Replace int with std::chrono in for the timer->setInterval() argument

- This commit is a follow-up to 51250b0
(PR#517)
- It addresses the suggestion of changing time instance in
trafficGraphWidget from int to std::chrono.
- This commit addressed it and made some other subsequent changes.

src/qt/rpcconsole.cpp

@@ -1140,7 +1140,7 @@ void RPCConsole::on_sldGraphRange_valueChanged(int value)
 
 void RPCConsole::setTrafficGraphRange(int mins)
 {
-    ui->trafficGraph->setGraphRangeMins(mins);
+    ui->trafficGraph->setGraphRange(std::chrono::minutes(mins));
     ui->lblGraphRange->setText(GUIUtil::formatDurationStr(std::chrono::minutes{mins}));
 }
 

src/qt/trafficgraphwidget.cpp

@@ -11,18 +11,20 @@
 #include <QColor>
 #include <QTimer>
 
+#include <chrono>
 #include <cmath>
 
 #define DESIRED_SAMPLES         800
 
 #define XMARGIN                 10
 #define YMARGIN                 10
 
+using namespace std::chrono_literals;
+
 TrafficGraphWidget::TrafficGraphWidget(QWidget *parent) :
     QWidget(parent),
     timer(nullptr),
     fMax(0.0f),
-    nMins(0),
     vSamplesIn(),
     vSamplesOut(),
     nLastBytesIn(0),
@@ -42,9 +44,9 @@ void TrafficGraphWidget::setClientModel(ClientModel *model)
     }
 }
 
-int TrafficGraphWidget::getGraphRangeMins() const
+std::chrono::minutes TrafficGraphWidget::getGraphRange() const
 {
-    return nMins;
+    return m_range;
 }
 
 void TrafficGraphWidget::paintPath(QPainterPath &path, QQueue<float> &samples)
@@ -153,10 +155,10 @@ void TrafficGraphWidget::updateRates()
     update();
 }
 
-void TrafficGraphWidget::setGraphRangeMins(int mins)
+void TrafficGraphWidget::setGraphRange(std::chrono::minutes mins)
 {
-    nMins = mins;
-    int msecsPerSample = nMins * 60 * 1000 / DESIRED_SAMPLES;
+    m_range = std::chrono::minutes(mins);
+    auto msecsPerSample = m_range * 60 * 1000 / DESIRED_SAMPLES;
     timer->stop();
     timer->setInterval(msecsPerSample);
 

src/qt/trafficgraphwidget.h

@@ -8,6 +8,8 @@
 #include <QWidget>
 #include <QQueue>
 
+#include <chrono>
+
 class ClientModel;
 
 QT_BEGIN_NAMESPACE
@@ -22,22 +24,22 @@ class TrafficGraphWidget : public QWidget
 public:
     explicit TrafficGraphWidget(QWidget *parent = nullptr);
     void setClientModel(ClientModel *model);
-    int getGraphRangeMins() const;
+    std::chrono::minutes getGraphRange() const;
 
 protected:
     void paintEvent(QPaintEvent *) override;
 
 public Q_SLOTS:
     void updateRates();
-    void setGraphRangeMins(int mins);
+    void setGraphRange(std::chrono::minutes mins);
     void clear();
 
 private:
     void paintPath(QPainterPath &path, QQueue<float> &samples);
 
     QTimer *timer;
     float fMax;
-    int nMins;
+    std::chrono::minutes m_range{0};
     QQueue<float> vSamplesIn;
     QQueue<float> vSamplesOut;
     quint64 nLastBytesIn;