ToolTip/Windows: Fix wrong size when font is modified by widget stylesheet

Factor out a function to calculate the size and update the size when a
style sheet parent is set.

Task-number: QTBUG-64550
Change-Id: I3afe997085eae3cd48b7fe0a4c98582a8f572260
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

src/widgets/kernel/qtooltip.cpp

@@ -127,6 +127,8 @@ public:
     ~QTipLabel();
     static QTipLabel *instance;
 
+    void updateSize();
+
     bool eventFilter(QObject *, QEvent *) override;
 
     QBasicTimer hideTimer, expireTimer;
@@ -214,13 +216,18 @@ void QTipLabel::reuseTip(const QString &text, int msecDisplayTime)
 
     setWordWrap(Qt::mightBeRichText(text));
     setText(text);
+    updateSize();
+    restartExpireTimer(msecDisplayTime);
+}
+
+void  QTipLabel::updateSize()
+{
     QFontMetrics fm(font());
     QSize extra(1, 0);
     // Make it look good with the default ToolTip font on Mac, which has a small descent.
     if (fm.descent() == 2 && fm.ascent() >= 11)
         ++extra.rheight();
     resize(sizeHint() + extra);
-    restartExpireTimer(msecDisplayTime);
 }
 
 void QTipLabel::paintEvent(QPaintEvent *ev)
@@ -387,6 +394,9 @@ void QTipLabel::placeTip(const QPoint &pos, QWidget *w)
         if (w) {
             connect(w, SIGNAL(destroyed()),
                 QTipLabel::instance, SLOT(styleSheetParentDestroyed()));
+            // QTBUG-64550: A font inherited by the style sheet might change the size,
+            // particular on Windows, where the tip is not parented on a window.
+            QTipLabel::instance->updateSize();
         }
     }
 #endif //QT_NO_STYLE_STYLESHEET

tests/auto/widgets/kernel/qtooltip/tst_qtooltip.cpp

@@ -28,6 +28,8 @@
 
 
 #include <QtTest/QtTest>
+#include <qfont.h>
+#include <qfontmetrics.h>
 #include <qtooltip.h>
 #include <qwhatsthis.h>
 #include <qscreen.h>
@@ -43,6 +45,7 @@ private slots:
     void task183679();
     void whatsThis();
     void setPalette();
+    void qtbug64550_stylesheet();
 };
 
 void tst_QToolTip::init()
@@ -53,6 +56,7 @@ void tst_QToolTip::init()
 void tst_QToolTip::cleanup()
 {
     QTRY_VERIFY(QApplication::topLevelWidgets().isEmpty());
+    qApp->setStyleSheet(QString());
 }
 
 class Widget_task183679 : public QWidget
@@ -66,10 +70,12 @@ public:
         QTimer::singleShot(msecs, this, SLOT(showToolTip()));
     }
 
+    static inline QString toolTipText() { return QStringLiteral("tool tip text"); }
+
 private slots:
     void showToolTip()
     {
-        QToolTip::showText(mapToGlobal(QPoint(0, 0)), "tool tip text", this);
+        QToolTip::showText(mapToGlobal(QPoint(0, 0)), Widget_task183679::toolTipText(), this);
     }
 };
 
@@ -146,6 +152,15 @@ void tst_QToolTip::whatsThis()
     QVERIFY2(whatsThisHeight > 100, QByteArray::number(whatsThisHeight)); // Test QTBUG-2416
 }
 
+static QWidget *findToolTip()
+{
+    const QWidgetList &topLevelWidgets = QApplication::topLevelWidgets();
+    for (QWidget *widget : topLevelWidgets) {
+        if (widget->windowType() == Qt::ToolTip && widget->objectName() == QLatin1String("qtooltip_label"))
+            return widget;
+    }
+    return nullptr;
+}
 
 void tst_QToolTip::setPalette()
 {
@@ -156,16 +171,7 @@ void tst_QToolTip::setPalette()
 
     QTRY_VERIFY(QToolTip::isVisible());
 
-    QWidget *toolTip = 0;
-    foreach (QWidget *widget, QApplication::topLevelWidgets()) {
-        if (widget->windowType() == Qt::ToolTip
-            && widget->objectName() == QLatin1String("qtooltip_label"))
-        {
-            toolTip = widget;
-            break;
-        }
-    }
-
+    QWidget *toolTip = findToolTip();
     QVERIFY(toolTip);
     QTRY_VERIFY(toolTip->isVisible());
 
@@ -178,5 +184,39 @@ void tst_QToolTip::setPalette()
     QToolTip::hideText();
 }
 
+static QByteArray msgSizeTooSmall(const QSize &actual, const QSize &expected)
+{
+    return QByteArray::number(actual.width()) + 'x'
+        + QByteArray::number(actual.height()) + " < "
+        + QByteArray::number(expected.width())  + 'x'
+        + QByteArray::number(expected.height());
+}
+
+// QTBUG-4550: When setting a style sheet specifying a font size on the tooltip's
+// parent widget (as opposed to setting on QApplication), the tooltip should
+// resize accordingly. This is an issue on Windows since the ToolTip widget is
+// not directly parented on the widget itself.
+// Set a large font size and verify that the tool tip is big enough.
+void tst_QToolTip::qtbug64550_stylesheet()
+{
+    Widget_task183679 widget;
+    widget.setStyleSheet(QStringLiteral("* { font-size: 48pt; }\n"));
+    widget.show();
+    QApplication::setActiveWindow(&widget);
+    QVERIFY(QTest::qWaitForWindowActive(&widget));
+
+    widget.showDelayedToolTip(100);
+    QTRY_VERIFY(QToolTip::isVisible());
+    QWidget *toolTip = findToolTip();
+    QVERIFY(toolTip);
+    QTRY_VERIFY(toolTip->isVisible());
+
+    const QRect boundingRect = QFontMetrics(widget.font()).boundingRect(Widget_task183679::toolTipText());
+    const QSize toolTipSize = toolTip->size();
+    QVERIFY2(toolTipSize.width() >= boundingRect.width()
+             && toolTipSize.height() >= boundingRect.height(),
+             msgSizeTooSmall(toolTipSize, boundingRect.size()).constData());
+}
+
 QTEST_MAIN(tst_QToolTip)
 #include "tst_qtooltip.moc"