image/decoders/nsIconDecoder.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsIconDecoder_h__
   8 #define nsIconDecoder_h__
   9
  10 #include "Decoder.h"
  11
  12 #include "nsCOMPtr.h"
  13
  14 namespace mozilla {
  15 namespace image {
  16 class RasterImage;
  17
  18 //////////////////////////////////////////////////////////////////////////////////////////////
  19 // The icon decoder is a decoder specifically tailored for loading icons
  20 // from the OS. We've defined our own little format to represent these icons
  21 // and this decoder takes that format and converts it into 24-bit RGB with alpha channel
  22 // support. It was modeled a bit off the PPM decoder.
  23 //
  24 // Assumptions about the decoder:
  25 // (1) We receive ALL of the data from the icon channel in one OnDataAvailable call. We don't
  26 //     support multiple ODA calls yet.
  27 // (2) the format of the incoming data is as follows:
  28 //     The first two bytes contain the width and the height of the icon.
  29 //     The remaining bytes contain the icon data, 4 bytes per pixel, in
  30 //       ARGB order (platform endianness, A in highest bits, B in lowest
  31 //       bits), row-primary, top-to-bottom, left-to-right, with
  32 //       premultiplied alpha.
  33 //
  34 //
  35 //////////////////////////////////////////////////////////////////////////////////////////////
  36
  37 class nsIconDecoder : public Decoder
  38 {
  39 public:
  40
  41   nsIconDecoder(RasterImage &aImage);
  42   virtual ~nsIconDecoder();
  43
  44   virtual void WriteInternal(const char* aBuffer, uint32_t aCount);
  45
  46   uint8_t mWidth;
  47   uint8_t mHeight;
  48   uint32_t mPixBytesRead;
  49   uint32_t mState;
  50 };
  51
  52 enum {
  53   iconStateStart      = 0,
  54   iconStateHaveHeight = 1,
  55   iconStateReadPixels = 2,
  56   iconStateFinished   = 3
  57 };
  58
  59 } // namespace image
  60 } // namespace mozilla
  61
  62 #endif // nsIconDecoder_h__