3rdpartylibs/fastreports.wpf/FastReport.Forms.WPF/Controls/TabControl.cs

namespace System.Windows.Forms
{
    public partial class TabControl : Control
    {
        protected new System.Windows.Controls.TabControl control { get; }

        public TabPageCollection TabPages { get; }

        private TabAppearance appearance;
        public TabAppearance Appearance
        {
            get => appearance;
            set
            {
                appearance = value;
                control.BorderThickness = new System.Windows.Thickness(value == TabAppearance.Normal ? 1 : 0);
                if (value != TabAppearance.Normal)
                    control.Background = null;
            }
        }

        private System.Drawing.Size itemSize;
        public System.Drawing.Size ItemSize
        {
            get => itemSize;
            set
            {
                itemSize = value;
                for (int i = 0; i < control.Items.Count; i++)
                {
                    var item = (System.Windows.Controls.TabItem)control.Items[i];
                    item.Width = value.Width;
                    item.Height = value.Height;
                }
            }
        }

        public bool Multiline { get; set; } // TODO? it's multiline by default

        public TabSizeMode SizeMode { get; set; }

        public int SelectedIndex
        {
            get => control.SelectedIndex;
            set => control.SelectedIndex = value;
        }

        public TabPage SelectedTab
        {
            get => ((System.Windows.Controls.TabItem)control.SelectedItem)?.Tag as TabPage;
            set => control.SelectedItem = value.control;
        }

        public event TabControlCancelEventHandler Selecting;

        protected virtual void OnSelecting(TabControlCancelEventArgs e) => Selecting?.Invoke(this, e);

        internal override void AddChild(Control child)
        {
            if (child is not TabPage)
                throw new ArgumentException("child must be of TabPage type");
            control.Items.Add(child.control);
        }
        
        internal override void SetChildIndex(Control child, int index)
        {
            control.Items.Insert(index, child.control);
        }

        internal override void RemoveChild(Control child)
        {
            control.Items.Remove(child.control);
        }

        public TabControl()
        {
            control = new();
            SetControl(control);
            TabPages = new TabPageCollection(Controls);

            int prevIndex = 0;
            control.SelectionChanged += (sender, e) =>
            {
                var args = new TabControlCancelEventArgs(SelectedTab, SelectedIndex, false, TabControlAction.Selecting);
                OnSelecting(args);
                if (args.Cancel)
                {
                    if (SelectedIndex != prevIndex)
                        SelectedIndex = prevIndex;
                    e.Handled = true;
                }
                else
                {
                    prevIndex = SelectedIndex;
                }
            };

            BackColor = System.Drawing.SystemColors.ControlLightLight;
        }
    }
}