Backspace and direction key echoing in InputField.

Voile/Source/UI/IElement.cs

@@ -1,4 +1,5 @@
 using System.Numerics;
+using Voile.Input;
 using Voile.Rendering;
 
 namespace Voile.UI;
@@ -18,6 +19,19 @@ public interface IElement
     public Rect Size { get; set; }
 }
 
+/// <summary>
+/// Represents a UI element that requires a frame-independent update tick loop.
+/// </summary>
+public interface ITickableElement
+{
+    /// <summary>
+    /// Excutes unconditionally on every frame engine loop step.
+    /// </summary>
+    /// <param name="dt">Elapsed delta frame time in seconds.</param>
+    /// <param name="input">InputSystem that this tickable element should use to poll input events.</param> 
+    void Tick(float dt, InputSystem input);
+}
+
 /// <summary>
 /// Represents a UI element that can contain child elements.
 /// </summary>

Voile/Source/UI/UIInputContext.cs

@@ -55,6 +55,8 @@ public class UIInputContext
     public bool IsUp => ActionName == "up";
     public bool IsDown => ActionName == "down";
 
+    public float DeltaTime { get; init; }
+
     /// <summary>
     /// Determines if control key is pressed.
     /// </summary>

Voile/Source/UI/UISystem.cs

@@ -39,14 +39,13 @@ public class UISystem : IUpdatableSystem, IRenderableSystem, IReloadableSystem
 
     public void Update(double deltaTime)
     {
-        // HandleInput();
+        float dt = (float)deltaTime;
+        PropagateTick(_elements, dt);
+        HandleInput((float)deltaTime);
     }
 
     public void Render(RenderSystem renderer)
     {
-        // Update elements each time UI system is rendered.
-        HandleInput();
-
         foreach (var element in _elements)
         {
             if (element is not IUpdatableElement updatable) continue;
@@ -104,54 +103,90 @@ public class UISystem : IUpdatableSystem, IRenderableSystem, IReloadableSystem
         }
     }
 
-    private void HandleInput()
+    private void HandleInput(float deltaTime)
     {
         int charPressed = _input.GetCharPressed();
         Vector2 mousePos = _input.GetMousePosition();
-
         Vector2 currentMousePosition = _input.GetMousePosition();
+        bool inputHandled = false;
 
+        // 1. Process Actions (Pressed or Held)
         foreach (var (actionName, mappings) in InputSystem.InputMappings)
         {
             foreach (var action in mappings)
             {
-                if (action.IsPressed(_input))
+                bool isPressed = action.IsPressed(_input);
+                bool isDown = action.IsDown(_input);
+
+                if (isPressed)
                 {
-                    // TODO: specify which mouse button is used in the context.
                     var context = new UIInputContext(action, mousePos, actionName, charPressed)
                     {
                         MouseDown = _input.IsMouseButtonDown(MouseButton.Left),
                         MouseReleased = _input.IsMouseButtonReleased(MouseButton.Left),
                         MousePressed = _input.IsMouseButtonPressed(MouseButton.Left),
+                        DeltaTime = deltaTime
                     };
 
                     if (PropagateInput(_elements, context))
+                    {
+                        inputHandled = true;
+                        break;
+                    }
+                }
+            }
+            if (inputHandled) break;
+        }
+
+        if (inputHandled)
+        {
+            _lastMousePosition = currentMousePosition;
             return;
         }
-            }
-        }
 
         if (charPressed != 0)
         {
-            var context = new UIInputContext(new KeyInputAction(KeyboardKey.Null), mousePos, "", charPressed);
+            var context = new UIInputContext(new KeyInputAction(KeyboardKey.Null), mousePos, "", charPressed)
-            PropagateInput(_elements, context);
+            {
+                DeltaTime = deltaTime
+            };
+            if (PropagateInput(_elements, context))
+            {
+                _lastMousePosition = currentMousePosition;
                 return;
             }
+        }
 
-
+        var frameContext = new UIInputContext(new MouseInputAction(MouseButton.Left), mousePos, "", charPressed)
-        if (currentMousePosition != _lastMousePosition)
-        {
-            // TODO: specify which mouse button is used in the context.
-            var context = new UIInputContext(new MouseInputAction(MouseButton.Left), mousePos, "", charPressed)
         {
             MouseDown = _input.IsMouseButtonDown(MouseButton.Left),
             MouseReleased = _input.IsMouseButtonReleased(MouseButton.Left),
             MousePressed = _input.IsMouseButtonPressed(MouseButton.Left),
+            DeltaTime = deltaTime
         };
 
-            PropagateInput(_elements, context);
+        PropagateInput(_elements, frameContext);
 
