using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;
namespace RubberBands
{
/// <summary>
/// Summary description for Form1.
/// </summary>
public class RubberBandForm : System.Windows.Forms.Form
{
/// API Declarations
private struct POINTAPI {
public int x;
public int y;
}
[DllImport("gdi32.DLL")]
private static extern Int32 SetROP2(IntPtr hDC,
int nDrawMode);
[DllImport("gdi32.dll")]
private static extern bool MoveToEx(IntPtr hDC,
int x,
int y,
POINTAPI lpPoint);
[DllImport("gdi32.dll")]
private static extern bool LineTo(IntPtr hDC,
int x,
int y);
[DllImport("gdi32.dll")]
private static extern IntPtr CreatePen(int nPenStyle,
int nWidth,
int crColor);
[DllImport("gdi32.dll")]
private static extern IntPtr SelectObject(IntPtr hDC,
IntPtr hObject);
[DllImport("gdi32.dll")]
private static extern bool DeleteObject(IntPtr hObject);
private const int R2_NOT = 6;
private const int R2_XORPEN = 7;
private const int PS_DOT = 2;
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.Container components = null;
private System.Drawing.Graphics m_oDrawingSurface;
private POINTAPI m_ptsStart = new POINTAPI();
private POINTAPI m_ptsPrevious;
public RubberBandForm()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//Add any initialization after the InitializeComponent() call
m_oDrawingSurface = this.CreateGraphics();
}
/// <summary>
/// Clean up any resources being used.
/// </summary>
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
protected override void OnMouseDown(MouseEventArgs e) {
// Check whether the left mouse button
// has generated the associated event.
if (e.Button == MouseButtons.Left) {
// Store the starting point for your rubber-band line.
m_ptsStart.x = e.X;
m_ptsStart.y = e.Y;
// Store the previous end point for your rubber-band line.
m_ptsPrevious = m_ptsStart;
}
base.OnMouseDown (e);
}
protected override void OnMouseMove(MouseEventArgs e) {
// Check if the left mouse button is pressed.
if( e.Button == MouseButtons.Left) {
// Declare local variables.
// handle to an appropriate device context obtained
// from m_oDrawingSurface
IntPtr hDC;
// previous mix mode; returned from SetROP2
Int32 Mix ;
// temporary variables used for rubber-banding logic
POINTAPI ptsCurrent;
POINTAPI ptsOld = new POINTAPI();
// determines whether MoveToEx and LineTo calls are successful
Boolean Success;
// Store the current end point of your rubber-band line.
ptsCurrent.x = e.X;
ptsCurrent.y = e.Y;
// Perform the requisite graphical operations.
// Obtain a handle to an appropriate device context
hDC = m_oDrawingSurface.GetHdc();
// Set the raster mode to invert the screen color
Mix = SetROP2(hDC, R2_NOT);
// Move to the starting point of the rubber-band line
Success = MoveToEx(hDC, m_ptsStart.x, m_ptsStart.y, ptsOld);
// Erase the previous line
Success = LineTo(hDC, m_ptsPrevious.x, m_ptsPrevious.y);
// Move to the starting point of the rubber-band line
Success = MoveToEx(hDC, m_ptsStart.x, m_ptsStart.y, ptsOld);
// Draw the new line
Success = LineTo(hDC, ptsCurrent.x, ptsCurrent.y);
// Release the obtained handle to a device context
m_oDrawingSurface.ReleaseHdc(hDC);
// Store the current end point for the next erase operation
m_ptsPrevious = ptsCurrent;
}
base.OnMouseMove (e);
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
//
// RubberBandForm
//
this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);
this.BackColor = System.Drawing.SystemColors.Window;
this.ClientSize = new System.Drawing.Size(350, 286);
this.Name = "RubberBandForm";
this.Text = "Using Unmanaged APIs";
}
#endregion
/// <summary>
/// The main entry point for the application.
/// </summary>
[STAThread]
static void Main()
{
Application.Run(new RubberBandForm());
}
}
}