Heuristic to detect controller triggers

2 files changed, 27 insertions, 3 deletions

diff --git a/src/input/joystick.cpp b/src/input/joystick.cpp
index 126d5018a..1072d3892 100644
--- a/src/input/joystick.cpp
+++ b/src/input/joystick.cpp
@@ -61,7 +61,10 @@ Joystick::Joystick(const int no) :
     mKeyTimeMap()
 {
     for (int i = 0; i < MAX_AXES; i++)
+    {
+        mIsTrigger[i] = false;
         mAxesPositions[i] = 0;
+    }
     for (int i = 0; i < MAX_BUTTONS; i++)
         mActiveButtons[i] = false;
 }
@@ -211,6 +214,14 @@ bool Joystick::open()
     mUseHatForMovement = config.getBoolValue("useHatForMovement");
     mUseInactive = config.getBoolValue("useInactiveJoystick");
 
+    for (int i = 0; i < mAxesNumber; i++)
+    {
+        // heuristic to detect controller triggers.
+        // their resting position is at SDL_JOYSTICK_AXIS_MIN = -32768
+        if (SDL_JoystickGetAxis(mJoystick, i) == SDL_JOYSTICK_AXIS_MIN)
+            mIsTrigger[i] = true;
+    }
+
     return true;
 }
 
@@ -253,7 +264,14 @@ void Joystick::logic()
         settings.inputFocused != KeyboardFocus::Unfocused)
     {
         for (int i = 0; i < mAxesNumber; i++)
-            mAxesPositions[i] = SDL_JoystickGetAxis(mJoystick, i);
+        {
+            int position = SDL_JoystickGetAxis(mJoystick, i);
+            // transform range [SDL_JOYSTICK_AXIS_MIN, SDL_JOYSTICK_AXIS_MAX]
+            // to [0, SDL_JOYSTICK_AXIS_MAX]
+            if (mIsTrigger[i])
+                position = (position - SDL_JOYSTICK_AXIS_MIN) / 2;
+            mAxesPositions[i] = position;
+        }
 
         // X-Axis
         int position = mAxesPositions[0];
@@ -434,10 +452,15 @@ int Joystick::getButtonFromEvent(const SDL_Event &event) const
         const int axis = event.jaxis.axis;
         if (axis < RESERVED_AXES)
             return -1;
-        if (event.jaxis.value < mTolerance * SDL_JOYSTICK_AXIS_MIN
+        int position = event.jaxis.value;
+        // transform range [SDL_JOYSTICK_AXIS_MIN, SDL_JOYSTICK_AXIS_MAX]
+        // to [0, SDL_JOYSTICK_AXIS_MAX]
+        if (mIsTrigger[axis])
+            position = (position - SDL_JOYSTICK_AXIS_MIN) / 2;
+        if (position < mTolerance * SDL_JOYSTICK_AXIS_MIN
             && mAxesPositions[axis] > mTolerance * SDL_JOYSTICK_AXIS_MIN)
             return KEY_NEGATIVE_AXIS_FIRST + axis;
-        if (event.jaxis.value > mTolerance * SDL_JOYSTICK_AXIS_MAX
+        if (position > mTolerance * SDL_JOYSTICK_AXIS_MAX
             && mAxesPositions[axis] < mTolerance * SDL_JOYSTICK_AXIS_MAX)
             return KEY_POSITIVE_AXIS_FIRST + axis;
     }
diff --git a/src/input/joystick.h b/src/input/joystick.h
index bd5ca533d..49c4e553a 100644
--- a/src/input/joystick.h
+++ b/src/input/joystick.h
@@ -179,6 +179,7 @@ class Joystick final
 
         unsigned char mHatPosition;
         int mAxesPositions[MAX_AXES];
+        bool mIsTrigger[MAX_AXES];
         bool mActiveButtons[MAX_BUTTONS];
 
         SDL_Joystick *mJoystick;