QObject: port findChild/ren() to QAnyStringView

Change the object's name type in QObject::findChild/ren() to
QAnyStringView, because they are only used for comparison against
objectName property.

qt_qFindChild{,ren}_helper() functions taking an objectname as
QString have to stay in the ABI as they were exported in inline
methods before Qt 6.7.

Unlike QString, constructing a null QAnyStringView doesn't involve
any code-size overhead. So, get rid of the split in qt_qFindChildren_helper
that was introduced for QString. Remove unneeded
qt_qFindChildren_with_name helper function and qt_qFindChildren_helper
overload without a name.
findChildren(options) method used to call qt_qFindChildren_helper overload.
Instead, call findChildren overload with name argument and pass
QAnyStringView{} as the object name.

[ChangeLog][QtCore][QObject] Ported QObject::findChild/ren() and
their helper functions to QAnyStringView.

Task-number: QTBUG-103986
Change-Id: I68bda0e581f984ae48b7581ad86cc1b95008c1b0
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/compat/removed_api.cpp

@@ -773,6 +773,20 @@ QString QLocale::bcp47Name() const
     return bcp47Name(TagSeparator::Dash);
 }
 
+#include "qobject.h"
+
+void qt_qFindChildren_helper(const QObject *parent, const QString &name, const QMetaObject &mo,
+                             QList<void*> *list, Qt::FindChildOptions options)
+{
+    qt_qFindChildren_helper(parent, QAnyStringView{name}, mo, list, options);
+}
+
+QObject *qt_qFindChild_helper(const QObject *parent, const QString &name, const QMetaObject &mo,
+                              Qt::FindChildOptions options)
+{
+    return qt_qFindChild_helper(parent, QAnyStringView{name}, mo, options);
+}
+
 #include "qobjectdefs.h"
 
 int QMetaObject::indexOfEnumerator(const char *name) const

src/corelib/kernel/qobject.cpp

@@ -1982,7 +1982,7 @@ void QObject::killTimer(int id)
 
 
 /*!
-    \fn template<typename T> T *QObject::findChild(const QString &name, Qt::FindChildOptions options) const
+    \fn template<typename T> T *QObject::findChild(QAnyStringView name, Qt::FindChildOptions options) const
 
     Returns the child of this object that can be cast into type T and
     that is called \a name, or \nullptr if there is no such object.
@@ -2016,11 +2016,14 @@ void QObject::killTimer(int id)
 
     \snippet code/src_corelib_kernel_qobject.cpp 42
 
+    \note In Qt versions prior to 6.7, this function took \a name as
+    \c{QString}, not \c{QAnyStringView}.
+
     \sa findChildren()
 */
 
 /*!
-    \fn template<typename T> QList<T> QObject::findChildren(const QString &name, Qt::FindChildOptions options) const
+    \fn template<typename T> QList<T> QObject::findChildren(QAnyStringView name, Qt::FindChildOptions options) const
 
     Returns all children of this object with the given \a name that can be
     cast to type T, or an empty list if there are no such objects.
@@ -2042,6 +2045,9 @@ void QObject::killTimer(int id)
 
     \snippet code/src_corelib_kernel_qobject.cpp 43
 
+    \note In Qt versions prior to 6.7, this function took \a name as
+    \c{QString}, not \c{QAnyStringView}.
+
     \sa findChild()
 */
 
@@ -2103,46 +2109,26 @@ void QObject::killTimer(int id)
     \sa QObject::findChildren()
 */
 
-static void qt_qFindChildren_with_name(const QObject *parent, const QString &name,
+static bool matches_objectName_non_null(QObject *obj, QAnyStringView name)
-                                       const QMetaObject &mo, QList<void *> *list,
-                                       Qt::FindChildOptions options)
 {
-    Q_ASSERT(parent);
+    if (auto ext = QObjectPrivate::get(obj)->extraData)
-    Q_ASSERT(list);
+        return ext ->objectName.valueBypassingBindings() == name;
-    Q_ASSERT(!name.isNull());
+    return name.isEmpty();
-    for (QObject *obj : parent->children()) {
-        if (mo.cast(obj) && obj->objectName() == name)
-            list->append(obj);
-        if (options & Qt::FindChildrenRecursively)
-            qt_qFindChildren_with_name(obj, name, mo, list, options);
-    }
 }
 
