sweep gradients etc

util/hb-test.c

@@ -1,10 +1,33 @@
 #include <hb.h>
+#include <hb-ot.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
+#include <cairo.h>
+#include <math.h>
+#include <unistd.h>
+#include <assert.h>
+
+#ifndef MIN
+#define MIN(x,y) ((x) < (y) ? (x) : (y))
+#endif
+
+#ifndef MAX
+#define MAX(x,y) ((x) > (y) ? (x) : (y))
+#endif
+
+#ifndef FALSE
+#define FALSE 0
+#define TRUE 1
+#endif
 
 typedef struct {
   int level;
+  cairo_t *cr;
+  hb_font_t *font;
+  hb_color_t *colors;
+  unsigned int num_colors;
+  hb_color_t foreground_color;
 } paint_data_t;
 
 #define INDENT 2
@@ -25,6 +48,82 @@ print (paint_data_t *data,
   printf ("\n");
 }
 
+typedef struct {
+  float r, g, b, a;
+} color_t;
+
+static void
+get_color (paint_data_t *data,
+           unsigned int color_index,
+           float alpha,
+           color_t *c)
+{
+  hb_color_t color;
+
+  if (color_index == 0xffff)
+    color = data->foreground_color;
+  else
+    color = data->colors[color_index];
+
+  c->r = hb_color_get_red (color) / 255.;
+  c->g = hb_color_get_green (color) / 255.;
+  c->b = hb_color_get_blue (color) / 255.;
+  c->a = (hb_color_get_alpha (color) / 255.) * alpha;
+}
+
+static cairo_operator_t
+to_operator (hb_paint_composite_mode_t mode)
+{
+  switch (mode)
+    {
+    case HB_PAINT_COMPOSITE_MODE_CLEAR: return CAIRO_OPERATOR_CLEAR;
+    case HB_PAINT_COMPOSITE_MODE_SRC: return CAIRO_OPERATOR_SOURCE;
+    case HB_PAINT_COMPOSITE_MODE_DEST: return CAIRO_OPERATOR_DEST;
+    case HB_PAINT_COMPOSITE_MODE_SRC_OVER: return CAIRO_OPERATOR_OVER;
+    case HB_PAINT_COMPOSITE_MODE_DEST_OVER: return CAIRO_OPERATOR_DEST_OVER;
+    case HB_PAINT_COMPOSITE_MODE_SRC_IN: return CAIRO_OPERATOR_IN;
+    case HB_PAINT_COMPOSITE_MODE_DEST_IN: return CAIRO_OPERATOR_DEST_IN;
+    case HB_PAINT_COMPOSITE_MODE_SRC_OUT: return CAIRO_OPERATOR_OUT;
+    case HB_PAINT_COMPOSITE_MODE_DEST_OUT: return CAIRO_OPERATOR_DEST_OUT;
+    case HB_PAINT_COMPOSITE_MODE_SRC_ATOP: return CAIRO_OPERATOR_ATOP;
+    case HB_PAINT_COMPOSITE_MODE_DEST_ATOP: return CAIRO_OPERATOR_DEST_ATOP;
+    case HB_PAINT_COMPOSITE_MODE_XOR: return CAIRO_OPERATOR_XOR;
+    case HB_PAINT_COMPOSITE_MODE_PLUS: return CAIRO_OPERATOR_ADD;
+    case HB_PAINT_COMPOSITE_MODE_SCREEN: return CAIRO_OPERATOR_SCREEN;
+    case HB_PAINT_COMPOSITE_MODE_OVERLAY: return CAIRO_OPERATOR_OVERLAY;
+    case HB_PAINT_COMPOSITE_MODE_DARKEN: return CAIRO_OPERATOR_DARKEN;
+    case HB_PAINT_COMPOSITE_MODE_LIGHTEN: return CAIRO_OPERATOR_LIGHTEN;
+    case HB_PAINT_COMPOSITE_MODE_COLOR_DODGE: return CAIRO_OPERATOR_COLOR_DODGE;
+    case HB_PAINT_COMPOSITE_MODE_COLOR_BURN: return CAIRO_OPERATOR_COLOR_BURN;
+    case HB_PAINT_COMPOSITE_MODE_HARD_LIGHT: return CAIRO_OPERATOR_HARD_LIGHT;
+    case HB_PAINT_COMPOSITE_MODE_SOFT_LIGHT: return CAIRO_OPERATOR_SOFT_LIGHT;
+    case HB_PAINT_COMPOSITE_MODE_DIFFERENCE: return CAIRO_OPERATOR_DIFFERENCE;
+    case HB_PAINT_COMPOSITE_MODE_EXCLUSION: return CAIRO_OPERATOR_EXCLUSION;
+    case HB_PAINT_COMPOSITE_MODE_MULTIPLY: return CAIRO_OPERATOR_MULTIPLY;
+    case HB_PAINT_COMPOSITE_MODE_HSL_HUE: return CAIRO_OPERATOR_HSL_HUE;
+    case HB_PAINT_COMPOSITE_MODE_HSL_SATURATION: return CAIRO_OPERATOR_HSL_SATURATION;
+    case HB_PAINT_COMPOSITE_MODE_HSL_COLOR: return CAIRO_OPERATOR_HSL_COLOR;
+    case HB_PAINT_COMPOSITE_MODE_HSL_LUMINOSITY: return CAIRO_OPERATOR_HSL_LUMINOSITY;
+    default:;
+    }
+
+  return CAIRO_OPERATOR_SOURCE;
+}
+
+static cairo_extend_t
+cairo_extend (hb_paint_extend_t extend)
+{
+  switch (extend)
+    {
+    case HB_PAINT_EXTEND_PAD: return CAIRO_EXTEND_PAD;
+    case HB_PAINT_EXTEND_REPEAT: return CAIRO_EXTEND_REPEAT;
+    case HB_PAINT_EXTEND_REFLECT: return CAIRO_EXTEND_REFLECT;
+    default:;
+    }
+
+  return CAIRO_EXTEND_PAD;
+}
+
 static void
 push_transform (hb_paint_funcs_t *funcs,
                 void *paint_data,
@@ -34,7 +133,14 @@ push_transform (hb_paint_funcs_t *funcs,
                 void *user_data)
 {
   paint_data_t *data = user_data;
+  cairo_matrix_t m;
+
   print (data, "start transform %f %f %f %f %f %f", xx, yx, xy, yy, dx, dy);
+
+  cairo_save (data->cr);
+  cairo_matrix_init (&m, xx, yx, xy, yy, dx, dy);
+  cairo_transform (data->cr, &m);
+
   data->level++;
 }
 
