From 8eeae7ae073ddd71a9210c0d3d1edaa6c199f509 Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Wed, 14 Apr 2021 12:59:20 +0200
Subject: [PATCH] Fix partial pixel coverage calculation

We want right - left, but the numbers we have are (1 - left) and right,
so we need right - (1 - left) = right + left - 1.

Fixes: QTBUG-91957
Fixes: QTBUG-92485
Change-Id: I238cbbe1eebddff1ce56da38127899cdbd21db0e
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit 004189b2d8e751021f26d9eb28948f753ea8208c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/gui/painting/qrasterizer.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gui/painting/qrasterizer.cpp b/src/gui/painting/qrasterizer.cpp
index 48d41f41f02..e851a3876a7 100644
--- a/src/gui/painting/qrasterizer.cpp
+++ b/src/gui/painting/qrasterizer.cpp
@@ -864,7 +864,7 @@ void QRasterizer::rasterizeLine(const QPointF &a, const QPointF &b, qreal width,
                 if (leftWidth == QScFixedFactor)
                     coverage[0] = rightWidth * 255;
                 else
-                    coverage[0] = (leftWidth + rightWidth) * 255;
+                    coverage[0] = (rightWidth + leftWidth - QScFixedFactor) * 255;
                 x[0] = iLeft;
                 len[0] = 1;
             } else {