Rework dispatch loop.

.vscode/settings.json

@@ -41,6 +41,7 @@
         "tuple": "cpp",
         "type_traits": "cpp",
         "stdexcept": "cpp",
-        "fstream": "cpp"
+        "fstream": "cpp",
+        "__locale": "cpp"
     }
 }

src/emucore/Console.cxx

@@ -987,6 +987,12 @@ void Console::setFramerate(float framerate)
   // myOSystem.sound().setFrameRate(framerate);
 }
 
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+float Console::getFramerate() const
+{
+  return myTIA->frameRate();
+}
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Console::toggleTIABit(TIABit bit, const string& bitname, bool show) const
 {

src/emucore/Console.hxx

@@ -272,7 +272,7 @@ class Console : public Serializable
       Returns the framerate based on a number of factors
       (whether 'framerate' is set, what display format is in use, etc)
     */
-    float getFramerate() const { return myFramerate; }
+    float getFramerate() const;
 
     /**
       Toggles the TIA bit specified in the method name.

src/emucore/FrameBuffer.cxx

@@ -47,10 +47,7 @@ FrameBuffer::FrameBuffer(OSystem& osystem)
     myInitializedCount(0),
     myPausedCount(0),
     myStatsEnabled(false),
-    myLastFrameRate(60),
-    myCurrentModeList(nullptr),
-    myTotalTime(0),
-    myTotalFrames(0)
+    myCurrentModeList(nullptr)
 {
 }
 
@@ -290,8 +287,7 @@ Int64 FrameBuffer::update()
       // Show frame statistics
       if(myStatsMsg.enabled)
         drawFrameStats();
-      else
-        myLastFrameRate = myOSystem.console().getFramerate();
+
       myLastScanlines = myOSystem.console().tia().scanlinesLastFrame();
       myPausedCount = 0;
       break;  // EventHandlerState::EMULATION
@@ -404,30 +400,7 @@ void FrameBuffer::drawFrameStats()
                                  myStatsMsg.w, myStatsMsg.color, TextAlign::Left, 0, true, kBGColor);
   xPos += font().getStringWidth(msg);
 
-  // draw framerate
-  float frameRate;
-  /*if(myOSystem.settings().getInt("framerate") == 0)
-  {
-    // if 'Auto' is selected, draw the calculated framerate
-    frameRate = myOSystem.console().getFramerate();
-  }
-  else*/
-  {
-    // if 'Auto' is not selected, draw the effective framerate
-    const TimingInfo& ti = myOSystem.timingInfo();
-    if(ti.totalFrames - myTotalFrames >= myLastFrameRate)
-    {
-      frameRate = 1000000.0 * (ti.totalFrames - myTotalFrames) / (ti.totalTime - myTotalTime);
-      if(frameRate > myOSystem.console().getFramerate() + 1)
-        frameRate = 1;
-      myTotalFrames = ti.totalFrames;
-      myTotalTime = ti.totalTime;
-    }
-    else
-      frameRate = myLastFrameRate;
-  }
-  myLastFrameRate = frameRate;
-  std::snprintf(msg, 30, " @ %5.2ffps", frameRate);
+  std::snprintf(msg, 30, " @ %5.2ffps", myOSystem.console().getFramerate());
   myStatsMsg.surface->drawString(font(), msg, xPos, YPOS,
                                  myStatsMsg.w, myStatsMsg.color, TextAlign::Left, 0, true, kBGColor);
 

src/emucore/FrameBuffer.hxx

@@ -517,7 +517,6 @@ class FrameBuffer
     Message myStatsMsg;
     bool myStatsEnabled;
     uInt32 myLastScanlines;
-    float myLastFrameRate;
 
     bool myGrabMouse;
 
@@ -538,9 +537,6 @@ class FrameBuffer
     // Holds UI palette data (standard and classic colours)
     static uInt32 ourGUIColors[3][kNumColors-256];
 
