libretro: add Wiimote IR passthrough

Adds dolphin_ir_passthrough, letting the frontend supply the Wiimote
camera's view of the sensor bar directly instead of having the core
synthesise it from a cursor position.

The cursor path parks a notional remote two metres from the bar and
rotates it by Total Yaw/Total Pitch, a scale with no physical
derivation, so where the game draws its hand depends on a constant
fitted per game. It also cannot express roll or distance. A frontend
that knows the real geometry (a VR room, a tracked light gun) can
compute the two dots outright, which BuildDesiredWiimoteState already
supports and nothing exposed.

  * The option itself, off by default, under Wiimote IR.

  * The Pointer device registers all four touch indices instead of only
    the first, so the four IR objects ride on indices 0-3. Index 0 keeps
    its old names, leaving the mouse-mode IR binding untouched.

  * IRPassthrough is bound and enabled when the option is on: object N
    takes Pointer:XN+/YN+ over the camera's 0..1 field, PressedN as
    presence, and a small constant size. Bindings are cleared when off,
    since AreInputsBound() is half of what selects this path.

  * irPassthrough is raised at controller setup as well as on an option
    change, so the setting applies on a cold boot.

Author: XenuIsWatching

Source/Core/DolphinLibretro/Common/Options.cpp

@@ -1715,6 +1715,20 @@ static struct retro_core_option_v2_definition option_defs[] = {
     },
     "disabled"
   },
+  {
+    Libretro::Options::wiimote::IR_PASSTHROUGH,
+    "Wiimote IR > Wiimote IR Passthrough",
+    "Wiimote IR Passthrough",
+    "Take the Wiimote camera's view of the sensor bar straight from the frontend, instead of deriving it from a cursor position. The frontend supplies up to four IR objects on pointer indices 1-4; Wiimote IR Mode, Total Yaw, Total Pitch and Vertical Offset are all bypassed. For frontends that know the real geometry (a VR room, a tracked light gun) this is exact, and it carries roll and distance, which a cursor cannot. Leave off for a mouse or a gamepad.",
+    nullptr,
+    CATEGORY_WIIMOTE,
+    {
+      { "disabled", nullptr },
+      { "enabled",  nullptr },
+      { nullptr, nullptr }
+    },
+    "disabled"
+  },
 
 #if defined(HAS_OPENGL) && defined(__WEBOS__)
   {

Source/Core/DolphinLibretro/Common/Options.h

@@ -302,6 +302,7 @@ namespace wiimote {
   constexpr const char IR_MODIFIER[] = "dolphin_ir_modifier";
   constexpr const char SWING_MODIFIER[] = "dolphin_swing_modifier";
   constexpr const char SWING_ANGLE[] = "dolphin_swing_angle";
+  constexpr const char IR_PASSTHROUGH[] = "dolphin_ir_passthrough";
 }  // namespace wiimote
 
 // ======================================================

Source/Core/DolphinLibretro/Input.cpp

@@ -38,6 +38,7 @@
 #include "InputCommon/ControlReference/ExpressionParser.h"
 #include "InputCommon/ControllerEmu/Control/Control.h"
 #include "InputCommon/ControllerEmu/ControlGroup/Attachments.h"
+#include "InputCommon/ControllerEmu/ControlGroup/IRPassthrough.h"
 #include "InputCommon/ControllerEmu/Setting/NumericSetting.h"
 #include "InputCommon/ControllerInterface/ControllerInterface.h"
 #include "InputCommon/GCAdapter.h"
@@ -407,11 +408,22 @@ Device::Device(unsigned device, unsigned p) : m_device(device), m_port(p)
     AddButton(RETRO_DEVICE_ID_MOUSE_BUTTON_5, "Button5");
     return;
   case RETRO_DEVICE_POINTER:
-    AddButton(RETRO_DEVICE_ID_POINTER_PRESSED, "Pressed0", 0);
-    AddAxis(RETRO_DEVICE_ID_POINTER_X, -0x8000, "X0-", 0);
-    AddAxis(RETRO_DEVICE_ID_POINTER_X, 0x7FFF, "X0+", 0);
-    AddAxis(RETRO_DEVICE_ID_POINTER_Y, -0x8000, "Y0-", 0);
-    AddAxis(RETRO_DEVICE_ID_POINTER_Y, 0x7FFF, "Y0+", 0);
+    // Four touch indices, one per IR object. Index 0 keeps its old names.
+    {
+      static const char* const kPressed[] = { "Pressed0", "Pressed1", "Pressed2", "Pressed3" };
+      static const char* const kXNeg[]    = { "X0-", "X1-", "X2-", "X3-" };
+      static const char* const kXPos[]    = { "X0+", "X1+", "X2+", "X3+" };
+      static const char* const kYNeg[]    = { "Y0-", "Y1-", "Y2-", "Y3-" };
+      static const char* const kYPos[]    = { "Y0+", "Y1+", "Y2+", "Y3+" };
+      for (unsigned i = 0; i < 4; ++i)
+      {
+        AddButton(RETRO_DEVICE_ID_POINTER_PRESSED, kPressed[i], i);
+        AddAxis(RETRO_DEVICE_ID_POINTER_X, -0x8000, kXNeg[i], i);
+        AddAxis(RETRO_DEVICE_ID_POINTER_X, 0x7FFF, kXPos[i], i);
+        AddAxis(RETRO_DEVICE_ID_POINTER_Y, -0x8000, kYNeg[i], i);
+        AddAxis(RETRO_DEVICE_ID_POINTER_Y, 0x7FFF, kYPos[i], i);
+      }
+    }
     return;
   case RETRO_DEVICE_KEYBOARD:
     return;
@@ -946,6 +958,37 @@ void UpdateWiimoteMappings(const WiimoteUpdateFlags& f, unsigned port, unsigned
     }
   }
 
