Fix text position with OpenGL engine and Freetype

If you use the OpenGL engine, the left bearing of
the glyph was incorrectly retrieved from the system
as the glyph was queried with the wrong format, and
adjustments for antialiasing were not applied. To
make the position identical to painting with, new
API was added to QFontEngine (The bounding box of
a glyph is also not logically necessarily the same
thing as the bounding box of the rasterized glyph.)

Done-with: Trond
Task-number: QTBUG-14410

3 files changed, 37 insertions, 12 deletions

diff --git a/src/gui/text/qfontengine_ft.cpp b/src/gui/text/qfontengine_ft.cpp
index 512afc87bb..6991143979 100644
--- a/src/gui/text/qfontengine_ft.cpp
+++ b/src/gui/text/qfontengine_ft.cpp
@@ -755,10 +755,10 @@ bool QFontEngineFT::init(FaceId faceId, bool antialias, GlyphFormat format)
     return true;
 }
 
-QFontEngineFT::Glyph *QFontEngineFT::loadGlyphMetrics(QGlyphSet *set, uint glyph) const
+QFontEngineFT::Glyph *QFontEngineFT::loadGlyphMetrics(QGlyphSet *set, uint glyph, GlyphFormat format) const
 {
     Glyph *g = set->getGlyph(glyph);
-    if (g)
+    if (g && g->format == format)
         return g;
 
     int load_flags = FT_LOAD_DEFAULT | default_load_flags;
@@ -766,6 +766,18 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyphMetrics(QGlyphSet *set, uint glyph
                       ? FT_LOAD_TARGET_LIGHT
                       : FT_LOAD_TARGET_NORMAL;
 
+    if (format == Format_Mono) {
+        load_target = FT_LOAD_TARGET_MONO;
+    } else if (format == Format_A32) {
+        if (subpixelType == QFontEngineFT::Subpixel_RGB || subpixelType == QFontEngineFT::Subpixel_BGR) {
+            if (default_hint_style == HintFull)
+                load_target = FT_LOAD_TARGET_LCD;
+        } else if (subpixelType == QFontEngineFT::Subpixel_VRGB || subpixelType == QFontEngineFT::Subpixel_VBGR) {
+            if (default_hint_style == HintFull)
+                load_target = FT_LOAD_TARGET_LCD_V;
+        }
+    }
+
     if (set->outline_drawing)
         load_flags = FT_LOAD_NO_BITMAP;
 
@@ -1767,6 +1779,11 @@ glyph_metrics_t QFontEngineFT::boundingBox(glyph_t glyph)
 
 glyph_metrics_t QFontEngineFT::boundingBox(glyph_t glyph, const QTransform &matrix)
 {
+    return alphaMapBoundingBox(glyph, matrix, QFontEngine::Format_None);
+}
+
+glyph_metrics_t QFontEngineFT::alphaMapBoundingBox(glyph_t glyph, const QTransform &matrix, QFontEngine::GlyphFormat format)
+{
     FT_Face face = 0;
     glyph_metrics_t overall;
     QGlyphSet *glyphSet = 0;
@@ -1810,9 +1827,9 @@ glyph_metrics_t QFontEngineFT::boundingBox(glyph_t glyph, const QTransform &matr
         glyphSet = &defaultGlyphSet;
     }
     Glyph * g = glyphSet->getGlyph(glyph);
-    if (!g) {
+    if (!g || g->format != format) {
         face = lockFace();
-        g = loadGlyphMetrics(glyphSet, glyph);
+        g = loadGlyphMetrics(glyphSet, glyph, format);
     }
 
     if (g) {
diff --git a/src/gui/text/qfontengine_ft_p.h b/src/gui/text/qfontengine_ft_p.h
index 72f7d9f855..1a1cadb252 100644
--- a/src/gui/text/qfontengine_ft_p.h
+++ b/src/gui/text/qfontengine_ft_p.h
@@ -130,13 +130,6 @@ private:
 class Q_GUI_EXPORT QFontEngineFT : public QFontEngine
 {
 public:
-    enum GlyphFormat {
-        Format_None,
-        Format_Render = Format_None,
-        Format_Mono,
-        Format_A8,
-        Format_A32
-    };
 
     /* we don't cache glyphs that are too large anyway, so we can make this struct rather small */
     struct Glyph {
@@ -242,6 +235,8 @@ private:
     virtual void recalcAdvances(QGlyphLayout *glyphs, QTextEngine::ShaperFlags flags) const;
     virtual QImage alphaMapForGlyph(glyph_t);
     virtual QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, int margin, const QTransform &t);
+    virtual glyph_metrics_t alphaMapBoundingBox(glyph_t glyph, const QTransform &matrix,
+                                                QFontEngine::GlyphFormat format);
     virtual void removeGlyphFromCache(glyph_t glyph);
 
     virtual int glyphCount() const;
@@ -311,7 +306,7 @@ protected:
     bool embeddedbitmap;
 
 private:
-    QFontEngineFT::Glyph *loadGlyphMetrics(QGlyphSet *set, uint glyph) const;
+    QFontEngineFT::Glyph *loadGlyphMetrics(QGlyphSet *set, uint glyph, GlyphFormat format) const;
 
     GlyphFormat defaultFormat;
     FT_Matrix matrix;
diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index d07c8c9cba..d1ec4c1c39 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -120,6 +120,14 @@ public:
         TestFontEngine = 0x1000
     };
 
+    enum GlyphFormat {
+        Format_None,
+        Format_Render = Format_None,
+        Format_Mono,
+        Format_A8,
+        Format_A32
+    };
+
     QFontEngine();
     virtual ~QFontEngine();
 
@@ -191,6 +199,11 @@ public:
     virtual QImage alphaMapForGlyph(glyph_t, const QTransform &t);
     virtual QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, int margin, const QTransform &t);
 
+    virtual glyph_metrics_t alphaMapBoundingBox(glyph_t glyph, const QTransform &matrix, GlyphFormat /*format*/)
+    {
+        return boundingBox(glyph, matrix);
+    }
+
     virtual void removeGlyphFromCache(glyph_t);
 
     virtual glyph_metrics_t boundingBox(const QGlyphLayout &glyphs) = 0;