From 6d14583f287c5b19ebb06636b9c6ecd1541436d2 Mon Sep 17 00:00:00 2001
From: Ryan Gonzalez <kirbyfan64@users.noreply.github.com>
Date: Tue, 15 Aug 2017 14:14:13 -0500
Subject: [PATCH] Better evdev joystick axis scaling (#3202)

Fix evdev scaling when the minimum value is <0
Declare a trigger as pressed as long as any value >0 is given
---
 rpcs3/evdev_joystick_handler.cpp | 56 +++++++++++++++++++-------------
 rpcs3/evdev_joystick_handler.h   |  5 +--
 2 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/rpcs3/evdev_joystick_handler.cpp b/rpcs3/evdev_joystick_handler.cpp
index 91e450da96..e3f92029bc 100644
--- a/rpcs3/evdev_joystick_handler.cpp
+++ b/rpcs3/evdev_joystick_handler.cpp
@@ -34,7 +34,6 @@ void evdev_joystick_handler::Init(const u32 max_connect)
 
     g_evdev_joystick_config.load();
 
-    needscale = static_cast<bool>(g_evdev_joystick_config.needscale);
     axistrigger = static_cast<bool>(g_evdev_joystick_config.axistrigger);
 
     revaxis.emplace_back(g_evdev_joystick_config.lxreverse);
@@ -173,12 +172,16 @@ bool evdev_joystick_handler::try_open_dev(u32 index)
     int axes=0;
     for (int i=ABS_X; i<=ABS_RZ; i++)
     {
-        // Skip ABS_Z and ABS_RZ on controllers where it's used for the triggers.
-        if (axistrigger && (i == ABS_Z || i == ABS_RZ)) continue;
 
         if (libevdev_has_event_code(dev, EV_ABS, i))
         {
             LOG_NOTICE(GENERAL, "Joystick #%d has axis %d as %d", index, i, axes);
+
+            axis_ranges[i].first = libevdev_get_abs_minimum(dev, i);
+            axis_ranges[i].second = libevdev_get_abs_maximum(dev, i);
+
+            // Skip ABS_Z and ABS_RZ on controllers where it's used for the triggers.
+            if (axistrigger && (i == ABS_Z || i == ABS_RZ)) continue;
             joy_axis_maps[index][i - ABS_X] = axes++;
         }
     }
@@ -220,6 +223,28 @@ void evdev_joystick_handler::Close()
     }
 }
 
+int evdev_joystick_handler::scale_axis(int axis, int value)
+{
+    auto range = axis_ranges[axis];
+    // Check if scaling is needed.
+    if (range.first != 0 || range.second != 255)
+    {
+        if (range.first < 0)
+        {
+            // Move the ranges up to make the following calculation actually *work*
+            value += -range.first;
+            range.second += -range.first;
+            range.first = 0;
+        }
+
+        return (static_cast<float>(value - range.first) / range.second) * 255;
+    }
+    else
+    {
+        return value;
+    }
+}
+
 void evdev_joystick_handler::thread_func()
 {
     while (active)
@@ -331,7 +356,7 @@ void evdev_joystick_handler::thread_func()
                 }
                 else if (axistrigger && (evt.code == ABS_Z || evt.code == ABS_RZ))
                 {
-                    // For Xbox 360 controllers, a third axis represent the left/right triggers.
+                    // For Xbox controllers, a third axis represent the left/right triggers.
                     int which_trigger=0;
 
                     if (evt.code == ABS_Z)
@@ -356,8 +381,10 @@ void evdev_joystick_handler::thread_func()
                         LOG_ERROR(GENERAL, "Joystick #%d's pad has no trigger %d", i, which_trigger);
                         break;
                     }
-                    which_button->m_pressed = evt.value == 255;
-                    which_button->m_value = evt.value;
+
+                    int value = scale_axis(evt.code, evt.value);
+                    which_button->m_pressed = value > 0;
+                    which_button->m_value = value;
                 }
                 else if (evt.code >= ABS_X && evt.code <= ABS_RZ)
                 {
@@ -369,22 +396,7 @@ void evdev_joystick_handler::thread_func()
                         break;
                     }
 
-                    auto& stick = pad.m_sticks[axis];
-
-                    int value = evt.value;
-
-                    if (needscale)
-                    {
-                        // Scale from the -32768...32768 range to the 0...256 range.
-                        value = (value / 256) + 128;
-                    }
-
-                    if (revaxis[axis])
-                    {
-                        value = 256 - value;
-                    }
-
-                    stick.m_value = value;
+                    pad.m_sticks[axis].m_value = scale_axis(evt.code, evt.value);
                 }
                 break;
             default:
diff --git a/rpcs3/evdev_joystick_handler.h b/rpcs3/evdev_joystick_handler.h
index 66285687fe..30e8a9a120 100644
--- a/rpcs3/evdev_joystick_handler.h
+++ b/rpcs3/evdev_joystick_handler.h
@@ -44,7 +44,6 @@ struct evdev_joystick_config final : cfg::node
     cfg::_bool lxreverse{this, "Reverse left stick X axis", false};
     cfg::_bool lyreverse{this, "Reverse left stick Y axis", false};
 
-    cfg::_bool needscale{this, "Axis scaling", true};
     cfg::_bool axistrigger{this, "Z axis triggers", true};
 
     bool load()
@@ -76,6 +75,7 @@ public:
 private:
     void update_devs();
     bool try_open_dev(u32 index);
+    int scale_axis(int axis, int value);
     void thread_func();
 
     std::unique_ptr<std::thread> joy_thread;
@@ -85,6 +85,7 @@ private:
     std::vector<std::vector<int>> joy_button_maps;
     std::vector<std::vector<int>> joy_axis_maps;
     std::vector<int> joy_hat_ids;
-    bool needscale, axistrigger;
+    bool axistrigger;
+    std::map<int, std::pair<int, int>> axis_ranges;
     std::vector<bool> revaxis;
 };