CoreText: Remove handling of the AppleAntiAliasingThreshold user default

The setting is not relevant for modern macOS applications, and none of
the applications shipped with macOS today are affected by it.

The only code path in macOS that picks it up is +[NSFont initialize] in
the UIFoundation framework, storing it for later so that -[NSFont screenFont]
and -[NSFont screenFontWithRenderingMode:] can use it, but these APIs are
deprecated and we don't use them in Qt.

Other NSFont code paths will not hit these APIs unless screen font
substitution is enabled, something it hasn't been since OSX 10.7.

 https://preview.tinyurl.com/yctpfnqp

Removing handling of this setting allows us to simplify the reasoning
for whether or not antialiasing and font smoothing is enabled for a given
engine.

Change-Id: Ie2809052a1a0815d9bddedd4a6236eb6c898f993
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm

@@ -614,20 +614,6 @@ glyph_metrics_t QCoreTextFontEngine::alphaMapBoundingBox(glyph_t glyph, QFixed s
     return br;
 }
 
-int QCoreTextFontEngine::antialiasingThreshold()
-{
-    static const int antialiasingThreshold = [] {
-        auto defaults = [NSUserDefaults standardUserDefaults];
-        int threshold = [defaults integerForKey:@"AppleAntiAliasingThreshold"];
-        qCDebug(lcQpaFonts) << "Resolved antialiasing threshold. Defaults ="
-            << [[defaults dictionaryRepresentation] dictionaryWithValuesForKeys:@[
-                @"AppleAntiAliasingThreshold"
-            ]] << "Result =" << threshold;
-        return threshold;
-    }();
-    return antialiasingThreshold;
-}
-
 /*
     Apple has gone through many iterations of its font smoothing algorithms,
     and there are many ways to enable or disable certain aspects of it. As
@@ -732,8 +718,7 @@ bool QCoreTextFontEngine::expectsGammaCorrectedBlending() const
     return (glyphFormat == Format_A32) && !(fontDef.styleStrategy & (QFont::NoAntialias | QFont::NoSubpixelAntialias));
 }
 
-QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition,
+QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &matrix)
-                        bool overrideAntialiasingThreshold, const QTransform &matrix)
 {
     glyph_metrics_t br = alphaMapBoundingBox(glyph, subPixelPosition, matrix, glyphFormat);
 
@@ -770,8 +755,7 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
                                              qt_mac_bitmapInfoForImage(im));
     Q_ASSERT(ctx);
     CGContextSetFontSize(ctx, fontDef.pixelSize);
-    const bool antialias = (overrideAntialiasingThreshold || fontDef.pointSize > antialiasingThreshold())
+    const bool antialias = !(fontDef.styleStrategy & QFont::NoAntialias);
-        && !(fontDef.styleStrategy & QFont::NoAntialias);
     CGContextSetShouldAntialias(ctx, antialias);
     const bool smoothing = antialias && !(fontDef.styleStrategy & QFont::NoSubpixelAntialias);
     CGContextSetShouldSmoothFonts(ctx, smoothing);
@@ -837,7 +821,7 @@ QImage QCoreTextFontEngine::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosit
     if (x.type() > QTransform::TxScale)
         return QFontEngine::alphaMapForGlyph(glyph, subPixelPosition, x);
 
-    QImage im = imageForGlyph(glyph, subPixelPosition, false, x);
+    QImage im = imageForGlyph(glyph, subPixelPosition, x);
 
     QImage alphaMap(im.width(), im.height(), QImage::Format_Alpha8);
 
@@ -859,7 +843,7 @@ QImage QCoreTextFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed subPixelPo
     if (x.type() > QTransform::TxScale)
         return QFontEngine::alphaRGBMapForGlyph(glyph, subPixelPosition, x);
 
-    QImage im = imageForGlyph(glyph, subPixelPosition, true, x);
+    QImage im = imageForGlyph(glyph, subPixelPosition, x);
     qGamma_correct_back_to_linear_cs(&im);
     return im;
 }
@@ -869,7 +853,7 @@ QImage QCoreTextFontEngine::bitmapForGlyph(glyph_t glyph, QFixed subPixelPositio
     if (t.type() > QTransform::TxScale)
         return QFontEngine::bitmapForGlyph(glyph, subPixelPosition, t);
 
-    return imageForGlyph(glyph, subPixelPosition, true, t);
+    return imageForGlyph(glyph, subPixelPosition, t);
 }
 
 void QCoreTextFontEngine::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::ShaperFlags flags) const

src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h

@@ -127,7 +127,6 @@ public:
     Q_ENUM(FontSmoothing);
 
     static FontSmoothing fontSmoothing();
-    static int antialiasingThreshold();
 
     static bool ct_getSfntTable(void *user_data, uint tag, uchar *buffer, uint *length);
     static QFont::Weight qtWeightFromCFWeight(float value);
@@ -137,7 +136,7 @@ public:
 protected:
     QCoreTextFontEngine(const QFontDef &def);
     void init();
-    QImage imageForGlyph(glyph_t glyph, QFixed subPixelPosition, bool colorful, const QTransform &m);
+    QImage imageForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &m);
     void loadAdvancesForGlyphs(QVarLengthArray<CGGlyph> &cgGlyphs, QGlyphLayout *glyphs) const;
     bool hasColorGlyphs() const;
 

src/plugins/platforms/cocoa/qpaintengine_mac.mm

@@ -914,7 +914,6 @@ void QCoreGraphicsPaintEngine::drawTextItem(const QPointF &pos, const QTextItem
     QFontEngine *fe = ti.fontEngine;
 
     const bool textAA = ((state->renderHints() & QPainter::TextAntialiasing)
-                         && (fe->fontDef.pointSize > QCoreTextFontEngine::antialiasingThreshold())
                          && !(fe->fontDef.styleStrategy & QFont::NoAntialias));
     const bool lineAA = state->renderHints() & QPainter::Antialiasing;
     if (textAA != lineAA)