From 1f51f27d44bfa29c56944f88f5c914bc8e3db220 Mon Sep 17 00:00:00 2001
From: Arisotura <thetotalworm@gmail.com>
Date: Mon, 7 Jul 2025 12:20:11 +0200
Subject: [PATCH] Revert "camera: model FIFO more accurately (avoids weird bugs
 when DMA fails)"

This reverts commit 2cb07bf126fba0d6d8960a1b2e23486809c067d0.
---
 src/DSi_Camera.cpp             | 47 ++++++++++++++++------------------
 src/DSi_Camera.h               |  4 +--
 src/FIFO.h                     |  1 -
 src/frontend/qt_sdl/Window.cpp |  2 +-
 4 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/src/DSi_Camera.cpp b/src/DSi_Camera.cpp
index d12f1e34..38251fd6 100644
--- a/src/DSi_Camera.cpp
+++ b/src/DSi_Camera.cpp
@@ -67,7 +67,9 @@ void DSi_CamModule::Reset()
     CropStart = 0;
     CropEnd = 0;
 
-    DataBuffer.Clear();
+    memset(DataBuffer, 0, 512*sizeof(u32));
+    BufferReadPos = 0;
+    BufferWritePos = 0;
     BufferNumLines = 0;
     CurCamera = nullptr;
 
@@ -87,8 +89,6 @@ void DSi_CamModule::DoSavestate(Savestate* file)
     file->Var16(&ModuleCnt);
     file->Var16(&Cnt);
 
-    // TODO: should other stuff be savestated? (pixel buffer, etc)
-
     /*file->VarArray(FrameBuffer, sizeof(FrameBuffer));
     file->Var32(&TransferPos);
     file->Var32(&FrameLength);*/
@@ -113,6 +113,8 @@ void DSi_CamModule::IRQ(u32 param)
 
         if (Cnt & (1<<15))
         {
+            BufferReadPos = 0;
+            BufferWritePos = 0;
             BufferNumLines = 0;
             CurCamera = activecam;
             DSi.ScheduleEvent(Event_DSi_CamTransfer, false, kTransferStart, 0, 0);
@@ -124,10 +126,8 @@ void DSi_CamModule::IRQ(u32 param)
 
 void DSi_CamModule::TransferScanline(u32 line)
 {
-    if (Cnt & (1<<4))
-        return;
-
-    int maxlen = DataBuffer.FreeSpace();
+    u32* dstbuf = &DataBuffer[BufferWritePos];
+    int maxlen = 512 - BufferWritePos;
 
     u32 tmpbuf[512];
     int lines_next;
@@ -195,28 +195,28 @@ void DSi_CamModule::TransferScanline(u32 line)
             u32 col1 = (r1 >> 3) | ((g1 >> 3) << 5) | ((b1 >> 3) << 10) | 0x8000;
             u32 col2 = (r2 >> 3) | ((g2 >> 3) << 5) | ((b2 >> 3) << 10) | 0x8000;
 
-            DataBuffer.Write(col1 | (col2 << 16));
+            dstbuf[i] = col1 | (col2 << 16);
         }
     }
     else
     {
         // return raw data
 
-        for (u32 i = 0; i < copylen; i++)
-        {
-            u32 val = tmpbuf[copystart + i];
-            DataBuffer.Write(val);
-        }
+        memcpy(dstbuf, &tmpbuf[copystart], copylen*sizeof(u32));
     }
 
     numscan = Cnt & 0x000F;
     if (BufferNumLines >= numscan)
     {
+        BufferReadPos = 0; // checkme
+        BufferWritePos = 0;
         BufferNumLines = 0;
         DSi.CheckNDMAs(0, 0x0B);
     }
     else
     {
+        BufferWritePos += copylen;
+        if (BufferWritePos > 512) BufferWritePos = 512;
         BufferNumLines++;
     }
 
@@ -225,9 +225,10 @@ skip_line:
     {
         // when the frame is finished, transfer any remaining data if needed
         // (if the frame height isn't a multiple of the DMA interval)
-        // (TODO: should it be done earlier?)
         if (BufferNumLines > 0)
         {
+            BufferReadPos = 0;
+            BufferWritePos = 0;
             BufferNumLines = 0;
             DSi.CheckNDMAs(0, 0x0B);
         }
@@ -265,19 +266,14 @@ u32 DSi_CamModule::Read32(u32 addr)
     {
     case 0x04004204:
         {
-            u32 ret;
+            u32 ret = DataBuffer[BufferReadPos];
             if (Cnt & (1<<15))
             {
-                if (DataBuffer.IsEmpty())
-                {
-                    ret = 0;
-                    Cnt |= (1<<4);
-                }
-                else
-                    ret = DataBuffer.Read();
+                if (BufferReadPos < 511)
+                    BufferReadPos++;
+                // CHECKME!!!!
+                // also presumably we should set bit4 in Cnt if there's no new data to be read
             }
-            else
-                ret = DataBuffer.Peek();
 
             return ret;
         }
@@ -343,7 +339,8 @@ void DSi_CamModule::Write16(u32 addr, u16 val)
             if (val & (1<<5))
             {
                 Cnt &= ~(1<<4);
-                DataBuffer.Clear();
+                BufferReadPos = 0;
+                BufferWritePos = 0;
             }
 
             if ((val & (1<<15)) && !(Cnt & (1<<15)))
diff --git a/src/DSi_Camera.h b/src/DSi_Camera.h
index bd588c72..61934bc8 100644
--- a/src/DSi_Camera.h
+++ b/src/DSi_Camera.h
@@ -22,7 +22,6 @@
 #include "types.h"
 #include "Savestate.h"
 #include "DSi_I2C.h"
-#include "FIFO.h"
 
 namespace melonDS
 {
@@ -120,7 +119,8 @@ private:
     u32 CropStart, CropEnd;
 
     // pixel data buffer holds a maximum of 512 words, regardless of how long scanlines are
-    FIFO<u32, 512> DataBuffer;
+    u32 DataBuffer[512];
+    u32 BufferReadPos, BufferWritePos;
     u32 BufferNumLines;
     DSi_Camera* CurCamera;
 
diff --git a/src/FIFO.h b/src/FIFO.h
index f8749ad3..ccb009b1 100644
--- a/src/FIFO.h
+++ b/src/FIFO.h
@@ -90,7 +90,6 @@ public:
     }
 
     u32 Level() const { return NumOccupied; }
-    u32 FreeSpace() const { return NumEntries - NumOccupied; }
     bool IsEmpty() const { return NumOccupied == 0; }
     bool IsFull() const { return NumOccupied >= NumEntries; }
 
diff --git a/src/frontend/qt_sdl/Window.cpp b/src/frontend/qt_sdl/Window.cpp
index b5a9b690..8e3b2390 100755
--- a/src/frontend/qt_sdl/Window.cpp
+++ b/src/frontend/qt_sdl/Window.cpp
@@ -979,7 +979,7 @@ void MainWindow::keyPressEvent(QKeyEvent* event)
     if (event->isAutoRepeat()) return;
 
     // TODO!! REMOVE ME IN RELEASE BUILDS!!
-    //if (event->key() == Qt::Key_F11) emuInstance->getNDS()->debug(0);
+    //if (event->key() == Qt::Key_F11) emuThread->NDS->debug(0);
 
     emuInstance->onKeyPress(event);
 }