QWidgetTextControl: Ignore unconsumed mouse release events

QWidgetTextControlPrivate::mouseReleaseEvent() has early returns
implemented, e.g. when link has been right clicked or no selection
anchor has been found. These early returns, however, still consume
the event.

This leads to events getting lost instead of getting propagated:
As an example, a QLabel with rich text uses QWidgetTextControl. While
it propagates mouse press events back to its parent, mouse release
events get lost. A QLabel with plain text propagates both events
back correctly.

This patch adds QEvent::ignore() to the early return.
Since no test class exists for QWidgetTextControl, it adds a test in
tst_QLabel.

Fixes: QTBUG-110055
Change-Id: I950f8c3f135793b01c59832835bb429db2282169
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 7689d4ad2f673317af432aae498da74d13703126)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/widgets/widgets/qwidgettextcontrol.cpp

@@ -1818,25 +1818,36 @@ void QWidgetTextControlPrivate::mouseReleaseEvent(QEvent *e, Qt::MouseButton but
     }
 
     if (interactionFlags & Qt::LinksAccessibleByMouse) {
-        if (!(button & Qt::LeftButton))
+
+        // Ignore event unless left button has been pressed
+        if (!(button & Qt::LeftButton)) {
+            e->ignore();
             return;
+        }
 
         const QString anchor = q->anchorAt(pos);
 
-        if (anchor.isEmpty())
+        // Ignore event without selection anchor
+        if (anchor.isEmpty()) {
+            e->ignore();
             return;
+        }
 
         if (!cursor.hasSelection()
             || (anchor == anchorOnMousePress && hadSelectionOnMousePress)) {
 
             const int anchorPos = q->hitTest(pos, Qt::ExactHit);
-            if (anchorPos != -1) {
-                cursor.setPosition(anchorPos);
 
-                QString anchor = anchorOnMousePress;
-                anchorOnMousePress = QString();
-                activateLinkUnderCursor(anchor);
+            // Ignore event without valid anchor position
+            if (anchorPos < 0) {
+                e->ignore();
+                return;
             }
+
+            cursor.setPosition(anchorPos);
+            QString anchor = anchorOnMousePress;
+            anchorOnMousePress = QString();
+            activateLinkUnderCursor(anchor);
         }
     }
 }

tests/auto/widgets/widgets/qlabel/tst_qlabel.cpp

@@ -83,6 +83,8 @@ private Q_SLOTS:
     void taskQTBUG_48157_dprMovie();
 
     void resourceProvider();
+    void mouseEventPropagation_data();
+    void mouseEventPropagation();
 
 private:
     QLabel *testWidget;
@@ -600,5 +602,85 @@ void tst_QLabel::resourceProvider()
     QVERIFY(providerCalled > 0);
 }
 
+// Test if mouse events are correctly propagated to the parent widget,
+// even if a label contains rich text (QTBUG-110055)
+void tst_QLabel::mouseEventPropagation_data()
+{
+    QTest::addColumn<const QString>("text");
+    QTest::addColumn<const Qt::TextInteractionFlag>("interaction");
+    QTest::addColumn<const bool>("expectPropagation");
+
+
+    QTest::newRow("RichText")
+            << QString("<b>This is a rich text propagating mouse events</b>")
+            << Qt::LinksAccessibleByMouse
+            << true;
+    QTest::newRow("PlainText")
+            << QString("This is a plain text propagating mouse events")
+            << Qt::LinksAccessibleByMouse
+            << true;
+    QTest::newRow("PlainTextConsume")
+            << QString("This is a plain text consuming mouse events")
+            << Qt::TextSelectableByMouse
+            << false;
+    QTest::newRow("RichTextConsume")
+            << QString("<b>This is a rich text consuming mouse events</b>")
+            << Qt::TextSelectableByMouse
+            << false;
+    QTest::newRow("PlainTextNoInteraction")
+            << QString("This is a text not interacting with mouse")
+            << Qt::NoTextInteraction
+            << true;
+    QTest::newRow("RichTextNoInteraction")
+            << QString("<b>This is a rich text not interacting with mouse</b>")
+            << Qt::NoTextInteraction
+            << true;
+}
+
+void tst_QLabel::mouseEventPropagation()
+{
+    class MouseEventWidget : public QWidget
+    {
+    public:
+        uint pressed() const { return m_pressed; }
+        uint released() const { return m_released; }
+
+    private:
+        uint m_pressed = 0;
+        uint m_released = 0;
+        void mousePressEvent(QMouseEvent *event) override
+        {
+            ++m_pressed;
+            return QWidget::mousePressEvent(event);
+        }
+
+        void mouseReleaseEvent(QMouseEvent *event) override
+        {
+            ++m_released;
+            return QWidget::mouseReleaseEvent(event);
+        }
+    };
+
+    QFETCH(const QString, text);
+    QFETCH(const Qt::TextInteractionFlag, interaction);
+    QFETCH(const bool, expectPropagation);
+
+    MouseEventWidget widget;
+    auto *layout = new QVBoxLayout(&widget);
+    auto *label = new QLabel(text);
+    label->setTextInteractionFlags(interaction);
+    const uint count = expectPropagation ? 1 : 0;
+
+    layout->addWidget(label);
+    widget.show();
+    QVERIFY(QTest::qWaitForWindowExposed(&widget));
+
+    const QPoint labelCenter = label->rect().center();
+    QTest::mouseClick(label, Qt::LeftButton, Qt::KeyboardModifiers(), labelCenter);
+
+    QTRY_COMPARE(widget.pressed(), count);
+    QTRY_COMPARE(widget.released(), count);
+}
+
 QTEST_MAIN(tst_QLabel)
 #include "tst_qlabel.moc"