From 7e7683cabb8df58097c5bc4638a2e08cf6e6ff71 Mon Sep 17 00:00:00 2001
From: Yulong Bai <yulong.bai@qt.io>
Date: Tue, 17 Oct 2017 14:41:42 +0200
Subject: [PATCH] QAction: fix ::setData() always emits changed()

QAction::setData() always emits changed() even without actual data change.
Original code lacks a guard to check if the data changes.
According to http://doc.qt.io/qt-4.8/signalsandslots.html,
adding guard also benefits to prevent infinite looping in case
of cyclic connections.

Task-number: QTBUG-62006
Change-Id: I776369b668082f9f02e4502a36b1ae234ee7e079
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
---
 src/widgets/kernel/qaction.cpp                   |  2 ++
 .../auto/widgets/kernel/qaction/tst_qaction.cpp  | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/src/widgets/kernel/qaction.cpp b/src/widgets/kernel/qaction.cpp
index f1788bb3f4d..7754defaac1 100644
--- a/src/widgets/kernel/qaction.cpp
+++ b/src/widgets/kernel/qaction.cpp
@@ -1118,6 +1118,8 @@ void
 QAction::setData(const QVariant &data)
 {
     Q_D(QAction);
+    if (d->userData == data)
+        return;
     d->userData = data;
     d->sendDataChanged();
 }
diff --git a/tests/auto/widgets/kernel/qaction/tst_qaction.cpp b/tests/auto/widgets/kernel/qaction/tst_qaction.cpp
index 83e1850524a..3535e465b3c 100644
--- a/tests/auto/widgets/kernel/qaction/tst_qaction.cpp
+++ b/tests/auto/widgets/kernel/qaction/tst_qaction.cpp
@@ -62,6 +62,7 @@ private slots:
     void task229128TriggeredSignalWithoutActiongroup();
     void task229128TriggeredSignalWhenInActiongroup();
     void repeat();
+    void setData();
 
 private:
     int m_lastEventType;
@@ -408,5 +409,20 @@ void tst_QAction::repeat()
     QCOMPARE(spy.count(), 2);
 }
 
+void tst_QAction::setData() // QTBUG-62006
+{
+    QAction act(nullptr);
+    QSignalSpy spy(&act, &QAction::changed);
+    QCOMPARE(act.data(), QVariant());
+    QCOMPARE(spy.count(), 0);
+    act.setData(QVariant());
+    QCOMPARE(spy.count(), 0);
+
+    act.setData(-1);
+    QCOMPARE(spy.count(), 1);
+    act.setData(-1);
+    QCOMPARE(spy.count(), 1);
+}
+
 QTEST_MAIN(tst_QAction)
 #include "tst_qaction.moc"