Win32: Fix invalid hat bit mask being accepted

It is reportedly possible to get opposing directions of an XInput DPad
bit mask set simultaneously with some controllers.

This commit ensures that those values are not passed on to other parts
of GLFW.

This commit is based on the PR #2291 by @ PeterJohnson but with the
following changes:
 - moved XInput-specific special case to XInput implementation
 - attempt to preserve data by only masking out the invalid axis
 - admin (credit, changelog, commit message)

Closes #2291

(cherry picked from commit 52405a9d59)

CONTRIBUTORS.md

@@ -100,6 +100,7 @@ video tutorials.
  - JannikGM
  - Erik S. V. Jansson
  - jjYBdx4IL
+ - Peter Johnson
  - Toni Jovanoski
  - Arseny Kapoulkine
  - Cem Karan

README.md

@@ -127,6 +127,7 @@ information on what to include when reporting a bug.
  - Bugfix: Failure to make a newly created context current could cause segfault (#2327)
  - [Win32] Fix pkg-config for dynamic library on Windows (#2386, #2420)
  - [Win32] Bugfix: `glfwWaitEventsTimeout` did not return for some sent messages (#2408)
+ - [Win32] Bugfix: XInput could reportedly provide invalid DPad bit masks (#2291)
  - [Wayland] Added improved fallback window decorations via libdecor (#1639,#1693)
  - [Wayland] Bugfix: Connecting a mouse after `glfwInit` would segfault (#1450)
  - [Wayland] Disabled alpha channel for opaque windows on systems lacking

src/win32_joystick.c

@@ -736,6 +736,13 @@ int _glfwPlatformPollJoystick(_GLFWjoystick* js, int mode)
         if (xis.Gamepad.wButtons & XINPUT_GAMEPAD_DPAD_LEFT)
             dpad |= GLFW_HAT_LEFT;
 
+        // Treat invalid combinations as neither being pressed
+        // while preserving what data can be preserved
+        if ((dpad & GLFW_HAT_RIGHT) && (dpad & GLFW_HAT_LEFT))
+            dpad &= ~(GLFW_HAT_RIGHT | GLFW_HAT_LEFT);
+        if ((dpad & GLFW_HAT_UP) && (dpad & GLFW_HAT_DOWN))
+            dpad &= ~(GLFW_HAT_UP | GLFW_HAT_DOWN);
+
         _glfwInputJoystickHat(js, 0, dpad);
     }