c# - How to make use of AutoScrollbar when drawing contents with GDI+

Question

I draw my contents on a form inside OnPaint event with e.graphics.DrawLine(), etc... . So far I was drawing according to form size (resizing my elements) but now I'd like draw as big as I want, and if I draw outside the visible area (the place where object will be drawn is decided at runtime dynamically), I want user to use scroll bars in order to see parts of whole content which I draw.

I have enabled AutoScrolling but I don't know how it may help me when I don't have any controls on that form.

How can I do it?

Answer 1

Simply set the AutoScrollMinSize property to the size you want. The scrollbar(s) automatically appear when the form's ClientSize is smaller than this value. You'll also need to offset what you draw according to the scroll position, like this:

public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        this.AutoScroll = true;
        this.AutoScrollMinSize = new Size(3000, 1000);
        this.ResizeRedraw = true;
    }
    protected override void OnPaint(PaintEventArgs e) {
        e.Graphics.TranslateTransform(this.AutoScrollPosition.X, this.AutoScrollPosition.Y);
        e.Graphics.DrawLine(Pens.Black, 0, 0, 3000, 1000);
        base.OnPaint(e);
    }
}