@@ -44,10 +150,59 @@ pop_transform (hb_paint_funcs_t *funcs,
                void *user_data)
 {
   paint_data_t *data = user_data;
+
   data->level--;
+
+  cairo_restore (data->cr);
+
   print (data, "end transform");
 }
 
+static void
+move_to (hb_draw_funcs_t *funcs, void *draw_data,
+         hb_draw_state_t *st,
+         float x, float y,
+         void *user_data)
+{
+  paint_data_t *data = user_data;
+
+  cairo_move_to (data->cr, x, y);
+}
+
+static void
+line_to (hb_draw_funcs_t *funcs, void *draw_data,
+         hb_draw_state_t *st,
+         float x, float y,
+         void *user_data)
+{
+  paint_data_t *data = user_data;
+
+  cairo_line_to (data->cr, x, y);
+}
+
+static void
+cubic_to (hb_draw_funcs_t *funcs, void *draw_data,
+          hb_draw_state_t *st,
+          float c1x, float c1y,
+          float c2x, float c2y,
+          float x, float y,
+          void *user_data)
+{
+  paint_data_t *data = user_data;
+
+  cairo_curve_to (data->cr, c1x, c1y, c2x, c2y, x, y);
+}
+
+static void
+close_path (hb_draw_funcs_t *funcs, void *draw_data,
+            hb_draw_state_t *st,
+            void *user_data)
+{
+  paint_data_t *data = user_data;
+
+  cairo_close_path (data->cr);
+}
+
 static void
 push_clip_glyph (hb_paint_funcs_t *funcs,
                  void *paint_data,
@@ -55,8 +210,26 @@ push_clip_glyph (hb_paint_funcs_t *funcs,
                  void *user_data)
 {
   paint_data_t *data = user_data;
+  hb_draw_funcs_t *dfuncs;
   print (data, "start clip glyph %u", glyph);
   data->level++;
+
+  cairo_save (data->cr);
+
+  dfuncs = hb_draw_funcs_create ();
+  hb_draw_funcs_set_move_to_func (dfuncs, move_to, data, NULL);
+  hb_draw_funcs_set_line_to_func (dfuncs, line_to, data, NULL);
+  hb_draw_funcs_set_cubic_to_func (dfuncs, cubic_to, data, NULL);
+  hb_draw_funcs_set_close_path_func (dfuncs, close_path, data, NULL);
+
+  cairo_new_path (data->cr);
+
+  hb_font_get_glyph_shape (data->font, glyph, dfuncs, data);
+  cairo_close_path (data->cr);
+
+  cairo_clip (data->cr);
+
+  hb_draw_funcs_destroy (dfuncs);
 }
 
