DirectWrite: Fix clipping bug with grayscale AA rendering

The code is using the same rasterizer for A8 and A32 glyphs,
in the former case it's just converting to grayscale afterwards.
Therefore, we need to pad the glyph cache with the same number of
pixels for both cases.

[ChangeLog][Windows][DirectWrite] Fixed clipping bug when rendering
unhinted text with grayscale antialiasing.

Task-number: QTBUG-49562
Change-Id: If85ff768451116278f6d2ccd1e77b5ce0664087d
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.cpp b/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.cpp
index 593ac7d810..2cd00d7b81 100644
--- a/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.cpp
+++ b/src/plugins/platforms/windows/qwindowsfontenginedirectwrite.cpp
@@ -487,7 +487,7 @@ qreal QWindowsFontEngineDirectWrite::maxCharWidth() const
 
 QImage QWindowsFontEngineDirectWrite::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition)
 {
-    QImage im = imageForGlyph(glyph, subPixelPosition, 0, QTransform());
+    QImage im = alphaRGBMapForGlyph(glyph, subPixelPosition, QTransform());
 
     QImage alphaMap(im.width(), im.height(), QImage::Format_Alpha8);
 
@@ -709,9 +709,9 @@ QString QWindowsFontEngineDirectWrite::fontNameSubstitute(const QString &familyN
 glyph_metrics_t QWindowsFontEngineDirectWrite::alphaMapBoundingBox(glyph_t glyph, QFixed pos, const QTransform &matrix, GlyphFormat format)
 {
     Q_UNUSED(pos);
-    int margin = 0;
-    if (format == QFontEngine::Format_A32 || format == QFontEngine::Format_ARGB)
-        margin = glyphMargin(QFontEngine::Format_A32);
+    Q_UNUSED(format);
+
+    int margin = glyphMargin(QFontEngine::Format_A32);
     glyph_metrics_t gm = QFontEngine::boundingBox(glyph, matrix);
     gm.width += margin * 2;
     gm.height += margin * 2;