[var] Implement hb_font_get_var_coords_design

Hold design coords and simulate when normalized coords are set directly.

docs/harfbuzz-sections.txt

@@ -346,6 +346,7 @@ hb_font_get_scale
 hb_font_get_user_data
 hb_font_get_variation_glyph
 hb_font_get_variation_glyph_func_t
+hb_font_get_var_coords_design
 hb_font_get_var_coords_normalized
 hb_font_glyph_from_string
 hb_font_glyph_to_string

src/hb-font.cc

@@ -33,6 +33,9 @@
 
 #include "hb-ot.h"
 
+#include "hb-ot-var-avar-table.hh"
+#include "hb-ot-var-fvar-table.hh"
+
 
 /**
  * SECTION:hb-font
@@ -1332,6 +1335,7 @@ DEFINE_NULL_INSTANCE (hb_font_t) =
 
   0, /* num_coords */
   nullptr, /* coords */
+  nullptr, /* design_coords */
 
   const_cast<hb_font_funcs_t *> (&_hb_Null_hb_font_funcs_t),
 
@@ -1383,6 +1387,20 @@ hb_font_create (hb_face_t *face)
   return font;
 }
 
+static void
+_hb_font_adopt_var_coords (hb_font_t *font,
+			   int *coords, /* 2.14 normalized */
+			   float *design_coords,
+			   unsigned int coords_length)
+{
+  free (font->coords);
+  free (font->design_coords);
+
+  font->coords = coords;
+  font->design_coords = design_coords;
+  font->num_coords = coords_length;
+}
+
 /**
  * hb_font_create_sub_font:
  * @parent: parent font.
@@ -1413,15 +1431,22 @@ hb_font_create_sub_font (hb_font_t *parent)
   font->y_ppem = parent->y_ppem;
   font->ptem = parent->ptem;
 
-  font->num_coords = parent->num_coords;
-  if (font->num_coords)
+  unsigned int num_coords = parent->num_coords;
+  if (num_coords)
   {
-    unsigned int size = parent->num_coords * sizeof (parent->coords[0]);
-    font->coords = (int *) malloc (size);
-    if (unlikely (!font->coords))
-      font->num_coords = 0;
+    int *coords = (int *) calloc (num_coords, sizeof (parent->coords[0]));
+    float *design_coords = (float *) calloc (num_coords, sizeof (parent->design_coords[0]));
+    if (likely (coords && design_coords))
+    {
+      memcpy (coords, parent->coords, num_coords * sizeof (parent->coords[0]));
+      memcpy (design_coords, parent->design_coords, num_coords * sizeof (parent->design_coords[0]));
+      _hb_font_adopt_var_coords (font, coords, design_coords, num_coords);
+    }
     else
-      memcpy (font->coords, parent->coords, size);
+    {
+      free (coords);
+      free (design_coords);
+    }
   }
 
   return font;
@@ -1481,6 +1506,7 @@ hb_font_destroy (hb_font_t *font)
   hb_font_funcs_destroy (font->klass);
 
   free (font->coords);
+  free (font->design_coords);
 
   free (font);
 }
@@ -1842,17 +1868,6 @@ hb_font_get_ptem (hb_font_t *font)
  * Variations
  */
 
-static void
-_hb_font_adopt_var_coords_normalized (hb_font_t *font,
-				      int *coords, /* 2.14 normalized */
-				      unsigned int coords_length)
-{
-  free (font->coords);
-
-  font->coords = coords;
-  font->num_coords = coords_length;
-}
-
 /**
  * hb_font_set_variations:
  *
@@ -1875,13 +1890,27 @@ hb_font_set_variations (hb_font_t *font,
   unsigned int coords_length = hb_ot_var_get_axis_count (font->face);
 
   int *normalized = coords_length ? (int *) calloc (coords_length, sizeof (int)) : nullptr;
-  if (unlikely (coords_length && !normalized))
+  float *design_coords = coords_length ? (float *) calloc (coords_length, sizeof (float)) : nullptr;
+
+  if (unlikely (coords_length && !(normalized && design_coords)))
+  {
+    free (normalized);
+    free (design_coords);
     return;
+  }
+
+  for (unsigned int i = 0; i < variations_length; i++)
+  {
+    hb_ot_var_axis_info_t info;
+    if (hb_ot_var_find_axis_info (font->face, variations[i].tag, &info) &&
+	info.axis_index < coords_length)
+      design_coords[info.axis_index] = variations[i].value;
+  }
 
   hb_ot_var_normalize_variations (font->face,
 				  variations, variations_length,
 				  normalized, coords_length);
-  _hb_font_adopt_var_coords_normalized (font, normalized, coords_length);
+  _hb_font_adopt_var_coords (font, normalized, design_coords, coords_length);
 }
 
 /**
@@ -1898,11 +1927,20 @@ hb_font_set_var_coords_design (hb_font_t *font,
     return;
 
   int *normalized = coords_length ? (int *) calloc (coords_length, sizeof (int)) : nullptr;
-  if (unlikely (coords_length && !normalized))
+  float *design_coords = coords_length ? (float *) calloc (coords_length, sizeof (float)) : nullptr;
+
+  if (unlikely (coords_length && !(normalized && design_coords)))
+  {
+    free (normalized);
+    free (design_coords);
     return;
+  }
+
+  if (coords_length)
+    memcpy (design_coords, coords, font->num_coords * sizeof (font->design_coords[0]));
 
   hb_ot_var_normalize_coords (font->face, coords_length, coords, normalized);
-  _hb_font_adopt_var_coords_normalized (font, normalized, coords_length);
+  _hb_font_adopt_var_coords (font, normalized, design_coords, coords_length);
 }
 
