[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
diff --git a/docs/harfbuzz-sections.txt b/docs/harfbuzz-sections.txt
index 9263994..f81058b 100644
--- a/docs/harfbuzz-sections.txt
+++ b/docs/harfbuzz-sections.txt
@@ -537,6 +537,7 @@
hb_ot_layout_get_attach_points
hb_ot_layout_get_horizontal_baseline_tag_for_script
hb_ot_layout_get_baseline
+hb_ot_layout_get_baseline_with_fallback
hb_ot_layout_get_glyph_class
hb_ot_layout_get_glyphs_in_class
hb_ot_layout_get_ligature_carets
diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index aaabc68..0d556aa 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1979,6 +1979,7 @@
hb_ot_layout_baseline_tag_t
hb_ot_layout_get_horizontal_baseline_tag_for_script (hb_script_t script)
{
+ /* Keep in sync with hb_ot_layout_get_baseline_with_fallback */
switch ((int) script)
{
/* Unicode-1.1 additions */
@@ -2043,7 +2044,7 @@
* @direction: text direction.
* @script_tag: script tag.
* @language_tag: language tag, currently unused.
- * @coord: (out): baseline value if found.
+ * @coord: (out) (nullable): baseline value if found.
*
* Fetches a baseline value from the face.
*
@@ -2066,6 +2067,187 @@
return result;
}
+
+/**
+ * hb_ot_layout_get_baseline_with_fallback:
+ * @font: a font
+ * @baseline_tag: a baseline tag
+ * @direction: text direction.
+ * @script_tag: script tag.
+ * @language_tag: language tag, currently unused.
+ * @coord: (out): baseline value if found.
+ *
+ * Fetches a baseline value from the face, and synthesizes
+ * it if the font does not have it.
+ *
+ * Since: REPLACEME
+ **/
+void
+hb_ot_layout_get_baseline_with_fallback (hb_font_t *font,
+ hb_ot_layout_baseline_tag_t baseline_tag,
+ hb_direction_t direction,
+ hb_tag_t script_tag,
+ hb_tag_t language_tag,
+ hb_position_t *coord /* OUT */)
+{
+ if (hb_ot_layout_get_baseline (font,
+ baseline_tag,
+ direction,
+ script_tag,
+ language_tag,
+ coord))
+ return;
+
+ /* Synthesize missing baselines.
+ * See https://www.w3.org/TR/css-inline-3/#baseline-synthesis-fonts
+ */
+ switch (baseline_tag)
+ {
+ case HB_OT_LAYOUT_BASELINE_TAG_ROMAN:
+ *coord = 0; // FIXME origin ?
+ break;
+
+ case HB_OT_LAYOUT_BASELINE_TAG_MATH:
+ {
+ hb_codepoint_t glyph;
+ hb_glyph_extents_t extents;
+ if (HB_DIRECTION_IS_HORIZONTAL (direction) &&
+ (hb_font_get_nominal_glyph (font, 0x2212u, &glyph) ||
+ hb_font_get_nominal_glyph (font, '-', &glyph)) &&
+ hb_font_get_glyph_extents (font, glyph, &extents))
+ {
+ *coord = extents.y_bearing + extents.height / 2;
+ }
+ else
+ {
+ hb_position_t x_height = 0;
+ hb_ot_metrics_get_position (font, HB_OT_METRICS_TAG_X_HEIGHT, &x_height);
+ *coord = x_height / 2;
+ }
+ }
+ break;
+
+ case HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT:
+ case HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT:
+ {
+ hb_position_t embox_top, embox_bottom;
+
+ hb_ot_layout_get_baseline_with_fallback (font,
+ HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT,
+ direction,
+ script_tag,
+ language_tag,
+ &embox_top);
+ hb_ot_layout_get_baseline_with_fallback (font,
+ HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT,
+ direction,
+ script_tag,
+ language_tag,
+ &embox_bottom);
+
+ if (baseline_tag == HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_TOP_OR_RIGHT)
+ *coord = embox_top + (embox_bottom - embox_top) / 10;
+ else
+ *coord = embox_bottom + (embox_top - embox_bottom) / 10;
+ }
+ break;
+
+ case HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT:
+ if (hb_ot_layout_get_baseline (font,
+ HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT,
+ direction,
+ script_tag,
+ language_tag,
+ coord))
+ *coord += HB_DIRECTION_IS_HORIZONTAL (direction) ? font->y_scale : font->x_scale;
+ else
+ {
+ hb_font_extents_t font_extents;
+ hb_font_get_extents_for_direction (font, direction, &font_extents);
+ *coord = font_extents.ascender;
+ }
+ break;
+
+ case HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_BOTTOM_OR_LEFT:
+ if (hb_ot_layout_get_baseline (font,
+ HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT,
+ direction,
+ script_tag,
+ language_tag,
+ coord))
+ *coord -= HB_DIRECTION_IS_HORIZONTAL (direction) ? font->y_scale : font->x_scale;
+ else
+ {
+ hb_font_extents_t font_extents;
+ hb_font_get_extents_for_direction (font, direction, &font_extents);
+ *coord = font_extents.descender;
+ }
+ break;
+
+ case HB_OT_LAYOUT_BASELINE_TAG_HANGING:
+ if (HB_DIRECTION_IS_HORIZONTAL (direction))
+ {
+ hb_codepoint_t ch;
+ hb_codepoint_t glyph;
+ hb_glyph_extents_t extents;
+
+ /* Keep in sync with hb_ot_layout_get_horizontal_baseline_for_script */
+ switch ((int) script_tag)
+ {
+ /* Unicode-1.1 additions */
+ case HB_SCRIPT_BENGALI: ch = 0x0995u; break;
+ case HB_SCRIPT_DEVANAGARI: ch = 0x0915u; break;
+ case HB_SCRIPT_GUJARATI: ch = 0x0a95u; break;
+ case HB_SCRIPT_GURMUKHI: ch = 0x0a15u; break;
+ /* Unicode-2.0 additions */
+ case HB_SCRIPT_TIBETAN: ch = 0x0f40u; break;
+ /* Unicode-4.0 additions */
+ case HB_SCRIPT_LIMBU: ch = 0x1901u; break;
+ /* Unicode-4.1 additions */
+ case HB_SCRIPT_SYLOTI_NAGRI: ch = 0xa807u; break;
+ /* Unicode-5.0 additions */
+ case HB_SCRIPT_PHAGS_PA: ch = 0xa840u; break;
+ /* Unicode-5.2 additions */
+ case HB_SCRIPT_MEETEI_MAYEK: ch = 0xabc0u; break;
+ /* Unicode-6.1 additions */
+ case HB_SCRIPT_SHARADA: ch = 0x11191u; break;
+ case HB_SCRIPT_TAKRI: ch = 0x1168cu; break;
+ /* Unicode-7.0 additions */
+ case HB_SCRIPT_MODI: ch = 0x1160eu;break;
+ case HB_SCRIPT_SIDDHAM: ch = 0x11590u; break;
+ case HB_SCRIPT_TIRHUTA: ch = 0x1148fu; break;
+ /* Unicode-9.0 additions */
+ case HB_SCRIPT_MARCHEN: ch = 0x11c72u; break;
+ case HB_SCRIPT_NEWA: ch = 0x1140eu; break;
+ /* Unicode-10.0 additions */
+ case HB_SCRIPT_SOYOMBO: ch = 0x11a5cu; break;
+ case HB_SCRIPT_ZANABAZAR_SQUARE: ch = 0x11a0bu; break;
+ /* Unicode-11.0 additions */
+ case HB_SCRIPT_DOGRA: ch = 0x1180au; break;
+ case HB_SCRIPT_GUNJALA_GONDI: ch = 0x11d6cu; break;
+ /* Unicode-12.0 additions */
+ case HB_SCRIPT_NANDINAGARI: ch = 0x119b0u; break;
+ default: ch = 0; break;
+ }
+
+ if (ch &&
+ hb_font_get_nominal_glyph (font, ch, &glyph) &&
