A New Perspective on Viewing

// Gfx.h    - graphics interface
//
// Copyright (C) 2009 John Hilton
//
// Declares
//      IGfx            - the general graphics interface
//      CGfxOpenGL      - implements IGfx using OpenGL
//      CGfxDirect3D    - implements IGfx using Direct3D
//
// Also provides declarations for a simple object definition based on a
// list of DWORDs for specifying color and triangle strips.
//
// The IGfx property 'Hwnd' attaches a window to the IGfx derived object.
// To trigger a redraw used the Win32 Invalidate() call.
// The IGfx callback 'OnPaint' is called by IGfx's WM_PAINT handler.
//
// To change the size or the window use the Win32 MoveWindow() call.
//
// In the OnPaint callback first use IGfx::ConfigureView() then 
// transformation and rendering calls to render the scene.

#pragma once

// Declare a general graphics interface
template< typename T >
struct IGfx
{
    // types
    struct ICallbacks
    {
        virtual void OnPaint( IGfx<T>& Gfx ) = 0;
        virtual void OnFinalMessage( HWND hWnd ) = 0;
    };

    virtual HWND Hwnd() = 0;
    virtual void Attach( HWND hwnd ) = 0;   // NULL will detach

    virtual void ConfigureView( T ViewVolume[7], T ViewToWorld[4][3] ) = 0;
    virtual void Push() = 0;
    virtual void Pop() = 0;
    virtual void Rotate( T Angle, T Axis[3] ) = 0;
    virtual void Rotate( T Matrix[3][3] ) = 0;
    virtual void Translate( T x, T y, T z ) = 0;
    virtual void Scale( T factor ) = 0;
    virtual void Scale( T xyz[3] ) = 0;

    virtual void Render( DWORD* pItem, int length ) = 0;
};

template< typename T > class CGfxOpenGLImpl;

template< typename T >
class CGfxOpenGL
    : public IGfx<T>
{
    class CGfxOpenGLImpl<T>* m_pImpl;
public:
    // construction
    CGfxOpenGL(ICallbacks& Callbacks);
    ~CGfxOpenGL();

    virtual HWND Hwnd();
    virtual void Attach( HWND hwnd );

    virtual void ConfigureView( T ViewVolume[7], T ViewToWorld[4][3] );
    virtual void Push();
    virtual void Pop();
    virtual void Rotate( T Angle, T Axis[3] );
    virtual void Rotate( T Matrix[3][3] );
    virtual void Translate( T x, T y, T z );
    virtual void Scale( T factor );
    virtual void Scale( T xyz[3] );

    virtual void Render( DWORD* pItem, int length );
};
typedef CGfxOpenGL<float> CGfxOpenGLf;
typedef CGfxOpenGL<double> CGfxOpenGLd;

template< typename T > class CGfxDirect3DImpl;

template< typename T >
class CGfxDirect3D : public IGfx<T>
{
    CGfxDirect3DImpl<T>* m_pImpl;
public:
    CGfxDirect3D(typename IGfx<T>::ICallbacks& Callbacks);
    ~CGfxDirect3D();

    virtual HWND Hwnd();
    virtual void Attach( HWND hwnd );

    virtual void ConfigureView( T ViewVolume[7], T ViewToWorld[4][3] );
    virtual void Push();
    virtual void Pop();
    virtual void Rotate( T Angle, T Axis[3] );
    virtual void Rotate( T Matrix[3][3] );
    virtual void Translate( T x, T y, T z );
    virtual void Scale( T factor );
    virtual void Scale( T xyz[3] );

    virtual void Render( DWORD* pItem, int length );
};
typedef CGfxDirect3D<float> CGfxDirect3Df;
typedef CGfxDirect3D<double> CGfxDirect3Dd;

// Hopefully the compiler will perform f2dw at compile-time rather than run-time
inline DWORD f2dw(float f) { return *(DWORD*)&f; }

enum TGfxItem { gfxColor=(DWORD)0x81<<24, gfxTriangleStrip=(DWORD)0x82<<24, gfxForceDWORD=0x7fffffff };
#define GFXCOLOR(r,g,b) \
        (DWORD) (gfxColor | \
        ((DWORD)(min(abs((float)r),1.0f)*255)<<16) | \
        ((DWORD)(min(abs((float)g),1.0f)*255)<< 8) | \
         (DWORD)(min(abs((float)b),1.0f)*255))
#define GFXTRIANGLESTRIP(TriangleCount) \
        (DWORD) (gfxTriangleStrip | (TriangleCount & 0x00000fff))
#define GFXV(x,y,z) \
        f2dw((float)x), \
        f2dw((float)y), \
        f2dw((float)z)

// Although not used in the interfaces above provide TViewVolume
template< typename T > union TViewVolume {
    T v7[7];
    struct { float hw, hh, zn, zf, iez, tsx, tsy; };
};
typedef TViewVolume<float> TViewVolumef;
typedef TViewVolume<double> TViewVolumed;