image/ImgDrawResult.h
author Kartikaya Gupta <kgupta@mozilla.com>
Thu, 15 Mar 2018 15:25:09 -0400
changeset 408344 a27ceb86fbd002b8aafd2f6377c315c11254af0c
parent 396187 4e2cf0afd644cc0f2dfb0f6def3f1c1d25a19d27
child 431442 69a4c2a0aac6e8bfc041a82b634611e1432af36b
permissions -rw-r--r--
Bug 1445662 - Remove ProcessTouchVelocity from PAPZCTreeManager.ipdl. r=rhunt This function is never actually called over IPDL. It is called directly on the concrete APZCTreeManager instance by the AndroidDynamicToolbarAnimator code, both of which live in the compositor. So we don't need to expose this method on IAPZCTreeManager or over PAPZCTreeManager.

/* -*- 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_ImgDrawResult_h
#define mozilla_image_ImgDrawResult_h

#include <cstdint> // for uint8_t
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"

namespace mozilla {
namespace image {

/**
 * An enumeration representing the result of a drawing operation.
 *
 * Most users of ImgDrawResult 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 ImgDrawResult : uint8_t
{
  SUCCESS,
  INCOMPLETE,
  WRONG_SIZE,
  NOT_READY,
  TEMPORARY_ERROR,
  BAD_IMAGE,
  BAD_ARGS
};

/**
 * You can combine ImgDrawResults with &. By analogy to bitwise-&, the result is
 * ImgDrawResult::SUCCESS only if both operands are ImgDrawResult::SUCCESS. Otherwise,
 * a failing ImgDrawResult 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 ImgDrawResult::BAD_IMAGE, since other failures
 * are recoverable and we want to know if any recoverable failures occurred.
 */
inline ImgDrawResult
operator&(const ImgDrawResult aLeft, const ImgDrawResult aRight)
{
  if (MOZ_LIKELY(aLeft == ImgDrawResult::SUCCESS)) {
    return aRight;
  }
  if (aLeft == ImgDrawResult::BAD_IMAGE && aRight != ImgDrawResult::SUCCESS) {
    return aRight;
  }
  return aLeft;
}

inline ImgDrawResult&
operator&=(ImgDrawResult& aLeft, const ImgDrawResult aRight)
{
  aLeft = aLeft & aRight;
  return aLeft;
}

/**
 * A struct used during painting to provide input flags to determine how
 * imagelib draw calls should behave and an output ImgDrawResult to return
 * information about the result of any imagelib draw calls that may have
 * occurred.
 */
struct imgDrawingParams {
  explicit imgDrawingParams(uint32_t aImageFlags = 0)
    : imageFlags(aImageFlags), result(ImgDrawResult::SUCCESS)
  {}

  const uint32_t imageFlags; // imgIContainer::FLAG_* image flags to pass to
                             // image lib draw calls.
  ImgDrawResult result;         // To return results from image lib painting.
};

} // namespace image
} // namespace mozilla

#endif // mozilla_image_ImgDrawResult_h