Use enums for ActionTypes in InputField, use ReadOnlySpan<char> for Font measurements, only measure placeholderSize if the input is empty.

Voile/Source/Resources/Font.cs

@@ -83,16 +83,26 @@ public class Font : Resource, IUpdatableResource, IDisposable
     /// <returns>A <see cref="Rect"/> with the sizes of a given text using this font.</returns>
     public Rect Measure(string text)
     {
-        if (string.IsNullOrEmpty(text))
+        return Measure(text.AsSpan());
+    }
+
+    /// <summary>
+    /// Measures a given <see cref="ReadOnlySpan"/> of characters.
+    /// </summary>
+    /// <param name="chars"></param>
+    /// <returns>A <see cref="Rect"/> with the sizes of a given text using this font.</returns>
+    public Rect Measure(ReadOnlySpan<char> chars)
+    {
+        if (chars.Length == 0)
             return Rect.Zero;
 
         float totalWidth = 0;
         float maxAscent = 0;
         float maxDescent = 0;
 
-        for (int i = 0; i < text.Length; i++)
+        for (int i = 0; i < chars.Length; i++)
         {
-            char c = text[i];
+            char c = chars[i];
             Glyph glyph = GetGlyph(c);
 
             totalWidth += glyph.Advance * SpacingScale + LetterSpacing;
@@ -107,7 +117,7 @@ public class Font : Resource, IUpdatableResource, IDisposable
 
             if (i > 0)
             {
-                char prevChar = text[i - 1];
+                char prevChar = chars[i - 1];
                 totalWidth += GetKerning(prevChar, c);
             }
         }

Voile/Source/UI/Widgets/InputField.cs

@@ -7,6 +7,8 @@ namespace Voile.UI.Widgets;
 
 public class InputField : Widget, ITickableElement
 {
+    enum ActionType { None, Backspace, Left, Right }
+
     public override Rect MinimumSize => _placeholderSize + _padding;
     public override string? StyleElementName => nameof(InputField);
 
@@ -58,7 +60,7 @@ public class InputField : Widget, ITickableElement
 
         if (!_isFocused)
         {
-            _lastActiveAction = string.Empty;
+            _lastActiveAction = ActionType.None;
             _repeatTimer = 0.0f;
             return;
         }
@@ -100,15 +102,15 @@ public class InputField : Widget, ITickableElement
 
     private void HandleRepeatingActions(float dt, InputSystem input)
     {
-        string currentAction = string.Empty;
+        ActionType currentAction = ActionType.None;
 
-        if (input.IsKeyboardKeyDown(KeyboardKey.Backspace)) currentAction = "backspace";
+        if (input.IsKeyboardKeyDown(KeyboardKey.Backspace)) currentAction = ActionType.Backspace;
-        else if (input.IsKeyboardKeyDown(KeyboardKey.Left)) currentAction = "left";
+        else if (input.IsKeyboardKeyDown(KeyboardKey.Left)) currentAction = ActionType.Left;
-        else if (input.IsKeyboardKeyDown(KeyboardKey.Right)) currentAction = "right";
+        else if (input.IsKeyboardKeyDown(KeyboardKey.Right)) currentAction = ActionType.Right;
 
-        if (string.IsNullOrEmpty(currentAction))
+        if (currentAction == ActionType.None)
         {
-            _lastActiveAction = string.Empty;
+            _lastActiveAction = ActionType.None;
             _repeatTimer = 0.0f;
             return;
         }
@@ -138,11 +140,11 @@ public class InputField : Widget, ITickableElement
         }
     }
 
-    private void ExecuteAction(string actionName)
+    private void ExecuteAction(ActionType action)
     {
-        switch (actionName)
+        switch (action)
         {
-            case "backspace":
+            case ActionType.Backspace:
                 if (_cursor > 0 && _input.Length > 0)
                 {
                     _input = _input.Remove(_cursor - 1, 1);
@@ -151,7 +153,7 @@ public class InputField : Widget, ITickableElement
                 }
                 break;
 
-            case "left":
+            case ActionType.Left:
                 if (_cursor > 0)
                 {
                     _cursor--;
@@ -159,7 +161,7 @@ public class InputField : Widget, ITickableElement
                 }
                 break;
 
-            case "right":
+            case ActionType.Right:
                 if (_cursor < _input.Length)
                 {
                     _cursor++;
@@ -211,7 +213,7 @@ public class InputField : Widget, ITickableElement
         // Caret
         if (_isFocused && _blink)
         {
-            var caretX = MeasureTextWidth(_input.Substring(0, _cursor));
+            var caretX = MeasureTextWidth(_input.AsSpan(0, _cursor));
 
             renderer.SetTransform(
                 new Vector2(GlobalPosition.X + caretX + _padding.Left, GlobalPosition.Y + _padding.Top),
@@ -247,7 +249,9 @@ public class InputField : Widget, ITickableElement
             var font = _suitableFont.Value;
 
             _textSize = font.Measure(_input);
-            _placeholderSize = font.Measure(PlaceholderText);
+
+            if (string.IsNullOrEmpty(_input))
+                _placeholderSize = font.Measure(PlaceholderText);
         }
 
         var size = Rect.MaxWidth(_placeholderSize, _textSize);
@@ -255,18 +259,18 @@ public class InputField : Widget, ITickableElement
         Size = _padding + size;
     }
 
-    private float MeasureTextWidth(string text)
+    private float MeasureTextWidth(ReadOnlySpan<char> chars)
     {
         if (!_suitableFont.HasValue)
         {
             return 0.0f;
         }
 
-        return _suitableFont.Value.Measure(text).Width;
+        return _suitableFont.Value.Measure(chars).Width;
     }
 
     private float _repeatTimer = 0.0f;
-    private string _lastActiveAction = string.Empty;
+    private ActionType _lastActiveAction = ActionType.None;
     private const float INITIAL_DELAY = 0.5f;
     private const float REPEAT_RATE = 0.05f;