From 8c2c4f178a1722fc8c749ca6ee894df151808138 Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Mon, 3 Jul 2023 07:29:29 +0200
Subject: [PATCH] QEventLoopLocker: add a visit() member

Still suffers from a bit of an impedance mismatch, because it's the
first step in making QEventLoopLocker shed its Private, but will be
used in a subsequent commit to DRY more code.

Task-number: QTBUG-114793
Pick-to: 6.6
Change-Id: Ia14effb6255961edae68eaf941fece9dca0cb844
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
---
 src/corelib/kernel/qeventloop.cpp | 34 ++++++++++++++++---------------
 src/corelib/kernel/qeventloop.h   |  7 +++++++
 2 files changed, 25 insertions(+), 16 deletions(-)

diff --git a/src/corelib/kernel/qeventloop.cpp b/src/corelib/kernel/qeventloop.cpp
index 59c93aa6e6..f3ddc84758 100644
--- a/src/corelib/kernel/qeventloop.cpp
+++ b/src/corelib/kernel/qeventloop.cpp
@@ -312,6 +312,7 @@ void QEventLoop::quit()
 
 class QEventLoopLockerPrivate
 {
+    friend class QEventLoopLocker;
 public:
     explicit QEventLoopLockerPrivate(QEventLoopPrivate *loop)
       : QEventLoopLockerPrivate(loop, EventLoop)
@@ -331,22 +332,6 @@ public:
         app->ref();
     }
 
-    ~QEventLoopLockerPrivate()
-    {
-        switch (type())
-        {
-        case EventLoop:
-            loop()->deref();
-            break;
-        case Thread:
-            thread()->deref();
-            break;
-        default:
-            app()->deref();
-            break;
-        }
-    }
-
 private:
     QEventLoopPrivate *loop() const { return static_cast<QEventLoopPrivate *>(pointer()); }
     QThreadPrivate *thread() const { return static_cast<QThreadPrivate *>(pointer()); }
@@ -432,9 +417,26 @@ QEventLoopLocker::QEventLoopLocker(QThread *thread)
  */
 QEventLoopLocker::~QEventLoopLocker()
 {
+    visit([](auto p) { p->deref(); });
     delete d_ptr;
 }
 
+/*!
+    \internal
+*/
+template <typename Func>
+void QEventLoopLocker::visit(Func f) const
+{
+    using Type = QEventLoopLockerPrivate::Type;
+    const auto ptr = d_ptr->pointer();
+    switch (d_ptr->type()) {
+    case Type::EventLoop:   return f(static_cast<QEventLoopPrivate *>(ptr));
+    case Type::Thread:      return f(static_cast<QThreadPrivate *>(ptr));
+    case Type::Application: return f(static_cast<QCoreApplicationPrivate *>(ptr));
+    }
+    Q_UNREACHABLE();
+}
+
 QT_END_NAMESPACE
 
 #include "moc_qeventloop.cpp"
diff --git a/src/corelib/kernel/qeventloop.h b/src/corelib/kernel/qeventloop.h
index 3c444e8fd3..265ec76047 100644
--- a/src/corelib/kernel/qeventloop.h
+++ b/src/corelib/kernel/qeventloop.h
@@ -63,7 +63,14 @@ public:
 
 private:
     Q_DISABLE_COPY(QEventLoopLocker)
+
+    //
+    // Private implementation details.
+    // Do not call from public inline API!
+    //
     QEventLoopLockerPrivate *d_ptr;
+    template <typename Func>
+    void visit(Func func) const;
 };
 
 QT_END_NAMESPACE