+ hb_font_get_glyph_extents (font, glyph, &extents))
+ *coord = extents.y_bearing;
+ else
+ *coord = font->y_scale * 6 / 10; // FIXME makes assumptions about origin
+ }
+ else
+ *coord = font->x_scale * 6 / 10; // FIXME makes assumptions about origin
+ break;
+
+ case _HB_OT_LAYOUT_BASELINE_TAG_MAX_VALUE:
+ default:
+ *coord = 0;
+ break;
+ }
+}
+
#endif
diff --git a/src/hb-ot-layout.h b/src/hb-ot-layout.h
index edbb7b8..22ba7c4 100644
--- a/src/hb-ot-layout.h
+++ b/src/hb-ot-layout.h
@@ -522,6 +522,14 @@
hb_tag_t language_tag,
hb_position_t *coord /* OUT. May be NULL. */);
+HB_EXTERN void
+hb_ot_layout_get_baseline_with_fallback (hb_font_t *font,
+ hb_ot_layout_baseline_tag_t baseline_tag,
+ hb_direction_t direction,
+ hb_tag_t script_tag,
+ hb_tag_t language_tag,
+ hb_position_t *coord /* OUT */);
+
HB_END_DECLS
#endif /* HB_OT_LAYOUT_H */
diff --git a/test/api/fonts/base2.ttf b/test/api/fonts/base2.ttf
new file mode 100644
index 0000000..5cb0d35
--- /dev/null
+++ b/test/api/fonts/base2.ttf
Binary files differ
diff --git a/test/api/test-baseline.c b/test/api/test-baseline.c
index 982c683..9f9542e 100644
--- a/test/api/test-baseline.c
+++ b/test/api/test-baseline.c
@@ -41,6 +41,58 @@
&position));
g_assert_cmpint (46, ==, position);
+ g_assert (!hb_ot_layout_get_baseline (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT, HB_DIRECTION_TTB,
+ HB_TAG ('h','a','n','i'),
+ HB_TAG ('E','N','G',' '),
+ &position));
+
+ hb_font_destroy (font);
+ hb_face_destroy (face);
+}
+
+static void
+test_ot_layout_base_with_fallback (void)
+{
+ hb_face_t *face = hb_test_open_font_file ("fonts/base.ttf");
+ hb_font_t *font = hb_font_create (face);
+
+ hb_position_t position;
+ hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_FACE_BOTTOM_OR_LEFT, HB_DIRECTION_TTB,
+ HB_TAG ('h','a','n','i'),
+ HB_TAG ('E','N','G',' '),
+ &position);
+ g_assert_cmpint (46, ==, position);
+
+ hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_IDEO_EMBOX_TOP_OR_RIGHT, HB_DIRECTION_TTB,
+ HB_TAG ('h','a','n','i'),
+ HB_TAG ('E','N','G',' '),
+ &position);
+ g_assert_cmpint (1000, ==, position);
+
+ hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_MATH, HB_DIRECTION_LTR,
+ HB_TAG ('h','a','n','i'),
+ HB_TAG ('E','N','G',' '),
+ &position);
+ g_assert_cmpint (271, ==, position);
+
+ hb_font_destroy (font);
+ hb_face_destroy (face);
+
+ face = hb_test_open_font_file ("fonts/base2.ttf");
+ font = hb_font_create (face);
+
+ hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_HANGING, HB_DIRECTION_LTR,
+ HB_SCRIPT_BENGALI,
+ HB_TAG ('E','N','G',' '),
+ &position);
+ g_assert_cmpint (622, ==, position);
+
+ hb_ot_layout_get_baseline_with_fallback (font, HB_OT_LAYOUT_BASELINE_TAG_HANGING, HB_DIRECTION_LTR,
+ HB_SCRIPT_TIBETAN,
+ HB_TAG ('E','N','G',' '),
+ &position);
+ g_assert_cmpint (600, ==, position);
+
hb_font_destroy (font);
hb_face_destroy (face);
}
@@ -51,6 +103,7 @@
hb_test_init (&argc, &argv);
hb_test_add (test_ot_layout_base);
+ hb_test_add (test_ot_layout_base_with_fallback);
return hb_test_run();
}