 static void
@@ -66,8 +239,15 @@ push_clip_rect (hb_paint_funcs_t *funcs,
                 void *user_data)
 {
   paint_data_t *data = user_data;
+
   print (data, "start clip rect %f %f %f %f", xmin, ymin, xmax, ymax);
   data->level++;
+
+  cairo_save (data->cr);
+
+  cairo_rectangle (data->cr, xmin, ymin, xmax - xmin, ymax - ymin);
+
+  cairo_clip (data->cr);
 }
 
 static void
@@ -76,6 +256,9 @@ pop_clip (hb_paint_funcs_t *funcs,
           void *user_data)
 {
   paint_data_t *data = user_data;
+
+  cairo_restore (data->cr);
+
   data->level--;
   print (data, "end clip");
 }
@@ -88,7 +271,86 @@ solid (hb_paint_funcs_t *funcs,
        void *user_data)
 {
   paint_data_t *data = user_data;
+  color_t c;
+
   print (data, "solid %u %f", color_index, alpha);
+
+  get_color (data, color_index, alpha, &c);
+  cairo_set_source_rgba (data->cr, c.r, c.g, c.b, c.a);
+  cairo_paint (data->cr);
+}
+
+static void
+reduce_anchors (float x0, float y0,
+                float x1, float y1,
+                float x2, float y2,
+                float *xx0, float *yy0,
+                float *xx1, float *yy1)
+{
+  float q1x, q1y, q2x, q2y;
+  float s;
+  float k;
+
+  q2x = x2 - x0;
+  q2y = y2 - y0;
+  q1x = y1 - x0;
+  q1y = y1 - y0;
+
+  s = q2x * q2x + q2y * q2y;
+  if (s < 0.000001)
+    {
+      *xx0 = x0; *yy0 = y0;
+      *xx1 = x1; *yy1 = y1;
+      return;
+    }
+
+  k = (q2x * q1x + q2y * q1y) / s;
+  *xx0 = x0;
+  *yy0 = y0;
+  *xx1 = x1 - k * q2x;
+  *yy1 = y1 - k * q2y;
+}
+
+static int
+cmp_color_stop (const void *p1,
+                const void *p2)
+{
+  const hb_color_stop_t *c1 = p1;
+  const hb_color_stop_t *c2 = p2;
+
+  if (c1->offset < c2->offset)
+    return -1;
+  else if (c1->offset > c2->offset)
+    return 1;
+  else
+    return 0;
+}
+
+static void
+normalize_color_line (hb_color_stop_t *stops,
+                      unsigned int len,
+                      float *omin,
+                      float *omax)
+{
+  float min, max;
+
+  qsort (stops, len, sizeof (hb_color_stop_t), cmp_color_stop);
+
+  min = max = stops[0].offset;
+  for (unsigned int i = 0; i < len; i++)
+    {
+      min = MIN (min, stops[i].offset);
+      max = MAX (max, stops[i].offset);
+    }
+
+  if (min != max)
+    {
+      for (unsigned int i = 0; i < len; i++)
+        stops[i].offset = (stops[i].offset - min) / (max - min);
+    }
+
+  *omin = min;
+  *omax = max;
 }
 
 static void
@@ -103,6 +365,10 @@ linear_gradient (hb_paint_funcs_t *funcs,
   paint_data_t *data = user_data;
   unsigned int len;
   hb_color_stop_t *stops;
+  float xx0, yy0, xx1, yy1;
+  float xxx0, yyy0, xxx1, yyy1;
+  float min, max;
+  cairo_pattern_t *pattern;
 
