xenadmin/XenAdmin/Controls/CustomGridView/GridTreeExpanderItem.cs

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using System.Drawing;
using System.Windows.Forms;
using System.Windows.Forms.VisualStyles;


namespace XenAdmin.Controls.CustomGridView
{
    class GridTreeExpanderItem : GridItemBase
    {
        private const int IconWidth = 9;
        private const int IconHeight = 9;
        private const int TopMargin = 4;

        public GridTreeExpanderItem()
            : base(false, 1, false, null, null)
        {
        }

        public override void OnPaint(ItemPaintArgs itemPaintArgs)
        {
            if (!Row.HasChildren)
                return;  // nothing to draw

            Point loc = itemPaintArgs.Rectangle.Location;
            Rectangle rect = new Rectangle(loc.X, loc.Y + TopMargin, IconWidth, IconHeight);

            if (Application.RenderWithVisualStyles)
            {
                VisualStyleRenderer renderer = new VisualStyleRenderer(
                    Row.Expanded ?
                    VisualStyleElement.TreeView.Glyph.Opened :
                    VisualStyleElement.TreeView.Glyph.Closed);
                renderer.DrawBackground(itemPaintArgs.Graphics, rect);
            }

            else
            {
                itemPaintArgs.Graphics.DrawImage(Row.Expanded ? Images.StaticImages.tree_minus : Images.StaticImages.tree_plus, rect);
            }
        }

        private bool IsOverIcon(Point point)
        {
            return (Row.HasChildren &&
                point.X >= 0 && point.X < IconWidth &&
                point.Y >= TopMargin && point.Y < IconHeight + TopMargin); 
        }

        public override void OnClick(Point point)
        {
            if (IsOverIcon(point))
            {
                Row.Expanded = !Row.Expanded;
                Row.GridView.Refresh();
            }
        }
    }
}