pjs/modules/libpr0n/decoders/nsIconDecoder.h

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#ifndef nsIconDecoder_h__
#define nsIconDecoder_h__

#include "Decoder.h"

#include "nsCOMPtr.h"

#include "imgIDecoderObserver.h"

namespace mozilla {
namespace imagelib {
class RasterImage;

//////////////////////////////////////////////////////////////////////////////////////////////
// The icon decoder is a decoder specifically tailored for loading icons 
// from the OS. We've defined our own little format to represent these icons
// and this decoder takes that format and converts it into 24-bit RGB with alpha channel
// support. It was modeled a bit off the PPM decoder.
//
// Assumptions about the decoder:
// (1) We receive ALL of the data from the icon channel in one OnDataAvailable call. We don't
//     support multiple ODA calls yet.
// (2) the format of the incoming data is as follows:
//     The first two bytes contain the width and the height of the icon. 
//     The remaining bytes contain the icon data, 4 bytes per pixel, in
//       ARGB order (platform endianness, A in highest bits, B in lowest
//       bits), row-primary, top-to-bottom, left-to-right, with
//       premultiplied alpha.
//
//
//////////////////////////////////////////////////////////////////////////////////////////////

class nsIconDecoder : public Decoder
{
public:

  nsIconDecoder();
  virtual ~nsIconDecoder();

  virtual nsresult InitInternal();
  virtual nsresult WriteInternal(const char* aBuffer, PRUint32 aCount);
  virtual nsresult ShutdownInternal(PRUint32 aFlags);

  PRUint8 mWidth;
  PRUint8 mHeight;
  PRUint32 mPixBytesRead;
  PRUint32 mPixBytesTotal;
  PRUint8* mImageData;
  PRUint32 mState;

  PRBool mNotifiedDone;
  void NotifyDone(PRBool aSuccess);
};

enum {
  iconStateStart      = 0,
  iconStateHaveHeight = 1,
  iconStateReadPixels = 2,
  iconStateFinished   = 3,
  iconStateError      = 4
};

} // namespace imagelib
} // namespace mozilla

#endif // nsIconDecoder_h__