Added option to 'desensitze' joysticks, i.e. make it less sensible

at values close to 0.

src/input/device_config.hpp

@@ -105,6 +105,10 @@ public:
      *  will not be affected by time-full-steer delays. */
     virtual bool isAnalog() const { return false;}
     // ------------------------------------------------------------------------
+    /** Returns true if this device should desensitize its input at values
+     *  close to 0 (to avoid 'oversteering'). */
+    virtual bool desensitize() const { return false;}
+    // ------------------------------------------------------------------------
     /** Should only be called for gamepads, which has its own implementation.
      *  of this function. */
     virtual int getNumberOfButtons() const

src/input/gamepad_config.cpp

@@ -45,8 +45,9 @@ GamepadConfig::GamepadConfig( const std::string &name,
 
 GamepadConfig::GamepadConfig() : DeviceConfig()
 {
-    m_deadzone  = 2000;
-    m_is_analog = true;
+    m_deadzone    = 2000;
+    m_is_analog   = true;
+    m_desensitize = false;
     setDefaultBinds();
 }   // GamepadConfig
 
@@ -57,8 +58,9 @@ GamepadConfig::GamepadConfig() : DeviceConfig()
  */
 bool GamepadConfig::load(const XMLNode *config)
 {
-    config->get("deadzone", &m_deadzone);
-    config->get("analog",  &m_is_analog);
+    config->get("deadzone",     &m_deadzone   );
+    config->get("analog",       &m_is_analog  );
+    config->get("desensitize",  &m_desensitize);
     bool ok = DeviceConfig::load(config);
 
     if(getName()=="")
@@ -80,6 +82,7 @@ void GamepadConfig::save (std::ofstream& stream)
 {
     stream << "<gamepad name =\"" << getName()
            << "\" deadzone=\""    << m_deadzone
+           << "\" desensitize=\"" << m_desensitize
            << "\" analog=\""      << m_is_analog<<"\"\n";
     stream << "         ";
     DeviceConfig::save(stream);
@@ -107,9 +110,7 @@ void GamepadConfig::setDefaultBinds ()
     setBinding(PA_MENU_RIGHT,   Input::IT_STICKMOTION, 0, Input::AD_POSITIVE);
     setBinding(PA_MENU_SELECT,  Input::IT_STICKBUTTON, 0);
     setBinding(PA_MENU_CANCEL,  Input::IT_STICKBUTTON, 3);
-}
-
-//------------------------------------------------------------------------------
+}   // setDefaultBinds
 
 //------------------------------------------------------------------------------
 /** Converts the configuration to a string.

src/input/gamepad_config.hpp

@@ -49,6 +49,11 @@ private:
     /** If this device has analog axis, steering etc. must be set immediately
      *  from the input values, not having a delayed time (time-full-steer). */
     bool m_is_analog;
+
+    /** If set to true, map any analog axis from x in [0,1] to x^x --> at
+     *  values close to 0 the joystick will react less sensitive. */
+    bool m_desensitize;
+
 public:
 
              GamepadConfig           ();
@@ -66,6 +71,11 @@ public:
     /** Returns if this device uses analog axes. */
     virtual bool isAnalog() const OVERRIDE { return m_is_analog; }
 
+    // ------------------------------------------------------------------------
+    /** Returns true if this device should desensitize its input at values
+     *  close to 0 (to avoid 'oversteering'). */
+    virtual bool desensitize() const { return m_desensitize;}
+
     // ------------------------------------------------------------------------
     /** Returns the number of buttons in this configuration. */
     virtual int getNumberOfButtons() const OVERRIDE { return m_button_count; }

src/input/gamepad_device.cpp

@@ -172,6 +172,18 @@ bool GamePadDevice::processAndMapInput(Input::InputType type, const int id,
         else if(*value==-32768)
             *value = -32767;
     }
+
+    // Desensitizing means to map an input in the range x in [0,1] to
+    // x^2. This results in changes close to 0 to have less impact
+    // (less sensitive).
+    if(m_configuration->desensitize())
+    {
+        // x/32767 is in [-1,1], (x/32767)^2 is in [0,1]. Take care of the
+        // sign and map this back to [0,32767] by multiplying by 32767.
+        // Which all in all results in:
+        *value = int( (*value / 32767) * fabsf(*value) );
+    }
+
     bool success = false;
     if(m_prev_axis_directions == NULL) return false; // device not open