Fixed text drawing on Windows in 16 bit mode.

There were several problems with antialiased text in 16 bit mode
under Windows. No gamma correction was done, yet we prepared the
cached glyphs for gamma correction. The mask format we rendered
the glyphs into was also set to the desktop depth, which implied
that information was lost and the text looked rather odd.

Reviewed-by: Samuel
BT: yes
(cherry picked from commit 35bdd8942716c716113e5b795186ca76199e8d96)

2 files changed, 16 insertions, 13 deletions

diff --git a/src/gui/text/qfontengine_win.cpp b/src/gui/text/qfontengine_win.cpp
index c1ef822..dbbb682 100644
--- a/src/gui/text/qfontengine_win.cpp
+++ b/src/gui/text/qfontengine_win.cpp
@@ -1335,7 +1335,7 @@ bool QFontEngineWin::getSfntTableData(uint tag, uchar *buffer, uint *length) con
 
 
 QNativeImage *QFontEngineWin::drawGDIGlyph(HFONT font, glyph_t glyph, int margin,
-                                           const QTransform &t)
+                                           const QTransform &t, QImage::Format mask_format)
 {
     glyph_metrics_t gm = boundingBox(glyph);
 
@@ -1408,7 +1408,7 @@ QNativeImage *QFontEngineWin::drawGDIGlyph(HFONT font, glyph_t glyph, int margin
 
     QNativeImage *ni = new QNativeImage(iw + 2 * margin + 4,
                                         ih + 2 * margin + 4,
-                                        QNativeImage::systemFormat(), true);
+                                        mask_format, true);
     ni->image.fill(0xffffffff);
 
     HDC hdc = ni->hdc;
@@ -1448,8 +1448,12 @@ QImage QFontEngineWin::alphaMapForGlyph(glyph_t glyph, const QTransform &xform)
         lf.lfQuality = ANTIALIASED_QUALITY;
         font = CreateFontIndirectW(&lf);
     }
+    QImage::Format mask_format = QNativeImage::systemFormat();
+#ifndef Q_OS_WINCE
+    mask_format = QImage::Format_RGB32;
+#endif
 
-    QNativeImage *mask = drawGDIGlyph(font, glyph, 0, xform);
+    QNativeImage *mask = drawGDIGlyph(font, glyph, 0, xform, mask_format);
     if (mask == 0)
         return QImage();
 
@@ -1466,22 +1470,20 @@ QImage QFontEngineWin::alphaMapForGlyph(glyph_t glyph, const QTransform &xform)
     // Alpha channel of the ni.image pixels...
     for (int y=0; y<mask->height(); ++y) {
         uchar *dest = indexed.scanLine(y);
-        if (mask->systemFormat() == QImage::Format_RGB16) {
+        if (mask->image.format() == QImage::Format_RGB16) {
             const qint16 *src = (qint16 *) ((const QImage &) mask->image).scanLine(y);
-            for (int x=0; x<mask->width(); ++x) {
-#ifdef Q_OS_WINCE
+            for (int x=0; x<mask->width(); ++x)
                 dest[x] = 255 - qGray(src[x]);
-#else
-                dest[x] = 255 - (qt_pow_gamma[qGray(src[x])] * 255. / 2047.);
-#endif
-            }
         } else {
             const uint *src = (uint *) ((const QImage &) mask->image).scanLine(y);
             for (int x=0; x<mask->width(); ++x) {
 #ifdef Q_OS_WINCE
                 dest[x] = 255 - qGray(src[x]);
 #else
-                dest[x] = 255 - (qt_pow_gamma[qGray(src[x])] * 255. / 2047.);
+                if (QNativeImage::systemFormat() == QImage::Format_RGB16)
+                    dest[x] = 255 - qGray(src[x]);
+                else
+                    dest[x] = 255 - (qt_pow_gamma[qGray(src[x])] * 255. / 2047.);
 #endif
             }
         }
@@ -1507,7 +1509,7 @@ QImage QFontEngineWin::alphaRGBMapForGlyph(glyph_t glyph, int margin, const QTra
     SystemParametersInfo(SPI_GETFONTSMOOTHINGCONTRAST, 0, &contrast, 0);
     SystemParametersInfo(SPI_SETFONTSMOOTHINGCONTRAST, 0, (void *) 1000, 0);
 
-    QNativeImage *mask = drawGDIGlyph(font, glyph, margin, t);
+    QNativeImage *mask = drawGDIGlyph(font, glyph, margin, t, QImage::Format_RGB32);
     SystemParametersInfo(SPI_SETFONTSMOOTHINGCONTRAST, 0, (void *) contrast, 0);
 
     if (mask == 0)
diff --git a/src/gui/text/qfontengine_win_p.h b/src/gui/text/qfontengine_win_p.h
index 3160a8a..389297f 100644
--- a/src/gui/text/qfontengine_win_p.h
+++ b/src/gui/text/qfontengine_win_p.h
@@ -138,7 +138,8 @@ public:
     mutable int designAdvancesSize;
 
 private:
-    QNativeImage *drawGDIGlyph(HFONT font, glyph_t, int margin, const QTransform &xform);
+    QNativeImage *drawGDIGlyph(HFONT font, glyph_t, int margin, const QTransform &xform,
+                               QImage::Format mask_format);
 
 };