   len = hb_color_line_get_color_stops (color_line, 0, NULL, NULL);
   stops = alloca (len * sizeof (hb_color_stop_t));
@@ -118,6 +384,28 @@ linear_gradient (hb_paint_funcs_t *funcs,
   for (unsigned int i = 0; i < len; i++)
     print (data, "%f %u %f", stops[i].offset, stops[i].color_index, stops[i].alpha);
   data->level -= 2;
+
+  reduce_anchors (x0, y0, x1, y1, x2, y2, &xx0, &yy0, &xx1, &yy1);
+  normalize_color_line (stops, len, &min, &max);
+
+  xxx0 = xx0 + min * (xx1 - xx0);
+  yyy0 = yy0 + min * (yy1 - yy0);
+  xxx1 = xx0 + max * (xx1 - xx0);
+  yyy1 = yy0 + max * (yy1 - yy0);
+
+  pattern = cairo_pattern_create_linear (xxx0, yyy0, xxx1, yyy1);
+  cairo_pattern_set_extend (pattern, cairo_extend (hb_color_line_get_extend (color_line)));
+  for (unsigned int i = 0; i < len; i++)
+    {
+      color_t c;
+      get_color (data, stops[i].color_index, stops[i].alpha, &c);
+      cairo_pattern_add_color_stop_rgba (pattern, stops[i].offset, c.r, c.g, c.b, c.a);
+    }
+
+  cairo_set_source (data->cr, pattern);
+  cairo_paint (data->cr);
+
+  cairo_pattern_destroy (pattern);
 }
 
