[ot-layout] Synthesize missing baselines
Add a variation of hb_ot_layout_get_baseline that synthesizes missing baselines, using heuristics in part taken from the CSS Inline Layout Module, Level 3. Includes some new tests for synthesized baselines. The base2.ttf is a subset of Noto Sans Bengali that includes just the Bengali Ka. New API: hb_ot_layout_get_baseline_with_fallback
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@ -537,6 +537,7 @@ hb_ot_layout_feature_with_variations_get_lookups
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hb_ot_layout_get_attach_points
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hb_ot_layout_get_horizontal_baseline_tag_for_script
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hb_ot_layout_get_baseline
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hb_ot_layout_get_baseline_with_fallback
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hb_ot_layout_get_glyph_class
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hb_ot_layout_get_glyphs_in_class
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hb_ot_layout_get_ligature_carets
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@ -1979,6 +1979,7 @@ hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
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hb_ot_layout_baseline_tag_t
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hb_ot_layout_get_horizontal_baseline_tag_for_script (hb_script_t script)
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{
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/* Keep in sync with hb_ot_layout_get_baseline_with_fallback */
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switch ((int) script)
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{
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/* Unicode-1.1 additions */
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@ -2043,7 +2044,7 @@ hb_ot_layout_get_horizontal_baseline_tag_for_script (hb_script_t script)
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* @direction: text direction.
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* @script_tag: script tag.
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* @language_tag: language tag, currently unused.
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* @coord: (out): baseline value if found.
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* @coord: (out) (nullable): baseline value if found.
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*
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* Fetches a baseline value from the face.
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*
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@ -2066,6 +2067,187 @@ hb_ot_layout_get_baseline (hb_font_t *font,
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return result;
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}
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/**
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* hb_ot_layout_get_baseline_with_fallback:
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* @font: a font
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* @baseline_tag: a baseline tag
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* @direction: text direction.
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* @script_tag: script tag.
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* @language_tag: language tag, currently unused.
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* @coord: (out): baseline value if found.
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*
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* Fetches a baseline value from the face, and synthesizes
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* it if the font does not have it.
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*
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* Since: REPLACEME
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**/
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void
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hb_ot_layout_get_baseline_with_fallback (hb_font_t *font,
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hb_ot_layout_baseline_tag_t baseline_tag,
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hb_direction_t direction,
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hb_tag_t script_tag,
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hb_tag_t language_tag,
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hb_position_t *coord /* OUT */)
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{
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if (hb_ot_layout_get_baseline (font,
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baseline_tag,
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direction,
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script_tag,
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language_tag,
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coord))
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return;
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/* Synthesize missing baselines.
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* See https://www.w3.org/TR/css-inline-3/#baseline-synthesis-fonts
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*/
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switch (baseline_tag)
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{
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case HB_OT_LAYOUT_BASELINE_TAG_ROMAN:
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*coord = 0; // FIXME origin ?
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break;
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case HB_OT_LAYOUT_BASELINE_TAG_MATH:
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{
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hb_codepoint_t glyph;
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hb_glyph_extents_t extents;
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if (HB_DIRECTION_IS_HORIZONTAL (direction) &&
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(hb_font_get_nominal_glyph (font, 0x2212u, &glyph) ||
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hb_font_get_nominal_glyph (font, '-', &glyph)) &&
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hb_font_get_glyph_extents (font, glyph, &extents))
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{
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*coord = extents.y_bearing + extents.height / 2;
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}
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else
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{
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hb_position_t x_height = 0;
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hb_ot_metrics_get_position (font, HB_OT_METRICS_TAG_X_HEIGHT, &x_height);
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*coord = x_height / 2;
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}
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}
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break;
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case HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT:
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case HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT:
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{
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hb_position_t embox_top, embox_bottom;
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hb_ot_layout_get_baseline_with_fallback (font,
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HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT,
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direction,
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script_tag,
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language_tag,
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&embox_top);
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hb_ot_layout_get_baseline_with_fallback (font,
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HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT,
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direction,
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script_tag,
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language_tag,
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&embox_bottom);
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if (baseline_tag == HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT)
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*coord = embox_top + (embox_bottom - embox_top) / 10;
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else
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*coord = embox_bottom + (embox_top - embox_bottom) / 10;
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}
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break;
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case HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT:
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if (hb_ot_layout_get_baseline (font,
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HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT,
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direction,
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script_tag,
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language_tag,
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coord))
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*coord += HB_DIRECTION_IS_HORIZONTAL (direction) ? font->y_scale : font->x_scale;
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else
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{
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hb_font_extents_t font_extents;
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hb_font_get_extents_for_direction (font, direction, &font_extents);
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*coord = font_extents.ascender;
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}
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break;
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case HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT:
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if (hb_ot_layout_get_baseline (font,
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HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT,
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direction,
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script_tag,
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language_tag,
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coord))
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*coord -= HB_DIRECTION_IS_HORIZONTAL (direction) ? font->y_scale : font->x_scale;
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else
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{
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hb_font_extents_t font_extents;
