QStyleSheet: never treat styled scrollbars as transient

If a style sheet is applied to a scrollbar, then we cannot treat it as
transient, as the QStyleSheetStyle doesn't implement any fade-in/out
animation logic. And we also need to set the overlap to 0 (in both
the style sheet and the macOS style) if the scrollbars are not
transient; otherwise the opaque scrollbar will be placed on top of the
content.

Since a style sheet might only apply to a scrollbar based on its
orientation, we also have to pass the style option through to all calls
of the styleHint function.

And since that function is also called from other QStyle implementations
in the macOS style, we have to make sure that we call styleHint() on the
widget's style to get the correct value based on the style sheet.

Fixes: QTBUG-63381
Pick-to: 6.5 6.4 6.2
Change-Id: Ic67ce3a7cb5089f885dabfd5a1951e3029915446
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 215e926031..00adefdf4f 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -5103,7 +5103,7 @@ int QStyleSheetStyle::pixelMetric(PixelMetric m, const QStyleOption *opt, const
         break;
 
     case PM_ScrollView_ScrollBarOverlap:
-        if (!rule.hasNativeBorder() || rule.hasBox())
+        if (!proxy()->styleHint(SH_ScrollBar_Transient, opt, w))
             return 0;
         break;
 #endif // QT_CONFIG(scrollbar)
@@ -5713,7 +5713,7 @@ int QStyleSheetStyle::styleHint(StyleHint sh, const QStyleOption *opt, const QWi
         case SH_TitleBar_ShowToolTipsOnButtons: s = "titlebar-show-tooltips-on-buttons"_L1; break;
         case SH_Widget_Animation_Duration: s = "widget-animation-duration"_L1; break;
         case SH_ScrollBar_Transient:
-            if (!rule.hasNativeBorder() || rule.hasBox())
+            if (!rule.hasNativeBorder() || rule.hasBox() || rule.hasDrawable())
                 return 0;
             break;
         default: break;