1 files changed, 246 insertions, 0 deletions
diff --git a/src/3rdparty/harfbuzz-ng/src/hb-shape.cc b/src/3rdparty/harfbuzz-ng/src/hb-shape.cc
index 7b5bf2c5ef..844f7b9e80 100644
--- a/src/3rdparty/harfbuzz-ng/src/hb-shape.cc
+++ b/src/3rdparty/harfbuzz-ng/src/hb-shape.cc
@@ -196,4 +196,250 @@ hb_shape (hb_font_t           *font,
 }
 
 
+#ifdef HB_EXPERIMENTAL_API
+
+static float
+buffer_advance (hb_buffer_t *buffer)
+{
+  float a = 0;
+  auto *pos = buffer->pos;
+  unsigned count = buffer->len;
+  if (HB_DIRECTION_IS_HORIZONTAL (buffer->props.direction))
+    for (unsigned i = 0; i < count; i++)
+      a += pos[i].x_advance;
+  else
+    for (unsigned i = 0; i < count; i++)
+      a += pos[i].y_advance;
+  return a;
+}
+
+static void
+reset_buffer (hb_buffer_t *buffer,
+	      hb_array_t<const hb_glyph_info_t> text)
+{
+  assert (buffer->ensure (text.length));
+  buffer->have_positions = false;
+  buffer->len = text.length;
+  hb_memcpy (buffer->info, text.arrayZ, text.length * sizeof (buffer->info[0]));
+  hb_buffer_set_content_type (buffer, HB_BUFFER_CONTENT_TYPE_UNICODE);
+}
+
+/**
+ * hb_shape_justify:
+ * @font: a mutable #hb_font_t to use for shaping
+ * @buffer: an #hb_buffer_t to shape
+ * @features: (array length=num_features) (nullable): an array of user
+ *    specified #hb_feature_t or `NULL`
+ * @num_features: the length of @features array
+ * @shaper_list: (array zero-terminated=1) (nullable): a `NULL`-terminated
+ *    array of shapers to use or `NULL`
+ * @min_target_advance: Minimum advance width/height to aim for.
+ * @max_target_advance: Maximum advance width/height to aim for.
+ * @advance: (inout): Input/output advance width/height of the buffer.
+ * @var_tag: (out): Variation-axis tag used for justification.
+ * @var_value: (out): Variation-axis value used to reach target justification.
+ *
+ * See hb_shape_full() for basic details. If @shaper_list is not `NULL`, the specified
+ * shapers will be used in the given order, otherwise the default shapers list
+ * will be used.
+ *
+ * In addition, justify the shaping results such that the shaping results reach
+ * the target advance width/height, depending on the buffer direction.
+ *
+ * If the advance of the buffer shaped with hb_shape_full() is already known,
+ * put that in *advance. Otherwise set *advance to zero.
+ *
+ * This API is currently experimental and will probably change in the future.
+ *
+ * Return value: false if all shapers failed, true otherwise
+ *
+ * XSince: EXPERIMENTAL
+ **/
+hb_bool_t
+hb_shape_justify (hb_font_t          *font,
+		  hb_buffer_t        *buffer,
+		  const hb_feature_t *features,
+		  unsigned int        num_features,
+		  const char * const *shaper_list,
+		  float               min_target_advance,
+		  float               max_target_advance,
+		  float              *advance, /* IN/OUT */
+		  hb_tag_t           *var_tag, /* OUT */
+		  float              *var_value /* OUT */)
+{
+  // TODO Negative font scales?
