Dashboard/Quik/Controls/Control.cs

using System;
using Quik.CommandMachine;

namespace Quik.Controls
{
    public abstract class Control : UIBase
    {
        private readonly CommandList drawCommands = new CommandList();

        public Style Style { get; set; } = new Style();
        public float Padding
        {
            get => (float)(Style["padding"] ?? 0.0f);
            set => Style["padding"] = value;
        }

        public bool IsVisualsValid { get; private set; } = false;
        public bool IsLayoutValid { get; private set; } = false;

        protected bool IsLayoutSuspended { get; private set; } = false;

        public void InvalidateVisual()
        {
            IsVisualsValid = false;
            OnVisualsInvalidated(this, EventArgs.Empty);
        }

        public void InvalidateLayout()
        {
            IsLayoutValid = false;
            OnLayoutInvalidated(this, EventArgs.Empty);
        }

        public void SuspendLayout()
        {
            IsLayoutSuspended = true;
        }

        public void ResumeLayout()
        {
            IsLayoutSuspended = false;
            InvalidateLayout();
        }

        protected abstract void ValidateVisual(CommandList cmd);
        protected abstract void ValidateLayout();

        protected override void PaintBegin(CommandList cmd)
        {
            base.PaintBegin(cmd);

            if (!IsLayoutValid && !IsLayoutSuspended)
            {
                ValidateLayout();
                OnLayoutValidated(this, EventArgs.Empty);
                IsLayoutValid = true;

                InvalidateVisual();
            }

            if (!IsVisualsValid)
            {
                ValidateVisual(drawCommands);
                OnVisualsValidated(this, EventArgs.Empty);
                IsVisualsValid = true;
            }

            cmd.PushStyle(Style);
            cmd.PushViewport();
            cmd.StoreViewport(AbsoluteBounds);

            cmd.Splice(drawCommands);

            cmd.PopViewport();
            cmd.PopStyle();
        }

        public event EventHandler StyleChanged;
        public event EventHandler VisualsInvalidated;
        public event EventHandler VisualsValidated;
        public event EventHandler LayoutInvalidated;
        public event EventHandler LayoutValidated;

        protected virtual void OnStyleChanged(object sender, EventArgs ea)
        {
            StyleChanged?.Invoke(sender, ea);
            InvalidateLayout();
        }

        protected virtual void OnVisualsInvalidated(object sender, EventArgs ea)
        {
            VisualsInvalidated?.Invoke(sender, ea);
        }

        protected virtual void OnVisualsValidated(object sender, EventArgs ea)
        {
            VisualsValidated?.Invoke(sender, ea);
        }

        protected virtual void OnLayoutInvalidated(object sender, EventArgs ea)
        {
            LayoutInvalidated?.Invoke(sender, ea);
        }

        protected virtual void OnLayoutValidated(object sender, EventArgs ea)
        {
            LayoutValidated?.Invoke(sender, ea);
        }
    }
}