NamcoGuncon: Add an option to scale X coordinates

Fixes what appears to be curvature correction at the edges of the
screen.

src/core/gpu.cpp

@@ -917,11 +917,21 @@ void GPU::UpdateCommandTickEvent()
     m_command_tick_event->SetIntervalAndSchedule(GPUTicksToSystemTicks(m_pending_command_ticks));
 }
 
-bool GPU::ConvertScreenCoordinatesToBeamTicksAndLines(s32 window_x, s32 window_y, u32* out_tick, u32* out_line) const
+bool GPU::ConvertScreenCoordinatesToBeamTicksAndLines(s32 window_x, s32 window_y, float x_scale, u32* out_tick,
+                                                      u32* out_line) const
 {
-  const auto [display_x, display_y] = m_host_display->ConvertWindowCoordinatesToDisplayCoordinates(
+  auto [display_x, display_y] = m_host_display->ConvertWindowCoordinatesToDisplayCoordinates(
     window_x, window_y, m_host_display->GetWindowWidth(), m_host_display->GetWindowHeight(),
     m_host_display->GetDisplayTopMargin());
+
+  if (x_scale != 1.0f)
+  {
+    const float dw = static_cast<float>(m_crtc_state.display_width);
+    float scaled_x = ((static_cast<float>(display_x) / dw) * 2.0f) - 1.0f; // 0..1 -> -1..1
+    scaled_x *= x_scale;
+    display_x = static_cast<s32>(((scaled_x + 1.0f) * 0.5f) * dw); // -1..1 -> 0..1
+  }
+
   Log_DebugPrintf("win %d,%d -> disp %d,%d (size %u,%u frac %f,%f)", window_x, window_y, display_x, display_y,
                   m_crtc_state.display_width, m_crtc_state.display_height,
                   static_cast<float>(display_x) / static_cast<float>(m_crtc_state.display_width),

src/core/gpu.h

@@ -154,7 +154,8 @@ public:
   static std::unique_ptr<GPU> CreateSoftwareRenderer();
 
   // Converts window coordinates into horizontal ticks and scanlines. Returns false if out of range. Used for lightguns.
-  bool ConvertScreenCoordinatesToBeamTicksAndLines(s32 window_x, s32 window_y, u32* out_tick, u32* out_line) const;
+  bool ConvertScreenCoordinatesToBeamTicksAndLines(s32 window_x, s32 window_y, float x_scale, u32* out_tick,
+                                                   u32* out_line) const;
 
   // Returns the video clock frequency.
   TickCount GetCRTCFrequency() const;

src/core/namco_guncon.cpp

@@ -177,7 +177,8 @@ void NamcoGunCon::UpdatePosition()
   // are we within the active display area?
   u32 tick, line;
   if (mouse_x < 0 || mouse_y < 0 ||
-      !g_gpu->ConvertScreenCoordinatesToBeamTicksAndLines(mouse_x, mouse_y, &tick, &line) || m_shoot_offscreen)
+      !g_gpu->ConvertScreenCoordinatesToBeamTicksAndLines(mouse_x, mouse_y, m_x_scale, &tick, &line) ||
+      m_shoot_offscreen)
   {
     Log_DebugPrintf("Lightgun out of range for window coordinates %d,%d", mouse_x, mouse_y);
     m_position_x = 0x01;
@@ -241,11 +242,14 @@ u32 NamcoGunCon::StaticGetVibrationMotorCount()
 
 Controller::SettingList NamcoGunCon::StaticGetSettings()
 {
-  static constexpr std::array<SettingInfo, 2> settings = {
+  static constexpr std::array<SettingInfo, 3> settings = {
     {{SettingInfo::Type::Path, "CrosshairImagePath", TRANSLATABLE("NamcoGunCon", "Crosshair Image Path"),
       TRANSLATABLE("NamcoGunCon", "Path to an image to use as a crosshair/cursor.")},
      {SettingInfo::Type::Float, "CrosshairScale", TRANSLATABLE("NamcoGunCon", "Crosshair Image Scale"),
-      TRANSLATABLE("NamcoGunCon", "Scale of crosshair image on screen."), "1.0", "0.0001", "100.0"}}};
+      TRANSLATABLE("NamcoGunCon", "Scale of crosshair image on screen."), "1.0", "0.0001", "100.0"},
+     {SettingInfo::Type::Float, "XScale", TRANSLATABLE("NamcoGunCon", "X Scale"),
+      TRANSLATABLE("NamcoGunCon", "Scales X coordinates relative to the center of the screen."), "1.0", "0.01", "2.0",
+      "0.01"}}};
 
   return SettingList(settings.begin(), settings.end());
 }
@@ -272,6 +276,8 @@ void NamcoGunCon::LoadSettings(const char* section)
   }
 
   m_crosshair_image_scale = g_host_interface->GetFloatSettingValue(section, "CrosshairScale", 1.0f);
+
+  m_x_scale = g_host_interface->GetFloatSettingValue(section, "XScale", 1.0f);
 }
 
 bool NamcoGunCon::GetSoftwareCursor(const Common::RGBA8Image** image, float* image_scale)

src/core/namco_guncon.h

@@ -62,6 +62,7 @@ private:
   Common::RGBA8Image m_crosshair_image;
   std::string m_crosshair_image_path;
   float m_crosshair_image_scale = 1.0f;
+  float m_x_scale = 1.0f;
 
   // buttons are active low
   u16 m_button_state = UINT16_C(0xFFFF);