QSingleShotTimer: use nanoseconds precision

This is a step towards making QChronoTimer have nanoseconds precision.

Not changing QTimer::singleShot() methods to take nanoseconds; QTimer
uses milliseconds for the most part, having the static singleShot()
methods take nanoseconds would be a bit surprising?

[ChangeLog][Core][QObject] Added startTimer() nanoseconds overload and
removed the milliseconds overload. This change is backwards compatible.

Change-Id: I69e79c8feb6354846c6d3be57dc529af7abd1313
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/corelib/compat/removed_api.cpp b/src/corelib/compat/removed_api.cpp
index a2d8d6f63e..b214ca4f36 100644
--- a/src/corelib/compat/removed_api.cpp
+++ b/src/corelib/compat/removed_api.cpp
@@ -4,6 +4,7 @@
 #define QT_CORE_BUILD_REMOVED_API
 
 #include "qglobal.h"
+#include "qnumeric.h"
 
 QT_USE_NAMESPACE
 
@@ -954,6 +955,20 @@ bool QUrlQuery::operator==(const QUrlQuery &other) const
     return comparesEqual(*this, other);
 }
 
+#include "qobject.h"
+
+int QObject::startTimer(std::chrono::milliseconds time, Qt::TimerType timerType)
+{
+    using namespace std::chrono;
+    using ratio = std::ratio_divide<std::milli, std::nano>;
+    if (nanoseconds::rep r; qMulOverflow<ratio::num>(time.count(), &r)) {
+        qWarning("QObject::startTimer(std::chrono::milliseconds time ...): "
+                 "'time' arg will overflow when converted to nanoseconds.");
+    }
+    return startTimer(nanoseconds{time}, timerType);
+}
+
+
 // #include "qotherheader.h"
 // // implement removed functions from qotherheader.h
 // order sections alphabetically to reduce chances of merge conflicts