WinFormsでアイコンエディタを作る2。「消去機能」

mkdir IconE
cd IconE
dotnet new winforms
code .

namespace IconE;

public partial class Form1 : Form
{
    const int ROW_MAX = 32;
    const int COLUMN_MAX = 32;
    const int CELL_WIDTH = 16;
    const int CELL_HEIGHT = 16;
    const int CELL_MARGIN = 2;
    bool _mouseDownFlag = false;
    bool _eraseFlag = false;

    public Form1()
    {
        InitializeComponent();

        this.Load += Form1_Load;
        this.MouseDown += Form1_MouseDown;
        this.MouseUp += Form1_MouseUp;
    }
    void Form1_Load(object? sender, EventArgs e)
    {
        this.Size = new Size(1280, 720);

        var picBoxs = new PictureBox[ROW_MAX, COLUMN_MAX];
        for(int i = 0; i < ROW_MAX; i++)
        {
            for(int j = 0; j < COLUMN_MAX; j++)
            {
                picBoxs[i, j] = new PictureBox
                {
                    Name = String.Format("PICS_{0}_{1}", i, j),
                    Size = new Size(CELL_WIDTH, CELL_HEIGHT),
                    Location = new Point
                    (
                        CELL_WIDTH+(CELL_MARGIN+CELL_WIDTH)*i,
                        CELL_HEIGHT+(CELL_MARGIN+CELL_HEIGHT)*j
                    ),
                    BorderStyle = BorderStyle.FixedSingle,
                    BackColor = Color.Empty,
                };
                picBoxs[i, j].MouseUp += Form1_MouseUp;
                picBoxs[i, j].MouseDown += Form1_MouseDown;
                picBoxs[i, j].MouseMove += PicBoxs_MouseMove;
                this.Controls.Add(picBoxs[i, j]);
            }
        }
        var groupBox1 = new GroupBox
        {
            Name = "GROUP_BOX_1",
            Size = new Size(140, 140),
            Location = new Point(
                CELL_WIDTH*2+(CELL_MARGIN+CELL_WIDTH)*COLUMN_MAX,
                CELL_HEIGHT
            ),
            Text = "モード",
        };
        var radioButtonErase = new RadioButton
        {
            Name = "RADIO_BUTTON_ERASE",
            Size = new Size(120, 60),
            Location = new Point(
                CELL_WIDTH,
                CELL_HEIGHT
            ),
            Text = "消去",
        };
        var radioButtonDraw = new RadioButton
        {
            Name = "RADIO_BUTTON_DRAW",
            Size = new Size(120, 60),
            Location = new Point(
                CELL_WIDTH ,
                CELL_HEIGHT + radioButtonErase.Height + CELL_MARGIN
            ),
            Text = "描画",
            Checked = true,
        };
        groupBox1.Controls.Add(radioButtonErase);
        groupBox1.Controls.Add(radioButtonDraw);
        this.Controls.Add(groupBox1);
        radioButtonErase.CheckedChanged += RadioButtonErase_CheckedChanged;
    }
    void Form1_MouseDown(object? sender, MouseEventArgs e)
    {
        if (sender == null) return;
        _mouseDownFlag = true;
        var cell = sender as PictureBox;
        if (cell == null) return;


        PicBoxs_MouseMove(sender, e);
    }
    void Form1_MouseUp(object? sender, MouseEventArgs e)
    {
        _mouseDownFlag = false;
    }
    void PicBoxs_MouseMove(object? sender, MouseEventArgs e)
    {
        if (sender == null || _mouseDownFlag == false) return;

        var c = sender as PictureBox;
        if (c == null) return;

        if (_eraseFlag == true)
        {
            c.BackColor = Color.Empty;
            c.BorderStyle = BorderStyle.FixedSingle;
        }
        else
        {
            c.BorderStyle = BorderStyle.FixedSingle;
            c.BackColor = Color.Blue;
            c.BorderStyle = BorderStyle.None;
        }
    }
    void RadioButtonErase_CheckedChanged(object? sender, EventArgs e)
    {
        if (sender == null) return;
        var radioButton = sender as RadioButton;
        if (radioButton == null) return;

        _eraseFlag = radioButton.Checked;
    }
}

dotnet run