Refactor lockedAlphaMapForGlyph

Simply return a Glyph pointer and not a QImage to avoid allocating and
deleting lots of d pointers for QImage when drawing text. Saves one
new/delete pair per glyph drawn and speeds up text drawing by 10% for
relatively large glyphs (probably more for smaller ones).

The qtext::paintLayoutToPixmap() benchmark shows a 16% improvement
in performance with this change.

Renamed the method to glyphData().

Change-Id: I7a353de521e4f4321c770fb1ac6043d33f6f332c
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

1 files changed, 3 insertions, 22 deletions

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 5506d88f02..1895ac8283 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -923,29 +923,10 @@ QFixed QFontEngine::subPixelPositionForX(QFixed x) const
     return subPixelPosition;
 }
 
-QImage *QFontEngine::lockedAlphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition,
-                                            QFontEngine::GlyphFormat neededFormat,
-                                            const QTransform &t, QPoint *offset)
+QFontEngine::Glyph *QFontEngine::glyphData(glyph_t, QFixed,
+                                           QFontEngine::GlyphFormat, const QTransform &)
 {
-    Q_ASSERT(currentlyLockedAlphaMap.isNull());
-    if (neededFormat == Format_None)
-        neededFormat = Format_A32;
-
-    if (neededFormat != Format_A32)
-        currentlyLockedAlphaMap = alphaMapForGlyph(glyph, subPixelPosition, t);
-    else
-        currentlyLockedAlphaMap = alphaRGBMapForGlyph(glyph, subPixelPosition, t);
-
-    if (offset != 0)
-        *offset = QPoint(0, 0);
-
-    return &currentlyLockedAlphaMap;
-}
-
-void QFontEngine::unlockAlphaMapForGlyph()
-{
-    Q_ASSERT(!currentlyLockedAlphaMap.isNull());
-    currentlyLockedAlphaMap = QImage();
+    return nullptr;
 }
 
 QImage QFontEngine::alphaMapForGlyph(glyph_t glyph)