FIX: Allow InputSystem class to set runtime runInBackground field (#1662)

* Allow InputSystem class to set runtime runInBackground field

* Exclude new public property from public documentation

* Update changelog

Author: jfreire-unity

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -12,6 +12,7 @@ however, it has to be formatted properly to pass verification tests.
 
 ### Added
 - Added `InputSystem.customBindingPathValidators` interface to allow showing warnings in the `InputAsset` Editor for specific InputBindings and draw custom UI in the properties panel.
+- Added `InputSystem.runInBackground` to be used internally by specific platforms packages. Allows telling the input system that a specific platform runs in background. It allows fixing of [case UUM-6744](https://issuetracker.unity3d.com/product/unity/issues/guid/UUM-6744).
 
 ## [1.5.1] - 2023-03-15
 

Packages/com.unity.inputsystem/Documentation~/filter.yml

@@ -37,3 +37,6 @@ apiRules:
   - exclude:
       uidRegex: ^UnityEngine\.InputSystem\.Samples\..*$
       type: Namespace
+  - exclude:
+      uidRegex: ^UnityEngine\.InputSystem\.InputSystem\.runInBackground$
+      type: Member

Packages/com.unity.inputsystem/InputSystem/IInputRuntime.cs

@@ -170,7 +170,7 @@ internal unsafe interface IInputRuntime
         /// </summary>
         double currentTimeOffsetToRealtimeSinceStartup { get; }
 
-        bool runInBackground { get; }
+        bool runInBackground { get; set; }
 
         Vector2 screenSize { get; }
         ScreenOrientation screenOrientation { get; }

Packages/com.unity.inputsystem/InputSystem/InputSystem.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
 using UnityEngine.InputSystem.Haptics;
 using Unity.Collections.LowLevel.Unsafe;
 using UnityEngine.InputSystem.Controls;
@@ -74,10 +75,12 @@ namespace UnityEngine.InputSystem
     /// be called on the main thread. However, select APIs like <see cref="QueueEvent"/> can be
     /// called from threads. Where this is the case, it is stated in the documentation.
     /// </remarks>
+
     [SuppressMessage("Microsoft.Naming", "CA1724:TypeNamesShouldNotMatchNamespaces", Justification = "Options for namespaces are limited due to the legacy input class. Agreed on this as the least bad solution.")]
 #if UNITY_EDITOR
     [InitializeOnLoad]
 #endif
+
     public static partial class InputSystem
     {
         #region Layouts
@@ -3279,6 +3282,20 @@ public static int ListEnabledActions(List<InputAction> actions)
         /// <value>Current version of the input system.</value>
         public static Version version => new Version(kAssemblyVersion);
 
+        /// <summary>
+        /// Property for internal use that allows setting the player to run in the background.
+        /// </summary>
+        /// <remarks>
+        /// Some platforms don't care about <see cref="Application.runInBackground"/> and for those we need to
+        /// enable it manually through this propriety.
+        /// </remarks>
+        /// <param name="value">The boolean value to set to <see cref="NativeInputRuntime.runInBackground"/></param>
+        public static bool runInBackground
+        {
+            get => s_Manager.m_Runtime.runInBackground;
+            set => s_Manager.m_Runtime.runInBackground = value;
+        }
+
         ////REVIEW: restrict metrics to editor and development builds?
         /// <summary>
         /// Get various up-to-date metrics about the input system.

Packages/com.unity.inputsystem/InputSystem/NativeInputRuntime.cs

@@ -227,11 +227,17 @@ public float pollingFrequency
         public double currentTimeOffsetToRealtimeSinceStartup => NativeInputSystem.currentTimeOffsetToRealtimeSinceStartup;
         public float unscaledGameTime => Time.unscaledTime;
 
-        public bool runInBackground => Application.runInBackground ||
-        // certain platforms ignore the runInBackground flag and always run. Make sure we're
-        // not running on one of those.
-        // TODO: Add more platforms here as they're discovered.
-        Application.platform == RuntimePlatform.PS5;
+        public bool runInBackground
+        {
+            get =>
+                Application.runInBackground ||
+                // certain platforms ignore the runInBackground flag and always run. Make sure we're
+                // not running on one of those and set the values when running on specific platforms.
+                m_RunInBackground;
+            set => m_RunInBackground = value;
+        }
+
+        bool m_RunInBackground;
 
         private Action m_ShutdownMethod;
         private InputUpdateDelegate m_OnUpdate;