Add a QML item that shows the FPS

resources/qml/FPSItem.qml

@@ -0,0 +1,81 @@
+import QtQuick 2.0
+import QtQuick.Window 2.2
+import UM 1.3 as UM
+
+// This is an QML item that shows the FPS and a running average of the FPS.
+Item
+{
+    id: base
+    property alias backgroundColor: background.color
+    property alias textColor: fpsText.color
+
+    property int numMeasurementsToAverage: 3
+
+    width:  fpsText.contentWidth + UM.Theme.getSize("default_margin").height
+    height: fpsText.contentHeight + UM.Theme.getSize("default_margin").height
+
+    Rectangle
+    {
+        id: background
+
+        // We use a trick here to figure out how often we can get a redraw triggered.
+        // By adding a rotating rectangle, we can increase a counter by one every time we get notified.
+        // After that, we trigger a timer once every second to look at that number.
+        property int frameCounter: 0
+        property int averageFrameCounter: 0
+        property int counter: 0
+        property int fps: 0
+        property real averageFps: 0.0
+
+        color: UM.Theme.getColor("primary")
+
+        width: parent.width
+        height: parent.height
+
+        Rectangle
+        {
+            width: 0
+            height: 0
+            NumberAnimation on rotation
+            {
+                from: 0
+                to: 360
+                duration: 1000
+                loops: Animation.Infinite
+            }
+            onRotationChanged: parent.frameCounter++;
+            visible: false
+        }
+
+        Text
+        {
+            id: fpsText
+            anchors.fill:parent
+            verticalAlignment: Text.AlignVCenter
+            horizontalAlignment: Text.AlignHCenter
+            color: UM.Theme.getColor("text")
+            font: UM.Theme.getFont("default")
+            text: "Ø " + parent.averageFps + " | " + parent.fps + " fps"
+        }
+
+        Timer
+        {
+            interval: 1000
+            repeat: true
+            running: true
+            onTriggered:
+            {
+                parent.averageFrameCounter += parent.frameCounter;
+                parent.fps = parent.frameCounter;
+                parent.counter++;
+                parent.frameCounter = 0;
+                if (parent.counter >= base.numMeasurementsToAverage)
+                {
+                    parent.averageFps = (parent.averageFrameCounter / parent.counter).toFixed(2)
+                    parent.averageFrameCounter = 0;
+                    parent.counter = 0;
+                }
+            }
+        }
+    }
+}