Fix font height metrics with embedded bitmaps

For fonts with embedded bitmaps, we cannot trust the HHEA and
OS/2 tables, since there are a different set of font metrics
in the EBLC/CBLC tables for each of the predefined bitmap
sizes.

In this case, we can safely fall back to the metrics returned
by the system, as the inconsistency we were originally fixing
was only between OS/2 and HHEA and will not matter for the
bitmap fonts.

This patch also simplifies the code path through the font
engines a bit. Instead of setting the system metrics in the
processHheaTable() function when the table cannot be found,
we instead always fetch the system metrics at the very start
of initializeHeightMetrics() and then override if there are
no embedded bitmaps, and if the HHEA and OS/2 tables are
available. This also reduces the number of virtual functions
needed to sort out the height metrics.

Fixes: QTBUG-83754
Change-Id: Ib9dc6fc6cf972e48209a4a272469d2b4bd1ebffe
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>

8 files changed, 24 insertions, 38 deletions

diff --git a/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp b/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
index 910a16bf95..1c9a17a3e4 100644
--- a/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
+++ b/src/platformsupport/fontdatabases/freetype/qfontengine_ft.cpp
@@ -1243,6 +1243,10 @@ int QFontEngineFT::synthesized() const
 
 void QFontEngineFT::initializeHeightMetrics() const
 {
+    m_ascent = QFixed::fromFixed(metrics.ascender);
+    m_descent = QFixed::fromFixed(-metrics.descender);
+    m_leading = QFixed::fromFixed(metrics.height - metrics.ascender + metrics.descender);
+
     QFontEngine::initializeHeightMetrics();
 
     if (scalableBitmapScaleFactor != 1) {
@@ -1252,17 +1256,6 @@ void QFontEngineFT::initializeHeightMetrics() const
     }
 }
 
-bool QFontEngineFT::processHheaTable() const
-{
-    if (!QFontEngine::processHheaTable()) {
-        m_ascent = QFixed::fromFixed(metrics.ascender);
-        m_descent = QFixed::fromFixed(-metrics.descender);
-        m_leading = QFixed::fromFixed(metrics.height - metrics.ascender + metrics.descender);
-    }
-
-    return true;
-}
-
 QFixed QFontEngineFT::capHeight() const
 {
     TT_OS2 *os2 = (TT_OS2 *)FT_Get_Sfnt_Table(freetype->face, ft_sfnt_os2);
diff --git a/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h b/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
index f8eca7e267..bc48963a9e 100644
--- a/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
+++ b/src/platformsupport/fontdatabases/freetype/qfontengine_ft_p.h
@@ -192,7 +192,6 @@ private:
     int synthesized() const override;
 
     void initializeHeightMetrics() const override;
-    bool processHheaTable() const override;
     QFixed capHeight() const override;
     QFixed xHeight() const override;
     QFixed averageCharWidth() const override;
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 7a6dfe266f..57fbf6032e 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -381,15 +381,13 @@ QT_WARNING_POP
     return ret;
 }
 
-bool QCoreTextFontEngine::processHheaTable() const
+void QCoreTextFontEngine::initializeHeightMetrics() const
 {
-    if (!QFontEngine::processHheaTable()) {
-        m_ascent = QFixed::fromReal(CTFontGetAscent(ctfont));
-        m_descent = QFixed::fromReal(CTFontGetDescent(ctfont));
-        m_leading = QFixed::fromReal(CTFontGetLeading(ctfont));
-    }
+    m_ascent = QFixed::fromReal(CTFontGetAscent(ctfont));
+    m_descent = QFixed::fromReal(CTFontGetDescent(ctfont));
+    m_leading = QFixed::fromReal(CTFontGetLeading(ctfont));
 
