QStyleKitStyle: Clear injected widget fonts when switching themes/styles

A font property defined in a theme or style persisted to some widgets
even after switching to a different theme/style. This was because
unsetStyleFont() reverted against QWidget::font() whose resolve mask
also covers inherited attributes. Since when switching style/theme
we walk QWidgetPrivate::allWidgets in no specified order, a widget
can be reverted while its ancestor carries the old font, so those bits
get written backs as a locally set font so next time setStyleFont()
is called, it captures them as baseline font. To fix, use
QWidgetPrivate::localFont instead which has the direct font resolve
mask.
While at it, remove the check in setStyleFont() which guarded
setFont() on QFont::operator==, which ignores the resolve mask, making
the widget's mask depend on whether the values happened to coincide.
setFont() already no-ops when the the font is unchanged.

Pick-to: 6.12
Change-Id: I2c249dc4a02e3b957b5b490a7da600432787c2a2
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 2 insertions, 3 deletions

diff --git a/src/labs/stylekit/widgets/qstylekitstyle.cpp b/src/labs/stylekit/widgets/qstylekitstyle.cpp
index 316d7039e8..5c53f36c75 100644
--- a/src/labs/stylekit/widgets/qstylekitstyle.cpp
+++ b/src/labs/stylekit/widgets/qstylekitstyle.cpp
@@ -729,7 +729,7 @@ void QStyleKitStylePrivate::unsetStyleFont(QWidget *widget)
 
     auto customFont = std::move(*it);
     customFontWidgets.erase(it);
-    widget->setFont(std::move(customFont).reverted(widget->font()));
+    widget->setFont(std::move(customFont).reverted(QWidgetPrivate::get(widget)->localFont()));
 }
 
 void QStyleKitStylePrivate::setStyleFont(QWidget *widget, const QFont &styleFont)
@@ -753,8 +753,7 @@ void QStyleKitStylePrivate::setStyleFont(QWidget *widget, const QFont &styleFont
     const QFont &baseline = it->oldWidgetValue;
     QFont merged = styleFont.resolve(baseline);
     merged.setResolveMask(baseline.resolveMask() | styleMask);
-    if (widget->font() != merged)
-        widget->setFont(merged);
+    widget->setFont(merged);
 }
 
 void QStyleKitStylePrivate::refreshStyleFont(QWidget *widget)