[Mono-docs-list] Example for using C code in C#

[Raphael J. Schmid]

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Hello there,

since I needed to use some C functions from a library in C#
I played around to figure out how it works. Many thanks to
Miguel and Mike (who gave the significant hint) :-). 

Anyway, since there doesn't seem to be such an example in the
Monkeyguide, I adopted my test app to mono/samples/embed/* and
commented it.

Maybe this can be useful for somebody.


Cheers, Raphael


Attached: gtkteste.c, gtktest.cs

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//
// Simple mono embedding example.
// Unlike test.cs/teste.c this uses
// C code in C#, not vice versa.
//
// Compile with: 
// 	gcc --shared -o gtkteste.so gtkteste.c `pkg-config --cflags --libs gtk+-2.0` -lm
// 	mcs --unsafe gtktest.cs -r gtk-sharp
//
// Run with:
// 	cp gtkteste.so $mono_prefix/lib; ldconfig; mono gtktest.exe
//  
//

using System;
using System.Runtime.InteropServices; // For DllImport().
using Gtk;
using GtkSharp;

class EmbedSample {
  // "Import" the create_button() function from
  // a library "gtkteste.so" which can be in any
  // of the system's library directories. Please
  // note the "unsafe" keyword. It is used because
  // with pointers it is possible to manipulate
  // memory locations directly. Normally this is
  // not possible with C#.
	[DllImport("gtkteste", SetLastError=true)]
	static extern unsafe IntPtr create_button();

	public static void Main()
	{
		Application.Init();
		Window window = new Window("Embed Sample");
		window.DeleteEvent += new DeleteEventHandler(On_window_DeleteEvent);
    
    // Using Gtk.Button's IntPtr ctor to create a 
    // managed button from the native "handle" returned 
    // by the -formerly PInvoked- create_button().
		Button button = new Button(create_button());
    
    // From now on the button can be used as 
    // if it had been created the normal way.
		button.Clicked += new EventHandler(On_button_Clicked);
		window.Add(button);
    
		window.ShowAll();
		Application.Run();
	}

	private static void On_window_DeleteEvent(object obj, DeleteEventArgs args)
	{
		Application.Quit();
	}
	
	private static void On_button_Clicked(object obj, EventArgs args)
	{
		Application.Quit();
	}
}

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/***
 * Simple mono embedding example.
 * Unlike test.cs/teste.c this uses
 * C code in C#, not vice versa.
 * 
 * Compile with: 
 * 	gcc --shared -o gtkteste.so gtkteste.c `pkg-config --cflags --libs gtk+-2.0` -lm
 * 	mcs --unsafe gtktest.cs -r gtk-sharp
 *
 * Run with:
 *  cp gtkteste.so $mono_prefix/lib; /sbin/ldconfig; mono gtktest.exe
 ***/

#include <gtk/gtk.h>

GtkWidget *create_button () {
  /* A Gtk Button is created, just as if the
   * container it will go in to was right here.
   */
	GtkWidget* button = NULL;
	button = gtk_button_new_with_label("Click to Quit");
  
  /* Please note: what is returned here is a _pointer_.
   * In the C# file we will be able to use it as IntPtr.
   */
	return button;
}

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