tommy.blog

Here's a little class in C#, that allows you to paint an existing Control onto a Graphics object. Nothing special, but useful if you need it. If you're using .NET 2.0, you don't need this class: see Control.DrawToBitmap.

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

public class ControlPainter
{
  private const int
    WM_PRINT = 0x317, PRF_CLIENT = 4,
    PRF_CHILDREN = 0x10, PRF_NON_CLIENT = 2,
    COMBINED_PRINTFLAGS = PRF_CLIENT | PRF_CHILDREN | PRF_NON_CLIENT;

  [DllImport("USER32.DLL")]
  private static extern int SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, int lParam);

  public static void PaintControl(Graphics graphics, Control control)
  { // paint control onto graphics
    IntPtr hWnd = control.Handle;
    IntPtr hDC = graphics.GetHdc();
    SendMessage(hWnd, WM_PRINT, hDC, COMBINED_PRINTFLAGS);
    graphics.ReleaseHdc(hDC);
  }
}

Using it is very easy: if you need to paint the Control myControl onto Graphics myGraphics, you just call ControlPainter.PaintControl(myGraphics, myControl)
Edited March 5th 2005: used some more flags, to also paint child controls and non-client elements like borders and titlebars. Thanks to Kent Boogaart. In this post on his blog, you can find a more flexible version of this method, where you can specify the flags yourself.
Edited October 29th 2005: as of .NET 2.0, the Control class has a method to draw itself to a Bitmap: DrawToBitmap. Thanks to an anonymous commenter for this tip.

I've uploaded a preview (not even an alpha version) of Win4Eu to my website. It contains the libraries, partial documentation, and 2 small demos. The available controls: Window and Button. The available modules: Application and Mouse. Properties that already work:

• Window: Visible, Enabled, X, Y, Width, Height, Location ( = {X, Y}), Size ( = {Width, Height}), Text, Children (read-only), Handle (read-only), Parent, DialogResult
• Button: Visible, Enabled, X, Y, Width, Height, Location, Size, Text, Handle (read-only), Parent
• Application: Name, MainWindow, FireIdleEvent
• Mouse: X, Y, Location

Events that already work:

• Window: Move, Resize, TextChange, Click, DoubleClick, MouseDown, MouseUp, MouseMove, MouseWheel
• Button: Move, Resize, TextChange, Click
• Application: IdleStart, Idle, IdleStop
• Mouse: none

The library is not ready to be used in applications, it's not even an alpha version yet. I didn't even plan on releasing this, but some people might be interested in how it works. And I would really appreciate some feedback: bug reports, new ideas, optimizations, ... Download it here (61 kB).