Force FT font engine to load the right glyph metrics

Change-Id: If027ea4c1a3b2ca8f972592abe3534165f62cf4e
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/gui/painting/qtextureglyphcache.cpp b/src/gui/painting/qtextureglyphcache.cpp
index 2166ae7975..b953f8d81f 100644
--- a/src/gui/painting/qtextureglyphcache.cpp
+++ b/src/gui/painting/qtextureglyphcache.cpp
@@ -152,6 +152,18 @@ bool QTextureGlyphCache::populate(QFontEngine *fontEngine, int numGlyphs, const
             continue;
         if (listItemCoordinates.contains(GlyphAndSubPixelPosition(glyph, subPixelPosition)))
             continue;
+
+        // This is a rather crude hack, but it works.
+        // The FreeType font engine is not capable of getting precise metrics for the alphamap
+        // without first rasterizing the glyph. If we force the glyph to be rasterized before
+        // we ask for the alphaMapBoundingBox(), the glyph will be loaded, rasterized and its
+        // proper metrics will be cached and used later.
+        if (fontEngine->hasInternalCaching()) {
+            QImage *locked = fontEngine->lockedAlphaMapForGlyph(glyph, subPixelPosition, format);
+            if (locked)
+                fontEngine->unlockAlphaMapForGlyph();
+        }
+
         glyph_metrics_t metrics = fontEngine->alphaMapBoundingBox(glyph, subPixelPosition, m_transform, format);
 
 #ifdef CACHE_DEBUG