Merge bitcoin-core#549: refactor: use std::chrono for formatDurationStr() helper

6f2593d gui, refactor: use std::chrono for formatDurationStr() helper (Jon Atack)

Pull request description:

  Updates `formatDurationStr()` to use the `chrono` standard lib. No change in behavior.

ACKs for top commit:
  RandyMcMillan:
    tACK 6f2593d
  shaavan:
    ACK 6f2593d
  w0xlt:
    tACK 6f2593d on Ubuntu 21.10 Qt 5.15.2
  promag:
    Code review ACK 6f2593d.

Tree-SHA512: 61e9afdb1db779150df338e6af08727c34f69639add465c2f7003ff775d97dce3e78e78d325bc6dea5bc13f0fce9ef1c3506d13f1661a5e083e52bba8a32ba44

Author: hebasto

src/qt/guiutil.cpp

@@ -713,23 +713,18 @@ QString ConnectionTypeToQString(ConnectionType conn_type, bool prepend_direction
 
 QString formatDurationStr(std::chrono::seconds dur)
 {
-    const auto secs = count_seconds(dur);
-    QStringList strList;
-    int days = secs / 86400;
-    int hours = (secs % 86400) / 3600;
-    int mins = (secs % 3600) / 60;
-    int seconds = secs % 60;
-
-    if (days)
-        strList.append(QObject::tr("%1 d").arg(days));
-    if (hours)
-        strList.append(QObject::tr("%1 h").arg(hours));
-    if (mins)
-        strList.append(QObject::tr("%1 m").arg(mins));
-    if (seconds || (!days && !hours && !mins))
-        strList.append(QObject::tr("%1 s").arg(seconds));
-
-    return strList.join(" ");
+    using days = std::chrono::duration<int, std::ratio<86400>>; // can remove this line after C++20
+    const auto d{std::chrono::duration_cast<days>(dur)};
+    const auto h{std::chrono::duration_cast<std::chrono::hours>(dur - d)};
+    const auto m{std::chrono::duration_cast<std::chrono::minutes>(dur - d - h)};
+    const auto s{std::chrono::duration_cast<std::chrono::seconds>(dur - d - h - m)};
+    QStringList str_list;
+    if (auto d2{d.count()}) str_list.append(QObject::tr("%1 d").arg(d2));
+    if (auto h2{h.count()}) str_list.append(QObject::tr("%1 h").arg(h2));
+    if (auto m2{m.count()}) str_list.append(QObject::tr("%1 m").arg(m2));
+    const auto s2{s.count()};
+    if (s2 || str_list.empty()) str_list.append(QObject::tr("%1 s").arg(s2));
+    return str_list.join(" ");
 }
 
 QString formatServicesStr(quint64 mask)