Implement non-XR Gamepad discovery and input (#31200)

* Create embedder event to send to constellation

* Handle gamepad message in constellation, send to script thread

* Handle GamepadEvent in script thread and dispatch event to document

* Add missing Clones, fix event

* Add gamepad task source

* Adjust GamepadIndex type, remove unused imports

* Add internal getter for gamepads list

* Update gamepad new methods

* Handle gamepad connect and disconnect events

* Proto will be none, no need for HandleObject

* Initialize buttons and axes to standard mapping

* Adjust update type index types

* Update GamepadButton update function

* Adjust Gamepad mapping comments to match spec, add update logic

* Amend comment

* Update button and axis inputs on Updated event

* Add GilRs as gamepad backend in servoshell

* Add spec links, queue gamepad updates on task source

* ./mach fmt

* Fix comment length

* Split out button init, update spec comments

* Move gamepad event handling from document to global

* Map and normalize axes/button values

* Use std::time for gamepad timestamp

* Adjust gamepad handling in event loop

* Move button press/touch check into map+normalize function

- Small change but is more in line with spec

* ./mach fmt

* Update comment spec links and warning messages

* Doc comments -> regular comments

* Add window event handlers for gamepad connect/disconnect

* Adjust gamepad disconnect behavior

* Add missing TODO's, adjust gamepad/gamepadbutton list methods and formatting

* Update button handling from gilrs, add comments

* Enable gamepad pref during WPT tests and update expectations

* Update WPT expectations in meta-legacy-layout

1 files changed, 35 insertions, 4 deletions

diff --git a/components/script/dom/gamepadbuttonlist.rs b/components/script/dom/gamepadbuttonlist.rs
index e28e33e05a8..961f265e37f 100644
--- a/components/script/dom/gamepadbuttonlist.rs
+++ b/components/script/dom/gamepadbuttonlist.rs
@@ -5,9 +5,10 @@
 use dom_struct::dom_struct;
 
 use crate::dom::bindings::codegen::Bindings::GamepadButtonListBinding::GamepadButtonListMethods;
-use crate::dom::bindings::reflector::Reflector;
-use crate::dom::bindings::root::{Dom, DomRoot};
+use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
+use crate::dom::bindings::root::{Dom, DomRoot, DomSlice};
 use crate::dom::gamepadbutton::GamepadButton;
+use crate::dom::globalscope::GlobalScope;
 
 // https://w3c.github.io/gamepad/#gamepadbutton-interface
 #[dom_struct]
@@ -16,8 +17,6 @@ pub struct GamepadButtonList {
     list: Vec<Dom<GamepadButton>>,
 }
 
-// TODO: support gamepad discovery
-#[allow(dead_code)]
 impl GamepadButtonList {
     #[allow(crown::unrooted_must_root)]
     fn new_inherited(list: &[&GamepadButton]) -> GamepadButtonList {
@@ -26,6 +25,10 @@ impl GamepadButtonList {
             list: list.iter().map(|button| Dom::from_ref(*button)).collect(),
         }
     }
+
+    pub fn new(global: &GlobalScope, list: &[&GamepadButton]) -> DomRoot<GamepadButtonList> {
+        reflect_dom_object(Box::new(GamepadButtonList::new_inherited(list)), global)
+    }
 }
 
 impl GamepadButtonListMethods for GamepadButtonList {
@@ -46,3 +49,31 @@ impl GamepadButtonListMethods for GamepadButtonList {
         self.Item(index)
     }
 }
+
+impl GamepadButtonList {
+    /// Initialize the number of buttons in the "standard" gamepad mapping.
+    /// <https://www.w3.org/TR/gamepad/#dfn-initializing-buttons>
+    pub fn init_buttons(global: &GlobalScope) -> DomRoot<GamepadButtonList> {
+        let standard_buttons = &[
+            GamepadButton::new(global, false, false), // Bottom button in right cluster
+            GamepadButton::new(global, false, false), // Right button in right cluster
+            GamepadButton::new(global, false, false), // Left button in right cluster
+            GamepadButton::new(global, false, false), // Top button in right cluster
+            GamepadButton::new(global, false, false), // Top left front button
+            GamepadButton::new(global, false, false), // Top right front button
+            GamepadButton::new(global, false, false), // Bottom left front button
+            GamepadButton::new(global, false, false), // Bottom right front button
+            GamepadButton::new(global, false, false), // Left button in center cluster
+            GamepadButton::new(global, false, false), // Right button in center cluster
+            GamepadButton::new(global, false, false), // Left stick pressed button
+            GamepadButton::new(global, false, false), // Right stick pressed button
+            GamepadButton::new(global, false, false), // Top button in left cluster
+            GamepadButton::new(global, false, false), // Bottom button in left cluster
+            GamepadButton::new(global, false, false), // Left button in left cluster
+            GamepadButton::new(global, false, false), // Right button in left cluster
+            GamepadButton::new(global, false, false), // Center button in center cluster
+        ];
+        rooted_vec!(let buttons <- standard_buttons.iter().map(|button| DomRoot::from_ref(&**button)));
+        Self::new(global, buttons.r())
+    }
+}