[gtk/wip/matthiasc/lottie-stroke: 24/24] wip: Enable subdividing

[Matthias Clasen <matthiasc src gnome org>]

commit a6021558787ae0f85a478834563b66cc50fb97d6
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Nov 29 00:47:40 2020 -0500

    wip: Enable subdividing
    
    This still needs more work.

 gsk/gskpath.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 87 insertions(+), 1 deletion(-)
---
diff --git a/gsk/gskpath.c b/gsk/gskpath.c
index aa61da0a03..ca04c4a65a 100644
--- a/gsk/gskpath.c
+++ b/gsk/gskpath.c
@@ -3577,6 +3577,92 @@ typedef struct
   GskStroke *stroke;
 } AddOpData;
 
+static int
+compare_pos (const void *p1, const void *p2)
+{
+  const float *f1 = p1;
+  const float *f2 = p2;
+  return f1 < f2 ? -1 : (f1 > f2 ? 1 : 0);
+}
+
+static void
+subdivide_and_add (const graphene_point_t  pts[4],
+                   const graphene_point_t *p0,
+                   const graphene_point_t *p1,
+                   AddOpData              *data)
+{
+  float pos[8];
+  int i, k, n = 0;
+  GList *l, *pass1 = NULL;
+  graphene_point_t p[4];
+  graphene_point_t *segment;
+
+  n += get_cubic_extrema (pts[0].x, pts[1].x, pts[2].x, pts[3].x, &pos[n]);
+  n += get_cubic_extrema (pts[0].y, pts[1].y, pts[2].y, pts[3].y, &pos[n]);
+  n += get_cubic_inflections (pts[0].x, pts[1].x, pts[2].x, pts[3].x, &pos[n]);
+  n += get_cubic_inflections (pts[0].y, pts[1].y, pts[2].y, pts[3].y, &pos[n]);
+
+  qsort (pos, n, sizeof (float), compare_pos);
+
+  for (i = 0; i < 4; i++)
+    p[i] = pts[i];
+
+  pass1 = NULL;
+
+  g_print ("splitting at ");
+  for (i = 0; i < n; i++)
+    g_print ("%f ", pos[i]);
+  g_print ("\n");
+
+  for (i = 0; i < n; i++)
+    {
+      graphene_point_t left[4];
+      graphene_point_t right[4];
+      float t;
+
+      t = pos[i];
+      if (t < 0.1 || t > 0.9)
+        continue;
+
+      split_bezier (p, 4, t, left, right);
+
+      segment = g_new (graphene_point_t, 4);
+      memcpy (segment, left, sizeof (graphene_point_t) * 4);
+      pass1 = g_list_append (pass1, segment);
+
+      for (k = 0; k < 4; k++)
+        p[k] = right[k];
+
+      for (k = i + 1; k < n; k++)
+        pos[k] = pos[k] / (1 - pos[i]);
+    }
+
+  segment = g_new (graphene_point_t, 4);
+  memcpy (segment, pts, sizeof (graphene_point_t) * 4);
+  pass1 = g_list_append (pass1, segment);
+
+  g_print ("after pass1: %d segments\n", g_list_length (pass1));
+
+  for (l = pass1; l; l = l->next)
+    {
+      segment = l->data;
+      if (cubic_is_simple (segment))
+        data->ops = g_list_prepend (data->ops, path_op_data_new (GSK_PATH_CURVE, segment, 4));
+      else
+        {
+          graphene_point_t left[4];
+          graphene_point_t right[4];
+
+          split_bezier (segment, 4, 0.5, left, right);
+
+          data->ops = g_list_prepend (data->ops, path_op_data_new (GSK_PATH_CURVE, left, 4));
+          data->ops = g_list_prepend (data->ops, path_op_data_new (GSK_PATH_CURVE, right, 4));
+        }
+    }
+
+  g_list_free_full (pass1, g_free);
+}
+
 static gboolean
 add_op_to_list (GskPathOperation        op,
                 const graphene_point_t *pts,
@@ -3598,7 +3684,7 @@ add_op_to_list (GskPathOperation        op,
       break;
 
     case GSK_PATH_CURVE:
-      data->ops = g_list_prepend (data->ops, path_op_data_new (GSK_PATH_CURVE, pts, 4));
+      subdivide_and_add (pts, &pts[0], &pts[1], data);
       break;
 
     case GSK_PATH_CONIC: