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[patch] Removes dead zone and outputs axis values in correct range.

SDL2_remove_dead_zone_correctly_patch.txt (text/plain), 4.17 KB, created by pj5085 on 2020-08-27 04:00:57 UTC

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Creator: pj5085

Created: 2020-08-27 04:00:57 UTC

Size: 4.17 KB

patch

obsolete

>--- SDL2-2.0.12/src/joystick/linux/SDL_sysjoystick_c.h	2020-03-10 21:36:18.000000000 -0400
>+++ SDL2-2.0.12-modified/src/joystick/linux/SDL_sysjoystick_c.h	2020-08-26 22:48:16.828237117 -0400
>@@ -56,7 +56,8 @@
>     struct axis_correct
>     {
>         int used;
>-        int coef[3];
>+        int minimum;
>+        int maximum;
>     } abs_correct[ABS_MAX];
> 
>     int fresh;
>--- SDL2-2.0.12/src/joystick/linux/SDL_sysjoystick.c	2020-03-10 21:36:18.000000000 -0400
>+++ SDL2-2.0.12-modified/src/joystick/linux/SDL_sysjoystick.c	2020-08-26 23:50:21.005187319 -0400
>@@ -28,6 +28,7 @@
> 
> /* This is the Linux implementation of the SDL joystick API */
> 
>+#include <math.h>
> #include <sys/stat.h>
> #include <errno.h>              /* errno, strerror */
> #include <fcntl.h>
>@@ -645,7 +646,7 @@
> static void
> ConfigJoystick(SDL_Joystick * joystick, int fd)
> {
>-    int i, t;
>+    int i;
>     unsigned long keybit[NBITS(KEY_MAX)] = { 0 };
>     unsigned long absbit[NBITS(ABS_MAX)] = { 0 };
>     unsigned long relbit[NBITS(REL_MAX)] = { 0 };
>@@ -698,17 +699,8 @@
>                     joystick->hwdata->abs_correct[i].used = 0;
>                 } else {
>                     joystick->hwdata->abs_correct[i].used = 1;
>-                    joystick->hwdata->abs_correct[i].coef[0] =
>-                        (absinfo.maximum + absinfo.minimum) - 2 * absinfo.flat;
>-                    joystick->hwdata->abs_correct[i].coef[1] =
>-                        (absinfo.maximum + absinfo.minimum) + 2 * absinfo.flat;
>-                    t = ((absinfo.maximum - absinfo.minimum) - 4 * absinfo.flat);
>-                    if (t != 0) {
>-                        joystick->hwdata->abs_correct[i].coef[2] =
>-                            (1 << 28) / t;
>-                    } else {
>-                        joystick->hwdata->abs_correct[i].coef[2] = 0;
>-                    }
>+                    joystick->hwdata->abs_correct[i].minimum = absinfo.minimum;
>+                    joystick->hwdata->abs_correct[i].maximum = absinfo.maximum;
>                 }
>                 ++joystick->naxes;
>             }
>@@ -903,24 +895,45 @@
> 
>     correct = &joystick->hwdata->abs_correct[which];
>     if (correct->used) {
>-        value *= 2;
>-        if (value > correct->coef[0]) {
>-            if (value < correct->coef[1]) {
>-                return 0;
>-            }
>-            value -= correct->coef[1];
>-        } else {
>-            value -= correct->coef[0];
>-        }
>-        value *= correct->coef[2];
>-        value >>= 13;
>+
>+      int original_value = value;
>+
>+      float ideal_minimum = -32767;
>+      float ideal_maximum = +32767;
>+      float ideal_range = ideal_maximum - ideal_minimum;
>+      float actual_range = (correct->maximum - correct->minimum);
>+      float coefficient = ideal_range / actual_range;
>+      float new_float = (original_value - correct->minimum) * coefficient + ideal_minimum;
>+      int new_integer = round(new_float);
>+
>+      // At least one gamepad has a minimum of 0 and a maximum is 255,
>+      // which makes it's center point a non-integer, 127.5.  Thus it
>+      // must report either 127 or 128, neither of which is center.
>+
>+      // At least one analog controller with the same range returns 128
>+      // easily when at center, but seems completely incapable of
>+      // returning 127 no matter how carefully the stick is moved.
>+
>+      // So here we detect if the axis' range does not have a center
>+      // point, and if so, and if the reported position is on either
>+      // side of center, we report that it is actually at the center.
>+
>+      if ((correct->maximum - correct->minimum) & 1) {
>+        int lower_center = (correct->maximum - correct->minimum - 1) / 2;
>+        int higher_center = (correct->maximum - correct->minimum + 1) / 2;
>+        if (original_value == lower_center) new_integer = 0;
>+        if (original_value == higher_center) new_integer = 0;
>+      };
>+
>+      //if (which == 2) printf("original=%d, new=%d\n", original_value, new_integer);
>+
>+      value = new_integer;
>+
>     }
> 
>     /* Clamp and return */
>-    if (value < -32768)
>-        return -32768;
>-    if (value > 32767)
>-        return 32767;
>+    if (value < -32767) return -32767;
>+    if (value > +32767) return +32767;
> 
>     return value;
> }

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Attachments on bug 5241: 4423 | 4446 | 4450 | 4451 | 4452 | 4619 | 4620

We are currently migrating Bugzilla to GitHub issues.Any changes made to the bug tracker now will be lost, so please do not post new bugs or make changes to them.When we're done, all bug URLs will redirect to their equivalent location on the new bug tracker.

We are currently migrating Bugzilla to GitHub issues.
Any changes made to the bug tracker now will be lost, so please do not post new bugs or make changes to them.
When we're done, all bug URLs will redirect to their equivalent location on the new bug tracker.