InputVerifier: make action_button a field of the action enum

Only MotionEvents with a button press or release action should have an
action button. Let's express this in the data structure by making
action_button a field of the relevant MotionActions, instead of a
separate field of MotionEvent that could potentially be set on
non-button actions.

This involves moving the translation from input_bindgen constants to
MotionAction into lib.rs, which I think makes more sense (as it keeps
the language interfacing code contained there), but also means we have
to move one piece of validation there too.

Bug: 245989146
Test: $ atest --host libinput_rust_test
Test: enable the verifier, check everything works as usual
Flag: EXEMPT refactor
Change-Id: Ida17429b0e12247b63a3ae44bab63e421d9fff0f

Author: HarryCutts

libs/input/rust/input.rs

@@ -101,7 +101,7 @@ bitflags! {
 
 /// A rust enum representation of a MotionEvent action.
 #[repr(u32)]
-#[derive(Eq, PartialEq)]
+#[derive(Clone, Copy, Eq, PartialEq)]
 pub enum MotionAction {
     /// ACTION_DOWN
     Down = input_bindgen::AMOTION_EVENT_ACTION_DOWN,
@@ -132,9 +132,15 @@ pub enum MotionAction {
     /// ACTION_SCROLL
     Scroll = input_bindgen::AMOTION_EVENT_ACTION_SCROLL,
     /// ACTION_BUTTON_PRESS
-    ButtonPress = input_bindgen::AMOTION_EVENT_ACTION_BUTTON_PRESS,
+    ButtonPress {
+        /// The button being pressed.
+        action_button: MotionButton,
+    } = input_bindgen::AMOTION_EVENT_ACTION_BUTTON_PRESS,
     /// ACTION_BUTTON_RELEASE
-    ButtonRelease = input_bindgen::AMOTION_EVENT_ACTION_BUTTON_RELEASE,
+    ButtonRelease {
+        /// The button being released.
+        action_button: MotionButton,
+    } = input_bindgen::AMOTION_EVENT_ACTION_BUTTON_RELEASE,
 }
 
 impl fmt::Display for MotionAction {
@@ -153,14 +159,20 @@ impl fmt::Display for MotionAction {
             MotionAction::Scroll => write!(f, "SCROLL"),
             MotionAction::HoverEnter => write!(f, "HOVER_ENTER"),
             MotionAction::HoverExit => write!(f, "HOVER_EXIT"),
-            MotionAction::ButtonPress => write!(f, "BUTTON_PRESS"),
-            MotionAction::ButtonRelease => write!(f, "BUTTON_RELEASE"),
+            MotionAction::ButtonPress { action_button } => {
+                write!(f, "BUTTON_PRESS({action_button:?})")
+            }
+            MotionAction::ButtonRelease { action_button } => {
+                write!(f, "BUTTON_RELEASE({action_button:?})")
+            }
         }
     }
 }
 
-impl From<u32> for MotionAction {
-    fn from(action: u32) -> Self {
+impl MotionAction {
+    /// Creates a [`MotionAction`] from an `AMOTION_EVENT_ACTION_…` constant and an action button
+    /// (which should be empty for all actions except `BUTTON_PRESS` and `…_RELEASE`).
+    pub fn from_code(action: u32, action_button: MotionButton) -> Self {
         let (action_masked, action_index) = MotionAction::breakdown_action(action);
         match action_masked {
             input_bindgen::AMOTION_EVENT_ACTION_DOWN => MotionAction::Down,
@@ -178,14 +190,16 @@ impl From<u32> for MotionAction {
             input_bindgen::AMOTION_EVENT_ACTION_HOVER_MOVE => MotionAction::HoverMove,
             input_bindgen::AMOTION_EVENT_ACTION_HOVER_EXIT => MotionAction::HoverExit,
             input_bindgen::AMOTION_EVENT_ACTION_SCROLL => MotionAction::Scroll,
-            input_bindgen::AMOTION_EVENT_ACTION_BUTTON_PRESS => MotionAction::ButtonPress,
-            input_bindgen::AMOTION_EVENT_ACTION_BUTTON_RELEASE => MotionAction::ButtonRelease,
+            input_bindgen::AMOTION_EVENT_ACTION_BUTTON_PRESS => {
+                MotionAction::ButtonPress { action_button }
+            }
+            input_bindgen::AMOTION_EVENT_ACTION_BUTTON_RELEASE => {
+                MotionAction::ButtonRelease { action_button }
+            }
             _ => panic!("Unknown action: {}", action),
         }
     }
-}
 
-impl MotionAction {
     fn breakdown_action(action: u32) -> (u32, usize) {
         let action_masked = action & input_bindgen::AMOTION_EVENT_ACTION_MASK;
         let index = (action & input_bindgen::AMOTION_EVENT_ACTION_POINTER_INDEX_MASK)