Added FPS counter.

[virtualjaguar] / src / gui / mainwin.cpp

diff --git a/src/gui/mainwin.cpp b/src/gui/mainwin.cpp
index 02da8c7ba3c8adf289fa29f201fe985474f7a8e6..ba2c0dd2c4682025b5ac549581724e8f87d9939d 100644 (file)
--- a/src/gui/mainwin.cpp
+++ b/src/gui/mainwin.cpp
@@ -89,6 +89,12 @@ MainWin::MainWin(bool autoRun): running(true), powerButtonOn(false),
        for(int i=0; i<8; i++)
                keyHeld[i] = false;
 
+       // FPS management
+       for(int i=0; i<RING_BUFFER_SIZE; i++)
+               ringBuffer[i] = 0;
+
+       ringBufferPointer = RING_BUFFER_SIZE - 1;
+
        videoWidget = new GLWidget(this);
        setCentralWidget(videoWidget);
        setWindowIcon(QIcon(":/res/vj-icon.png"));
@@ -674,6 +680,36 @@ void MainWin::Timer(void)
        }
 
        videoWidget->updateGL();
+
+#if 1
+       // FPS handling
+       // Approach: We use a ring buffer to store timestamps over a given amount
+       // of frames, then sum them to figure out the FPS.
+       uint32_t timestamp = SDL_GetTicks();
+       // This assumes the ring buffer size is a power of 2
+       ringBufferPointer = (ringBufferPointer + 1) & (RING_BUFFER_SIZE - 1);
+       ringBuffer[ringBufferPointer] = timestamp - oldTimestamp;
+       uint32_t elapsedTime = 0;
+
+       for(uint32_t i=0; i<RING_BUFFER_SIZE; i++)
+               elapsedTime += ringBuffer[i];
+
+       // elapsedTime must be non-zero
+       if (elapsedTime == 0)
+               elapsedTime = 1;
+
+#if 0
+       float framesPerSecond = ((float)RING_BUFFER_SIZE / (float)elapsedTime) * 1000.0;
+       statusBar()->showMessage(QString("%1 FPS").arg(framesPerSecond));
+#else
+       // This is in frames per 10 seconds, so we can have 1 decimal
+       uint32_t framesPerSecond = (uint32_t)(((float)RING_BUFFER_SIZE / (float)elapsedTime) * 10000.0);
+       uint32_t fpsIntegerPart = framesPerSecond / 10;
+       uint32_t fpsDecimalPart = framesPerSecond % 10;
+       statusBar()->showMessage(QString("%1.%2 FPS").arg(fpsIntegerPart).arg(fpsDecimalPart));
+#endif
+       oldTimestamp = timestamp;
+#endif
 }