add bindings for d-pad directions

ffi/glfw-input.c

@@ -101,3 +101,19 @@ int isR1ButtonPressed() {
 int isL1ButtonPressed() {
   return state.buttons[GLFW_GAMEPAD_BUTTON_LEFT_BUMPER];
 }
+
+int isDpadUpPressed() {
+  return state.buttons[GLFW_GAMEPAD_BUTTON_DPAD_UP];
+}
+
+int isDpadDownPressed() {
+  return state.buttons[GLFW_GAMEPAD_BUTTON_DPAD_DOWN];
+}
+
+int isDpadLeftPressed() {
+  return state.buttons[GLFW_GAMEPAD_BUTTON_DPAD_LEFT];
+}
+
+int isDpadRightPressed() {
+  return state.buttons[GLFW_GAMEPAD_BUTTON_DPAD_RIGHT];
+}

ffi/glfw-input.sml

@@ -75,6 +75,15 @@ struct
   val isL1ButtonPressed =
     _import "isL1ButtonPressed" public : unit -> int;
 
+  val isDpadUpButtonPressed =
+    _import "isDpadUpButtonPressed" public : unit -> int;
+  val isDpadDownButtonPressed =
+    _import "isDpadDownButtonPressed" public : unit -> int;
+  val isDpadLeftButtonPressed =
+    _import "isDpadLeftButtonPressed" public : unit -> int;
+  val isDpadRightButtonPressed =
+    _import "isDpadRightButtonPressed" public : unit -> int;
+
   val getR2State =
     _import "getR2State" public : unit -> Real32.real;
   val getL2State =