DUI OpenGL support

DUI OpenGL API was changed (the previous API will not be deprecated as it's a thin layer on gtkglext).
DUI OpenGL API now makes use of D mixins resulting on a clean an simple way add
OpenGL capailities to any widget (unfortunatly only DrawingArea is support on th new API)
/*
 * This file is part of dui.
 * 
 * dui is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 * 
 * dui is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with dui; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

module simpleGL.SimpleGL;

import dui.All;
import ggl.All;

/**
 * This is a Simple class extending the DrawingArea widget.
 * A really simple Demo illustrating OpenGL with DUI
 * It uses the new GLCapability mixin to add the GL capabilities to the widget.
 * This example is provided under the terms of the GPL License.
 * Note the initialization of the GLCapabilities on the constructor.
 * 
 * @author pac@tuxfamily.org
 */
class SimpleGL : DrawingArea
{

    /** need to include the mixin to add GL capabilities to this widget */
    mixin GLCapability;

    /**
     * Construct a simple DrawingArea and sets the GLCapabilities
     */
    this()
    {
        super(300, 300);
        setGLCapability();  // set the GL capabilities for this widget
    }

    /**
     * put any gl initializations here
     * returns true to consume the event
     */
    bit initGL(Event event)
    {
        resizeGL(null);
        return true;
    }
    
    /**
     * This method is called every time the window must be paint or repaint
     * This is where you put the OpenGL call to draw something.
     * This method call be called directly by the application without an event object
     * to force redrawing of the scene.
     * returns true to consume the event
     */
    bit drawGL(EventExpose event = null)
    {
        glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        glLoadIdentity ();

        gluLookAt(0, 0, 10, 0, 0, 0, 0, 1,0); //Set the camera position

        //Just Draw a tri-colored triangle
        glBegin(GL_TRIANGLES);
        glColor3f(1.0f,0.0f,0.0f);
        glVertex3f( 0.0f, 1.0f, 0.0f);
        glColor3f(0.0f,1.0f,0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);
        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);
        glEnd();
            
        return true;
    }

    /**
     * This method is called when the window is resized
     * returns true to consume the event
     */
    bit resizeGL(EventConfigure event = null)
    {
        GLfloat w = getWidth();
        GLfloat h = getHeight();
        
        glViewport (0, 0, cast(int)w, cast(int)h); //Adjust the viewport according to new window dimensions 

        /*
         * Update the projection Matrix accoding to the new dimension
         * and reset the OpenGL state to MODELVIEW
         */
        glMatrixMode (GL_PROJECTION);
        glLoadIdentity ();
        gluPerspective(20, w/h, 0.1, 10);
        glMatrixMode (GL_MODELVIEW);
            
        return true;
    }
}
 
void main(char[][] args)
{
    DUI dui;
    dui = DUI.dui(args);

    GL.init(args);
    
    SimpleGL simpleGL = new SimpleGL();
    MainWindow window = new MainWindow("Simplest OpenGL Example");
    window.add(simpleGL);
    window.show();
        
    dui.go();

}