 static void
@@ -129,20 +417,478 @@ radial_gradient (hb_paint_funcs_t *funcs,
                  void *user_data)
 {
   paint_data_t *data = user_data;
+  unsigned int len;
+  hb_color_stop_t *stops;
+  cairo_extend_t extend;
+  float min, max;
+  float xx0, yy0, xx1, yy1;
+  float rr0, rr1;
+  cairo_pattern_t *pattern;
+
   print (data, "radial gradient");
+
+  len = hb_color_line_get_color_stops (color_line, 0, NULL, NULL);
+  stops = alloca (len * sizeof (hb_color_stop_t));
+  hb_color_line_get_color_stops (color_line, 0, &len, stops);
+
+  extend = cairo_extend (hb_color_line_get_extend (color_line));
+
+  normalize_color_line (stops, len, &min, &max);
+  xx0 = x0 + min * (x1 - x0);
+  yy0 = y0 + min * (y1 - y0);
+  xx1 = x0 + max * (x1 - x0);
+  yy1 = y0 + max * (y1 - y0);
+  rr0 = r0 + min * (r1 - r0);
+  rr1 = r0 + max * (r1 - r0);
+
+  pattern = cairo_pattern_create_radial (xx0, yy0, rr0, xx1, yy1, rr1);
+  cairo_pattern_set_extend (pattern, extend);
+
+  for (unsigned int i = 0; i < len; i++)
+    {
+      color_t c;
+
+      get_color (data, stops[i].color_index, stops[i].alpha, &c);
+      cairo_pattern_add_color_stop_rgba (pattern, stops[i].offset, c.r, c.g, c.b, c.a);
+    }
+
+  cairo_set_source (data->cr, pattern);
+  cairo_paint (data->cr);
+
+  cairo_pattern_destroy (pattern);
+}
+
+typedef struct {
+  float x, y;
+} Point;
+
+static inline float
+interpolate (float f0, float f1, float f)
+{
+  return f0 + f * (f1 - f0);
+}
+
+static inline void
+interpolate_points (Point *p0, Point *p1, float f, Point *out)
+{
+  out->x = interpolate (p0->x, p1->x, f);
+  out->y = interpolate (p0->y, p1->y, f);
+}
+
+void
+interpolate_colors (color_t *c0, color_t *c1, float k, color_t *c)
+{
+  c->r = c0->r + k * (c1->r - c0->r);
+  c->g = c0->g + k * (c1->g - c0->g);
+  c->b = c0->b + k * (c1->b - c0->b);
+  c->a = c0->a + k * (c1->a - c0->a);
+}
+
+static inline float
+dot (Point p, Point q)
+{
+  return p.x * q.x + p.y * q.y;
+}
+
+static inline Point
+normalize (Point p)
+{
+  float len = sqrt (dot (p, p));
+
+  return (Point) { p.x / len, p.y / len };
+}
+
+static inline Point
+sum (Point p, Point q)
+{
+  return (Point) { p.x + q.x, p.y + q.y };
+}
+
+static inline Point
+difference (Point p, Point q)
+{
+  return (Point) { p.x - q.x, p.y - q.y };
+}
+
+static inline Point
+scale (Point p, float f)
+{
+  return (Point) { p.x * f, p.y * f };
+}
+
+typedef struct {
+  Point center, p0, c0, c1, p1;
+  color_t color0, color1;
+} Patch;
+
+static void
+add_patch (cairo_pattern_t *pattern, Point *center, Patch *p)
+{
+  cairo_mesh_pattern_begin_patch (pattern);
+  cairo_mesh_pattern_move_to (pattern, center->x, center->y);
+  cairo_mesh_pattern_line_to (pattern, p->p0.x, p->p0.y);
+  cairo_mesh_pattern_curve_to (pattern,
+                               p->c0.x, p->c0.y,
+                               p->c1.x, p->c1.y,
+                               p->p1.x, p->p1.y);
+  cairo_mesh_pattern_line_to (pattern, center->x, center->y);
+  cairo_mesh_pattern_set_corner_color_rgba (pattern, 0,
+                                            p->color0.r,
+                                            p->color0.g,
+                                            p->color0.b,
+                                            p->color0.a);
+  cairo_mesh_pattern_set_corner_color_rgba (pattern, 1,
+                                            p->color0.r,
+                                            p->color0.g,
+                                            p->color0.b,
+                                            p->color0.a);
+  cairo_mesh_pattern_set_corner_color_rgba (pattern, 2,
+                                            p->color1.r,
+                                            p->color1.g,
+                                            p->color1.b,
+                                            p->color1.a);
+  cairo_mesh_pattern_set_corner_color_rgba (pattern, 3,
+                                            p->color1.r,
+                                            p->color1.g,
+                                            p->color1.b,
+                                            p->color1.a);
+  cairo_mesh_pattern_end_patch (pattern);
+}
+
+#define MAX_ANGLE (M_PI / 8.)
+
+static void
+add_sweep_gradient_patches1 (float cx, float cy, float radius,
+                             float a0, color_t *c0,
+                             float a1, color_t *c1,
+                             cairo_pattern_t *pattern)
+{
+  Point center = (Point) { cx, cy };
+  int num_splits;
+  Point p0;
+  color_t color0, color1;
+
+  num_splits = ceilf (fabs (a1 - a0) / MAX_ANGLE);
+  p0 = (Point) { cosf (a0), sinf (a0) };
+  color0 = *c0;
+
+  for (int a = 0; a < num_splits; a++)
+    {
+      float k = (a + 1.) / num_splits;
+      float angle1;
+      Point p1;
+      Point A, U;
+      Point C0, C1;
+      Patch patch;
+
+      angle1 = interpolate (a0, a1, k);
+      interpolate_colors (c0, c1, k, &color1);
+
+      patch.color0 = color0;
+      patch.color1 = color1;
+
+      p1 = (Point) { cosf (angle1), sinf (angle1) };
+      patch.p0 = sum (center, scale (p0, radius));
+      patch.p1 = sum (center, scale (p1, radius));
+
+      A = normalize (sum (p0, p1));
+      U = (Point) { -A.y, A.x };
+      C0 = sum (A, scale (U, dot (difference (p0, A), p0) / dot (U, p0)));
+      C1 = sum (A, scale (U, dot (difference (p1, A), p1) / dot (U, p1)));
+
+      patch.c0 = sum (center, scale (sum (C0, scale (difference (C0, p0), 0.33333)), radius));
+      patch.c1 = sum (center, scale (sum (C1, scale (difference (C1, p1), 0.33333)), radius));
+
+      add_patch (pattern, &center, &patch);
+
+      p0 = p1;
+      color0 = color1;
+    }
+}
+
+static void
+add_sweep_gradient_patches (paint_data_t *data,
+                            hb_color_stop_t *stops,
+                            unsigned int n_stops,
+                            cairo_extend_t extend,
+                            float cx, float cy,
+                            float radius,
+                            float start_angle,
+                            float end_angle,
+                            cairo_pattern_t *pattern)
+{
+  float *angles;
+  color_t *colors;
+  color_t color0, color1;
+
+  if (start_angle == end_angle)
+    {
+      if (extend == CAIRO_EXTEND_PAD)
+        {
+          color_t c;
+          if (start_angle > 0)
+            {
+              get_color (data, stops[0].color_index, stops[0].alpha, &c);
+              add_sweep_gradient_patches1 (cx, cy, radius,
+                                           0.,          &c,
+                                           start_angle, &c,