-    uInt64 myTotalTime;
-    uInt64 myTotalFrames;
-
   private:
     // Following constructors and assignment operators not supported
     FrameBuffer() = delete;

src/emucore/OSystem.cxx

@@ -35,6 +35,8 @@
   #include "CheatManager.hxx"
 #endif
 
+#include <chrono>
+
 #include "FSNode.hxx"
 #include "MD5.hxx"
 #include "Cart.hxx"
@@ -58,6 +60,8 @@
 
 #include "OSystem.hxx"
 
+using namespace std::chrono;
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 OSystem::OSystem()
   : myLauncherUsed(false),
@@ -615,52 +619,36 @@ uInt64 OSystem::getTicks() const
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void OSystem::mainLoop()
 {
-  if(mySettings->getString("timing") == "sleep")
-  {
   // Sleep-based wait: good for CPU, bad for graphical sync
+  bool busyWait = mySettings->getString("timing") != "sleep";
+  time_point<high_resolution_clock> virtualTime = high_resolution_clock::now();
+
   for(;;)
   {
-      myTimingInfo.start = getTicks();
     myEventHandler->poll(myTimingInfo.start);
     if(myQuitLoop) break;  // Exit if the user wants to quit
-      myFrameBuffer->update();
-      myTimingInfo.current = getTicks();
-      myTimingInfo.virt += myTimePerFrame;
 
-      // Timestamps may periodically go out of sync, particularly on systems
-      // that can have 'negative time' (ie, when the time seems to go backwards)
-      // This normally results in having a very large delay time, so we check
-      // for that and reset the timers when appropriate
-      if((myTimingInfo.virt - myTimingInfo.current) > (myTimePerFrame << 1))
-      {
-        myTimingInfo.current = myTimingInfo.virt = getTicks();
+    Int64 cycles = myFrameBuffer->update();
+    duration<double> timeslice (
+      (cycles >= 0) ?
+      static_cast<double>(cycles) / static_cast<double>(76 * ((myConsole->timing() == ConsoleTiming::ntsc) ? (262 * 60) : (312 * 50))) :
+      1. / 30.
+     );
+
+    virtualTime += duration_cast<high_resolution_clock::duration>(timeslice);
+    time_point<high_resolution_clock> now = high_resolution_clock::now();
+
+    if (duration_cast<duration<double>>(now - virtualTime).count() > 0.5)
+      virtualTime = now;
+    else if (virtualTime > now) {
+      if (busyWait && cycles >= 0) {
+        while (high_resolution_clock::now() < virtualTime);
+      }
+      else std::this_thread::sleep_until(virtualTime);
     }
 
-      if(myTimingInfo.current < myTimingInfo.virt)
-        SDL_Delay(uInt32(myTimingInfo.virt - myTimingInfo.current) / 1000);
-
-      myTimingInfo.totalTime += (getTicks() - myTimingInfo.start);
     myTimingInfo.totalFrames++;
   }
-  }
-  else
-  {
-    // Busy-wait: bad for CPU, good for graphical sync
-    for(;;)
-    {
-      myTimingInfo.start = getTicks();
-      myEventHandler->poll(myTimingInfo.start);
-      if(myQuitLoop) break;  // Exit if the user wants to quit
-      myFrameBuffer->update();
-      myTimingInfo.virt += myTimePerFrame;
-
-      while(getTicks() < myTimingInfo.virt)
-        ;  // busy-wait
-
-      myTimingInfo.totalTime += (getTicks() - myTimingInfo.start);
-      myTimingInfo.totalFrames++;
-    }
-  }
 
   // Cleanup time
 #ifdef CHEATCODE_SUPPORT

src/emucore/tia/TIA.hxx

@@ -237,6 +237,8 @@ class TIA : public Device
     */
     void enableAutoFrame(bool enabled) { myAutoFrameEnabled = enabled; }
 
+    float frameRate() const { return myFrameManager ? myFrameManager->frameRate() : 0; }
+
     /**
       Enables/disables color-loss for PAL modes only.