Fix output with box font engine

The box font engine was passing in alpha values in the blue
channel instead of alpha channel to QImage::setPixel(), probably
assuming that setPixel() accepts the input in the format of the
QImage. But the whole point of setPixel() is that it converts
the input. If we just want to set the alpha value, we can do
it directly on the QImage::bits().

[ChangeLog][Text] Fixed showing boxes for glyphs when there are
no fonts available in the font database.

Pick-to: 5.15
Change-Id: I7ae067c26b9ecba6aaa046e7e4b9ae520c4b3d23
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 5 insertions, 5 deletions

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 15036718c3..9dd59e58f9 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -1670,12 +1670,12 @@ QImage QFontEngineBox::alphaMapForGlyph(glyph_t)
     QImage image(_size, _size, QImage::Format_Alpha8);
     image.fill(0);
 
-    // FIXME: use qpainter
+    uchar *bits = image.bits();
     for (int i=2; i <= _size-3; ++i) {
-        image.setPixel(i, 2, 255);
-        image.setPixel(i, _size-3, 255);
-        image.setPixel(2, i, 255);
-        image.setPixel(_size-3, i, 255);
+        bits[i + 2 * image.bytesPerLine()] = 255;
+        bits[i + (_size - 3) * image.bytesPerLine()] = 255;
+        bits[2 + i * image.bytesPerLine()] = 255;
+        bits[_size - 3 + i * image.bytesPerLine()] = 255;
     }
     return image;
 }