ControllerInterface: Input detection improvements.

Source/Core/InputCommon/ControllerInterface/DInput/DInputJoystick.cpp

@@ -259,7 +259,7 @@ std::string Joystick::Hat::GetName() const
 
 ControlState Joystick::Axis::GetState() const
 {
-  return std::max(0.0, ControlState(m_axis - m_base) / m_range);
+  return ControlState(m_axis - m_base) / m_range;
 }
 
 ControlState Joystick::Button::GetState() const

Source/Core/InputCommon/ControllerInterface/Device.cpp

@@ -4,6 +4,7 @@
 
 #include "InputCommon/ControllerInterface/Device.h"
 
+#include <cmath>
 #include <memory>
 #include <sstream>
 #include <string>
@@ -68,6 +69,11 @@ Device::Output* Device::FindOutput(const std::string& name) const
   return nullptr;
 }
 
+ControlState Device::FullAnalogSurface::GetState() const
+{
+  return (1 + std::max(0.0, m_high.GetState()) - std::max(0.0, m_low.GetState())) / 2;
+}
+
 //
 // DeviceQualifier :: ToString
 //
@@ -214,5 +220,5 @@ bool DeviceContainer::HasConnectedDevice(const DeviceQualifier& qualifier) const
   const auto device = FindDevice(qualifier);
   return device != nullptr && device->IsValid();
 }
-}
-}
+}  // namespace Core
+}  // namespace ciface

Source/Core/InputCommon/ControllerInterface/Device.h

@@ -55,9 +55,22 @@ public:
   class Input : public Control
   {
   public:
-    // things like absolute axes/ absolute mouse position will override this
+    // Things like absolute axes/ absolute mouse position should override this to prevent
+    // undesirable behavior in our mapping logic.
     virtual bool IsDetectable() { return true; }
+
+    // Implementations should return a value from 0.0 to 1.0 across their normal range.
+    // One input should be provided for each "direction". (e.g. 2 for each axis)
+    // If possible, negative values may be returned in situations where an opposing input is
+    // activated. (e.g. When an underlying axis, X, is currently negative, "Axis X-", will return a
+    // positive value and "Axis X+" may return a negative value.)
+    // Doing so is solely to allow our input detection logic to better detect false positives.
+    // This is necessary when making use of "FullAnalogSurface" as multiple inputs will be seen
+    // increasing from 0.0 to 1.0 as a user tries to map just one. The negative values provide a
+    // view of the underlying axis. (Negative values are clamped off before they reach
+    // expression-parser or controller-emu)
     virtual ControlState GetState() const = 0;
+
     Input* ToInput() override { return this; }
   };
 
@@ -96,11 +109,7 @@ protected:
   {
   public:
     FullAnalogSurface(Input* low, Input* high) : m_low(*low), m_high(*high) {}
-    ControlState GetState() const override
-    {
-      return (1 + m_high.GetState() - m_low.GetState()) / 2;
-    }
-
+    ControlState GetState() const override;
     std::string GetName() const override { return m_low.GetName() + *m_high.GetName().rbegin(); }
 
   private:

Source/Core/InputCommon/ControllerInterface/XInput/XInput.cpp

@@ -228,7 +228,7 @@ ControlState Device::Trigger::GetState() const
 
 ControlState Device::Axis::GetState() const
 {
-  return std::max(0.0, ControlState(m_axis) / m_range);
+  return ControlState(m_axis) / m_range;
 }
 
 void Device::Motor::SetState(ControlState state)
@@ -236,5 +236,5 @@ void Device::Motor::SetState(ControlState state)
   m_motor = (WORD)(state * m_range);
   m_parent->UpdateMotors();
 }
-}
-}
+}  // namespace XInput
+}  // namespace ciface

Source/Core/InputCommon/ControllerInterface/evdev/evdev.cpp

@@ -343,7 +343,7 @@ ControlState evdevDevice::Axis::GetState() const
   int value = 0;
   libevdev_fetch_event_value(m_dev, EV_ABS, m_code, &value);
 
-  return std::max(0.0, ControlState(value - m_base) / m_range);
+  return ControlState(value - m_base) / m_range;
 }
 
 evdevDevice::Effect::Effect(int fd) : m_fd(fd)