gecko/image/decoders/nsIconDecoder.h

72 lines
2.2 KiB
C++

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_image_decoders_nsIconDecoder_h
#define mozilla_image_decoders_nsIconDecoder_h
#include "Decoder.h"
#include "nsCOMPtr.h"
namespace mozilla {
namespace image {
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:
virtual ~nsIconDecoder();
virtual nsresult SetTargetSize(const nsIntSize& aSize) override;
virtual void WriteInternal(const char* aBuffer, uint32_t aCount) override;
private:
friend class DecoderFactory;
// Decoders should only be instantiated via DecoderFactory.
explicit nsIconDecoder(RasterImage* aImage);
Maybe<Downscaler> mDownscaler;
uint32_t mExpectedDataLength;
uint32_t mPixBytesRead;
uint32_t mState;
uint8_t mWidth;
uint8_t mHeight;
};
enum {
iconStateStart = 0,
iconStateHaveHeight = 1,
iconStateReadPixels = 2,
iconStateFinished = 3
};
} // namespace image
} // namespace mozilla
#endif // mozilla_image_decoders_nsIconDecoder_h