// Computergrafik I
// Prof. Dr. Juergen Doellner
// Sommersemester 2001
// 
// Programmrahmen fuer Aufgabe 4

#ifndef CG_APPLICATION_H
#define CG_APPLICATION_H

// to use the OpenGL Utility Library
#include <GL/glut.h>

class CGApplication {
public:
    // This abstract base class provides a frame set to solve 
	// your exercises. For that purpose the virtual on*-methods
	// below should be overwritten.
	// This class is a "singleton", so there can be only one instance 
	// at a time.
    CGApplication();
    virtual ~CGApplication();

	// Starts the application and initializes glut.
	// This method should be invoked from within the main function.
	// The default parameters are a string variable to name the window,
	// a boolean flag to allow double-buffering and 
	// two integer values to define the window dimensions.
    void start(const char* windowTitle = "CGApplication",
               bool doubleBuffering = true,
               int windowWidth = 400, int windowHeight = 400);

	// This method will be invoked only once during the initialization 
	// process to initialize OpenGL (e.g., to specify the background color 
	// of the window).
	// This method may be overwritten by a derived class.
    virtual void onInit();

	// This method must be invoked whenever the content 
	// of a window needs to be redrawn.
	// The pure virtual method must be overwritten by a derived class!
    virtual void onDraw() = 0;

	// This method will be invoked whenever the window size has been changed. 
	// Additionally, the onDraw() method will be invoked implicitly.
	// The pure virtual method must be overwritten by a derived class!
    virtual void onSize(int newWidth, int newHeight) = 0;

	// Constant values indicating the left and right mouse button.
    enum MouseButton { LeftMouseButton, RightMouseButton };

	// This method will be invoked whenever a mouse button has been pressed 
	// within the window area. The parameter button indicates which button has been
	// pressed. The parameters x and y provide window coordinates in pixels. 
	// The origin is located in the lower left corner of the window.
	// This method may be overwritten by a derived class.
    virtual void onButton(MouseButton button, int x, int y);

	// This method will be invoked whenever a mouse pointer has been moved
	// within the window area. The parameters x and y provide window 
	// coordinates in pixel. 
	// The origin is located in the lower left corner of the window.
	// This method may be overwritten by a derived class.
    virtual void onMove(int x, int y);

	// This method will be invoked whenever a key has been pressed. 
	// The parameter key is the generated ASCII value.
	// This method may be overwritten by a derived class.
    virtual void onKey(unsigned char key);

	// This method should be invoked whenever drawing is made (e.g. finishing the 
	// onDraw()-method) to swap front- and backbuffer and to make changes visible.
    void swapBuffers();

private:
	// This class is a singleton and must not be copied.
	// Copy constructor and assignment operator are prohibited.
    CGApplication(const CGApplication&);
    CGApplication& operator=(const CGApplication&);
};

#endif // CG_APPLICATION_H