[arabic/stch] Zero advances
This was working for our test suite because those glyphs were
declared mark and their advances zeroed automatically. But is
not the case in eg. the font posted at:
https://github.com/harfbuzz/harfbuzz/issues/4369
diff --git a/src/hb-ot-shaper-arabic.cc b/src/hb-ot-shaper-arabic.cc
index 256f8f1..12c7da2 100644
--- a/src/hb-ot-shaper-arabic.cc
+++ b/src/hb-ot-shaper-arabic.cc
@@ -599,6 +599,7 @@
DEBUG_MSG (ARABIC, nullptr, "appending %u copies of glyph %u; j=%u",
repeat, info[k - 1].codepoint, j);
+ pos[k - 1].x_advance = 0;
for (unsigned int n = 0; n < repeat; n++)
{
x_offset -= width;