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hb_font_get_extents_for_direction (font, direction, &font_extents);
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*coord = font_extents.descender;
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}
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break;
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case HB_OT_LAYOUT_BASELINE_TAG_HANGING:
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if (HB_DIRECTION_IS_HORIZONTAL (direction))
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{
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hb_codepoint_t ch;
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hb_codepoint_t glyph;
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hb_glyph_extents_t extents;
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/* Keep in sync with hb_ot_layout_get_horizontal_baseline_for_script */
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switch ((int) script_tag)
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{
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/* Unicode-1.1 additions */
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case HB_SCRIPT_BENGALI: ch = 0x0995u; break;
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case HB_SCRIPT_DEVANAGARI: ch = 0x0915u; break;
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case HB_SCRIPT_GUJARATI: ch = 0x0a95u; break;
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case HB_SCRIPT_GURMUKHI: ch = 0x0a15u; break;
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/* Unicode-2.0 additions */
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case HB_SCRIPT_TIBETAN: ch = 0x0f40u; break;
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/* Unicode-4.0 additions */
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case HB_SCRIPT_LIMBU: ch = 0x1901u; break;
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/* Unicode-4.1 additions */
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case HB_SCRIPT_SYLOTI_NAGRI: ch = 0xa807u; break;
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/* Unicode-5.0 additions */
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case HB_SCRIPT_PHAGS_PA: ch = 0xa840u; break;
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/* Unicode-5.2 additions */
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case HB_SCRIPT_MEETEI_MAYEK: ch = 0xabc0u; break;
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/* Unicode-6.1 additions */
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case HB_SCRIPT_SHARADA: ch = 0x11191u; break;
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case HB_SCRIPT_TAKRI: ch = 0x1168cu; break;
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/* Unicode-7.0 additions */
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case HB_SCRIPT_MODI: ch = 0x1160eu;break;
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case HB_SCRIPT_SIDDHAM: ch = 0x11590u; break;
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case HB_SCRIPT_TIRHUTA: ch = 0x1148fu; break;
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/* Unicode-9.0 additions */
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case HB_SCRIPT_MARCHEN: ch = 0x11c72u; break;
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case HB_SCRIPT_NEWA: ch = 0x1140eu; break;
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/* Unicode-10.0 additions */
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case HB_SCRIPT_SOYOMBO: ch = 0x11a5cu; break;
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case HB_SCRIPT_ZANABAZAR_SQUARE: ch = 0x11a0bu; break;
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/* Unicode-11.0 additions */
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case HB_SCRIPT_DOGRA: ch = 0x1180au; break;
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case HB_SCRIPT_GUNJALA_GONDI: ch = 0x11d6cu; break;
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/* Unicode-12.0 additions */
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case HB_SCRIPT_NANDINAGARI: ch = 0x119b0u; break;
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default: ch = 0; break;
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}
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if (ch &&
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hb_font_get_nominal_glyph (font, ch, &glyph) &&
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hb_font_get_glyph_extents (font, glyph, &extents))
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*coord = extents.y_bearing;
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else
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*coord = font->y_scale * 6 / 10; // FIXME makes assumptions about origin
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}
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else
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*coord = font->x_scale * 6 / 10; // FIXME makes assumptions about origin
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break;
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case _HB_OT_LAYOUT_BASELINE_TAG_MAX_VALUE:
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default:
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*coord = 0;
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break;
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}
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}
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#endif
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@ -522,6 +522,14 @@ hb_ot_layout_get_baseline (hb_font_t *font,
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hb_tag_t language_tag,
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hb_position_t *coord /* OUT. May be NULL. */);
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HB_EXTERN void
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hb_ot_layout_get_baseline_with_fallback (hb_font_t *font,
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hb_ot_layout_baseline_tag_t baseline_tag,
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hb_direction_t direction,
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hb_tag_t script_tag,
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hb_tag_t language_tag,
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hb_position_t *coord /* OUT */);
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HB_END_DECLS
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#endif /* HB_OT_LAYOUT_H */
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Binary file not shown.
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@ -41,6 +41,58 @@ test_ot_layout_base (void)
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&position));
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g_assert_cmpint (46, ==, position);
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g_assert (!hb_ot_layout_get_baseline (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT, HB_DIRECTION_TTB,
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HB_TAG ('h','a','n','i'),
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HB_TAG ('E','N','G',' '),
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&position));
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hb_font_destroy (font);
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hb_face_destroy (face);
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}
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static void
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test_ot_layout_base_with_fallback (void)
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{
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hb_face_t *face = hb_test_open_font_file ("fonts/base.ttf");
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hb_font_t *font = hb_font_create (face);
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hb_position_t position;
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hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT, HB_DIRECTION_TTB,
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HB_TAG ('h','a','n','i'),
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HB_TAG ('E','N','G',' '),
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&position);
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g_assert_cmpint (46, ==, position);
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hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT, HB_DIRECTION_TTB,
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HB_TAG ('h','a','n','i'),
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HB_TAG ('E','N','G',' '),
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&position);
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g_assert_cmpint (1000, ==, position);
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hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_MATH, HB_DIRECTION_LTR,
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HB_TAG ('h','a','n','i'),
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HB_TAG ('E','N','G',' '),
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&position);
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g_assert_cmpint (271, ==, position);
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hb_font_destroy (font);
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hb_face_destroy (face);
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face = hb_test_open_font_file ("fonts/base2.ttf");
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font = hb_font_create (face);
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hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_HANGING, HB_DIRECTION_LTR,
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HB_SCRIPT_BENGALI,
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HB_TAG ('E','N','G',' '),
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&position);
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g_assert_cmpint (622, ==, position);
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hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_HANGING, HB_DIRECTION_LTR,
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HB_SCRIPT_TIBETAN,
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HB_TAG ('E','N','G',' '),
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&position);
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g_assert_cmpint (600, ==, position);
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hb_font_destroy (font);
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hb_face_destroy (face);
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}
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@ -51,6 +103,7 @@ main (int argc, char **argv)
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hb_test_init (&argc, &argv);
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hb_test_add (test_ot_layout_base);
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hb_test_add (test_ot_layout_base_with_fallback);
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return hb_test_run();
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}
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