Simple screen area picker for WinForms apps.

readme.md

MouseForm.cs

Simple screen area picker for WinForms apps.

Usage

// this is the calling form
// will hide/show automatically
MouseForm.Show(this, region => {
    // work with Rectangle region...
});

MouseForm.cs

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

namespace Common
{
    public class MouseForm : Form
    {
        bool down;
        Point start;
        Rectangle region;

        readonly Pen pen;
        Action<Rectangle> callback;

        public MouseForm()
        {
            Opacity = 0.25;
            TopMost = true;
            Cursor = Cursors.Cross;
            this.BackColor = Color.White;

            Bounds = Screen.PrimaryScreen.Bounds;
            FormBorderStyle = FormBorderStyle.None;
            WindowState = FormWindowState.Maximized;
            StartPosition = FormStartPosition.Manual;

            region = Rectangle.Empty;
            pen = new Pen(Color.Red, 2);

            Shown += MouseForm_Shown;
            FormClosed += MouseForm_FormClosed;

            MouseDown += MouseForm_MouseDown;
            MouseMove += MouseForm_MouseMove;
            MouseUp += MouseForm_MouseUp;
            Paint += MouseForm_Paint;
        }

        void MouseForm_Shown(object sender, EventArgs e)
        {
            Owner.Hide();
        }

        void MouseForm_FormClosed(object sender, FormClosedEventArgs e)
        {
            Owner.Show();
        }

        void MouseForm_MouseDown(object sender, MouseEventArgs e)
        {
            down = true;
            start = e.Location;
        }

        void MouseForm_MouseMove(object sender, MouseEventArgs e)
        {
            if (!down)
                return;
            region.X = Math.Min(e.X, start.X);
            region.Y = Math.Min(e.Y, start.Y);
            region.Width = Math.Abs(e.X - start.X);
            region.Height = Math.Abs(e.Y - start.Y);
            Refresh();
        }

        void MouseForm_MouseUp(object sender, MouseEventArgs e)
        {
            down = false;

            callback(region);
            Close();
        }

        void MouseForm_Paint(object sender, PaintEventArgs e)
        {
            e.Graphics.DrawRectangle(pen, region);
        }

        public static void Show(Form owner, Action<Rectangle> callback)
        {
            var form = new MouseForm();
            form.callback = callback;
            form.Show(owner);
        }
    }
}