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Details

Type: Bug
Resolution: Done
Priority: P4: Low
Fix Version/s: 5.9.2
Affects Version/s: 5.9.0 Alpha, 5.9
Component/s: GUI: Look'n'Feel
Labels:
- Reported_by_support_premium
Environment:
all, DPR > 1

Commits:
b6d5026b1f8d7ed6424f9a395d47fc4c62d4751b (qtbase/5.9, 7.7.2017, 5.9.2.)

Description

QFrame with FusionStyle, WindowsStyle (and other styles), or anything that calls qDrawPlainRect() has painting artifacts in the left and top, when in scaled/HighDpi mode.

The lines are too thin, perhaps clipped. The reason seems to be the typical off-by-one of code that was written for normal resolution usinf the integer QPainter-API.

Some adjustments like the following one fix the issue. However, that needs to be thoroughly tested, especially to prevent regressions in the unscaled mode.

--- a/src/widgets/styles/qdrawutil.cpp
+++ b/src/widgets/styles/qdrawutil.cpp
@@ -520,10 +520,12 @@ void qDrawPlainRect(QPainter *p, int x, int y, int w, int h, const QColor &c,
     }
     QPen   oldPen   = p->pen();
     QBrush oldBrush = p->brush();
-    p->setPen(c);
+    QPen   newPen(c);
+    newPen.setJoinStyle(Qt::MiterJoin);
+    p->setPen(newPen);
     p->setBrush(Qt::NoBrush);
     for (int i=0; i<lineWidth; i++)
-        p->drawRect(x+i, y+i, w-i*2 - 1, h-i*2 - 1);
+        p->drawRect(QRectF(x+i + 0.5, y+i + 0.5, w-i*2 - 1, h-i*2 - 1));
     if (fill) {                                // fill with fill color
         p->setPen(Qt::NoPen);
         p->setBrush(*fill);
--