Question

I’ve been having problems with onPaint event handler for a pictureBox. I’ve simplified the code, so right now I’m trying to achieve this: load the bitmap from path into pictureBox1 and draw a small rectangle around mouse cursor when moving over the pictureBox1.

    private int mouseX;
    private int mouseY;
    private String path;

    public Form1()
    {
        InitializeComponent();
        path = "images\\image.jpg";
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        pictureBox1.Image = new Bitmap(path);
    }

    private void pictureBox1_MouseMove(object sender, MouseEventArgs e)
    {
        mouseX = e.X;
        mouseY = e.Y;
    }

    private void pictureBox1_Paint(object sender, PaintEventArgs e)
    {
        e.Graphics.DrawRectangle(Pens.Black, mouseX - 10, mouseY - 10, 20, 20);
        pictureBox1.Invalidate();
    }

When I run the application the bitmap is loaded successfully and the rectangle is being drawn nicely wherever I drag the mouse. Anyway there are two problems:

1) When the Form is loaded everything is white but pictureBox until I move the window somewhere. It means menuStrip, toolStrip eg is cleared with white color. When I add pictureBox.Invalidate(); into Form1_Load it seems to take care of that problem (everything is loaded and visible) but on the toolStrip there are some buttons and comboBoxes that are interacting, changing its visibility and this still causes problems. I’d like to reduce the funcionality of the Paint only on pictureBox.

2) The rectangle is drawn the moment the Form is loaded despite the mouse cursor didn’t enter pictureBox. Also when cursor leaves the pictureBox the last drawn rectangle stays there. I’ve tried to remove it but I couldn’t figure it out.

Thanks for any suggestions, it seems to me that something fundamental is missing there but don’t know what.

Answer 1

2) MouseMove works only when cursor is over picture box. Try to use MouseEnter and MouseLeave in order to handle when to start drawing rectangle and when to stop doing that.