+  // Raw IR: the frontend supplies the camera's view directly, bypassing the
+  // Point group and Total Yaw/Pitch. Objects arrive on pointer indices 0-3,
+  // X/Y over the camera's 0..1 field, PRESSED marking the object visible.
+  // Size is a constant; games only read it to reject noise.
+  if (f.irPassthrough)
+  {
+    auto* wmIRPass = static_cast<ControllerEmu::IRPassthrough*>(
+      wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::IRPassthrough));
+    const bool passthrough =
+      Libretro::Options::GetCached<bool>(Libretro::Options::wiimote::IR_PASSTHROUGH);
+
+    if (wmIRPass)
+    {
+      const std::string devPointer =
+        Libretro::Input::GetQualifiedName(port, RETRO_DEVICE_POINTER);
+      wmIRPass->enabled.SetValue(passthrough);
+      static const char* const kObj[] = { "0", "1", "2", "3" };
+      for (int i = 0; i < 4; ++i)
+      {
+        // Cleared when off; AreInputsBound() is half of what selects this path.
+        const std::string idx = kObj[i];
+        wmIRPass->SetControlExpression(i * 3 + 0,
+          passthrough ? "`" + devPointer + ":X" + idx + "+`" : "");
+        wmIRPass->SetControlExpression(i * 3 + 1,
+          passthrough ? "`" + devPointer + ":Y" + idx + "+`" : "");
+        wmIRPass->SetControlExpression(i * 3 + 2,
+          passthrough ? "`" + devPointer + ":Pressed" + idx + "` * 0.2" : "");
+      }
+    }
+  }
+
   if (f.swingAngle)
   {
     ControllerEmu::ControlGroup* wmSwing = wm->GetWiimoteGroup(WiimoteEmu::WiimoteGroup::Swing);
@@ -1516,6 +1559,8 @@ void retro_set_controller_port_device_wii(unsigned port, unsigned device)
     f.irModifier = true;
     f.swingModifier = true;
     f.sideways = true;
+    // Raised at setup so the option applies on a cold boot.
+    f.irPassthrough = true;
     Libretro::Input::UpdateWiimoteMappings(f, port, device);
 
     wmShake->SetControlExpression(0, bindMouse("L2", devMouse + ":Middle"));  // Wiimote shake X

Source/Core/DolphinLibretro/Input.h

@@ -19,11 +19,12 @@ struct WiimoteUpdateFlags
     bool sideways      = false;
     bool rumble        = false;
     bool gcMicBtn      = false;
+    bool irPassthrough = false;
 
     bool any() const {
         return irMode || irOffset || irYaw || irPitch ||
                irDeadzone || irModifier || swingModifier ||
-               swingAngle || sideways || rumble || gcMicBtn;
+               swingAngle || sideways || rumble || gcMicBtn || irPassthrough;
     }
 };
 

Source/Core/DolphinLibretro/Main.cpp

@@ -389,6 +389,7 @@ void retro_run(void)
     flags.swingModifier = Libretro::Options::IsUpdated(Libretro::Options::wiimote::SWING_MODIFIER);
     flags.swingAngle = Libretro::Options::IsUpdated(Libretro::Options::wiimote::SWING_ANGLE);
     flags.sideways = Libretro::Options::IsUpdated(Libretro::Options::wiimote::HOTKEY_SIDEWAYS_TOGGLE);
+    flags.irPassthrough = Libretro::Options::IsUpdated(Libretro::Options::wiimote::IR_PASSTHROUGH);
   }
 
   flags.rumble = Libretro::Options::IsUpdated(Libretro::Options::sysconf::ENABLE_RUMBLE);