Merge pull request #4144 from harfbuzz/justify

Justify
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Behdad Esfahbod 2023-03-01 16:34:01 -07:00 committed by GitHub
commit e8f94f9e12
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7 changed files with 337 additions and 6 deletions

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@ -780,6 +780,7 @@ hb_set_t
<FILE>hb-shape</FILE>
hb_shape
hb_shape_full
hb_shape_justify
hb_shape_list_shapers
</SECTION>

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@ -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]

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@ -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 <typename func_t>
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 */

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@ -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

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@ -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<const hb_glyph_info_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<const hb_glyph_info_t> (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

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@ -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);

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@ -160,6 +160,8 @@ struct shape_options_t
}
}
else
{
if (advance <= 0)
{
if (!hb_shape_full (font, buffer, features, num_features, shapers))
{
@ -167,6 +169,44 @@ struct shape_options_t
*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},