Element styling, rename IsMousePressed to IsMouseButtonPressed in InputSystem, Button widget.

Voile/Source/UI/UIElement.cs

@@ -1,4 +1,6 @@
+using System.Diagnostics.CodeAnalysis;
 using System.Numerics;
+using System.Text;
 using Voile.Rendering;
 
 namespace Voile.UI;
@@ -13,6 +15,23 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
     public Vector2 LocalPosition { get; set; } = Vector2.Zero;
     public Vector2 GlobalPosition => _parent?.GlobalPosition + LocalPosition ?? LocalPosition;
 
+    public string StyleName => $"{StyleElementName ?? "UIElement"}{GetStyleVariantString()}{ConstructStyleModifiers(StyleModifiers)}";
+
+    /// <summary>
+    /// An element name for style.
+    /// </summary>
+    public virtual string? StyleElementName { get; }
+
+    public string StyleVariant { get; set; } = string.Empty;
+
+    /// <summary>
+    /// List of style modifiers for this <see cref="UIElement"/>.
+    /// </summary>
+    public virtual string[]? StyleModifiers { get; }
+
+    public StyleSheet StyleSheet => Parent?.StyleSheet ?? StyleSheetOverride;
+    public StyleSheet StyleSheetOverride { get; set; } = new(string.Empty);
+
     /// <summary>
     /// Parent <see cref="UIElement"/> of this element.
     /// </summary>
@@ -47,6 +66,11 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
     public abstract Rect MinimumSize { get; }
     public bool Dirty => _dirty;
 
+    public bool TryGetStyle(StyleSheet styleSheet, [NotNullWhen(true)] out Style? style)
+    {
+        return styleSheet.TryGet(StyleName, out style);
+    }
+
     public virtual void MarkDirty()
     {
         if (Parent != null && !Parent.Dirty)
@@ -112,6 +136,30 @@ public abstract class UIElement : IElement, IRenderableElement, IResizeableEleme
         LocalPosition = Anchor.Calculate(parentPosition, parentRect, Size) + new Vector2(AnchorOffset.X, AnchorOffset.Y);
     }
 
+    private string ConstructStyleModifiers(string[]? modifiers)
+    {
+        if (modifiers == null)
+        {
+            return string.Empty;
+        }
+
+        var sb = new StringBuilder();
+        foreach (var modifier in modifiers)
+        {
+            sb.Append($".{modifier}");
+        }
+
+        return sb.ToString();
+    }
+
+    private string GetStyleVariantString()
+    {
+        if (string.IsNullOrEmpty(StyleVariant))
+            return string.Empty;
+
+        return $".{StyleVariant}";
+    }
+
     private bool _dirty = true;
     private Rect _size = Rect.Zero;