Control Base Classes

Base Use Case

Control

Interactive elements (buttons, inputs)

ContentControl

Single-child containers

Panel

Multi-child layouts

Basic Control Structure

public class MyButton : Control { private bool _isPressed;

// Property with invalidation
public string Text
{
    get;
    set
    {
        if (field != value)
        {
            field = value;
            InvalidateMeasure();
        }
    }
} = "";

// Enable focus by overriding (not setting property)
public override bool Focusable => true;

// Measure: calculate desired size
protected override Size MeasureContent(Size availableSize)
{
    var factory = GetGraphicsFactory();
    using var ctx = factory.CreateMeasurementContext(GetDpi());
    var textSize = ctx.MeasureText(Text, GetFont());
    return new Size(textSize.Width + Padding.Horizontal, textSize.Height + Padding.Vertical);
}

// Render: draw the control
protected override void OnRender(IGraphicsContext context)
{
    var bounds = new Rect(0, 0, Bounds.Width, Bounds.Height);

    var bgColor = _isPressed ? Theme.Palette.ButtonPressedBackground
        : IsMouseOver ? Theme.Palette.ButtonHoverBackground
        : Theme.Palette.ButtonFace;

    context.FillRoundedRectangle(bounds, 4, 4, bgColor);
    context.DrawRoundedRectangle(bounds, 4, 4, Theme.Palette.BorderColor, 1);
    context.DrawText(Text, bounds, GetFont(), Foreground,
        TextAlignment.Center, TextAlignment.Center, TextWrapping.NoWrap);
}

}

Input Handling

// Mouse - note: MouseEventArgs, not MouseButtonEventArgs protected override void OnMouseDown(MouseEventArgs e) { if (e.LeftButton) { _isPressed = true; // Capture via Window var root = FindVisualRoot(); if (root is Window window) window.CaptureMouse(this); InvalidateVisual(); e.Handled = true; } }

protected override void OnMouseUp(MouseEventArgs e) { if (_isPressed) { _isPressed = false; var root = FindVisualRoot(); if (root is Window window) window.ReleaseMouseCapture(); if (IsMouseOver) Click?.Invoke(this, EventArgs.Empty); InvalidateVisual(); } }

// Keyboard protected override void OnKeyDown(KeyEventArgs e) { if (e.Key == Key.Space || e.Key == Key.Enter) { Click?.Invoke(this, EventArgs.Empty); e.Handled = true; } }

Adding Binding Support

private ValueBinding<string>? _textBinding;

public void SetTextBinding(Func<string> get, Action<string>? set = null, Action<Action>? subscribe = null, Action<Action>? unsubscribe = null) { _textBinding?.Dispose(); _textBinding = new ValueBinding<string>(get, set, subscribe, unsubscribe, () => Text = get()); // RegisterBinding is internal - use within MewUI assembly Text = get(); }

Fluent Extensions

public static class MyButtonExtensions { public static MyButton Text(this MyButton btn, string text) { btn.Text = text; return btn; } public static MyButton OnClick(this MyButton btn, Action handler) { btn.Click += (s,e) => handler(); return btn; } public static MyButton BindText(this MyButton btn, ObservableValue<string> src) { btn.SetTextBinding(() => src.Value, v => src.Value = v, h => src.Changed += h, h => src.Changed -= h); return btn; } }

Input details: See input-handling.md ContentControl pattern: See content-control.md