diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index b475bbae3..4cf1aeb32 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -780,6 +780,7 @@ hb_set_t
hb-shape
hb_shape
hb_shape_full
+hb_shape_justify
hb_shape_list_shapers
diff --git a/src/gen-def.py b/src/gen-def.py
index 9b4efd4f3..6011817bc 100755
--- a/src/gen-def.py
+++ b/src/gen-def.py
@@ -19,7 +19,8 @@ symbols = sorted (re.findall (r"^hb_\w+(?= \()", "\n".join (headers_content), re
if '--experimental-api' not in sys.argv:
# Move these to harfbuzz-sections.txt when got stable
experimental_symbols = \
-"""hb_subset_repack_or_fail
+"""hb_shape_justify
+hb_subset_repack_or_fail
hb_subset_input_override_name_table
""".splitlines ()
symbols = [x for x in symbols if x not in experimental_symbols]
diff --git a/src/hb-algs.hh b/src/hb-algs.hh
index 8c7ad434d..13587eac0 100644
--- a/src/hb-algs.hh
+++ b/src/hb-algs.hh
@@ -1344,4 +1344,62 @@ struct
HB_FUNCOBJ (hb_dec);
+/* Adapted from kurbo implementation with extra parameters added,
+ * and finding for a particular range instead of 0.
+ *
+ * For documentation and implementation see:
+ *
+ * [ITP method]: https://en.wikipedia.org/wiki/ITP_Method
+ * [An Enhancement of the Bisection Method Average Performance Preserving Minmax Optimality]: https://dl.acm.org/doi/10.1145/3423597
+ * https://docs.rs/kurbo/0.8.1/kurbo/common/fn.solve_itp.html
+ * https://github.com/linebender/kurbo/blob/fd839c25ea0c98576c7ce5789305822675a89938/src/common.rs#L162-L248
+ */
+template
+double solve_itp (func_t f,
+ double a, double b,
+ double epsilon,
+ double min_y, double max_y,
+ double &ya, double &yb, double &y)
+{
+ unsigned n1_2 = (unsigned) (hb_max (ceil (log2 ((b - a) / epsilon)) - 1.0, 0.0));
+ const unsigned n0 = 1; // Hardwired
+ const double k1 = 0.2 / (b - a); // Hardwired.
+ unsigned nmax = n0 + n1_2;
+ double scaled_epsilon = epsilon * double (1llu << nmax);
+ double _2_epsilon = 2.0 * epsilon;
+ while (b - a > _2_epsilon)
+ {
+ double x1_2 = 0.5 * (a + b);
+ double r = scaled_epsilon - 0.5 * (b - a);
+ double xf = (yb * a - ya * b) / (yb - ya);
+ double sigma = x1_2 - xf;
+ double b_a = b - a;
+ // This has k2 = 2 hardwired for efficiency.
+ double b_a_k2 = b_a * b_a;
+ double delta = k1 * b_a_k2;
+ int sigma_sign = sigma >= 0 ? +1 : -1;
+ double xt = delta <= fabs (x1_2 - xf) ? xf + delta * sigma_sign : x1_2;
+ double xitp = fabs (xt - x1_2) <= r ? xt : x1_2 - r * sigma_sign;
+ double yitp = f (xitp);
+ if (yitp > max_y)
+ {
+ b = xitp;
+ yb = yitp;
+ }
+ else if (yitp < min_y)
+ {
+ a = xitp;
+ ya = yitp;
+ }
+ else
+ {
+ y = yitp;
+ return xitp;
+ }
+ scaled_epsilon *= 0.5;
+ }
+ return 0.5 * (a + b);
+}
+
+
#endif /* HB_ALGS_HH */
diff --git a/src/hb-debug.hh b/src/hb-debug.hh
index efab37464..0ac4515fa 100644
--- a/src/hb-debug.hh
+++ b/src/hb-debug.hh
@@ -373,6 +373,10 @@ struct hb_no_trace_t {
#define HB_DEBUG_FT (HB_DEBUG+0)
#endif
+#ifndef HB_DEBUG_JUSTIFY
+#define HB_DEBUG_JUSTIFY (HB_DEBUG+0)
+#endif
+
#ifndef HB_DEBUG_OBJECT
#define HB_DEBUG_OBJECT (HB_DEBUG+0)
#endif
diff --git a/src/hb-shape.cc b/src/hb-shape.cc
index 7b5bf2c5e..13bda36f3 100644
--- a/src/hb-shape.cc
+++ b/src/hb-shape.cc
@@ -26,6 +26,8 @@
* Google Author(s): Behdad Esfahbod
*/
+#define HB_DEBUG_JUSTIFY 1
+
#include "hb.hh"
#include "hb-shaper.hh"
@@ -196,4 +198,212 @@ 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 text)
+{
+ assert (buffer->ensure (text.length));
+ buffer->have_positions = false;
+ buffer->len = text.length;
+ 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.