-            return;
+        _lastMousePosition = currentMousePosition;
+    }
+
+    private void PropagateTick(List<UIElement> elements, float dt)
+    {
+        for (int i = 0; i < elements.Count; i++)
+        {
+            var element = elements[i];
+
+            if (!element.Visible) continue;
+
+            if (element is ITickableElement tickable)
+            {
+                tickable.Tick(dt, _input);
+            }
+
+            if (element is IParentableElement parentable)
+            {
+                PropagateTick(parentable.Children.ToList(), dt);
+            }
         }
     }
 

Voile/Source/UI/Widgets/InputField.cs

@@ -1,10 +1,11 @@
 using System.Numerics;
+using Voile.Input;
 using Voile.Rendering;
 using Voile.Resources;
 
 namespace Voile.UI.Widgets;
 
-public class InputField : Widget
+public class InputField : Widget, ITickableElement
 {
     public override Rect MinimumSize => _placeholderSize + _padding;
     public override string? StyleElementName => nameof(InputField);
@@ -43,20 +44,30 @@ public class InputField : Widget
         Update();
     }
 
+    public void Tick(float dt, InputSystem input)
+    {
+        if (!_isFocused)
+            return;
+
+        HandleRepeatingActions(dt, input);
+    }
+
     protected override void OnInput(UIInputContext context)
     {
         HandleFocus(context);
 
         if (!_isFocused)
+        {
+            _lastActiveAction = string.Empty;
+            _repeatTimer = 0.0f;
             return;
+        }
 
         HandleTextInput(context);
-        HandleBackspace(context);
-        HandleCursorMovement(context);
-
         ClampCursor();
     }
 
+
     private void HandleFocus(UIInputContext context)
     {
         if (!context.MousePressed)
@@ -87,35 +98,74 @@ public class InputField : Widget
         context.SetHandled();
     }
 
-    private void HandleBackspace(UIInputContext context)
+    private void HandleRepeatingActions(float dt, InputSystem input)
     {
-        if (!context.IsBackspace)
+        string currentAction = string.Empty;
-            return;
 
-        if (_cursor <= 0 || _input.Length == 0)
+        if (input.IsKeyboardKeyDown(KeyboardKey.Backspace)) currentAction = "backspace";
-            return;
+        else if (input.IsKeyboardKeyDown(KeyboardKey.Left)) currentAction = "left";
+        else if (input.IsKeyboardKeyDown(KeyboardKey.Right)) currentAction = "right";
 
+        if (string.IsNullOrEmpty(currentAction))
+        {
+            _lastActiveAction = string.Empty;
+            _repeatTimer = 0.0f;
+            return;
+        }
+
+        bool shouldExecute = false;
+
+        if (_lastActiveAction != currentAction)
+        {
+            shouldExecute = true;
+            _repeatTimer = 0.0f;
+            _lastActiveAction = currentAction;
+        }
+        else
+        {
+            _repeatTimer += dt;
+
+            if (_repeatTimer >= INITIAL_DELAY)
+            {
+                shouldExecute = true;
+                _repeatTimer = INITIAL_DELAY - REPEAT_RATE;
+            }
+        }
+
+        if (shouldExecute)
+        {
+            ExecuteAction(currentAction);
+        }
+    }
+
+    private void ExecuteAction(string actionName)
+    {
+        switch (actionName)
+        {
+            case "backspace":
+                if (_cursor > 0 && _input.Length > 0)
+                {
                     _input = _input.Remove(_cursor - 1, 1);
                     _cursor--;
                     MarkDirty();
-
-        context.SetHandled();
                 }
+                break;
 
-    private void HandleCursorMovement(UIInputContext context)
+            case "left":
-    {
+                if (_cursor > 0)
-        if (context.IsLeft && _cursor > 0)
                 {
                     _cursor--;
                     MarkDirty();
-            context.SetHandled();
                 }
+                break;
 
-        if (context.IsRight && _cursor < _input.Length)
+            case "right":
+                if (_cursor < _input.Length)
                 {
                     _cursor++;
                     MarkDirty();
-            context.SetHandled();
+                }
+                break;
         }
     }
 
@@ -215,7 +265,12 @@ public class InputField : Widget
         return _suitableFont.Value.Measure(text).Width;
     }
 
-    private string _input = "";
+    private float _repeatTimer = 0.0f;
+    private string _lastActiveAction = string.Empty;
+    private const float INITIAL_DELAY = 0.5f;
+    private const float REPEAT_RATE = 0.05f;
+
+    private string _input = string.Empty;
     private bool _isFocused;
 
     private int _cursor;