[ot-font] Fix sign of ascent/descent

Some fonts, like msmincho, have positive number as descent
in vhea table.  That's wrong.  Just enforce sign on ascent/descent
when reading both horizontal and vertical metrics.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1248

diff --git a/src/hb-ot-hmtx-table.hh b/src/hb-ot-hmtx-table.hh
index 5293fda..935ddd7 100644 (file)
--- a/src/hb-ot-hmtx-table.hh
+++ b/src/hb-ot-hmtx-table.hh
@@ -199,8 +199,8 @@ struct hmtxvmtx
 #define USE_TYPO_METRICS (1u<<7)
        if (0 != (os2_table->fsSelection & USE_TYPO_METRICS))
        {
-         ascender = os2_table->sTypoAscender;
-         descender = os2_table->sTypoDescender;
+         ascender = abs (os2_table->sTypoAscender);
+         descender = -abs (os2_table->sTypoDescender);
          line_gap = os2_table->sTypoLineGap;
          got_font_extents = (ascender | descender) != 0;
        }
@@ -212,8 +212,8 @@ struct hmtxvmtx
       num_advances = _hea_table->numberOfLongMetrics;
       if (!got_font_extents)
       {
-       ascender = _hea_table->ascender;
-       descender = _hea_table->descender;
+       ascender = abs (_hea_table->ascender);
+       descender = -abs (_hea_table->descender);
        line_gap = _hea_table->lineGap;
        got_font_extents = (ascender | descender) != 0;
       }