From 35af4c4ede2b5afa3712ece77c8c97c854db584a Mon Sep 17 00:00:00 2001
From: Cameron Gutman <aicommander@gmail.com>
Date: Sun, 25 Jul 2021 16:47:06 -0500
Subject: [PATCH] Add half-axis support for triggers

---
 src/input/evdev.c   | 37 ++++++++++++++++++++++++++-----------
 src/input/mapping.c | 21 +++++++++++++++------
 src/input/mapping.h |  1 +
 3 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/src/input/evdev.c b/src/input/evdev.c
index 46c6ca5..93aa3ad 100644
--- a/src/input/evdev.c
+++ b/src/input/evdev.c
@@ -166,18 +166,28 @@ static short evdev_convert_value(struct input_event *ev, struct input_device *de
     return (long long)(ev->value - (ev->value>parms->avg?parms->flat*2:0) - parms->min) * (SHRT_MAX-SHRT_MIN) / (parms->max-parms->min-parms->flat*2) + SHRT_MIN;
 }
 
-static char evdev_convert_value_byte(struct input_event *ev, struct input_device *dev, struct input_abs_parms *parms) {
+static char evdev_convert_value_byte(struct input_event *ev, struct input_device *dev, struct input_abs_parms *parms, char halfaxis) {
   if (parms->max == 0 && parms->min == 0) {
     fprintf(stderr, "Axis not found: %d\n", ev->code);
     return 0;
   }
 
-  if (abs(ev->value-parms->min)<parms->flat)
-    return 0;
-  else if (ev->value>parms->max)
-    return UCHAR_MAX;
-  else
-    return (ev->value - parms->flat - parms->min) * UCHAR_MAX / (parms->diff - parms->flat);
+  if (halfaxis == 0) {
+    if (abs(ev->value-parms->min)<parms->flat)
+      return 0;
+    else if (ev->value>parms->max)
+      return UCHAR_MAX;
+    else
+      return (ev->value - parms->flat - parms->min) * UCHAR_MAX / (parms->diff - parms->flat);
+  } else {
+    short val = evdev_convert_value(ev, dev, parms, false);
+    if (halfaxis == '-' && val < 0)
+      return -(int)val * UCHAR_MAX / (SHRT_MAX-SHRT_MIN);
+    else if (halfaxis == '+' && val > 0)
+      return (int)val * UCHAR_MAX / (SHRT_MAX-SHRT_MIN);
+    else
+      return 0;
+  }
 }
 
 static bool evdev_handle_event(struct input_event *ev, struct input_device *dev) {
@@ -437,12 +447,17 @@ static bool evdev_handle_event(struct input_event *ev, struct input_device *dev)
         dev->rightStickX = evdev_convert_value(ev, dev, &dev->rxParms, dev->map->reverse_rightx);
       else if (index == dev->map->abs_righty)
         dev->rightStickY = evdev_convert_value(ev, dev, &dev->ryParms, !dev->map->reverse_righty);
-      else if (index == dev->map->abs_lefttrigger)
-        dev->leftTrigger = evdev_convert_value_byte(ev, dev, &dev->zParms);
-      else if (index == dev->map->abs_righttrigger)
-        dev->rightTrigger = evdev_convert_value_byte(ev, dev, &dev->rzParms);
       else
         gamepadModified = false;
+
+      if (index == dev->map->abs_lefttrigger) {
+        dev->leftTrigger = evdev_convert_value_byte(ev, dev, &dev->zParms, dev->map->halfaxis_lefttrigger);
+        gamepadModified = true;
+      }
+      if (index == dev->map->abs_righttrigger) {
+        dev->rightTrigger = evdev_convert_value_byte(ev, dev, &dev->rzParms, dev->map->halfaxis_righttrigger);
+        gamepadModified = true;
+      }
     }
   }
 
diff --git a/src/input/mapping.c b/src/input/mapping.c
index 5371002..166ba3d 100644
--- a/src/input/mapping.c
+++ b/src/input/mapping.c
@@ -43,11 +43,17 @@ struct mapping* mapping_parse(char* mapping) {
 
   char* option;
   while ((option = strtok_r(NULL, ",", &strpoint)) != NULL) {
-    char *key = NULL, *value = NULL;
+    char *key = NULL, *orig_value = NULL;
     int ret;
-    if ((ret = sscanf(option, "%m[^:]:%ms", &key, &value)) == 2) {
+    if ((ret = sscanf(option, "%m[^:]:%ms", &key, &orig_value)) == 2) {
       int int_value, direction_value;
+      char *value = orig_value;
       char flag = 0;
+      char half_axis = 0;
+      if (value[0] == '-' || value[0] == '+') {
+        half_axis = value[0];
+        value++;
+      }
       if (strcmp("platform", key) == 0)
         strncpy(map->platform, value, sizeof(map->platform));
       else if (sscanf(value, "b%d", &int_value) == 1) {
@@ -98,10 +104,13 @@ struct mapping* mapping_parse(char* mapping) {
         } else if (strcmp("righty", key) == 0) {
           map->abs_righty = int_value;
           map->reverse_righty = flag == '~';
-        } else if (strcmp("lefttrigger", key) == 0)
+        } else if (strcmp("lefttrigger", key) == 0) {
           map->abs_lefttrigger = int_value;
-        else if (strcmp("righttrigger", key) == 0)
+          map->halfaxis_lefttrigger = half_axis;
+        } else if (strcmp("righttrigger", key) == 0) {
           map->abs_righttrigger = int_value;
+          map->halfaxis_righttrigger = half_axis;
+        }
       } else if (sscanf(value, "h%d.%d", &int_value, &direction_value) == 2) {
         if (strcmp("dpright", key) == 0) {
           map->hat_dpright = int_value;
@@ -124,8 +133,8 @@ struct mapping* mapping_parse(char* mapping) {
     if (key != NULL)
       free(key);
 
-    if (value != NULL)
-      free(value);
+    if (orig_value != NULL)
+      free(orig_value);
   }
   map->guid[32] = '\0';
   map->name[256] = '\0';
diff --git a/src/input/mapping.h b/src/input/mapping.h
index b450c14..7604845 100644
--- a/src/input/mapping.h
+++ b/src/input/mapping.h
@@ -28,6 +28,7 @@ struct mapping {
 
   bool reverse_leftx, reverse_lefty;
   bool reverse_rightx, reverse_righty;
+  bool halfaxis_lefttrigger, halfaxis_righttrigger;
 
   short abs_leftx, abs_lefty;
   short abs_rightx, abs_righty;