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A struct used during painting to provide input flags to determine how imagelib draw calls should behave, plus an output DrawResult to return information about the result of any imagelib draw calls that may have occurred. MozReview-Commit-ID: 3jGEh5vEPF
107 lines
3.7 KiB
C++
107 lines
3.7 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_image_DrawResult_h
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#define mozilla_image_DrawResult_h
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#include <cstdint> // for uint8_t
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#include "mozilla/Attributes.h"
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#include "mozilla/Likely.h"
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namespace mozilla {
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namespace image {
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/**
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* An enumeration representing the result of a drawing operation.
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*
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* Most users of DrawResult will only be interested in whether the value is
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* SUCCESS or not. The other values are primarily useful for debugging and error
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* handling.
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*
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* SUCCESS: We successfully drew a completely decoded frame of the requested
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* size. Drawing again with FLAG_SYNC_DECODE would not change the result.
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*
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* INCOMPLETE: We successfully drew a frame that was partially decoded. (Note
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* that successfully drawing a partially decoded frame may not actually draw any
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* pixels!) Drawing again with FLAG_SYNC_DECODE would improve the result.
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*
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* WRONG_SIZE: We successfully drew a wrongly-sized frame that had to be scaled.
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* This is only returned if drawing again with FLAG_SYNC_DECODE would improve
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* the result; if the size requested was larger than the intrinsic size of the
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* image, for example, we would generally have to scale whether FLAG_SYNC_DECODE
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* was specified or not, and therefore we would not return WRONG_SIZE.
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*
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* NOT_READY: We failed to draw because no decoded version of the image was
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* available. Drawing again with FLAG_SYNC_DECODE would improve the result.
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* (Though FLAG_SYNC_DECODE will not necessarily work until after the image's
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* load event!)
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*
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* TEMPORARY_ERROR: We failed to draw due to a temporary error. Drawing may
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* succeed at a later time.
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*
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* BAD_IMAGE: We failed to draw because the image has an error. This is a
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* permanent condition.
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*
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* BAD_ARGS: We failed to draw because bad arguments were passed to draw().
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*/
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enum class MOZ_MUST_USE_TYPE DrawResult : uint8_t
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{
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SUCCESS,
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INCOMPLETE,
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WRONG_SIZE,
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NOT_READY,
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TEMPORARY_ERROR,
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BAD_IMAGE,
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BAD_ARGS
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};
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/**
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* You can combine DrawResults with &. By analogy to bitwise-&, the result is
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* DrawResult::SUCCESS only if both operands are DrawResult::SUCCESS. Otherwise,
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* a failing DrawResult is returned; we favor the left operand's failure when
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* deciding which failure to return, with the exception that we always prefer
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* any other kind of failure over DrawResult::BAD_IMAGE, since other failures
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* are recoverable and we want to know if any recoverable failures occurred.
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*/
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inline DrawResult
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operator&(const DrawResult aLeft, const DrawResult aRight)
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{
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if (MOZ_LIKELY(aLeft == DrawResult::SUCCESS)) {
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return aRight;
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}
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if (aLeft == DrawResult::BAD_IMAGE && aRight != DrawResult::SUCCESS) {
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return aRight;
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}
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return aLeft;
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}
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inline DrawResult&
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operator&=(DrawResult& aLeft, const DrawResult aRight)
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{
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aLeft = aLeft & aRight;
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return aLeft;
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}
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/**
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* A struct used during painting to provide input flags to determine how
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* imagelib draw calls should behave and an output DrawResult to return
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* information about the result of any imagelib draw calls that may have
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* occurred.
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*/
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struct imgDrawingParams {
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explicit imgDrawingParams(uint32_t aImageFlags = 0)
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: imageFlags(aImageFlags), result(DrawResult::SUCCESS)
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{}
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const uint32_t imageFlags; // imgIContainer::FLAG_* image flags to pass to
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// image lib draw calls.
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DrawResult result; // To return results from image lib painting.
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};
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} // namespace image
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} // namespace mozilla
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#endif // mozilla_image_DrawResult_h
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