GTE: Add widescreen hack

README.md

@@ -11,6 +11,7 @@ A "BIOS" ROM image is required to to start the emulator and to play games. You c
 
 ## Latest News
 
+- 2020/07/18: Widescreen hack enhancement added.
 - 2020/07/04: Vulkan renderer now available in libretro core.
 - 2020/07/02: Now available as a libretro core.
 - 2020/07/01: Lightgun support with custom crosshairs.

src/core/cpu_core.h

@@ -54,6 +54,9 @@ public:
   ALWAYS_INLINE TickCount GetDowncount() const { return m_downcount; }
   ALWAYS_INLINE void SetDowncount(TickCount downcount) { m_downcount = downcount; }
 
+  ALWAYS_INLINE const GTE::Core& GetCop2() const { return m_cop2; }
+  ALWAYS_INLINE GTE::Core& GetCop2() { return m_cop2; }
+
   // Sets the PC and flushes the pipeline.
   void SetPC(u32 new_pc);
 

src/core/gte.cpp

@@ -578,7 +578,10 @@ void Core::RTPS(const s16 V[3], u8 shift, bool lm, bool last)
   // MAC0=(((H*20000h/SZ3)+1)/2)*IR1+OFX, SX2=MAC0/10000h ;ScrX FIFO -400h..+3FFh
   // MAC0=(((H*20000h/SZ3)+1)/2)*IR2+OFY, SY2=MAC0/10000h ;ScrY FIFO -400h..+3FFh
   const s64 result = static_cast<s64>(ZeroExtend64(UNRDivide(m_regs.H, m_regs.SZ3)));
-  const s64 Sx = s64(result) * s64(m_regs.IR1) + s64(m_regs.OFX);
+
+  // (4 / 3) / (16 / 9) -> 0.75 -> (3 / 4)
+  const s64 Sx = m_widescreen_hack ? ((((s64(result) * s64(m_regs.IR1)) * s64(3)) / s64(4)) + s64(m_regs.OFX)) :
+                                     (s64(result) * s64(m_regs.IR1) + s64(m_regs.OFX));
   const s64 Sy = s64(result) * s64(m_regs.IR2) + s64(m_regs.OFY);
   CheckMACOverflow<0>(Sx);
   CheckMACOverflow<0>(Sy);

src/core/gte.h

@@ -21,6 +21,8 @@ public:
   Core();
   ~Core();
 
+  ALWAYS_INLINE void SetWidescreenHack(bool enabled) { m_widescreen_hack = enabled; }
+
   void Initialize();
   void Reset();
   bool DoState(StateWrapper& sw);
@@ -109,6 +111,7 @@ private:
   void Execute_GPF(Instruction inst);
 
   Regs m_regs = {};
+  bool m_widescreen_hack = false;
 };
 
 #include "gte.inl"

src/core/host_interface.cpp

@@ -8,6 +8,7 @@
 #include "common/log.h"
 #include "common/string_util.h"
 #include "controller.h"
+#include "cpu_core.h"
 #include "dma.h"
 #include "gpu.h"
 #include "host_display.h"
@@ -345,6 +346,7 @@ void HostInterface::SetDefaultSettings(SettingsInterface& si)
   si.SetBoolValue("GPU", "TextureFiltering", false);
   si.SetBoolValue("GPU", "DisableInterlacing", false);
   si.SetBoolValue("GPU", "ForceNTSCTimings", false);
+  si.SetBoolValue("GPU", "WidescreenHack", false);
 
   si.SetStringValue("Display", "CropMode", Settings::GetDisplayCropModeName(Settings::DEFAULT_DISPLAY_CROP_MODE));
   si.SetStringValue("Display", "AspectRatio",
@@ -468,6 +470,9 @@ void HostInterface::CheckForSettingsChanges(const Settings& old_settings)
 
     m_system->GetDMA()->SetMaxSliceTicks(m_settings.dma_max_slice_ticks);
     m_system->GetDMA()->SetHaltTicks(m_settings.dma_halt_ticks);
+
+    if (m_settings.gpu_widescreen_hack != old_settings.gpu_widescreen_hack)
+      m_system->GetCPU()->GetCop2().SetWidescreenHack(m_settings.gpu_widescreen_hack);
   }
 