+ *
+ * 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 (min_target_advance <= *advance && *advance <= max_target_advance)
+ return hb_shape_full (font, buffer,
+ features, num_features,
+ shaper_list);
+
+ hb_face_t *face = font->face;
+
+ 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 (!tag)
+ {
+ if (hb_shape_full (font, buffer,
+ features, num_features,
+ shaper_list))
+ {
+ *advance = buffer_advance (buffer);
+ return true;
+ }
+ else
+ return false;
+ }
+
+ 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 (text_info, text_len);
+
+ 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 (min_target_advance <= *advance && *advance <= max_target_advance)
+ return true;
+
+ double a, b, ya, yb;
+ if (*advance < min_target_advance)
+ {
+ ya = *advance;
+ a = axis_info.default_value;
+ b = axis_info.max_value;
+
+ 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 = buffer_advance (buffer);
+ if (yb <= 0)
+ {
+ *advance = (float) yb;
+ return true;
+ }
+ }
+ else
+ {
+ yb = *advance;
+ a = axis_info.min_value;
+ b = axis_info.default_value;
+
+ 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 = buffer_advance (buffer);
+ if (ya >= 0)
+ {
+ *advance = (float) ya;
+ return true;
+ }
+ }
+
+ 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 = 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,
+ min_target_advance, 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
diff --git a/src/hb-shape.h b/src/hb-shape.h
index 922f8c011..d4d4fdfd2 100644
--- a/src/hb-shape.h
+++ b/src/hb-shape.h
@@ -53,6 +53,18 @@ hb_shape_full (hb_font_t *font,
unsigned int num_features,
const char * const *shaper_list);
+HB_EXTERN 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 */);
+
HB_EXTERN const char **
hb_shape_list_shapers (void);
diff --git a/util/shape-options.hh b/util/shape-options.hh
index b4d9b2c00..b22b95883 100644
--- a/util/shape-options.hh
+++ b/util/shape-options.hh
@@ -161,12 +161,52 @@ struct shape_options_t
}
else
{
- if (!hb_shape_full (font, buffer, features, num_features, shapers))
+ if (advance <= 0)
{
- if (error)
- *error = "Shaping failed.";
- goto fail;
+ if (!hb_shape_full (font, buffer, features, num_features, shapers))
+ {
+ if (error)
+ *error = "Shaping failed.";
+ goto fail;
+ }
+
+ if (advance < 0)
+ {
+ float unit = (1 << SUBPIXEL_BITS);
+
+ /* Calculate buffer advance */
+ float w = 0;
+ unsigned count = 0;
+ hb_glyph_position_t *pos = hb_buffer_get_glyph_positions (buffer, &count);
+ if (HB_DIRECTION_IS_HORIZONTAL (hb_buffer_get_direction (buffer)))
+ for (unsigned i = 0; i < count; i++)
+ w += pos[i].x_advance;
+ else
+ for (unsigned i = 0; i < count; i++)
+ w += pos[i].y_advance;
+
+ printf ("Default size: %u\n", (unsigned) roundf (w / unit));
+ exit (0);
+ }
}
+#ifdef HB_EXPERIMENTAL_API
+ else
+ {
+ float unit = (1 << SUBPIXEL_BITS);
+ float target_advance = advance * unit;
+ float w = 0;
+ hb_tag_t var_tag;
+ float var_value;
+ if (!hb_shape_justify (font, buffer, features, num_features, shapers,
+ target_advance - unit * 0.5f, target_advance + unit * 0.5f,
+ &w, &var_tag, &var_value))
+ {
+ if (error)
+ *error = "Shaping failed.";
+ goto fail;
+ }
+ }
+#endif
}
if (normalize_glyphs)
@@ -202,6 +242,7 @@ struct shape_options_t
hb_feature_t *features = nullptr;
unsigned int num_features = 0;
char **shapers = nullptr;
+ signed advance = 0;
hb_bool_t utf8_clusters = false;
hb_codepoint_t invisible_glyph = 0;
hb_codepoint_t not_found_glyph = 0;
@@ -328,6 +369,10 @@ shape_options_t::add_options (option_parser_t *parser)
{"script", 0, 0, G_OPTION_ARG_STRING, &this->script, "Set text script (default: auto)", "ISO-15924 tag"},
{"bot", 0, 0, G_OPTION_ARG_NONE, &this->bot, "Treat text as beginning-of-paragraph", nullptr},
{"eot", 0, 0, G_OPTION_ARG_NONE, &this->eot, "Treat text as end-of-paragraph", nullptr},
+#ifdef HB_EXPERIMENTAL_API
+ {"justify-to", 0, 0,
+ G_OPTION_ARG_INT, &this->advance, "Target size to justify to", "SIZE, or -1"},
+#endif
{"preserve-default-ignorables",0, 0, G_OPTION_ARG_NONE, &this->preserve_default_ignorables, "Preserve Default-Ignorable characters", nullptr},
{"remove-default-ignorables",0, 0, G_OPTION_ARG_NONE, &this->remove_default_ignorables, "Remove Default-Ignorable characters", nullptr},
{"invisible-glyph", 0, 0, G_OPTION_ARG_INT, &this->invisible_glyph, "Glyph value to replace Default-Ignorables with", nullptr},
@@ -339,7 +384,7 @@ shape_options_t::add_options (option_parser_t *parser)
{"safe-to-insert-tatweel",0, 0, G_OPTION_ARG_NONE, &this->safe_to_insert_tatweel, "Produce safe-to-insert-tatweel glyph flag", nullptr},
{"glyphs", 0, 0, G_OPTION_ARG_NONE, &this->glyphs, "Interpret input as glyph string", nullptr},
{"verify", 0, 0, G_OPTION_ARG_NONE, &this->verify, "Perform sanity checks on shaping results", nullptr},
- {"num-iterations", 'n', G_OPTION_FLAG_IN_MAIN,
+ {"num-iterations", 'n',G_OPTION_FLAG_IN_MAIN,
G_OPTION_ARG_INT, &this->num_iterations, "Run shaper N times (default: 1)", "N"},
{nullptr}
};