add support for writing to VCount. incl. fucked-up display and altering framerate accordingly.

src/GPU.cpp

@@ -30,6 +30,8 @@ namespace GPU
 #define FRAME_CYCLES  (LINE_CYCLES * 263)
 
 u16 VCount;
+u32 NextVCount;
+u16 TotalScanlines;
 
 u16 DispStat[2], VMatch[2];
 
@@ -50,9 +52,6 @@ u8* VRAM[9] = {VRAM_A, VRAM_B, VRAM_C, VRAM_D, VRAM_E, VRAM_F, VRAM_G, VRAM_H, V
 u8 VRAMCNT[9];
 u8 VRAMSTAT;
 
-//u32 VRAM_Base[9];
-//u32 VRAM_Mask[9];
-
 u32 VRAMMap_LCDC;
 
 u32 VRAMMap_ABG[0x20];
@@ -95,6 +94,8 @@ void DeInit()
 void Reset()
 {
     VCount = 0;
+    NextVCount = -1;
+    TotalScanlines = 0;
 
     DispStat[0] = 0;
     DispStat[1] = 0;
@@ -607,6 +608,7 @@ void DisplaySwap(u32 val)
 
 void StartFrame()
 {
+    TotalScanlines = 0;
     StartScanline(0);
 }
 
@@ -615,23 +617,37 @@ void StartHBlank(u32 line)
     DispStat[0] |= (1<<1);
     DispStat[1] |= (1<<1);
 
-    if (line < 192) NDS::CheckDMAs(0, 0x02);
+    if (VCount < 192) NDS::CheckDMAs(0, 0x02);
 
     if (DispStat[0] & (1<<4)) NDS::SetIRQ(0, NDS::IRQ_HBlank);
     if (DispStat[1] & (1<<4)) NDS::SetIRQ(1, NDS::IRQ_HBlank);
 
-    if (line < 262)
+    if (VCount < 262)
         NDS::ScheduleEvent(NDS::Event_LCD, true, (LINE_CYCLES - HBLANK_CYCLES), StartScanline, line+1);
+    else
+        NDS::ScheduleEvent(NDS::Event_LCD, true, (LINE_CYCLES - HBLANK_CYCLES), FinishFrame, line+1);
+}
+
+void FinishFrame(u32 lines)
+{
+    TotalScanlines = lines;
 }
 
 void StartScanline(u32 line)
 {
-    VCount = line;
+    if (line == 0)
+        VCount = 0;
+    else if (NextVCount != -1)
+        VCount = NextVCount;
+    else
+        VCount++;
+
+    NextVCount = -1;
 
     DispStat[0] &= ~(1<<1);
     DispStat[1] &= ~(1<<1);
 
-    if (line == VMatch[0])
+    if (VCount == VMatch[0])
     {
         DispStat[0] |= (1<<2);
 
@@ -640,7 +656,7 @@ void StartScanline(u32 line)
     else
         DispStat[0] &= ~(1<<2);
 
-    if (line == VMatch[1])
+    if (VCount == VMatch[1])
     {
         DispStat[1] |= (1<<2);
 
@@ -649,12 +665,12 @@ void StartScanline(u32 line)
     else
         DispStat[1] &= ~(1<<2);
 
-    GPU2D_A->CheckWindows(line);
-    GPU2D_B->CheckWindows(line);
+    GPU2D_A->CheckWindows(VCount);
+    GPU2D_B->CheckWindows(VCount);
 
-    if (line >= 2 && line < 194)
+    if (VCount >= 2 && VCount < 194)
         NDS::CheckDMAs(0, 0x03);
-    else if (line == 194)
+    else if (VCount == 194)
         NDS::StopDMAs(0, 0x03);
 
     if (line < 192)
@@ -664,7 +680,8 @@ void StartScanline(u32 line)
         // properly would be too much trouble given barely anything
         // uses FIFO display
         // (TODO, eventually: emulate it properly)
-        NDS::CheckDMAs(0, 0x04);
+        if (VCount < 192)
+            NDS::CheckDMAs(0, 0x04);
 
         if (line == 0)
         {
@@ -676,7 +693,8 @@ void StartScanline(u32 line)
         GPU2D_A->DrawScanline(line);
         GPU2D_B->DrawScanline(line);
     }
-    else if (line == 262)
+
+    if (VCount == 262)
     {
         // frame end
 
@@ -685,7 +703,7 @@ void StartScanline(u32 line)
     }
     else
     {
-        if (line == 192)
+        if (VCount == 192)
         {
             // VBlank
             DispStat[0] |= (1<<0);
@@ -703,7 +721,7 @@ void StartScanline(u32 line)
             GPU2D_B->VBlank();
             GPU3D::VBlank();
         }
-        else if (line == 215)
+        else if (VCount == 215)
         {
             GPU3D::VCount215();
         }
@@ -722,4 +740,14 @@ void SetDispStat(u32 cpu, u16 val)
     VMatch[cpu] = (val >> 8) | ((val & 0x80) << 1);
 }
 