-    return true;
+    QFontEngine::initializeHeightMetrics();
 }
 
 QFixed QCoreTextFontEngine::capHeight() const
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
index 5111e2ce2e..da75594fde 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
@@ -139,7 +139,7 @@ protected:
     bool hasColorGlyphs() const;
     bool shouldAntialias() const;
     bool shouldSmoothFont() const;
-    bool processHheaTable() const override;
+    void initializeHeightMetrics() const override;
 
     QCFType<CTFontRef> ctfont;
     QCFType<CGFontRef> cgFont;
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontengine.cpp b/src/platformsupport/fontdatabases/windows/qwindowsfontengine.cpp
index 6c1088c019..6248041a3d 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontengine.cpp
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontengine.cpp
@@ -610,15 +610,13 @@ void QWindowsFontEngine::getGlyphBearings(glyph_t glyph, qreal *leftBearing, qre
 }
 #endif // Q_CC_MINGW
 
-bool QWindowsFontEngine::processHheaTable() const
+void QWindowsFontEngine::initializeHeightMetrics() const
 {
-    if (!QFontEngine::processHheaTable()) {
-        m_ascent = tm.tmAscent;
-        m_descent = tm.tmDescent;
-        m_leading = tm.tmExternalLeading;
-    }
+    m_ascent = tm.tmAscent;
+    m_descent = tm.tmDescent;
+    m_leading = tm.tmExternalLeading;
 
-    return true;
+    QFontEngine::initializeHeightMetrics();
 }
 
 bool QWindowsFontEngine::hasUnreliableGlyphOutline() const
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontengine_p.h b/src/platformsupport/fontdatabases/windows/qwindowsfontengine_p.h
index 4f5629dd0f..8a676affcd 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontengine_p.h
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontengine_p.h
@@ -130,7 +130,7 @@ public:
     void setUniqueFamilyName(const QString &newName) { uniqueFamilyName = newName; }
 
 protected:
-    bool processHheaTable() const override;
+    void initializeHeightMetrics() const override;
 
 private:
     QWindowsNativeImage *drawGDIGlyph(HFONT font, glyph_t, int margin, const QTransform &xform,
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
index 7e5c1a2a9e..6c9d4b29a0 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite.cpp
@@ -343,18 +343,16 @@ QString QWindowsFontEngineDirectWrite::filenameFromFontFile(IDWriteFontFile *fon
     return ret;
 }
 
-bool QWindowsFontEngineDirectWrite::processHheaTable() const
+void QWindowsFontEngineDirectWrite::initializeHeightMetrics() const
 {
-    if (!QFontEngine::processHheaTable()) {
-        DWRITE_FONT_METRICS metrics;
-        m_directWriteFontFace->GetMetrics(&metrics);
+    DWRITE_FONT_METRICS metrics;
+    m_directWriteFontFace->GetMetrics(&metrics);
 
-        m_ascent = DESIGN_TO_LOGICAL(metrics.ascent);
-        m_descent = DESIGN_TO_LOGICAL(metrics.descent);
-        m_leading = DESIGN_TO_LOGICAL(metrics.lineGap);
-    }
+    m_ascent = DESIGN_TO_LOGICAL(metrics.ascent);
+    m_descent = DESIGN_TO_LOGICAL(metrics.descent);
+    m_leading = DESIGN_TO_LOGICAL(metrics.lineGap);
 
-    return true;
+    QFontEngine::initializeHeightMetrics();
 }
 
 void QWindowsFontEngineDirectWrite::collectMetrics()
diff --git a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
index ccef808486..6e79190ce4 100644
--- a/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
+++ b/src/platformsupport/fontdatabases/windows/qwindowsfontenginedirectwrite_p.h
@@ -122,7 +122,7 @@ public:
 
     void setUniqueFamilyName(const QString &newName) { m_uniqueFamilyName = newName; }
 
-    bool processHheaTable() const override;
+    void initializeHeightMetrics() const override;
 
 private:
     QImage imageForGlyph(glyph_t t, QFixed subPixelPosition, int margin, const QTransform &xform, const QColor &color = QColor());