Fix linear RGB16 gradients

Writing to solid overwrites part of the gradient input messing up later
lines. In particular repeating gradients tended to be broken.

Tested by lancelot (once the baseline is correct).

Change-Id: I64222048ba67b0424b44822f09ddc947973145a6
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index ee3863ceb8..39ff4142b8 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -5638,15 +5638,16 @@ static void qt_gradient_quint16(int count, const QSpan *spans, void *userData)
         int yinc = int((linear.dy * data->m22 * gss) * FIXPT_SIZE);
         int off = int((((linear.dy * (data->m22 * qreal(0.5) + data->dy) + linear.off) * gss) * FIXPT_SIZE));
 
-        QRgba64 oldColor = data->solid.color;
+        // Save the fillData since we overwrite it when setting solid.color.
+        QGradientData gradient = data->gradient;
         while (count--) {
             int y = spans->y;
 
-            data->solid.color = QRgba64::fromArgb32(qt_gradient_pixel_fixed(&data->gradient, yinc * y + off));
+            data->solid.color = QRgba64::fromArgb32(qt_gradient_pixel_fixed(&gradient, yinc * y + off));
             blend_color_rgb16(1, spans, userData);
             ++spans;
         }
-        data->solid.color = oldColor;
+        data->gradient = gradient;
 
     } else {
         blend_src_generic(count, spans, userData);