Unify QFontEngine::boundingRect for coretext and Windows

They were both using the same algorithm, and also both had the same
mistake of not handling left-bearing. This unifies them and adds left
bearing handling.

Change-Id: Id06392abde0bfeb8b49faf4632082b2e25352497
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/gui/text/coretext/qfontengine_coretext.mm

@@ -301,14 +301,6 @@ bool QCoreTextFontEngine::stringToCMap(const QChar *str, int len, QGlyphLayout *
     return true;
 }
 
-glyph_metrics_t QCoreTextFontEngine::boundingBox(const QGlyphLayout &glyphs)
-{
-    QFixed w;
-    for (int i = 0; i < glyphs.numGlyphs; ++i)
-        w += glyphs.effectiveAdvance(i);
-    return glyph_metrics_t(0, -(ascent()), w - lastRightBearing(glyphs), ascent()+descent(), w, 0);
-}
-
 glyph_metrics_t QCoreTextFontEngine::boundingBox(glyph_t glyph)
 {
     glyph_metrics_t ret;

src/gui/text/coretext/qfontengine_coretext_p.h

@@ -41,7 +41,6 @@ public:
     bool stringToCMap(const QChar *str, int len, QGlyphLayout *glyphs, int *nglyphs, ShaperFlags flags) const override;
     void recalcAdvances(QGlyphLayout *, ShaperFlags) const override;
 
-    glyph_metrics_t boundingBox(const QGlyphLayout &glyphs) override;
     glyph_metrics_t boundingBox(glyph_t glyph) override;
 
     QFixed capHeight() const override;

src/gui/text/qfontengine.cpp

@@ -562,6 +562,16 @@ qreal QFontEngine::minRightBearing() const
     return m_minRightBearing;
 }
 
+glyph_metrics_t QFontEngine::boundingBox(const QGlyphLayout &glyphs)
+{
+    QFixed w;
+    for (int i = 0; i < glyphs.numGlyphs; ++i)
+        w += glyphs.effectiveAdvance(i);
+    const QFixed leftBearing = firstLeftBearing(glyphs);
+    const QFixed rightBearing = lastRightBearing(glyphs);
+    return glyph_metrics_t(leftBearing, -(ascent()), w - leftBearing - rightBearing, ascent() + descent(), w, 0);
+}
+
 glyph_metrics_t QFontEngine::tightBoundingBox(const QGlyphLayout &glyphs)
 {
     glyph_metrics_t overall;
@@ -1452,6 +1462,17 @@ bool QFontEngine::hasUnreliableGlyphOutline() const
     return glyphFormat == QFontEngine::Format_ARGB;
 }
 
+QFixed QFontEngine::firstLeftBearing(const QGlyphLayout &glyphs)
+{
+    if (glyphs.numGlyphs >= 1) {
+        glyph_t glyph = glyphs.glyphs[0];
+        glyph_metrics_t gi = boundingBox(glyph);
+        if (gi.isValid())
+            return gi.leftBearing();
+    }
+    return 0;
+}
+
 QFixed QFontEngine::lastRightBearing(const QGlyphLayout &glyphs)
 {
     if (glyphs.numGlyphs >= 1) {

src/gui/text/qfontengine_p.h

@@ -189,7 +189,7 @@ public:
 
     virtual void removeGlyphFromCache(glyph_t);
 
-    virtual glyph_metrics_t boundingBox(const QGlyphLayout &glyphs) = 0;
+    virtual glyph_metrics_t boundingBox(const QGlyphLayout &glyphs);
     virtual glyph_metrics_t boundingBox(glyph_t glyph) = 0;
     virtual glyph_metrics_t boundingBox(glyph_t glyph, const QTransform &matrix);
     glyph_metrics_t tightBoundingBox(const QGlyphLayout &glyphs);
@@ -332,6 +332,7 @@ public:
 protected:
     explicit QFontEngine(Type type);
 
+    QFixed firstLeftBearing(const QGlyphLayout &glyphs);
     QFixed lastRightBearing(const QGlyphLayout &glyphs);
 
     QFixed calculatedCapHeight() const;

src/gui/text/windows/qwindowsfontengine.cpp

@@ -352,18 +352,6 @@ void QWindowsFontEngine::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::Shape
     }
 }
 
-glyph_metrics_t QWindowsFontEngine::boundingBox(const QGlyphLayout &glyphs)
-{
-    if (glyphs.numGlyphs == 0)
-        return glyph_metrics_t();
-
-    QFixed w = 0;
-    for (int i = 0; i < glyphs.numGlyphs; ++i)
-        w += glyphs.effectiveAdvance(i);
-
-    return glyph_metrics_t(0, -tm.tmAscent, w - lastRightBearing(glyphs), tm.tmHeight, w, 0);
-}
-
 bool QWindowsFontEngine::getOutlineMetrics(glyph_t glyph, const QTransform &t, glyph_metrics_t *metrics) const
 {
     Q_ASSERT(metrics != 0);

src/gui/text/windows/qwindowsfontengine_p.h

@@ -57,7 +57,6 @@ public:
 
     HGDIOBJ selectDesignFont() const;
 
-    glyph_metrics_t boundingBox(const QGlyphLayout &glyphs) override;
     glyph_metrics_t boundingBox(glyph_t g) override { return boundingBox(g, QTransform()); }
     glyph_metrics_t boundingBox(glyph_t g, const QTransform &t) override;