From 071a73c6d98a9a187be03fcfa7c9b623fa6977a2 Mon Sep 17 00:00:00 2001
From: Chandler Cox <mr.chandlercox@gmail.com>
Date: Tue, 26 Sep 2023 10:03:34 -0500
Subject: [PATCH] Add AxisChanged event to InputAxis.

---
 Source/Engine/Engine/InputAxis.cs | 32 +++++++++++++++++++++++++++++++
 Source/Engine/Input/Input.cpp     |  9 +++++++++
 Source/Engine/Input/Input.h       |  6 ++++++
 3 files changed, 47 insertions(+)

diff --git a/Source/Engine/Engine/InputAxis.cs b/Source/Engine/Engine/InputAxis.cs
index f8ba7e72b..7b4da3191 100644
--- a/Source/Engine/Engine/InputAxis.cs
+++ b/Source/Engine/Engine/InputAxis.cs
@@ -1,5 +1,7 @@
 // Copyright (c) 2012-2023 Wojciech Figat. All rights reserved.
 
+using System;
+
 namespace FlaxEngine
 {
     /// <summary>
@@ -23,11 +25,17 @@ namespace FlaxEngine
         /// </summary>
         public float ValueRaw => Input.GetAxisRaw(Name);
 
+        /// <summary>
+        /// Occurs when axis is changed. Called before scripts update.
+        /// </summary>
+        public event Action ValueChanged;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="InputAxis"/> class.
         /// </summary>
         public InputAxis()
         {
+            Input.AxisChanged += Handler;
         }
 
         /// <summary>
@@ -36,7 +44,31 @@ namespace FlaxEngine
         /// <param name="name">The axis name.</param>
         public InputAxis(string name)
         {
+            Input.AxisChanged += Handler;
             Name = name;
         }
+        
+        private void Handler(string name)
+        {
+            if (string.Equals(Name, name, StringComparison.OrdinalIgnoreCase))
+                ValueChanged?.Invoke();
+        }
+        
+        /// <summary>
+        /// Finalizes an instance of the <see cref="InputAxis"/> class.
+        /// </summary>
+        ~InputAxis()
+        {
+            Input.AxisChanged -= Handler;
+        }
+        
+        /// <summary>
+        /// Releases this object.
+        /// </summary>
+        public void Dispose()
+        {
+            Input.AxisChanged -= Handler;
+            GC.SuppressFinalize(this);
+        }
     }
 }
diff --git a/Source/Engine/Input/Input.cpp b/Source/Engine/Input/Input.cpp
index af5600823..a54b6d631 100644
--- a/Source/Engine/Input/Input.cpp
+++ b/Source/Engine/Input/Input.cpp
@@ -98,6 +98,7 @@ Delegate<const Float2&, int32> Input::TouchDown;
 Delegate<const Float2&, int32> Input::TouchMove;
 Delegate<const Float2&, int32> Input::TouchUp;
 Delegate<StringView, const InputActionState&> Input::ActionTriggered;
+Delegate<StringView> Input::AxisChanged;
 Array<ActionConfig> Input::ActionMappings;
 Array<AxisConfig> Input::AxisMappings;
 
@@ -1020,6 +1021,14 @@ void InputService::Update()
     // Send events for the active actions (send events only in play mode)
     if (!Time::GetGamePaused())
     {
+        for (auto i = Axes.Begin(); i.IsNotEnd(); ++i)
+        {
+            if (Math::NotNearEqual(i->Value.Value, i->Value.PrevKeyValue))
+            {
+                Input::AxisChanged(i->Key);
+            }
+        }
+        
         for (auto i = Actions.Begin(); i.IsNotEnd(); ++i)
         {
             if (i->Value.State != InputActionState::Waiting)
diff --git a/Source/Engine/Input/Input.h b/Source/Engine/Input/Input.h
index 5ff02eda9..ed66a6cd9 100644
--- a/Source/Engine/Input/Input.h
+++ b/Source/Engine/Input/Input.h
@@ -295,6 +295,12 @@ public:
     /// <seealso cref="InputEvent"/>
     API_EVENT() static Delegate<StringView, const InputActionState&> ActionTriggered;
 
+    /// <summary>
+    /// Event fired when virtual input axis is changed. Called before scripts update. See <see cref="AxisMappings"/> to edit configuration.
+    /// </summary>
+    /// <seealso cref="InputAxis"/>
+    API_EVENT() static Delegate<StringView> AxisChanged;
+
     /// <summary>
     /// Gets the value of the virtual action identified by name. Use <see cref="ActionMappings"/> to get the current config.
     /// </summary>