Gamepad: Align closer to spec and implement missing slots (#31385)

* Implement missing gamepad slots, align to spec more

- Fixes TODO's from initial gamepad implementation
- Adds some missing spec steps

* Only handle gamepad events when pref is enabled

* Return empty list in getGamepads if document not active

* ./mach fmt

* Update getGamepads to return an array instead of GamepadList

* Add spec link for [[exposed]] slot

* Remove failing test expectations for not-fully-active

* A few fixes

- Change should_notify to has_gesture
- Add spec links and TODO to navigator
- Remove unneeded clone from GamepadList::list
- Move gamepadconnected event firing into has_gesture block

* Use queue_with_canceller for tasks and add expects

* Explicitly check for gamepad user gesture

* Move user gesture check into separate function

* Change contains_user_gesture to be a gamepad function

* mach fmt

* Change axis/button threshold constants to be private to module

components/script/dom/navigator.rs

@@ -2,6 +2,7 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
+use std::cell::Cell;
 use std::convert::TryInto;
 
 use dom_struct::dom_struct;
@@ -9,11 +10,13 @@ use js::jsval::JSVal;
 use lazy_static::lazy_static;
 
 use crate::dom::bindings::codegen::Bindings::NavigatorBinding::NavigatorMethods;
+use crate::dom::bindings::codegen::Bindings::WindowBinding::Window_Binding::WindowMethods;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{DomRoot, MutNullableDom};
 use crate::dom::bindings::str::DOMString;
 use crate::dom::bindings::utils::to_frozen_array;
 use crate::dom::bluetooth::Bluetooth;
+use crate::dom::gamepad::Gamepad;
 use crate::dom::gamepadlist::GamepadList;
 use crate::dom::gpu::GPU;
 use crate::dom::mediadevices::MediaDevices;
@@ -43,10 +46,13 @@ pub struct Navigator {
     service_worker: MutNullableDom<ServiceWorkerContainer>,
     xr: MutNullableDom<XRSystem>,
     mediadevices: MutNullableDom<MediaDevices>,
+    /// <https://www.w3.org/TR/gamepad/#dfn-gamepads>
     gamepads: MutNullableDom<GamepadList>,
     permissions: MutNullableDom<Permissions>,
     mediasession: MutNullableDom<MediaSession>,
     gpu: MutNullableDom<GPU>,
+    /// <https://www.w3.org/TR/gamepad/#dfn-hasgamepadgesture>
+    has_gamepad_gesture: Cell<bool>,
 }
 
 impl Navigator {
@@ -63,6 +69,7 @@ impl Navigator {
             permissions: Default::default(),
             mediasession: Default::default(),
             gpu: Default::default(),
+            has_gamepad_gesture: Cell::new(false),
         }
     }
 
@@ -73,6 +80,21 @@ impl Navigator {
     pub fn xr(&self) -> Option<DomRoot<XRSystem>> {
         self.xr.get()
     }
+
+    pub fn gamepads(&self) -> DomRoot<GamepadList> {
+        let gamepads = self
+            .gamepads
+            .or_init(|| GamepadList::new(&self.global(), &[]));
+        gamepads
+    }
+
+    pub fn has_gamepad_gesture(&self) -> bool {
+        self.has_gamepad_gesture.get()
+    }
+
+    pub fn set_has_gamepad_gesture(&self, has_gamepad_gesture: bool) {
+        self.has_gamepad_gesture.set(has_gamepad_gesture);
+    }
 }
 
 impl NavigatorMethods for Navigator {
@@ -169,14 +191,20 @@ impl NavigatorMethods for Navigator {
         true
     }
 
-    // https://www.w3.org/TR/gamepad/#navigator-interface-extension
-    fn GetGamepads(&self) -> DomRoot<GamepadList> {
-        let root = self
-            .gamepads
-            .or_init(|| GamepadList::new(&self.global(), &[]));
+    /// <https://www.w3.org/TR/gamepad/#dom-navigator-getgamepads>
+    fn GetGamepads(&self) -> Vec<Option<DomRoot<Gamepad>>> {
+        let global = self.global();
+        let window = global.as_window();
+        let doc = window.Document();
 
-        // TODO: Add gamepads
-        root
+        // TODO: Handle permissions policy once implemented
+        if !doc.is_fully_active() || !self.has_gamepad_gesture.get() {
+            return Vec::new();
+        }
+
+        let root = self.gamepads.or_init(|| GamepadList::new(&global, &[]));
+
+        root.list()
     }
     // https://w3c.github.io/permissions/#navigator-and-workernavigator-extension
     fn Permissions(&self) -> DomRoot<Permissions> {