Correct last right bearing in boundingBox(glyphs)

Commit 07880542ecc479807c23c5646d263135240822ff introduced regression to
QFontMetrics::boundingRect and QTextEngine::boundingBox on FT, XLFD and
QPF font engine. Because on these platforms, rightBearing of the last
glyphs is already removed from the width returned in glyph_metrics_t.
Subtracting that rightBearing twice will cause the resulting boundingBox
smaller than expected.

This patch fix this by removing last right bearing accounting code from
generic QTextEngine::boundingBox, instead, we put it into font engines
that need them: QFontEngineWin, QCoreTextFontEngine, QFontEngineMac,
QFontEngineS60 and QFontEngineQWS. So that the resulting width should be
correct on all platforms without introducing any performance penalties.

Task-number: QTBUG-6854, QTBUG-12950
Reviewed-by: Eskil

1 files changed, 12 insertions, 0 deletions

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 194c5f3dd4..3f758b1dd2 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -1093,6 +1093,18 @@ const QVector<QRgb> &QFontEngine::grayPalette()
     return *qt_grayPalette();
 }
 
+QFixed QFontEngine::lastRightBearing(const QGlyphLayout &glyphs, bool round)
+{
+    if (glyphs.numGlyphs >= 1) {
+        glyph_t glyph = glyphs.glyphs[glyphs.numGlyphs - 1];
+        glyph_metrics_t gi = boundingBox(glyph);
+        if (gi.isValid())
+            return round ? QFixed(qRound(gi.xoff - gi.x - gi.width))
+                         : QFixed(gi.xoff - gi.x - gi.width);
+    }
+    return 0;
+}
+
 // ------------------------------------------------------------------
 // The box font engine
 // ------------------------------------------------------------------