QTimer: do not set active state when setting a negative interval

QObject::startTimer() returns 0 in case of failure, for example when
someone tries to register a timer with a negative interval.

However, QTimer internally uses -1 as an invalid timer id.
This could lead to a situation when the timer was not really started,
but QTimer::isActive() returned true.

This patch fixes it in two ways:
- check the return value of QObject::startTimer() and treat 0 as an
  error.
- do not treat 0 as a valid timer id when calculating the active state.

As a drive-by: move the `using namespace std::chrono_literals;`
declaration to the top of tst_qtimer.cpp, so that we do not need to
repeat it in each test case.

Fixes: QTBUG-122087
Pick-to: 6.7 6.6 6.5
Change-Id: I0e21152b2173ebb5fb0dada1b99a903a321ca9c4
Reviewed-by: Ahmad Samir <a.samirh78@gmail.com>

1 files changed, 37 insertions, 1 deletions

diff --git a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
index 18ffbe2908..c318c3a625 100644
--- a/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
+++ b/tests/auto/corelib/kernel/qtimer/tst_qtimer.cpp
@@ -39,6 +39,8 @@ static bool glibDisabled = []() {
 }();
 #endif
 
+using namespace std::chrono_literals;
+
 class tst_QTimer : public QObject
 {
     Q_OBJECT
@@ -94,6 +96,8 @@ private slots:
     void bindToTimer();
     void bindTimer();
     void automatedBindingTests();
+
+    void negativeInterval();
 };
 
 void tst_QTimer::zeroTimer()
@@ -166,7 +170,6 @@ void tst_QTimer::singleShotNormalizes_data()
 
 void tst_QTimer::singleShotNormalizes()
 {
-    using namespace std::chrono_literals;
     static constexpr auto TestTimeout = 250ms;
     QFETCH(QByteArray, slotName);
     QEventLoop loop;
@@ -1287,6 +1290,16 @@ void tst_QTimer::bindToTimer()
 
     timer.stop();
     QVERIFY(!active);
+
+    // also test that using negative interval updates the binding correctly
+    timer.start(100);
+    QVERIFY(active);
+    timer.setInterval(-100);
+    QVERIFY(!active);
+    timer.start(100);
+    QVERIFY(active);
+    timer.start(-100);
+    QVERIFY(!active);
 }
 
 void tst_QTimer::bindTimer()
@@ -1367,6 +1380,29 @@ void tst_QTimer::automatedBindingTests()
     }
 }
 
+void tst_QTimer::negativeInterval()
+{
+    QTimer timer;
+
+    // Starting with a negative interval does not change active state.
+    timer.start(-100ms);
+    QVERIFY(!timer.isActive());
+
+    // Updating the interval to a negative value stops the timer and changes
+    // the active state.
+    timer.start(100ms);
+    QVERIFY(timer.isActive());
+    timer.setInterval(-100);
+    QVERIFY(!timer.isActive());
+
+    // Starting with a negative interval when already started leads to stop
+    // and inactive state.
+    timer.start(100);
+    QVERIFY(timer.isActive());
+    timer.start(-100ms);
+    QVERIFY(!timer.isActive());
+}
+
 class OrderHelper : public QObject
 {
     Q_OBJECT