From 0dd2561d54209666cf78d053caf9b2d94fb1d80e Mon Sep 17 00:00:00 2001
From: Christian Ehrlicher <ch.ehrlicher@gmx.de>
Date: Fri, 6 Dec 2024 13:38:34 +0100
Subject: [PATCH] QStyleSheetStyle: Fix resetting fonts for subwidgets

When a compound widget is styled with a font through a property and the
default styling has no font settings, the font was not reset to the
parent font but left it the styled state.
Fix it by not resolving the current font when the style rule has no font
settings - use the parent font directly instead.

Fixes: QTBUG-131685
Pick-to: 6.8
Change-Id: I8e79423cfeff24143cd051b282503c4565125b4d
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 5731fe051e48e7a256ef31ae93cfb89ce8d871cc)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/widgets/styles/qstylesheetstyle.cpp       |  6 ++---
 .../qstylesheetstyle/tst_qstylesheetstyle.cpp | 24 +++++++++++++++++++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 6528615c694..583d2061ed4 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -6485,9 +6485,9 @@ void QStyleSheetStyle::updateStyleSheetFont(QWidget* w) const
         font.setResolveMask(wf.resolveMask() | rule.font.resolveMask());
 
         if ((!w->isWindow() || w->testAttribute(Qt::WA_WindowPropagation))
-            && isNaturalChild(w) && qobject_cast<QWidget *>(w->parent())) {
-
-            font = font.resolve(static_cast<QWidget *>(w->parent())->font());
+            && isNaturalChild(w) && w->parentWidget()) {
+            const auto parentFont = w->parentWidget()->font();
+            font = rule.hasFont ? font.resolve(parentFont) : parentFont;
         }
 
         if (wf.resolveMask() == font.resolveMask() && wf == font)
diff --git a/tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp b/tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp
index a9a1817b8a0..a1bbf14bd61 100644
--- a/tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp
+++ b/tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp
@@ -125,6 +125,8 @@ private slots:
     void inheritWidgetPalette_data();
     void inheritWidgetPalette();
 
+    void resetFont();
+
 private:
     static QColor COLOR(const QWidget &w)
     {
@@ -2528,6 +2530,28 @@ void tst_QStyleSheetStyle::inheritWidgetPalette()
     QCOMPARE(phColor, phColorPalette);
 }
 
+void tst_QStyleSheetStyle::resetFont()
+{
+    QDoubleSpinBox sb;
+    sb.setStyleSheet(R"(QDoubleSpinBox[changed="true"] {font: italic;})");
+
+    auto checkFont = [&sb](bool isItalic) {
+        sb.setProperty("changed", isItalic);
+        sb.style()->polish(&sb);
+        const auto children = sb.findChildren<QWidget *>();
+        for (const auto *w : children) {
+            auto diagnostics = qScopeGuard([&] {
+                qWarning() << "Failure with" << w << "should be italic:" << isItalic;
+            });
+            QCOMPARE(w->font().italic(), isItalic);
+            diagnostics.dismiss();
+        }
+    };
+    checkFont(false);
+    checkFont(true);
+    checkFont(false);
+}
+
 QTEST_MAIN(tst_QStyleSheetStyle)
 #include "tst_qstylesheetstyle.moc"