 /*!
     \internal
 */
-void qt_qFindChildren_helper(const QObject *parent, const QString &name,
+void qt_qFindChildren_helper(const QObject *parent, QAnyStringView name,
                              const QMetaObject &mo, QList<void*> *list, Qt::FindChildOptions options)
-{
-    if (name.isNull())
-        return qt_qFindChildren_helper(parent, mo, list, options);
-    else
-        return qt_qFindChildren_with_name(parent, name, mo, list, options);
-}
-
-/*!
-    \internal
-*/
-void qt_qFindChildren_helper(const QObject *parent, const QMetaObject &mo,
-                             QList<void*> *list, Qt::FindChildOptions options)
 {
     Q_ASSERT(parent);
     Q_ASSERT(list);
     for (QObject *obj : parent->children()) {
-        if (mo.cast(obj))
+        if (mo.cast(obj) && (name.isNull() || matches_objectName_non_null(obj, name)))
             list->append(obj);
         if (options & Qt::FindChildrenRecursively)
-            qt_qFindChildren_helper(obj, mo, list, options);
+            qt_qFindChildren_helper(obj, name, mo, list, options);
     }
 }
 
@@ -2169,13 +2155,13 @@ void qt_qFindChildren_helper(const QObject *parent, const QRegularExpression &re
 
 /*!
     \internal
- */
+*/
-QObject *qt_qFindChild_helper(const QObject *parent, const QString &name, const QMetaObject &mo, Qt::FindChildOptions options)
+QObject *qt_qFindChild_helper(const QObject *parent, QAnyStringView name, const QMetaObject &mo, Qt::FindChildOptions options)
 {
     Q_ASSERT(parent);
     for (QObject *obj : parent->children()) {
-        if (mo.cast(obj) && (name.isNull() || obj->objectName() == name))
+        if (mo.cast(obj) && (name.isNull() || matches_objectName_non_null(obj, name)))
-            return obj;
+           return obj;
     }
     if (options & Qt::FindChildrenRecursively) {
         for (QObject *child : parent->children()) {

src/corelib/kernel/qobject.h

@@ -43,13 +43,22 @@ struct QDynamicMetaObjectData;
 
 typedef QList<QObject*> QObjectList;
 
+#if QT_CORE_REMOVED_SINCE(6, 7)
 Q_CORE_EXPORT void qt_qFindChildren_helper(const QObject *parent, const QString &name,
                                            const QMetaObject &mo, QList<void *> *list, Qt::FindChildOptions options);
+#endif
+Q_CORE_EXPORT void qt_qFindChildren_helper(const QObject *parent, QAnyStringView name,
+                                           const QMetaObject &mo, QList<void *> *list,
+                                           Qt::FindChildOptions options);
 Q_CORE_EXPORT void qt_qFindChildren_helper(const QObject *parent, const QMetaObject &mo,
                                            QList<void *> *list, Qt::FindChildOptions options);
 Q_CORE_EXPORT void qt_qFindChildren_helper(const QObject *parent, const QRegularExpression &re,
                                            const QMetaObject &mo, QList<void *> *list, Qt::FindChildOptions options);
+#if QT_CORE_REMOVED_SINCE(6, 7)
 Q_CORE_EXPORT QObject *qt_qFindChild_helper(const QObject *parent, const QString &name, const QMetaObject &mo, Qt::FindChildOptions options);
+#endif
+Q_CORE_EXPORT QObject *qt_qFindChild_helper(const QObject *parent, QAnyStringView name,
+                                            const QMetaObject &mo, Qt::FindChildOptions options);
 