   bool controllers_updated = false;

src/core/settings.cpp

@@ -98,6 +98,7 @@ void Settings::Load(SettingsInterface& si)
   gpu_texture_filtering = si.GetBoolValue("GPU", "TextureFiltering", false);
   gpu_disable_interlacing = si.GetBoolValue("GPU", "DisableInterlacing", false);
   gpu_force_ntsc_timings = si.GetBoolValue("GPU", "ForceNTSCTimings", false);
+  gpu_widescreen_hack = si.GetBoolValue("GPU", "WidescreenHack", false);
 
   display_crop_mode =
     ParseDisplayCropMode(
@@ -200,6 +201,7 @@ void Settings::Save(SettingsInterface& si) const
   si.SetBoolValue("GPU", "TextureFiltering", gpu_texture_filtering);
   si.SetBoolValue("GPU", "DisableInterlacing", gpu_disable_interlacing);
   si.SetBoolValue("GPU", "ForceNTSCTimings", gpu_force_ntsc_timings);
+  si.SetBoolValue("GPU", "WidescreenHack", gpu_widescreen_hack);
 
   si.SetStringValue("Display", "CropMode", GetDisplayCropModeName(display_crop_mode));
   si.SetStringValue("Display", "AspectRatio", GetDisplayAspectRatioName(display_aspect_ratio));
@@ -437,10 +439,10 @@ const char* Settings::GetDisplayCropModeDisplayName(DisplayCropMode crop_mode)
   return s_display_crop_mode_display_names[static_cast<int>(crop_mode)];
 }
 
-static std::array<const char*, 6> s_display_aspect_ratio_names =
-  {{"4:3", "16:9", "8:7", "2:1 (VRAM 1:1)", "1:1", "PAR 1:1"}};
-static constexpr std::array<float, 6> s_display_aspect_ratio_values =
-  {{4.0f / 3.0f, 16.0f / 9.0f, 8.0f / 7.0f, 2.0f / 1.0f, 1.0f, -1.0f}};
+static std::array<const char*, 6> s_display_aspect_ratio_names = {
+  {"4:3", "16:9", "8:7", "2:1 (VRAM 1:1)", "1:1", "PAR 1:1"}};
+static constexpr std::array<float, 6> s_display_aspect_ratio_values = {
+  {4.0f / 3.0f, 16.0f / 9.0f, 8.0f / 7.0f, 2.0f / 1.0f, 1.0f, -1.0f}};
 
 std::optional<DisplayAspectRatio> Settings::ParseDisplayAspectRatio(const char* str)
 {

src/core/settings.h

@@ -88,6 +88,7 @@ struct Settings
   bool gpu_texture_filtering = false;
   bool gpu_disable_interlacing = false;
   bool gpu_force_ntsc_timings = false;
+  bool gpu_widescreen_hack = false;
   DisplayCropMode display_crop_mode = DisplayCropMode::None;
   DisplayAspectRatio display_aspect_ratio = DisplayAspectRatio::R4_3;
   bool display_linear_filtering = true;

src/core/system.cpp

@@ -242,7 +242,8 @@ bool System::Boot(const SystemBootParameters& params)
 
 bool System::InitializeComponents(bool force_software_renderer)
 {
-  if (!CreateGPU(force_software_renderer ? GPURenderer::Software : GetSettings().gpu_renderer))
+  const Settings& settings = GetSettings();
+  if (!CreateGPU(force_software_renderer ? GPURenderer::Software : settings.gpu_renderer))
     return false;
 
   m_cpu->Initialize(m_bus.get());
@@ -261,6 +262,9 @@ bool System::InitializeComponents(bool force_software_renderer)
   m_spu->Initialize(this, m_dma.get(), m_interrupt_controller.get());
   m_mdec->Initialize(this, m_dma.get());
 
+  // load settings
+  m_cpu->GetCop2().SetWidescreenHack(settings.gpu_widescreen_hack);
+
   UpdateThrottlePeriod();
   return true;
 }