1 files changed, 32 insertions, 23 deletions

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index d526dcc7ac..0a8de97b38 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtGui module of the Qt Toolkit.
@@ -796,7 +796,7 @@ void QFontEngine::addGlyphsToPath(glyph_t *glyphs, QFixedPoint *positions, int n
     addBitmapFontToPath(x, y, g, path, flags);
 }
 
-QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, QFixed /*subPixelPosition*/)
+QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, const QFixedPoint &/*subPixelPosition*/)
 {
     // For font engines don't support subpixel positioning
     return alphaMapForGlyph(glyph);
@@ -812,9 +812,9 @@ QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, const QTransform &t)
     return i;
 }
 
-QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, const QFixedPoint &subPixelPosition, const QTransform &t)
 {
-    if (! supportsSubPixelPositions())
+    if (!supportsHorizontalSubPixelPositions() && !supportsVerticalSubPixelPositions())
         return alphaMapForGlyph(glyph, t);
 
     QImage i = alphaMapForGlyph(glyph, subPixelPosition);
@@ -825,7 +825,7 @@ QImage QFontEngine::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, con
     return i;
 }
 
-QImage QFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed /*subPixelPosition*/, const QTransform &t)
+QImage QFontEngine::alphaRGBMapForGlyph(glyph_t glyph, const QFixedPoint &/*subPixelPosition*/, const QTransform &t)
 {
     const QImage alphaMask = alphaMapForGlyph(glyph, t);
     QImage rgbMask(alphaMask.width(), alphaMask.height(), QImage::Format_RGB32);
@@ -842,32 +842,37 @@ QImage QFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed /*subPixelPosition
     return rgbMask;
 }
 
-QImage QFontEngine::bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform&, const QColor &)
+QImage QFontEngine::bitmapForGlyph(glyph_t, const QFixedPoint &subPixelPosition, const QTransform&, const QColor &)
 {
     Q_UNUSED(subPixelPosition);
 
     return QImage();
 }
 
-QFixed QFontEngine::subPixelPositionForX(QFixed x) const
+QFixedPoint QFontEngine::subPixelPositionFor(const QFixedPoint &position) const
 {
-    if (m_subPixelPositionCount <= 1 || !supportsSubPixelPositions())
-        return QFixed();
+    if (m_subPixelPositionCount <= 1
+            || (!supportsHorizontalSubPixelPositions()
+                && !supportsVerticalSubPixelPositions())) {
+        return QFixedPoint();
+    }
 
-    QFixed subPixelPosition;
-    if (x != 0) {
-        subPixelPosition = x - x.floor();
-        QFixed fraction = (subPixelPosition / QFixed::fromReal(1.0 / m_subPixelPositionCount)).floor();
+    auto f = [&](QFixed v) {
+        if (v != 0) {
+            v = v - v.floor() + QFixed::fromFixed(1);
+            QFixed fraction = (v / QFixed::fromReal(1.0 / m_subPixelPositionCount)).floor();
+            v = fraction / QFixed(m_subPixelPositionCount);
+        }
+        return v;
+    };
 
-        // Compensate for precision loss in fixed point to make sure we are always drawing at a subpixel position over
-        // the lower boundary for the selected rasterization by adding 1/64.
-        subPixelPosition = fraction / QFixed(m_subPixelPositionCount) + QFixed::fromReal(0.015625);
-    }
-    return subPixelPosition;
+    return QFixedPoint(f(position.x), f(position.y));
 }
 
-QFontEngine::Glyph *QFontEngine::glyphData(glyph_t, QFixed,
-                                           QFontEngine::GlyphFormat, const QTransform &)
+QFontEngine::Glyph *QFontEngine::glyphData(glyph_t,
+                                           const QFixedPoint &,
+                                           QFontEngine::GlyphFormat,
+                                           const QTransform &)
 {
     return nullptr;
 }
@@ -2215,7 +2220,7 @@ QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph)
     return engine(which)->alphaMapForGlyph(stripped(glyph));
 }
 
-QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition)
+QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph, const QFixedPoint &subPixelPosition)
 {
     const int which = highByte(glyph);
     return engine(which)->alphaMapForGlyph(stripped(glyph), subPixelPosition);
@@ -2227,13 +2232,17 @@ QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph, const QTransform &t)
     return engine(which)->alphaMapForGlyph(stripped(glyph), t);
 }
 
-QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+QImage QFontEngineMulti::alphaMapForGlyph(glyph_t glyph,
+                                          const QFixedPoint &subPixelPosition,
+                                          const QTransform &t)
 {
     const int which = highByte(glyph);
     return engine(which)->alphaMapForGlyph(stripped(glyph), subPixelPosition, t);
 }
 
-QImage QFontEngineMulti::alphaRGBMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+QImage QFontEngineMulti::alphaRGBMapForGlyph(glyph_t glyph,
+                                             const QFixedPoint &subPixelPosition,
+                                             const QTransform &t)
 {
     const int which = highByte(glyph);
     return engine(which)->alphaRGBMapForGlyph(stripped(glyph), subPixelPosition, t);