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/* -*- 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_DrawResult_h
#define mozilla_image_DrawResult_h
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"
namespace mozilla {
namespace image {
/**
* An enumeration representing the result of a drawing operation.
*
* Most users of DrawResult will only be interested in whether the value is
* SUCCESS or not. The other values are primarily useful for debugging and error
* handling.
*
* SUCCESS: We successfully drew a completely decoded frame of the requested
* size. Drawing again with FLAG_SYNC_DECODE would not change the result.
*
* INCOMPLETE: We successfully drew a frame that was partially decoded. (Note
* that successfully drawing a partially decoded frame may not actually draw any
* pixels!) Drawing again with FLAG_SYNC_DECODE would improve the result.
*
* WRONG_SIZE: We successfully drew a wrongly-sized frame that had to be scaled.
* This is only returned if drawing again with FLAG_SYNC_DECODE would improve
* the result; if the size requested was larger than the intrinsic size of the
* image, for example, we would generally have to scale whether FLAG_SYNC_DECODE
* was specified or not, and therefore we would not return WRONG_SIZE.
*
* NOT_READY: We failed to draw because no decoded version of the image was
* available. Drawing again with FLAG_SYNC_DECODE would improve the result.
* (Though FLAG_SYNC_DECODE will not necessarily work until after the image's
* load event!)
*
* TEMPORARY_ERROR: We failed to draw due to a temporary error. Drawing may
* succeed at a later time.
*
* BAD_IMAGE: We failed to draw because the image has an error. This is a
* permanent condition.
*
* BAD_ARGS: We failed to draw because bad arguments were passed to draw().
*/
enum class MOZ_MUST_USE_TYPE DrawResult : uint8_t
{
SUCCESS,
INCOMPLETE,
WRONG_SIZE,
NOT_READY,
TEMPORARY_ERROR,
BAD_IMAGE,
BAD_ARGS
};
/**
* You can combine DrawResults with &. By analogy to bitwise-&, the result is
* DrawResult::SUCCESS only if both operands are DrawResult::SUCCESS. Otherwise,
* a failing DrawResult is returned; we favor the left operand's failure when
* deciding which failure to return, with the exception that we always prefer
* any other kind of failure over DrawResult::BAD_IMAGE, since other failures
* are recoverable and we want to know if any recoverable failures occurred.
*/
inline DrawResult
operator&(const DrawResult aLeft, const DrawResult aRight)
{
if (MOZ_LIKELY(aLeft == DrawResult::SUCCESS)) {
return aRight;
}
if (aLeft == DrawResult::BAD_IMAGE && aRight != DrawResult::SUCCESS) {
return aRight;
}
return aLeft;
}
inline DrawResult&
operator&=(DrawResult& aLeft, const DrawResult aRight)
{
aLeft = aLeft & aRight;
return aLeft;
}
} // namespace image
} // namespace mozilla
#endif // mozilla_image_DrawResult_h
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