QMac/FusionStyle: fix the background color for transient scrollbars

Task-number: QTBUG-39922
Change-Id: I4b313296ae845bc9e116494aa66c577b432b4a67
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>

4 files changed, 13 insertions, 2 deletions

diff --git a/src/widgets/styles/qfusionstyle.cpp b/src/widgets/styles/qfusionstyle.cpp
index 2172c9082f..82c53def7d 100644
--- a/src/widgets/styles/qfusionstyle.cpp
+++ b/src/widgets/styles/qfusionstyle.cpp
@@ -2493,7 +2493,7 @@ void QFusionStyle::drawComplexControl(ComplexControl control, const QStyleOption
             QColor arrowColor = option->palette.foreground().color();
             arrowColor.setAlpha(220);
 
-            const QColor bgColor = option->palette.color(QPalette::Base);
+            const QColor bgColor = QStyleHelper::backgroundColor(option->palette, widget);
             const bool isDarkBg = bgColor.red() < 128 && bgColor.green() < 128 && bgColor.blue() < 128;
 
             if (transient) {
diff --git a/src/widgets/styles/qmacstyle_mac.mm b/src/widgets/styles/qmacstyle_mac.mm
index 8bc454a795..8cb7ce1c87 100644
--- a/src/widgets/styles/qmacstyle_mac.mm
+++ b/src/widgets/styles/qmacstyle_mac.mm
@@ -5133,7 +5133,7 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
                 [scroller initWithFrame:NSMakeRect(0, 0, slider->rect.width(), slider->rect.height())];
                 // mac os behaviour: as soon as one color channel is >= 128,
                 // the bg is considered bright, scroller is dark
-                const QColor bgColor = opt->palette.color(QPalette::Base);
+                const QColor bgColor = QStyleHelper::backgroundColor(opt->palette, widget);
                 const bool isDarkBg = bgColor.red() < 128 && bgColor.green() < 128 &&
                                       bgColor.blue() < 128;
                 if (isDarkBg)
diff --git a/src/widgets/styles/qstylehelper.cpp b/src/widgets/styles/qstylehelper.cpp
index fc73488154..6be07a3f45 100644
--- a/src/widgets/styles/qstylehelper.cpp
+++ b/src/widgets/styles/qstylehelper.cpp
@@ -45,6 +45,8 @@
 #include <private/qmath_p.h>
 #include <private/qstyle_p.h>
 #include <qmath.h>
+#include <qscrollbar.h>
+#include <qabstractscrollarea.h>
 
 #include "qstylehelper_p.h"
 #include <qstringbuilder.h>
@@ -387,5 +389,13 @@ void drawBorderPixmap(const QPixmap &pixmap, QPainter *painter, const QRect &rec
 
     }
 }
+
+QColor backgroundColor(const QPalette &pal, const QWidget* widget)
+{
+    if (qobject_cast<const QScrollBar *>(widget) && widget->parent() &&
+            qobject_cast<const QAbstractScrollArea *>(widget->parent()->parent()))
+        return widget->parentWidget()->parentWidget()->palette().color(QPalette::Base);
+    return pal.color(QPalette::Base);
+}
 }
 QT_END_NAMESPACE
diff --git a/src/widgets/styles/qstylehelper_p.h b/src/widgets/styles/qstylehelper_p.h
index 6355cbc985..73e5c94dcd 100644
--- a/src/widgets/styles/qstylehelper_p.h
+++ b/src/widgets/styles/qstylehelper_p.h
@@ -86,6 +86,7 @@ namespace QStyleHelper
     bool isInstanceOf(QObject *obj, QAccessible::Role role);
     bool hasAncestor(QObject *obj, QAccessible::Role role);
 #endif
+    QColor backgroundColor(const QPalette &pal, const QWidget* widget = 0);
 }