 /**
@@ -1946,13 +1984,30 @@ hb_font_set_var_coords_normalized (hb_font_t *font,
     return;
 
   int *copy = coords_length ? (int *) calloc (coords_length, sizeof (coords[0])) : nullptr;
-  if (unlikely (coords_length && !copy))
+  int *unmapped = coords_length ? (int *) calloc (coords_length, sizeof (coords[0])) : nullptr;
+  float *design_coords = coords_length ? (float *) calloc (coords_length, sizeof (design_coords[0])) : nullptr;
+
+  if (unlikely (coords_length && !(copy && unmapped && design_coords)))
+  {
+    free (copy);
+    free (unmapped);
+    free (design_coords);
     return;
+  }
 
   if (coords_length)
+  {
     memcpy (copy, coords, coords_length * sizeof (coords[0]));
+    memcpy (unmapped, coords, coords_length * sizeof (coords[0]));
+  }
+
+  /* Best effort design coords simulation */
+  font->face->table.avar->unmap_coords (unmapped, coords_length);
+  for (unsigned int i = 0; i < coords_length; ++i)
+    design_coords[i] = font->face->table.fvar->unnormalize_axis_value (i, unmapped[i]);
+  free (unmapped);
 
-  _hb_font_adopt_var_coords_normalized (font, copy, coords_length);
+  _hb_font_adopt_var_coords (font, copy, design_coords, coords_length);
 }
 
 /**
@@ -1972,6 +2027,24 @@ hb_font_get_var_coords_normalized (hb_font_t *font,
 
   return font->coords;
 }
+
+/**
+ * hb_font_get_var_coords_design:
+ *
+ * Return value is valid as long as variation coordinates of the font
+ * are not modified.
+ *
+ * Since: REPLACEME
+ */
+const float *
+hb_font_get_var_coords_design (hb_font_t *font,
+			       unsigned int *length)
+{
+  if (length)
+    *length = font->num_coords;
+
+  return font->design_coords;
+}
 #endif
 
 #ifndef HB_DISABLE_DEPRECATED

src/hb-font.h

@@ -705,6 +705,10 @@ hb_font_set_var_coords_design (hb_font_t *font,
 			       const float *coords,
 			       unsigned int coords_length);
 
+HB_EXTERN const float *
+hb_font_get_var_coords_design (hb_font_t *font,
+			       unsigned int *length);
+
 HB_EXTERN void
 hb_font_set_var_coords_normalized (hb_font_t *font,
 				   const int *coords, /* 2.14 normalized */

src/hb-font.hh

@@ -120,6 +120,7 @@ struct hb_font_t
   /* Font variation coordinates. */
   unsigned int num_coords;
   int *coords;
+  float *design_coords;
 
   hb_font_funcs_t   *klass;
   void              *user_data;

test/api/Makefile.am

@@ -61,6 +61,7 @@ TEST_PROGS = \
 	test-subset-colr \
 	test-subset-cbdt \
 	test-unicode \
+	test-var-coords \
 	test-version \
 	test-subset-nameids \
 	$(NULL)

test/api/test-var-coords.c

@@ -0,0 +1,76 @@
+/*
+ * Copyright © 2019  Ebrahim Byagowi
+ *
+ *  This is part of HarfBuzz, a text shaping library.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and its documentation for any purpose, provided that the
+ * above copyright notice and the following two paragraphs appear in
+ * all copies of this software.
+ *
+ * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
+ * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
+ * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
+ * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
+ * DAMAGE.
+ *
+ * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
+ * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
+ * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
+ * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
+ */
+
+#include "hb-test.h"
+
+#include <hb-ot.h>
+
+/* Unit tests for hb_font_[gs]et_var_coords_ */
+
+#ifndef G_APPROX_VALUE
+#define G_APPROX_VALUE(a, b, epsilon) \
+  (((a) > (b) ? (a) - (b) : (b) - (a)) < (epsilon))
+#endif
+
+#define EPSILON 0.05f
+
+static void
+test_get_var_coords (void)
+{
+  hb_face_t *face = hb_test_open_font_file ("fonts/TestCFF2VF.otf");
+  hb_font_t *font = hb_font_create (face);
+
+  /* Normalized coords as input */
+  int normalized_coords[] = {100, 0};
+  hb_font_set_var_coords_normalized (font, normalized_coords, 2);
+  g_assert_cmpint ((int) hb_font_get_var_coords_design (font, NULL)[0], ==, 403);
+  g_assert_cmpint ((int) hb_font_get_var_coords_normalized (font, NULL)[0], ==, 100);
+
+  /* Design coords as input */
+  float design_coords[] = {206.f, 0};
+  hb_font_set_var_coords_design (font, design_coords, 2);
+  g_assert_cmpint ((int) hb_font_get_var_coords_normalized (font, NULL)[0], ==, -16117);
+  g_assert_cmpint ((int) hb_font_get_var_coords_design (font, NULL)[0], ==, 206);
+
+  for (float weight = 200; weight < 901; ++weight)
+  {
+    int normalized;
+    hb_ot_var_normalize_coords (face, 1, &weight, &normalized);
+    hb_font_set_var_coords_normalized (font, &normalized, 1);
+    float converted_back = hb_font_get_var_coords_design (font, NULL)[0];
+    // fprintf (stderr, "%f: %d => %f\n", weight, normalized, converted_back);
+    g_assert_true (G_APPROX_VALUE (converted_back, weight, EPSILON));
+  }
+
+  hb_font_destroy (font);
+  hb_face_destroy (face);
+}
+
+int
+main (int argc, char **argv)
+{
+  hb_test_init (&argc, &argv);
+  hb_test_add (test_get_var_coords);
+  return hb_test_run ();
+}