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[ot-metrics] Synthesize missing metrics 

Add a variant of hb_ot_metrics_get_position that
synthesizes missing values.

New api: hb_ot_metrics_get_position_with_fallback
This commit is contained in:
Matthias Clasen 2022-02-15 17:17:09 -06:00 committed by Behdad Esfahbod
parent f8e9e315bb
commit f6efe34f5e
3 changed files with 145 additions and 0 deletions
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1
docs/harfbuzz-sections.txt
View File

@ -600,6 +600,7 @@ hb_ot_meta_reference_entry
<FILE>hb-ot-metrics</FILE>
hb_ot_metrics_tag_t
hb_ot_metrics_get_position
hb_ot_metrics_get_position_with_fallback
hb_ot_metrics_get_variation
hb_ot_metrics_get_x_variation
hb_ot_metrics_get_y_variation

139
src/hb-ot-metrics.cc
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@ -238,6 +238,145 @@ hb_ot_metrics_get_position (hb_font_t *font,
}
}
/**
* hb_ot_metrics_get_position_with_fallback:
* @font: an #hb_font_t object.
* @metrics_tag: tag of metrics value you like to fetch.
* @position: (out) (optional): result of metrics value from the font.
*
* Fetches metrics value corresponding to @metrics_tag from @font,
* and synthesizes a value if it the value is missing in the font.
*
* Since: REPLACEME
**/
void
hb_ot_metrics_get_position_with_fallback (hb_font_t *font,
hb_ot_metrics_tag_t metrics_tag,
hb_position_t *position /* OUT */)
{
hb_font_extents_t font_extents;
hb_codepoint_t glyph;
hb_glyph_extents_t extents;
if (hb_ot_metrics_get_position (font, metrics_tag, position))
{
if ((metrics_tag != HB_OT_METRICS_TAG_STRIKEOUT_SIZE &&
metrics_tag != HB_OT_METRICS_TAG_UNDERLINE_SIZE) ||
*position != 0)
return;
}
switch (metrics_tag)
{
case HB_OT_METRICS_TAG_HORIZONTAL_ASCENDER:
case HB_OT_METRICS_TAG_HORIZONTAL_CLIPPING_ASCENT:
hb_font_get_extents_for_direction (font, HB_DIRECTION_LTR, &font_extents);
*position = font_extents.ascender;
break;
case HB_OT_METRICS_TAG_VERTICAL_ASCENDER:
hb_font_get_extents_for_direction (font, HB_DIRECTION_TTB, &font_extents);
*position = font_extents.ascender;
break;
case HB_OT_METRICS_TAG_HORIZONTAL_DESCENDER:
case HB_OT_METRICS_TAG_HORIZONTAL_CLIPPING_DESCENT:
hb_font_get_extents_for_direction (font, HB_DIRECTION_LTR, &font_extents);
*position = font_extents.descender;
break;
case HB_OT_METRICS_TAG_VERTICAL_DESCENDER:
hb_font_get_extents_for_direction (font, HB_DIRECTION_TTB, &font_extents);
*position = font_extents.ascender;
break;
case HB_OT_METRICS_TAG_HORIZONTAL_LINE_GAP:
hb_font_get_extents_for_direction (font, HB_DIRECTION_LTR, &font_extents);
*position = font_extents.line_gap;
break;
case HB_OT_METRICS_TAG_VERTICAL_LINE_GAP:
hb_font_get_extents_for_direction (font, HB_DIRECTION_TTB, &font_extents);
*position = font_extents.line_gap;
break;
case HB_OT_METRICS_TAG_HORIZONTAL_CARET_RISE:
case HB_OT_METRICS_TAG_VERTICAL_CARET_RISE:
*position = 1;
break;
case HB_OT_METRICS_TAG_HORIZONTAL_CARET_RUN:
case HB_OT_METRICS_TAG_VERTICAL_CARET_RUN:
*position = 0;
break;
case HB_OT_METRICS_TAG_HORIZONTAL_CARET_OFFSET:
case HB_OT_METRICS_TAG_VERTICAL_CARET_OFFSET:
*position = 0;
break;
case HB_OT_METRICS_TAG_X_HEIGHT:
if (hb_font_get_nominal_glyph (font, 'o', &glyph) &&
hb_font_get_glyph_extents (font, glyph, &extents))
*position = extents.height + 2 * extents.y_bearing;
else
*position = font->y_scale / 2;
break;
case HB_OT_METRICS_TAG_CAP_HEIGHT:
if (hb_font_get_nominal_glyph (font, 'O', &glyph) &&
hb_font_get_glyph_extents (font, glyph, &extents))
*position = extents.height + 2 * extents.y_bearing;
else
*position = font->y_scale * 2 / 3;
break;
case HB_OT_METRICS_TAG_STRIKEOUT_SIZE:
case HB_OT_METRICS_TAG_UNDERLINE_SIZE:
*position = font->y_scale / 18;
break;
case HB_OT_METRICS_TAG_STRIKEOUT_OFFSET:
{
hb_position_t ascender;
hb_ot_metrics_get_position_with_fallback (font,
HB_OT_METRICS_TAG_HORIZONTAL_ASCENDER,
&ascender);
*position = ascender / 2;
}
break;
case HB_OT_METRICS_TAG_UNDERLINE_OFFSET:
*position = - font->y_scale / 18;
break;
case HB_OT_METRICS_TAG_SUBSCRIPT_EM_X_SIZE:
case HB_OT_METRICS_TAG_SUPERSCRIPT_EM_X_SIZE:
*position = font->x_scale * 10 / 12;
break;
case HB_OT_METRICS_TAG_SUBSCRIPT_EM_Y_SIZE:
case HB_OT_METRICS_TAG_SUPERSCRIPT_EM_Y_SIZE:
*position = font->y_scale * 10 / 12;
break;
case HB_OT_METRICS_TAG_SUBSCRIPT_EM_X_OFFSET:
case HB_OT_METRICS_TAG_SUPERSCRIPT_EM_X_OFFSET:
*position = 0;
break;
case HB_OT_METRICS_TAG_SUBSCRIPT_EM_Y_OFFSET:
case HB_OT_METRICS_TAG_SUPERSCRIPT_EM_Y_OFFSET:
*position = font->y_scale / 5;
break;
case _HB_OT_METRICS_TAG_MAX_VALUE:
default:
*position = 0;
break;
}
}
#ifndef HB_NO_VAR
/**
* hb_ot_metrics_get_variation:

5
src/hb-ot-metrics.h
View File

@ -110,6 +110,11 @@ hb_ot_metrics_get_position (hb_font_t *font,
hb_ot_metrics_tag_t metrics_tag,
hb_position_t *position /* OUT. May be NULL. */);
HB_EXTERN void
hb_ot_metrics_get_position_with_fallback (hb_font_t *font,
hb_ot_metrics_tag_t metrics_tag,
hb_position_t *position /* OUT */);
HB_EXTERN float
hb_ot_metrics_get_variation (hb_font_t *font, hb_ot_metrics_tag_t metrics_tag);