FpsDisplay.qml Example File

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 import QtQuick 2.0

 Item {
     id: fpsDisplayControl
     property bool hidden: true
     property real fps: 0.0

     onHiddenChanged: {
         if (fpsDisplayControl.hidden)
             fpsDisplay.color = "transparent";
         else
             fpsDisplay.color = "#000000FF";
     }

     onFpsChanged: {
         fpsDisplay.updateFps();
     }

     Rectangle {
         anchors.fill: parent
         id: fpsDisplay
         color: "transparent"

         property real maxFps: 60.0
         property color maxFpsColor: "#00FF00"
         property color minFpsColor: "#FF0000"

         function updateFps() {
             var scale = (fps > maxFps)?1.0:(fps/maxFps);
             var r = (1 - scale) * minFpsColor.r + scale * maxFpsColor.r;
             var g = (1 - scale) * minFpsColor.g + scale * maxFpsColor.g;
             var b = (1 - scale) * minFpsColor.b + scale * maxFpsColor.b;
             var a = (1 - scale) * minFpsColor.a + scale * maxFpsColor.a;
             fpsCauge.height = scale * fpsDisplay.height;
             fpsCauge.color = Qt.rgba(r,g,b,a);
         }

         Rectangle {
             id: fpsCauge
             width: parent.width
             anchors.bottom: parent.bottom
             visible: !fpsDisplayControl.hidden
         }

         Text {
             id: fpsText
             text: ""+(fps | 0)
             font.family: "Helvetica"
             font.pixelSize: 16
             font.weight: Font.Light
             color: "white"
             anchors.fill: parent
             verticalAlignment: Text.AlignVCenter
             horizontalAlignment: Text.AlignHCenter
             visible: !fpsDisplayControl.hidden
         }
     }
     MouseArea {
         anchors.fill: parent
         onClicked: {
             fpsDisplayControl.hidden = !fpsDisplayControl.hidden;
         }
     }
 }