A hack to fix mark placement in old fonts

We need a way to recognize non spacing marks in fonts lacking GDEF table
(like old Arabic fonts), so I just check for zero advance width and hope
nothing elsewhere will break...

Change-Id: I6fa848e97ba24d71fc9a381ae439e0fb98e50419

1 files changed, 19 insertions, 1 deletions

diff --git a/vcl/generic/glyphs/gcach_layout.cxx b/vcl/generic/glyphs/gcach_layout.cxx
index 6ac7fd43e4fa..4fd4cf40e088 100644
--- a/vcl/generic/glyphs/gcach_layout.cxx
+++ b/vcl/generic/glyphs/gcach_layout.cxx
@@ -428,7 +428,25 @@ bool HbLayoutEngine::layout(ServerFontLayout& rLayout, ImplLayoutArgs& rArgs)
             if (bInCluster)
                 nGlyphFlags |= GlyphItem::IS_IN_CLUSTER;
 
-            if (hb_ot_layout_get_glyph_class(mpHbFace, nGlyphIndex) == HB_OT_LAYOUT_GLYPH_CLASS_MARK)
+            bool bDiacritic = false;
+            if (hb_ot_layout_has_glyph_classes(mpHbFace))
+            {
+                // the font has GDEF table
+                if (hb_ot_layout_get_glyph_class(mpHbFace, nGlyphIndex) == HB_OT_LAYOUT_GLYPH_CLASS_MARK)
+                    bDiacritic = true;
+            }
+            else
+            {
+                // the font lacks GDEF table
+                // HACK: if the resolved glyph advance is zero assume it is a
+                // combining mark.  The whole IS_DIACRITIC concept is a hack to
+                // fix the other hacks we use to second-guess glyph advances in
+                // ApplyDXArray and the likes and it needs to die
+                if (pHbPositions[i].x_advance == 0)
+                    bDiacritic = true;
+            }
+
+            if (bDiacritic)
                 nGlyphFlags |= GlyphItem::IS_DIACRITIC;
 
             int32_t nXOffset =  pHbPositions[i].x_offset >> 6;