Improve QtGui start-up time and memory use.

The gamma lookup tables can be allocated and computed on demand, as
they're not always needed, depending on the platform and the use case.

Change-Id: I2d4c2860746366a0e46edb53bd4ecd2778de2464
Reviewed-by: Olivier Goffart <ogoffart@kde.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/src/gui/text/qfontenginedirectwrite.cpp b/src/gui/text/qfontenginedirectwrite.cpp
index 5bac1172fa..952e06d151 100644
--- a/src/gui/text/qfontenginedirectwrite.cpp
+++ b/src/gui/text/qfontenginedirectwrite.cpp
@@ -508,7 +508,7 @@ qreal QFontEngineDirectWrite::maxCharWidth() const
     return 0;
 }
 
-extern uint qt_pow_gamma[256];
+extern const uint *qt_pow_gamma();
 
 QImage QFontEngineDirectWrite::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition,
                                                 const QTransform &xform)
@@ -521,11 +521,13 @@ QImage QFontEngineDirectWrite::alphaMapForGlyph(glyph_t glyph, QFixed subPixelPo
         colors[i] = qRgba(0, 0, 0, i);
     indexed.setColorTable(colors);
 
+    uint *gamma = qt_pow_gamma();
     for (int y=0; y<im.height(); ++y) {
         uint *src = (uint*) im.scanLine(y);
         uchar *dst = indexed.scanLine(y);
         for (int x=0; x<im.width(); ++x) {
-            *dst = 255 - (qt_pow_gamma[qGray(0xffffffff - *src)] * 255. / 2047.);
+            uint gray = qGray(0xffffffff - *src);
+            *dst = 255 - (gamma ? gamma[gray] * 255. / 2047. : gray);
             ++dst;
             ++src;
         }