+                                           pattern);
+            }
+          if (end_angle < 2 * M_PI)
+            {
+              get_color (data, stops[n_stops - 1].color_index, stops[n_stops - 1].alpha, &c);
+              add_sweep_gradient_patches1 (cx, cy, radius,
+                                           end_angle, &c,
+                                           2 * M_PI,  &c,
+                                           pattern);
+            }
+        }
+      return;
+    }
+
+  assert (start_angle != end_angle);
+
+  /* handle directions */
+  if (end_angle < start_angle)
+    {
+      float angle = end_angle;
+      end_angle = start_angle;
+      start_angle = angle;
+
+      for (int i = 0; i < n_stops - 1 - i; i++)
+        {
+          hb_color_stop_t stop = stops[i];
+          stops[i] = stops[n_stops - 1 - i];
+          stops[n_stops - 1 - i] = stop;
+        }
+    }
+
+  angles = alloca (sizeof (float) * n_stops);
+  colors = alloca (sizeof (color_t) * n_stops);
+
+  for (int i = 0; i < n_stops; i++)
+    {
+      angles[i] = start_angle + stops[i].offset * (end_angle - start_angle);
+      get_color (data, stops[i].color_index, stops[i].alpha, &colors[i]);
+    }
+
+  if (extend == CAIRO_EXTEND_PAD)
+    {
+      int pos;
+
+      color0 = colors[0];
+      for (pos = 0; pos < n_stops; pos++)
+        {
+          if (angles[pos] >= 0)
+            {
+              if (pos > 0)
+                {
+                  float k = (0 - angles[pos - 1]) / (angles[pos] - angles[pos - 1]);
+                  interpolate_colors (&colors[pos-1], &colors[pos], k, &color0);
+                }
+              break;
+            }
+        }
+      if (pos == n_stops)
+        {
+          /* everything is below 0 */
+          color0 = colors[n_stops-1];
+          add_sweep_gradient_patches1 (cx, cy, radius,
+                                       0.,       &color0,
+                                       2 * M_PI, &color0,
+                                       pattern);
+          return;
+        }
+
+      add_sweep_gradient_patches1 (cx, cy, radius,
+                                   0.,          &color0,
+                                   angles[pos], &colors[pos],
+                                   pattern);
+
+      for (pos++; pos < n_stops; pos++)
+        {
+          if (angles[pos] <= 2 * M_PI)
+            {
+              add_sweep_gradient_patches1 (cx, cy, radius,
+                                           angles[pos - 1], &colors[pos-1],
+                                           angles[pos],     &colors[pos],
+                                           pattern);
+            }
+          else
+            {
+              float k = (2 * M_PI - angles[pos - 1]) / (angles[pos] - angles[pos - 1]);
+              interpolate_colors (&colors[pos - 1], &colors[pos], k, &color1);
+              add_sweep_gradient_patches1 (cx, cy, radius,
+                                           angles[pos - 1], &colors[pos - 1],
+                                           2 * M_PI,        &color1,
+                                           pattern);
+              break;
+            }
+        }
+
+      if (pos == n_stops)
+        {
+          /* everything is below 2*M_PI */
+          color0 = colors[n_stops - 1];
+          add_sweep_gradient_patches1 (cx, cy, radius,
+                                       angles[n_stops - 1], &color0,
+                                       2 * M_PI,            &color0,
+                                       pattern);
+          return;
+        }
+    }
+  else
+    {
+      int k;
+      float span;
+
+      span = angles[n_stops - 1] - angles[0];
+      k = 0;
+      if (angles[0] >= 0)
+        {
+          float ss = angles[0];
+          while (ss > 0)
+            {
+              if (span > 0)
+                {
+                  ss -= span;
+                  k--;
+                }
+              else
+                {
+                  ss += span;
+                  k++;
+                }
+            }
+        }
+      else if (angles[0] < 0)
+        {
+          float ee = angles[n_stops - 1];
+          while (ee < 0)
+            {
+              if (span > 0)
+                {
+                  ee += span;
+                  k++;
+                }
+              else
+                {
+                  ee -= span;
+                  k--;
+                }
+            }
+        }
+
+      //assert (angles[0] + k * span <= 0 && 0 < angles[n_stops - 1] + k * span);
+
+     for (int l = k; TRUE; l++)
+        {
+          for (int i = 1; i < n_stops; i++)
+            {
+              float a0, a1;
+              color_t *c0, *c1;
+
+              if ((l % 2 != 0) && (extend == CAIRO_EXTEND_REFLECT))
+                {
+                  a0 = angles[0] + angles[n_stops - 1] - angles[n_stops - 1 - (i-1)] + l * span;
+                  a1 = angles[0] + angles[n_stops - 1] - angles[n_stops - 1 - i] + l * span;
+                  c0 = &colors[n_stops - 1 - (i - 1)];
+                  c1 = &colors[n_stops - 1 - i];
+                }
+              else
+                {
+                  a0 = angles[i-1] + l * span;
+                  a1 = angles[i] + l * span;
+                  c0 = &colors[i-1];
+                  c1 = &colors[i];
+                }
+
+              if (a1 < 0)
+                continue;
+              if (a0 < 0)
+                {
+                  color_t color;
+                  float f = (0 - a0)/(a1 - a0);
+                  interpolate_colors (c0, c1, f, &color);
+                  add_sweep_gradient_patches1 (cx, cy, radius,
+                                               0,  &color,
+                                               a1, c1,
+                                               pattern);
+                }
+              else if (a1 >= 2 * M_PI)
+                {
+                  color_t color;
+                  float f = (2 * M_PI - a0)/(a1 - a0);
+                  interpolate_colors (c0, c1, f, &color);
+                  add_sweep_gradient_patches1 (cx, cy, radius,
+                                               a0,       c0,
+                                               2 * M_PI, &color,
+                                               pattern);
+                  goto done;
+                }
+              else
+                {
+                  add_sweep_gradient_patches1 (cx, cy, radius,
+                                               a0, c0,
+                                               a1, c1,
+                                               pattern);
+                }
+            }
+        }
+done:
+    }
 }
 
