QLayout: make its indexOf functions take pointer-to-const

Try to fix an API mistake there: there is no reason why these
functions should take pointers to non-const widgets, as that
actually preventing reasonable code (e.g. finding out the index
of "this" inside a const method of a QWidget subclass).

Unfortunately, indexOf(QWidget*) is also virtual, meaning that
changing its signature is an API break. Hopefully, there are
only few users that override this method (Woboq says 0).

[ChangeLog][Potentially Source-Incompatible Changes]
The QLayout::indexOf(QWidget *) virtual function has changed
signature, becoming QLayout::indexOf(const QWidget *).
This is source incompatible, although the fix (for the few
users that do override indexOf() in their layouts) is
straightforward.

Change-Id: Id2183f5ecd9dc7e2a37c7355266e8494ef7929f2
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/widgets/kernel/qlayout.h b/src/widgets/kernel/qlayout.h
index ff04c4d334..2748ebab9f 100644
--- a/src/widgets/kernel/qlayout.h
+++ b/src/widgets/kernel/qlayout.h
@@ -117,8 +117,8 @@ public:
     virtual void setGeometry(const QRect&) override;
     virtual QLayoutItem *itemAt(int index) const = 0;
     virtual QLayoutItem *takeAt(int index) = 0;
-    virtual int indexOf(QWidget *) const;
-    QT6_VIRTUAL int indexOf(QLayoutItem *) const;
+    virtual int indexOf(const QWidget *) const;
+    virtual int indexOf(const QLayoutItem *) const;
     virtual int count() const = 0;
     bool isEmpty() const override;
     QSizePolicy::ControlTypes controlTypes() const override;