Windows API Tutorials

unsigned long ColorValue (COLORREF color) {

switch (_bpp) {

case 16:

return ColorValue16 (color);

case 24:

return ColorValue24 (color);

case 32:

return ColorValue32 (color);

default:

throw "PixelFormat: only 16, 24 and 32 bits supported";

}

}

private:

int _bpp; // bits per pixel 4, 8, 16, 24, or 32

unsigned long _redMask;

unsigned long _greenMask;

unsigned long _blueMask;

unsigned _redShift;

unsigned _greenShift;

unsigned _blueShift;

unsigned long _mask;

};

unsigned HiBitShift (unsigned val) {

unsigned i = 0;

while (val != 0) {

val >>= 1;

++i;

}

return i;

}

void PixelFormat::Init (SurfaceDesc & desc) {

DDPIXELFORMAT & format = desc.PixelFormat ();

if (format.dwFlags != DDPF_RGB) throw "Direct Draw: Non-RGB formats not supported";

_bpp = format.dwRGBBitCount;

_redMask = format.dwRBitMask;

_greenMask = format.dwGBitMask;

_blueMask = format.dwBBitMask;

_mask = ~(_redMask | _greenMask | _blueMask);

switch (_bpp) {

case 16:

_redShift = HiBitShift (_redMask) + 8;

_greenShift = HiBitShift (_greenMask) + 8;

_blueShift = HiBitShift (_blueMask) + 8;

break;

case 24:

break;

case 32:

break;

default:

throw "Only 16, 24 and 32 bit graphics supported";

}

}

Notice that this tutorial only scratches the surface of DirectX. There are several versions of DirectDraw. There is Direct3D for three-dimensional graphics (although it seems like Open GL might be a better platform). Sound can be dealt with using DirectSound and input devices have their DirectInput. All these subsystems can be encapsulated using similar techniques.

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It really cracked me up when I read the introduction to the chapter on Aggregation in the otherwise fine (although somehow dorky) book "Inside COM" by Dale Rogerson. If he knew the real story, he wouldn't be so adamant in his defense of aggregation.