+void SetVCount(u16 val)
+{
+    // VCount write is delayed until the next scanline
+
+    // TODO: how does the 3D engine react to VCount writes while it's rendering?
+    // TODO: also check the various DMA types that can be involved
+
+    NextVCount = val;
+}
+
 }

src/GPU.h

@@ -26,6 +26,7 @@ namespace GPU
 {
 
 extern u16 VCount;
+extern u16 TotalScanlines;
 
 extern u16 DispStat[2];
 
@@ -385,10 +386,13 @@ T ReadVRAM_TexPal(u32 addr)
 void DisplaySwap(u32 val);
 
 void StartFrame();
+void FinishFrame(u32 lines);
 void StartScanline(u32 line);
 
 void SetDispStat(u32 cpu, u16 val);
 
+void SetVCount(u16 val);
+
 }
 
 #endif

src/GPU2D.cpp

@@ -380,6 +380,18 @@ void GPU2D::DrawScanline(u32 line)
 {
     u32* dst = &Framebuffer[256*line];
 
+    line = GPU::VCount;
+
+    // scanlines that end up outside of the GPU drawing range
+    // (as a result of writing to VCount) are filled white
+    if (line > 192)
+    {
+        for (int i = 0; i < 256; i++)
+            dst[i] = 0xFF3F3F3F;
+
+        return;
+    }
+
     u32 dispmode = DispCnt >> 16;
     dispmode &= (Num ? 0x1 : 0x3);
 

src/NDS.cpp

@@ -380,16 +380,16 @@ void RunSystem(s32 cycles)
     }
 }
 
-void RunFrame()
+u32 RunFrame()
 {
     s32 framecycles = 560190;
 
-    if (!Running) return; // dorp
+    if (!Running) return 263; // dorp
 
 
     GPU::StartFrame();
 
-    while (Running && framecycles>0)
+    while (Running && GPU::TotalScanlines==0)
     {
         s32 ndscyclestorun;
         s32 ndscycles = 0;
@@ -430,21 +430,9 @@ void RunFrame()
 
         RunSystem(ndscyclestorun);
         //GPU3D::Run(ndscyclestorun);
-
-        /*while (ndscycles < ndscyclestorun)
-        {
-            ARM7->CyclesToRun = ndscyclestorun - ndscycles - ARM7Offset;
-            ARM7->Execute();
-            ARM7Offset = 0;
-
-            RunEvents(ARM7->Cycles);
-            ndscycles += ARM7->Cycles;
-        }
-
-        ARM7Offset = ndscycles - ndscyclestorun;*/
-
-        framecycles -= ndscyclestorun;
     }
+
+    return GPU::TotalScanlines;
 }
 
 void Reschedule()
@@ -1657,6 +1645,7 @@ void ARM9IOWrite16(u32 addr, u16 val)
     switch (addr)
     {
     case 0x04000004: GPU::SetDispStat(0, val); return;
+    case 0x04000006: GPU::SetVCount(val); return;
 
     case 0x04000060: GPU3D::Write16(addr, val); return;
 
@@ -2198,6 +2187,7 @@ void ARM7IOWrite16(u32 addr, u16 val)
     switch (addr)
     {
     case 0x04000004: GPU::SetDispStat(1, val); return;
+    case 0x04000006: GPU::SetVCount(val); return;
 
     case 0x040000B8: DMAs[4]->WriteCnt((DMAs[4]->Cnt & 0xFFFF0000) | val); return;
     case 0x040000BA: DMAs[4]->WriteCnt((DMAs[4]->Cnt & 0x0000FFFF) | (val << 16)); return;

src/NDS.h

@@ -104,7 +104,7 @@ void LoadROM(const char* path, bool direct);
 void LoadBIOS();
 void SetupDirectBoot();
 
-void RunFrame();
+u32 RunFrame();
 
 void PressKey(u32 key);
 void ReleaseKey(u32 key);

src/wx/main.cpp

@@ -386,7 +386,7 @@ wxThread::ExitCode EmuThread::Entry()
 
         if (emustatus == 1)
         {
-            NDS::RunFrame();
+            u32 nlines = NDS::RunFrame();
 
             SDL_LockTexture(sdltex, NULL, &texpixels, &texstride);
             if (texstride == 256*4)
@@ -410,7 +410,9 @@ wxThread::ExitCode EmuThread::Entry()
             SDL_RenderPresent(sdlrend);
 
             // framerate limiter based off SDL2_gfx
-            float framerate = 1000.0f / 60.0f;
+            float framerate;
+            if (nlines == 263) framerate = 1000.0f / 60.0f;
+            else               framerate = 1000.0f / ((60.0f * nlines) / 263.0f);
 
             fpslimitcount++;
             u32 curtick = SDL_GetTicks();