From 4ba8f330c4d5cd6c25f6acddf2866b40e698d35f Mon Sep 17 00:00:00 2001
From: Jakly <102590697+Jaklyy@users.noreply.github.com>
Date: Wed, 30 Oct 2024 14:40:33 -0400
Subject: [PATCH] fix framerate target not adjusting with vcount writes (#2181)

---
 src/frontend/qt_sdl/EmuInstance.cpp | 12 ++++++------
 src/frontend/qt_sdl/EmuThread.cpp   | 21 ++++++++++++---------
 src/frontend/qt_sdl/Window.cpp      |  6 +++---
 3 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/src/frontend/qt_sdl/EmuInstance.cpp b/src/frontend/qt_sdl/EmuInstance.cpp
index 90116692..e9550f8c 100644
--- a/src/frontend/qt_sdl/EmuInstance.cpp
+++ b/src/frontend/qt_sdl/EmuInstance.cpp
@@ -93,25 +93,25 @@ EmuInstance::EmuInstance(int inst) : deleting(false),
     if (val == 0.0)
     {
         Platform::Log(Platform::LogLevel::Error, "Target FPS in config invalid\n");
-        targetFPS = 1.0 / 60.0;
+        targetFPS = 60.0;
     }
-    else targetFPS = 1.0 / val;
+    else targetFPS = val;
 
     val = globalCfg.GetDouble("FastForwardFPS");
     if (val == 0.0)
     {
         Platform::Log(Platform::LogLevel::Error, "Fast-Forward FPS in config invalid\n");
-        fastForwardFPS = 1.0 / 60.0;
+        fastForwardFPS = 60.0;
     }
-    else fastForwardFPS = 1.0 / val;
+    else fastForwardFPS = val;
 
     val = globalCfg.GetDouble("SlowmoFPS");
     if (val == 0.0)
     {
         Platform::Log(Platform::LogLevel::Error, "Slow-Mo FPS in config invalid\n");
-        slowmoFPS = 1.0 / 60.0;
+        slowmoFPS = 60.0;
     }
-    else slowmoFPS = 1.0 / val;
+    else slowmoFPS = val;
 
     doAudioSync = globalCfg.GetBool("AudioSync");
 
diff --git a/src/frontend/qt_sdl/EmuThread.cpp b/src/frontend/qt_sdl/EmuThread.cpp
index 3371a03b..f4112cd3 100644
--- a/src/frontend/qt_sdl/EmuThread.cpp
+++ b/src/frontend/qt_sdl/EmuThread.cpp
@@ -359,7 +359,7 @@ void EmuThread::run()
 
             if (slowmo) emuInstance->curFPS = emuInstance->slowmoFPS;
             else if (fastforward) emuInstance->curFPS = emuInstance->fastForwardFPS;
-            else if (!emuInstance->doLimitFPS) emuInstance->curFPS = 1.0 / 1000.0;
+            else if (!emuInstance->doLimitFPS) emuInstance->curFPS = 1000.0;
             else emuInstance->curFPS = emuInstance->targetFPS;
 
             if (emuInstance->audioDSiVolumeSync && emuInstance->nds->ConsoleType == 1)
@@ -378,16 +378,18 @@ void EmuThread::run()
             if (emuInstance->doAudioSync && !(fastforward || slowmo))
                 emuInstance->audioSync();
 
-            double frametimeStep = nlines / (60.0 * 263.0);
+            double frametimeStep = nlines / (emuInstance->curFPS * 263.0);
+
+            if (frametimeStep < 0.001) frametimeStep = 0.001;
 
             {
                 double curtime = SDL_GetPerformanceCounter() * perfCountsSec;
 
-                frameLimitError += emuInstance->curFPS - (curtime - lastTime);
-                if (frameLimitError < -emuInstance->curFPS)
-                    frameLimitError = -emuInstance->curFPS;
-                if (frameLimitError > emuInstance->curFPS)
-                    frameLimitError = emuInstance->curFPS;
+                frameLimitError += frametimeStep - (curtime - lastTime);
+                if (frameLimitError < -frametimeStep)
+                    frameLimitError = -frametimeStep;
+                if (frameLimitError > frametimeStep)
+                    frameLimitError = frametimeStep;
 
                 if (round(frameLimitError * 1000.0) > 0.0)
                 {
@@ -415,10 +417,11 @@ void EmuThread::run()
                 winUpdateFreq = fps / (u32)round(fpstarget);
                 if (winUpdateFreq < 1)
                     winUpdateFreq = 1;
-
+                    
+                double actualfps = (59.8261 * 263.0) / nlines;
                 int inst = emuInstance->instanceID;
                 if (inst == 0)
-                    sprintf(melontitle, "[%d/%.0f] melonDS " MELONDS_VERSION, fps, fpstarget);
+                    sprintf(melontitle, "[%d/%.0f] melonDS " MELONDS_VERSION, fps, actualfps);
                 else
                     sprintf(melontitle, "[%d/%.0f] melonDS (%d)", fps, fpstarget, inst+1);
                 changeWindowTitle(melontitle);
diff --git a/src/frontend/qt_sdl/Window.cpp b/src/frontend/qt_sdl/Window.cpp
index 0af72ef6..1d207949 100644
--- a/src/frontend/qt_sdl/Window.cpp
+++ b/src/frontend/qt_sdl/Window.cpp
@@ -1942,9 +1942,9 @@ void MainWindow::onOpenInterfaceSettings()
 void MainWindow::onUpdateInterfaceSettings()
 {
     pauseOnLostFocus = globalCfg.GetBool("PauseLostFocus");
-    emuInstance->targetFPS = 1.0 / globalCfg.GetDouble("TargetFPS");
-    emuInstance->fastForwardFPS = 1.0 / globalCfg.GetDouble("FastForwardFPS");
-    emuInstance->slowmoFPS = 1.0 / globalCfg.GetDouble("SlowmoFPS");
+    emuInstance->targetFPS = globalCfg.GetDouble("TargetFPS");
+    emuInstance->fastForwardFPS = globalCfg.GetDouble("FastForwardFPS");
+    emuInstance->slowmoFPS = globalCfg.GetDouble("SlowmoFPS");
     panel->setMouseHide(globalCfg.GetBool("MouseHide"),
                         globalCfg.GetInt("MouseHideSeconds")*1000);
 }