 static void
 sweep_gradient (hb_paint_funcs_t *funcs,
                 void *paint_data,
                 hb_color_line_t *color_line,
-                float x0, float y0,
+                float cx, float cy,
                 float start_angle,
                 float end_angle,
                 void *user_data)
 {
   paint_data_t *data = user_data;
+  unsigned int len;
+  hb_color_stop_t *stops;
+  cairo_extend_t extend;
+  double x1, y1, x2, y2;
+  float max_x, max_y, radius;
+  cairo_pattern_t *pattern;
+
+  len = hb_color_line_get_color_stops (color_line, 0, NULL, NULL);
+  stops = alloca (len * sizeof (hb_color_stop_t));
+  hb_color_line_get_color_stops (color_line, 0, &len, stops);
+  qsort (stops, len, sizeof (hb_color_stop_t), cmp_color_stop);
+
   print (data, "sweep gradient");
+  data->level++;
+  print (data, "center %f %f", cx, cy);
+  print (data, "angles %f %f", start_angle, end_angle);
+
+  data->level += 1;
+  for (unsigned int i = 0; i < len; i++)
+    print (data, "%f %u %f", stops[i].offset, stops[i].color_index, stops[i].alpha);
+  data->level -= 2;
+
+  cairo_clip_extents (data->cr, &x1, &y1, &x2, &y2);
+  max_x = MAX ((x1 - cx) * (x1 - cx), (x2 - cx) * (x2 - cx));
+  max_y = MAX ((y1 - cy) * (y1 - cy), (y2 - cy) * (y2 - cy));
+  radius = sqrt (max_x + max_y);
+
+  extend = cairo_extend (hb_color_line_get_extend (color_line));
+
+  pattern = cairo_pattern_create_mesh ();
+
+  add_sweep_gradient_patches (data, stops, len, extend, cx, cy,
+                              radius, start_angle, end_angle, pattern);
+
+  cairo_set_source (data->cr, pattern);
+  cairo_paint (data->cr);
+
+  cairo_pattern_destroy (pattern);
+
+  data->level--;
 }
 
