Win32: Fix XInput axis normalization

Fixes #1045.

README.md

@@ -187,6 +187,7 @@ information on what to include when reporting a bug.
 - [Win32] Bugfix: Monitors with no display devices were not enumerated (#960)
 - [Win32] Bugfix: Monitor events were not emitted (#784)
 - [Win32] Bugfix: The Cygwin DLL was installed to the wrong directory (#1035)
+- [Win32] Bugfix: Normalization of axis data via XInput was incorrect (#1045)
 - [X11] Moved to XI2 `XI_RawMotion` for disable cursor mode motion input (#125)
 - [X11] Replaced `_GLFW_HAS_XF86VM` compile-time option with dynamic loading
 - [X11] Bugfix: `glfwGetVideoMode` would segfault on Cygwin/X

src/win32_joystick.c

@@ -701,10 +701,10 @@ int _glfwPlatformPollJoystick(_GLFWjoystick* js, int mode)
         if (mode == _GLFW_POLL_PRESENCE)
             return GLFW_TRUE;
 
-        _glfwInputJoystickAxis(js, 0, (xis.Gamepad.sThumbLX + 0.5f) / 32767.f);
-        _glfwInputJoystickAxis(js, 1, (xis.Gamepad.sThumbLY + 0.5f) / 32767.f);
-        _glfwInputJoystickAxis(js, 2, (xis.Gamepad.sThumbRX + 0.5f) / 32767.f);
-        _glfwInputJoystickAxis(js, 3, (xis.Gamepad.sThumbRY + 0.5f) / 32767.f);
+        _glfwInputJoystickAxis(js, 0, (xis.Gamepad.sThumbLX + 0.5f) / 32767.5f);
+        _glfwInputJoystickAxis(js, 1, (xis.Gamepad.sThumbLY + 0.5f) / 32767.5f);
+        _glfwInputJoystickAxis(js, 2, (xis.Gamepad.sThumbRX + 0.5f) / 32767.5f);
+        _glfwInputJoystickAxis(js, 3, (xis.Gamepad.sThumbRY + 0.5f) / 32767.5f);
         _glfwInputJoystickAxis(js, 4, xis.Gamepad.bLeftTrigger / 127.5f - 1.f);
         _glfwInputJoystickAxis(js, 5, xis.Gamepad.bRightTrigger / 127.5f - 1.f);