Merge pull request #121 from 1492083648/fix/fps-getfps-nan-and-smoothing

fix: GetFPS NaN/unstable at high SetFPS, use 60-frame average

Author: Demonese

LuaSTG/LuaSTG/AppFrame.cpp

@@ -395,8 +395,18 @@ void AppFrame::onBeforeUpdate() {
 		m_frame_rate_controller->update();
 	}
 
-	m_fFPS = 1.0 / m_frame_rate_controller->getStatistics()->getDuration(0);
-	m_fAvgFPS = 1.0 / m_frame_rate_controller->getStatistics()->getAverage(10);
+	// Avoid NaN/inf: only invert positive finite duration; use minimum duration to cap FPS and avoid 1/0
+	constexpr double min_duration = 1e-6; // cap reported FPS at 1e6
+	const auto* stats = m_frame_rate_controller->getStatistics();
+	double d0 = stats->getDuration(0);
+	if (d0 == d0 && d0 > 0.0) {
+		m_fFPS = 1.0 / (d0 < min_duration ? min_duration : d0);
+	}
+	// Use 60-frame average so GetFPS is stable at high FPS (10-frame window was too noisy at 2000+ FPS)
+	double avg = stats->getAverage(60);
+	if (avg == avg && avg > 0.0) {
+		m_fAvgFPS = 1.0 / (avg < min_duration ? min_duration : avg);
+	}
 	m_frame_rate_controller->setFrameRate(m_target_fps);
 	m_message_timer = core::ScopeTimer(&m_message_time);
 }

engine/window-system/core/FrameRateController.cpp

@@ -21,6 +21,9 @@ namespace core {
                 l += 1;
             }
         }
+        if (l == 0) {
+            return 0.0;
+        }
         return result / static_cast<double>(l);
     }