 static void
@@ -153,6 +899,9 @@ push_group (hb_paint_funcs_t *funcs,
   paint_data_t *data = user_data;
   print (data, "push group");
   data->level++;
+
+  cairo_save (data->cr);
+  cairo_push_group (data->cr);
 }
 
 static void
@@ -162,19 +911,64 @@ pop_group (hb_paint_funcs_t *funcs,
            void *user_data)
 {
   paint_data_t *data = user_data;
+
+  cairo_pop_group_to_source (data->cr);
+  cairo_set_operator (data->cr, to_operator (mode));
+  cairo_paint (data->cr);
+
+  cairo_restore (data->cr);
+
   data->level--;
   print (data, "pop group mode %d", mode);
 }
 
 int main (int argc, char *argv[])
 {
-  paint_data_t data = { 0 };
+  paint_data_t data;
   hb_paint_funcs_t *funcs;
   hb_blob_t *blob = hb_blob_create_from_file (argv[1]);
   hb_face_t *face = hb_face_create (blob, 0);
   hb_font_t *font = hb_font_create (face);
   hb_font_set_scale (font, 20, 20);
   hb_codepoint_t gid = atoi (argv[2]);
+  hb_glyph_extents_t extents;
+  cairo_surface_t *surface;
+  cairo_pattern_t *pattern;
+  cairo_matrix_t m;
+  float xmin, ymin, xmax, ymax;
+
+  float size = 120.;
+  int upem = hb_face_get_upem (hb_font_get_face (font));
+
+  hb_font_set_scale (font, size, size);
+  hb_font_get_glyph_extents (font, gid, &extents);
+  hb_font_set_scale (font, upem, upem);
+
+  xmin = extents.x_bearing;
+  xmax = xmin + extents.width;
+  ymin = - extents.y_bearing;
+  ymax = - extents.y_bearing - extents.height;
+
+  printf ("surface %f %f, offset %f %f\n", ceil (xmax - xmin), ceil (ymax - ymin), - xmin, - ymin);
+
+  surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
+                                        (int) ceil (xmax - xmin),
+                                        (int) ceil (ymax - ymin));
+
+  cairo_surface_set_device_offset (surface, - xmin, ymax);
+
+  data.level = 0;
+  data.cr = cairo_create (surface);
+  cairo_push_group (data.cr);
+
+  data.font = font;
+  data.foreground_color = HB_COLOR (0, 0, 0, 255);
+
+  data.num_colors = hb_ot_color_palette_get_colors (hb_font_get_face (font),
+                                                    0, 0, NULL, NULL);
+  data.colors = alloca (data.num_colors * sizeof (hb_color_t));
+  hb_ot_color_palette_get_colors (hb_font_get_face (font),
+                                  0, 0, &data.num_colors, data.colors);
 
   funcs = hb_paint_funcs_create ();
   hb_paint_funcs_set_push_transform_func (funcs, push_transform, &data, NULL);
@@ -189,7 +983,28 @@ int main (int argc, char *argv[])
   hb_paint_funcs_set_radial_gradient_func (funcs, radial_gradient, &data, NULL);
   hb_paint_funcs_set_sweep_gradient_func (funcs, sweep_gradient, &data, NULL);
 
+  cairo_save (data.cr);
+  cairo_scale (data.cr, size/upem, size/upem); // root transform
+
   hb_font_paint_glyph (font, gid, funcs, NULL);
 
+  cairo_restore (data.cr);
+
+  pattern = cairo_pop_group (data.cr);
+
+  cairo_matrix_init_scale (&m, 1, -1);
+  cairo_matrix_translate (&m, 0, (ymax - ymin) + 2 * ymin);
+  cairo_pattern_set_matrix (pattern, &m);
+  cairo_set_source (data.cr, pattern);
+
+  cairo_paint (data.cr);
+
+  cairo_surface_set_device_offset (surface, - xmin, - ymin);
+
+  printf ("writing glyph.png\n");
+  cairo_surface_write_to_png (surface, "glyph.png");
+
+  execvp ("eog", (char *const[]) { "eog", "glyph.png", NULL });
+
   return 0;
 }