 class Q_CORE_EXPORT QObjectData
 {
@@ -131,14 +140,14 @@ public:
     void killTimer(int id);
 
     template<typename T>
-    inline T findChild(const QString &aName = QString(), Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
+    T findChild(QAnyStringView aName = {}, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
         typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         return static_cast<T>(qt_qFindChild_helper(this, aName, ObjType::staticMetaObject, options));
     }
 
     template<typename T>
-    inline QList<T> findChildren(const QString &aName, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
+    QList<T> findChildren(QAnyStringView aName, Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
         typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
         QList<T> list;
@@ -150,11 +159,7 @@ public:
     template<typename T>
     QList<T> findChildren(Qt::FindChildOptions options = Qt::FindChildrenRecursively) const
     {
-        typedef typename std::remove_cv<typename std::remove_pointer<T>::type>::type ObjType;
+        return findChildren<T>(QAnyStringView{}, options);
-        QList<T> list;
-        qt_qFindChildren_helper(this, ObjType::staticMetaObject,
-                                reinterpret_cast<QList<void *> *>(&list), options);
-        return list;
     }
 
 #if QT_CONFIG(regularexpression)

tests/auto/corelib/kernel/qobject/tst_qobject.cpp

@@ -39,6 +39,8 @@
 
 #include <math.h>
 
+using namespace Qt::StringLiterals;
+
 class tst_QObject : public QObject
 {
     Q_OBJECT
@@ -520,6 +522,10 @@ void tst_QObject::findChildren()
     QTimer t1(&o);
     QTimer t121(&o12);
     QTimer emptyname(&o);
+    QObject oo;
+    QObject o21(&oo);
+    QObject o22(&oo);
+    QObject o23(&oo);
 
     Q_SET_OBJECT_NAME(o);
     Q_SET_OBJECT_NAME(o1);
@@ -530,6 +536,13 @@ void tst_QObject::findChildren()
     Q_SET_OBJECT_NAME(t1);
     Q_SET_OBJECT_NAME(t121);
     emptyname.setObjectName("");
+    Q_SET_OBJECT_NAME(oo);
+    const QUtf8StringView utf8_name = u8"utf8 ⁎ obj";
+    o21.setObjectName(utf8_name);
+    const QStringView utf16_name = u"utf16 ⁎ obj";
+    o22.setObjectName(utf16_name);
+    constexpr QLatin1StringView L1_name("L1 ⁎ obj");
+    o23.setObjectName(L1_name);
 
     QObject *op = nullptr;
 
@@ -560,6 +573,27 @@ void tst_QObject::findChildren()
     op = o.findChild<QObject*>("o1");
     QCOMPARE(op, &o1);
 
+    op = oo.findChild<QObject*>(utf8_name);
+    QCOMPARE(op, &o21);
+    op = oo.findChild<QObject*>(utf8_name.chopped(1));
+    QCOMPARE(op, nullptr);
+    const QUtf8StringView utf8_name_with_trailing_data = u8"utf8 ⁎ obj_data";
+    op = oo.findChild<QObject*>(utf8_name_with_trailing_data.chopped(5));
+    QCOMPARE(op, &o21);
+    op = oo.findChild<QObject*>(utf16_name);
+    QCOMPARE(op, &o22);
+    op = oo.findChild<QObject*>(utf16_name.chopped(1));
+    QCOMPARE(op, nullptr);
+    const QStringView utf16_name_with_trailing_data = u"utf16 ⁎ obj_data";
+    op = oo.findChild<QObject*>(utf16_name_with_trailing_data.chopped(5));
+    QCOMPARE(op, &o22);
+    op = oo.findChild<QObject*>(L1_name);
+    QCOMPARE(op, &o23);
+    op = oo.findChild<QObject*>(L1_name.chopped(1));
+    QCOMPARE(op, nullptr);
+    op = oo.findChild<QObject*>((L1_name + "_data"_L1).chopped(5));
+    QCOMPARE(op, &o23);
+
     QList<QObject*> l;
     QList<QTimer*> tl;