shaper: update invisible codepoint list to match HarfBuzz

1 files changed, 25 insertions, 11 deletions

diff --git a/libass/ass_shaper.c b/libass/ass_shaper.c
index 960dab1..dc47759 100644
--- a/libass/ass_shaper.c
+++ b/libass/ass_shaper.c
@@ -792,22 +792,36 @@ void ass_shaper_set_kerning(ASS_Shaper *shaper, bool kern)
 }
 
 /**
+ * \brief Determine whether HarfBuzz ignores any font-provided glyph
+ * for this Unicode codepoint and replaces it with a zero-width glyph.
+ * Matches hb_unicode_funcs_t::is_default_ignorable in hb-unicode.hh.
+ * The affected codepoints are a subset of Unicode's Default_Ignorable list.
+ */
+static inline bool is_harfbuzz_ignorable(unsigned symbol) {
+    switch (symbol >> 8) {
+        case 0x00: return symbol == 0x00AD;
+        case 0x03: return symbol == 0x034F;
+        case 0x06: return symbol == 0x061C;
+        case 0x17: return symbol >= 0x17B4 && symbol <= 0x17B5;
+        case 0x18: return symbol >= 0x180B && symbol <= 0x180E;
+        case 0x20: return (symbol >= 0x200B && symbol <= 0x200F) ||
+                          (symbol >= 0x202A && symbol <= 0x202E) ||
+                          (symbol >= 0x2060 && symbol <= 0x206F);
+        case 0xFE: return (symbol >= 0xFE00 && symbol <= 0xFE0F) ||
+                          symbol == 0xFEFF;
+        case 0xFF: return symbol >= 0xFFF0 && symbol <= 0xFFF8;
+        case 0x1D1: return symbol >= 0x1D173 && symbol <= 0x1D17A;
+        default: return symbol >= 0xE0000 && symbol <= 0xE0FFF;
+    }
+}
+
+/**
   * \brief Remove all zero-width invisible characters from the text.
   */
 static void ass_shaper_skip_characters(GlyphInfo *glyphs, size_t len)
 {
     for (int i = 0; i < len; i++) {
-        // Skip direction override control characters
-        if ((glyphs[i].symbol <= 0x202e && glyphs[i].symbol >= 0x202a)
-                || (glyphs[i].symbol <= 0x200f && glyphs[i].symbol >= 0x200b)
-                || (glyphs[i].symbol <= 0x206f && glyphs[i].symbol >= 0x2060)
-                || (glyphs[i].symbol <= 0xfe0f && glyphs[i].symbol >= 0xfe00)
-                || (glyphs[i].symbol <= 0xe01ef && glyphs[i].symbol >= 0xe0100)
-                || (glyphs[i].symbol <= 0x180f && glyphs[i].symbol >= 0x180b)
-                || glyphs[i].symbol == 0x061c
-                || glyphs[i].symbol == 0xfeff
-                || glyphs[i].symbol == 0x00ad
-                || glyphs[i].symbol == 0x034f) {
+        if (is_harfbuzz_ignorable(glyphs[i].symbol)) {
             glyphs[i].skip = true;
         }
     }