ContextGL++ tute1: Howto create a window as the OpenGL context.

First things first. I assume you all know about how to compile a program using either VC++ or gcc. I am also assuming that you have installed ContextGL++ in the appropriate directory. OK, now lets get down to business. ContextGL++ is a C++ class library for OpenGL context creation. To be able to render any OpenGL commands we need a context to render to, this can be quite an issue for the novice and has of course led to many libraries that can open contexts in a simple and platform independent fashion. So why use ContextGL++ instead of all those other ones?
   ContextGL++ provides context and event notification as well as a simple interface into the Window Manager's (Win, X11 ...) core bitmap fonts. That's all, there are no plans to ever expand beyond those limits. If you want a library that holds your hand all the way, use OpenGLUT or SDL or Allegro.
   Lets now have a look at a simple example that opens up a window ready for rendering.

The correct way to include the ContextGL++ project into a gcc project is to use 
`contextglpp-config --cxxflags`
and
`contextglpp-config --libs`
 
as appropriate in your makefiles.

Now, in a skeleton .cpp file enter the following lines:

#include <ContextGL++/GLWindow.h>
#include <ContextGL++/WMhelper.h>

using namespace contextglpp;

#ifdef _WIN32
int APIENTRY WinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR     lpCmdLine,
                     int       nCmdShow)
{
#else
int main()
{
    void* hInstance = 0;
#endif
    //user code goes from here
    
    
    
    //to here
    return 0;
}

That should provide a simple base to build upon.

Lets now add a context to the program.

    //user code goes from here
    
    //Prepare a depth & double buffered window at 0,0 with dimensions 400 by 400 
    
    GLWindow* context = new GLWindow(GLContext::DOUBLE | GLContext::DEPTH,0,0, 400,400, hInstance);
    
    //create it, Windows doesn't like to play fair with window creation and requires a callback so 
    //we have to wait for the WndProc to recieve the WM_CREATE message. Therefore all creating is
    //in the create method.
    
    context->create("Simple Example");
    
    //Display it on the screen
    
    context->show();
    
    //Associate OpenGL calls with this context 
    
    context->makeCurrent();
    
    //You all know this one
    
    glClear(GL_COLOR_BUFFER_BIT);
    
    //Same for single and double buffered windows. 
    
    context->swapBuffers();
    
    //You will have to kill the window by hand with a loop like this.
    
    while(1)
    { }
    
    //to here


Compile and run and you should have something like this

OK, so the window isn't very cooperative (yet) but you have at least created a context to draw onto. Lets now add some WindowManager event support so that the app at least responds to closing the window.

    //You will have to kill the window by hand with a loop like this.
    //Not any more :-)
    
    WMEvent* event = new WMEvent(*context);
    
    bool done = false;
    
    while(!done)
    {
        //Draw with OpenGL here
        
        //Check for and iterate through events 
        while(event->nextEvent())
        {
            //Filter the event
            switch(event->type())
            {
                case WMEvent::CLOSE:
                    done = true;
                    break;
                default:               
            }
            //To satisfy Windows' messaging system
            event->passAlong();
        } 
    }
    
    
    //clean up
    delete event;
    delete context;
    
    //to here

OK, that concludes the first tutorial on ContextGL++, the source for the program can be found under the src/tutorial directory in the source tree of contextglpp. Happy Coding everyone.