Qt: OpenIGTLink: add a FPS label

A simple first attempt, calculating FPS simply based on the time it
took between sending two images.

Author: ClaudioHoffmann

examples/solum_qt/solum/openigtlink.cpp

@@ -10,6 +10,18 @@ SolumIGTL::SolumIGTL()
         {
             emit clientConnected(true);
             clientConnectTimer_.stop();
+            fpsSignalTimer_.start(1000);
+        }
+    });
+
+    QObject::connect(&fpsSignalTimer_, &QTimer::timeout, [this]()
+    {
+        if (!imageTimer_.isValid())
+            emit msSinceLastFrame(0);
+        else
+        {
+            const auto elapsed = imageTimer_.elapsed();
+            emit msSinceLastFrame((elapsed >= 1000) ? elapsed : msSinceLastFrame_);
         }
     });
 }
@@ -63,11 +75,18 @@ void SolumIGTL::sendImage(const void* img, int w, int h, int bpp, size_t sz)
     msg_->Pack();
     if (client_->Send(msg_->GetPackPointer(), msg_->GetPackSize()) == 0)
         reconnectClient();
+
+    if (!imageTimer_.isValid())
+        imageTimer_.start();
+    else
+        msSinceLastFrame_ = imageTimer_.restart();
 }
 
 void SolumIGTL::disconnectClient()
 {
     clientConnectTimer_.stop();
+    fpsSignalTimer_.stop();
+    imageTimer_.invalidate();
     if (client_)
         client_->CloseSocket();
     emit clientConnected(false);

examples/solum_qt/solum/openigtlink.h

@@ -22,6 +22,7 @@ class SolumIGTL : public QObject
 
 signals:
     void clientConnected(bool);
+    void msSinceLastFrame(qint64);
 
 private:
     void disconnectClient();
@@ -34,4 +35,12 @@ class SolumIGTL : public QObject
 
     // Sharing an allocation for all images of the same size.
     igtl::ImageMessage::Pointer msg_;
+
+    // Periodically sends a msSinceLastFrame() signal.
+    QTimer fpsSignalTimer_;
+
+    // FPS timer
+    QElapsedTimer imageTimer_;
+
+    qint64 msSinceLastFrame_;
 };

examples/solum_qt/solum/solumqt.cpp

@@ -315,6 +315,13 @@ Solum::Solum(QWidget *parent) : QMainWindow(parent), imaging_(false)
             ui_.igtlStatusClient->setText(tr("🟢 Client connected"));
         else
             ui_.igtlStatusClient->setText(tr("⌛ Waiting for client connection…"));
+        ui_.igtlStatusFPS->clear();
+    });
+
+    connect(&igtl_, &SolumIGTL::msSinceLastFrame, [this](auto ms)
+    {
+        const auto fps = ((ms == 0) ? 0 : (1000.0 / ms));
+        ui_.igtlStatusFPS->setText(tr("🎥 %1 fps").arg(fps, 0, 'f', 1));
     });
 
     imagingState(ImagingNotReady, false);
@@ -1121,6 +1128,7 @@ void Solum::onIGTLServe()
         igtl_.close();
         ui_.igtlStatusServer->setText(tr("🔴 Server is stopped"));
         ui_.igtlStatusClient->clear();
+        ui_.igtlStatusFPS->clear();
         ui_.igtlport->setEnabled(true);
         ui_.igtlserve->setText(tr("Serve"));
     }

examples/solum_qt/solum/solumqt.ui

@@ -1015,10 +1015,27 @@ After clicking the button, wait for the SSID to be published via BLE, then conne
         <item row="2" column="0" colspan="3">
          <layout class="QGridLayout">
           <item row="0" column="0">
-           <widget class="QLabel" name="igtlStatusServer"/>
+           <widget class="QLabel" name="igtlStatusServer">
+            <property name="sizePolicy">
+             <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
+              <horstretch>1</horstretch>
+              <verstretch>0</verstretch>
+             </sizepolicy>
+            </property>
+           </widget>
           </item>
           <item row="0" column="1">
-           <widget class="QLabel" name="igtlStatusClient"/>
+           <widget class="QLabel" name="igtlStatusClient">
+            <property name="sizePolicy">
+             <sizepolicy hsizetype="Preferred" vsizetype="Preferred">
+              <horstretch>1</horstretch>
+              <verstretch>0</verstretch>
+             </sizepolicy>
+            </property>
+           </widget>
+          </item>
+          <item row="0" column="2" alignment="Qt::AlignRight">
+           <widget class="QLabel" name="igtlStatusFPS"/>
           </item>
          </layout>
         </item>