Improve fps logging

Give some time for the newly loaded test to stabilize before
starting the performance measurement.

BenchmarkDemoQt6/BenchmarkUI/Logger.qml

@@ -68,12 +68,14 @@ Item {
             }
         }
         source = view;
-        measureTimer.start();
+        stabilizationTimer.start();
     }
 
-    function reset() {
-        source = null;
-        measurementLog = "";
+    function reset(full) {
+        if (full) {
+            source = null;
+            measurementLog = "";
+        }
         maxFrameTime = 0;
         minFrameTime = 5000;
         maxRenderTime = 0;
@@ -87,41 +89,58 @@ Item {
     }
 
     onFrameTimeChanged: {
+        if (!measureTimer.running)
+            return;
         maxFrameTime = Math.max(maxFrameTime, frameTime);
         minFrameTime = Math.min(minFrameTime, frameTime);
-        // If this is done in onFpsChanged, average will not be correct
-        avgFps += fps;
+        if (fpsUpdates === 0) {
+            avgFps = fps;
+            minFps = fps;
+            maxFps = fps;
+        } else {
+            // If this is done in onFpsChanged, average will not be correct
+            avgFps += fps;
+        }
         ++fpsUpdates;
     }
 
     onFpsChanged: {
+        if (!measureTimer.running)
+            return;
         maxFps = Math.max(maxFps, fps);
         minFps = Math.min(minFps, fps);
     }
 
     onRenderTimeChanged: {
+        if (!measureTimer.running)
+            return;
         maxRenderTime = Math.max(maxRenderTime, renderTime);
         minRenderTime = Math.min(minRenderTime, renderTime);
     }
 
     onSyncTimeChanged: {
+        if (!measureTimer.running)
+            return;
         maxSyncTime = Math.max(maxSyncTime, syncTime);
         minSyncTime = Math.min(minSyncTime, syncTime);
     }
 
+    Timer {
+        id: stabilizationTimer
+        interval: 5000
+        running: false
+        onTriggered: {
+            reset();
+            measureTimer.start();
+        }
+    }
+
     Timer {
         id: measureTimer
         interval: 60000
         running: false
         onTriggered: {
-            if (fpsUpdates === 0) {
-                // Rerun with constant FPS
-                avgFps = fps;
-                minFps = fps;
-                maxFps = fps;
-            } else {
-                avgFps /= fpsUpdates;
-            }
+            avgFps /= fpsUpdates;
             if (testName.length)
                 measurementLog += "Test Set: " + testName + "\n";
             measurementLog += "Screen Size: (" + source.width + "x" + source.height + ")";
@@ -243,7 +262,7 @@ Item {
                 logContainer.visible = true;
             }
 
-            reset();
+            reset(true);
 
             if (quitAfter)
                 Qt.callLater(Qt.quit);