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117 lines
4.5 KiB
C++
117 lines
4.5 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_ImgDrawResult_h
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#define mozilla_image_ImgDrawResult_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 ImgDrawResult 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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* SUCCESS_NOT_COMPLETE: The image was drawn successfully and completely, but
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* it hasn't notified about the sync-decode yet. This can only happen when
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* layout pokes at the internal image state beforehand via the result of
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* StartDecodingWithResult. This should probably go away eventually, somehow,
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* see bug 1471583.
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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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* NOT_SUPPORTED: The requested operation is not supported, but the image is
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* otherwise valid.
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*/
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enum class [[nodiscard]] ImgDrawResult : uint8_t{
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SUCCESS, SUCCESS_NOT_COMPLETE, INCOMPLETE, WRONG_SIZE,
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NOT_READY, TEMPORARY_ERROR, BAD_IMAGE, BAD_ARGS,
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NOT_SUPPORTED};
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/**
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* You can combine ImgDrawResults with &. By analogy to bitwise-&, the result is
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* ImgDrawResult::SUCCESS only if both operands are ImgDrawResult::SUCCESS.
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* Otherwise, a failing ImgDrawResult is returned; we favor the left operand's
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* failure when deciding which failure to return, with the exception that we
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* always prefer any other kind of failure over ImgDrawResult::BAD_IMAGE, since
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* other failures are recoverable and we want to know if any recoverable
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* failures occurred.
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*/
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inline ImgDrawResult operator&(const ImgDrawResult aLeft,
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const ImgDrawResult aRight) {
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if (MOZ_LIKELY(aLeft == ImgDrawResult::SUCCESS)) {
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return aRight;
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}
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if (aLeft == ImgDrawResult::NOT_SUPPORTED ||
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aRight == ImgDrawResult::NOT_SUPPORTED) {
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return ImgDrawResult::NOT_SUPPORTED;
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}
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if ((aLeft == ImgDrawResult::BAD_IMAGE ||
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aLeft == ImgDrawResult::SUCCESS_NOT_COMPLETE) &&
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aRight != ImgDrawResult::SUCCESS &&
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aRight != ImgDrawResult::SUCCESS_NOT_COMPLETE) {
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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 ImgDrawResult& operator&=(ImgDrawResult& aLeft,
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const ImgDrawResult aRight) {
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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 ImgDrawResult 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(ImgDrawResult::SUCCESS) {}
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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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ImgDrawResult 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_ImgDrawResult_h
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