+
+  /* If default advance already matches target, nothing to do. Shape and return. */
+  if (min_target_advance <= *advance && *advance <= max_target_advance)
+  {
+    *var_tag = HB_TAG_NONE;
+    *var_value = 0.0f;
+    return hb_shape_full (font, buffer,
+			  features, num_features,
+			  shaper_list);
+  }
+
+  hb_face_t *face = font->face;
+
+  /* Choose variation tag to use for justification. */
+
+  hb_tag_t tag = HB_TAG_NONE;
+  hb_ot_var_axis_info_t axis_info;
+
+  hb_tag_t tags[] =
+  {
+    HB_TAG ('j','s','t','f'),
+    HB_TAG ('w','d','t','h'),
+  };
+  for (unsigned i = 0; i < ARRAY_LENGTH (tags); i++)
+    if (hb_ot_var_find_axis_info (face, tags[i], &axis_info))
+    {
+      tag = *var_tag = tags[i];
+      break;
+    }
+
+  /* If no suitable variation axis found, can't justify.  Just shape and return. */
+  if (!tag)
+  {
+    *var_tag = HB_TAG_NONE;
+    *var_value = 0.0f;
+    if (hb_shape_full (font, buffer,
+		       features, num_features,
+		       shaper_list))
+    {
+      *advance = buffer_advance (buffer);
+      return true;
+    }
+    else
+      return false;
+  }
+
+  /* Copy buffer text as we need it so we can shape multiple times. */
+  unsigned text_len = buffer->len;
+  auto *text_info = (hb_glyph_info_t *) hb_malloc (text_len * sizeof (buffer->info[0]));
+  if (unlikely (text_len && !text_info))
+    return false;
+  hb_memcpy (text_info, buffer->info, text_len * sizeof (buffer->info[0]));
+  auto text = hb_array<const hb_glyph_info_t> (text_info, text_len);
+
+  /* If default advance was not provided to us, calculate it. */
+  if (!*advance)
+  {
+    hb_font_set_variation (font, tag, axis_info.default_value);
+    if (!hb_shape_full (font, buffer,
+			features, num_features,
+			shaper_list))
+      return false;
+    *advance = buffer_advance (buffer);
+  }
+
+  /* If default advance already matches target, nothing to do. Shape and return.
+   * Do this again, in case advance was just calculated.
+   */
+  if (min_target_advance <= *advance && *advance <= max_target_advance)
+  {
+    *var_tag = HB_TAG_NONE;
+    *var_value = 0.0f;
+    return true;
+  }
+
+  /* Prepare for running the solver. */
+  double a, b, ya, yb;
+  if (*advance < min_target_advance)
+  {
+    /* Need to expand. */
+    ya = (double) *advance;
+    a = (double) axis_info.default_value;
+    b = (double) axis_info.max_value;
+
+    /* Shape buffer for maximum expansion to use as other
+     * starting point for the solver. */
+    hb_font_set_variation (font, tag, (float) b);
+    reset_buffer (buffer, text);
+    if (!hb_shape_full (font, buffer,
+			features, num_features,
+			shaper_list))
+      return false;
+    yb = (double) buffer_advance (buffer);
+    /* If the maximum expansion is less than max target,
+     * there's nothing to solve for. Just return it. */
+    if (yb <= (double) max_target_advance)
+    {
+      *var_value = (float) b;
+      *advance = (float) yb;
+      return true;
+    }
+  }
+  else
+  {
+    /* Need to shrink. */
+    yb = (double) *advance;
+    a = (double) axis_info.min_value;
+    b = (double) axis_info.default_value;
+
+    /* Shape buffer for maximum shrinkate to use as other
+     * starting point for the solver. */
+    hb_font_set_variation (font, tag, (float) a);
+    reset_buffer (buffer, text);
+    if (!hb_shape_full (font, buffer,
+			features, num_features,
+			shaper_list))
+      return false;
+    ya = (double) buffer_advance (buffer);
+    /* If the maximum shrinkate is more than min target,
+     * there's nothing to solve for. Just return it. */
+    if (ya >= (double) min_target_advance)
+    {
+      *var_value = (float) a;
+      *advance = (float) ya;
+      return true;
+    }
+  }
+
+  /* Run the solver to find a var axis value that hits
+   * the desired width. */
+
+  double epsilon = (b - a) / (1<<14);
+  bool failed = false;
+
+  auto f = [&] (double x)
+  {
+    hb_font_set_variation (font, tag, (float) x);
+    reset_buffer (buffer, text);
+    if (unlikely (!hb_shape_full (font, buffer,
+				  features, num_features,
+				  shaper_list)))
+    {
+      failed = true;
+      return (double) min_target_advance;
+    }
+
+    double w = (double) buffer_advance (buffer);
+    DEBUG_MSG (JUSTIFY, nullptr, "Trying '%c%c%c%c' axis parameter %f. Advance %g. Target: min %g max %g",
+	       HB_UNTAG (tag), x, w,
+	       (double) min_target_advance, (double) max_target_advance);
+    return w;
+  };
+
+  double y = 0;
+  double itp = solve_itp (f,
+			  a, b,
+			  epsilon,
+			  (double) min_target_advance, (double) max_target_advance,
+			  ya, yb, y);
+
+  hb_free (text_info);
+
+  if (failed)
+    return false;
+
+  *var_value = (float) itp;
+  *advance = (float) y;
+
+  return true;
+}
+
+#endif
+
+
 #endif