custom popup listbox window

customPopupListBox.cs

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

namespace customPopupListBox
{

    public partial class Form1 : Form
    {
        ListBox listBox1 = new ListBox();
        Size listBoxSize;

        public Form1()
        {
            InitializeComponent();
            Console.WriteLine($" this.listBox1.Font.Name == {this.listBox1.Font.Name}");
            Console.WriteLine($" this.listBox1.Font.Size == {this.listBox1.Font.Size}");
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            SizeF sizeF;

            // listBox1 크기 자동 설정용.
            using (Graphics g = this.CreateGraphics())
            {
                sizeF = g.MeasureString("한", this.listBox1.Font); // 기본 1글자 height, width 구함.
                //Console.WriteLine($"sizeF.Width = {sizeF.Width}, sizeF.Height={sizeF.Height}");  
            }

            int stringLengthMax = 1; // 초기화 -- 가장 긴 글자길이

            // Shutdown the painting of the ListBox as items are added.
            listBox1.BeginUpdate();

            int itemCount = 5;
            for (int x = 1; x <= itemCount; x++)
            {
                var txt = "Item " + x.ToString();
                stringLengthMax = (txt.Length > stringLengthMax) ? txt.Length : stringLengthMax;
                listBox1.Items.Add(txt);
            }
            // Allow the ListBox to repaint and display the new items.
            listBox1.EndUpdate();

            int height = (int)(itemCount * sizeF.Height) + 1; // 형변환시, 소수점이하 짤리는 경우를 고려해서 +1 해줌.
            int width = (int)(stringLengthMax * sizeF.Width) + 1;  // 형변환시, 소수점이하 짤리는 경우를 고려해서 +1 해줌.

            // listBox1 크기 설정하기.
            listBoxSize = new Size(width, height);

            Console.WriteLine($"listBox1.Size = {listBox1.Size}");
            Console.WriteLine($"new listBox1.Size => height={height}, width={width}");
        }


        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            Control c = sender as Control;

            if (e.Button == MouseButtons.Right)
            {
                listBox1.MinimumSize = listBoxSize;  //new Size(120, 88);
                listBox1.Size = listBoxSize;  //new Size(120, 88);

                var popup = new PopupWindow(listBox1);
                popup.Show(c, e.Location);
                //popup.Show(c, e.Location, this.dropDownDirection);
            }
        }
    }

    public class PopupWindow : System.Windows.Forms.ToolStripDropDown
    {
        private System.Windows.Forms.Control _content;
        private System.Windows.Forms.ToolStripControlHost _host;

        public PopupWindow(System.Windows.Forms.Control content)
        {
            //Basic setup...
            this.AutoSize = false;
            this.DoubleBuffered = true;
            this.ResizeRedraw = true;
            
            this._content = content;
            this._host = new System.Windows.Forms.ToolStripControlHost(content);

            //Positioning and Sizing
            this.MinimumSize = content.MinimumSize;
            this.MaximumSize = content.Size;

            //this.SetMinimumSize(new Size(200, 200));

            this.Size = content.Size;
            this.Margin = Padding.Empty;
            this.Padding = Padding.Empty;
            this._host.Margin = Padding.Empty;
            this._host.Padding = Padding.Empty;

            content.Location = Point.Empty;

            //Console.WriteLine($"MinimumSize={MinimumSize}, MaximumSize={MaximumSize}, content.Size={content.Size}");
            
            //Add the host to the list
            this.Items.Add(this._host);

        }

        public void SetMinimumSize(Size size)
        {
            this.MinimumSize = size;
        }

        public void SetMaximumSize(Size size)
        {
            this.MaximumSize = size;
        }

    }


}