return self->klass->get_closest_point (self, point, threshold, result, out_dist);
}

gsize
gsk_contour_get_n_ops (const GskContour *self)
{
  return self->klass->get_n_ops (self);
}

void
gsk_contour_get_position (const GskContour *self,
                          GskRealPathPoint *point,
                          graphene_point_t *pos)
{
  self->klass->get_position (self, point, pos);
}

void
gsk_contour_get_tangent (const GskContour *self,
                         GskRealPathPoint *point,
                         GskPathDirection  direction,
                         graphene_vec2_t  *tangent)
{
  self->klass->get_tangent (self, point, direction, tangent);
}

float
gsk_contour_get_curvature (const GskContour *self,
                           GskRealPathPoint *point,
                           graphene_point_t *center)
{
  return self->klass->get_curvature (self, point, center);
}

void
gsk_contour_add_segment (const GskContour *self,
                         GskPathBuilder   *builder,
                         gboolean          emit_move_to,
                         GskRealPathPoint *start,
                         GskRealPathPoint *end)
{
  self->klass->add_segment (self, builder, emit_move_to, start, end);
}

/* }}} */

/* vim:set foldmethod=marker expandtab: */