HandyControl/src/Shared/HandyControl_Shared/Controls/Panel/SimpleStackPanel.cs

using System;
using System.Windows;
using System.Windows.Controls;

namespace HandyControl.Controls
{
    public class SimpleStackPanel : Panel
    {
        public static readonly DependencyProperty OrientationProperty =
            StackPanel.OrientationProperty.AddOwner(typeof(SimpleStackPanel),
                new FrameworkPropertyMetadata(Orientation.Vertical, FrameworkPropertyMetadataOptions.AffectsMeasure));

        public Orientation Orientation
        {
            get => (Orientation) GetValue(OrientationProperty);
            set => SetValue(OrientationProperty, value);
        }

        protected override Size MeasureOverride(Size constraint)
        {
            var stackDesiredSize = new Size();
            var children = InternalChildren;
            var layoutSlotSize = constraint;

            if (Orientation == Orientation.Horizontal)
            {
                layoutSlotSize.Width = double.PositiveInfinity;

                for (int i = 0, count = children.Count; i < count; ++i)
                {
                    var child = children[i];
                    if (child == null) continue;

                    child.Measure(layoutSlotSize);
                    var childDesiredSize = child.DesiredSize;

                    stackDesiredSize.Width += childDesiredSize.Width;
                    stackDesiredSize.Height = Math.Max(stackDesiredSize.Height, childDesiredSize.Height);
                }
            }
            else
            {
                layoutSlotSize.Height = double.PositiveInfinity;

                for (int i = 0, count = children.Count; i < count; ++i)
                {
                    var child = children[i];
                    if (child == null) continue;

                    child.Measure(layoutSlotSize);
                    var childDesiredSize = child.DesiredSize;

                    stackDesiredSize.Width = Math.Max(stackDesiredSize.Width, childDesiredSize.Width);
                    stackDesiredSize.Height += childDesiredSize.Height;
                }
            }

            return stackDesiredSize;
        }

        protected override Size ArrangeOverride(Size arrangeSize)
        {
            var children = InternalChildren;
            var rcChild = new Rect(arrangeSize);
            var previousChildSize = 0.0;

            if (Orientation == Orientation.Horizontal)
            {
                for (int i = 0, count = children.Count; i < count; ++i)
                {
                    var child = children[i];
                    if (child == null) continue;

                    rcChild.X += previousChildSize;
                    previousChildSize = child.DesiredSize.Width;
                    rcChild.Width = previousChildSize;
                    rcChild.Height = Math.Max(arrangeSize.Height, child.DesiredSize.Height);

                    child.Arrange(rcChild);
                }
            }
            else
            {
                for (int i = 0, count = children.Count; i < count; ++i)
                {
                    var child = children[i];
                    if (child == null) continue;

                    rcChild.Y += previousChildSize;
                    previousChildSize = child.DesiredSize.Height;
                    rcChild.Height = previousChildSize;
                    rcChild.Width = Math.Max(arrangeSize.Width, child.DesiredSize.Width);

                    child.Arrange(rcChild);
                }
            }

            return arrangeSize;
        }
    }
}