using System;
using System.Drawing;
using System.Windows.Forms;
class BlockOut: Form
{
bool bBlocking, bValidBox;
Point ptBeg, ptEnd;
Rectangle rectBox;
public static void Main()
{
Application.Run(new BlockOut());
}
protected override void OnMouseDown(MouseEventArgs mea)
{
if (mea.Button == MouseButtons.Left)
{
ptBeg = ptEnd = new Point(mea.X, mea.Y);
Graphics grfx = CreateGraphics();
grfx.DrawRectangle(new Pen(ForeColor), Rect(ptBeg, ptEnd));
grfx.Dispose();
bBlocking = true;
}
}
protected override void OnMouseMove(MouseEventArgs mea)
{
if (bBlocking)
{
Graphics grfx = CreateGraphics();
grfx.DrawRectangle(new Pen(BackColor), Rect(ptBeg, ptEnd));
ptEnd = new Point(mea.X, mea.Y);
grfx.DrawRectangle(new Pen(ForeColor), Rect(ptBeg, ptEnd));
grfx.Dispose();
Invalidate();
}
}
protected override void OnMouseUp(MouseEventArgs mea)
{
if (bBlocking && mea.Button == MouseButtons.Left)
{
Graphics grfx = CreateGraphics();
rectBox = Rect(ptBeg, new Point(mea.X, mea.Y));
grfx.DrawRectangle(new Pen(ForeColor), rectBox);
grfx.Dispose();
bBlocking = false;
bValidBox = true;
Invalidate();
}
}
protected override void OnPaint(PaintEventArgs pea)
{
Graphics grfx = pea.Graphics;
if (bValidBox)
grfx.FillRectangle(new SolidBrush(ForeColor), rectBox);
if (bBlocking)
grfx.DrawRectangle(new Pen(ForeColor), Rect(ptBeg, ptEnd));
}
Rectangle Rect(Point ptBeg, Point ptEnd)
{
return new Rectangle(Math.Min(ptBeg.X, ptEnd.X),
Math.Min(ptBeg.Y, ptEnd.Y),
Math.Abs(ptEnd.X - ptBeg.X),
Math.Abs(ptEnd.Y - ptBeg.Y));
}
}
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