gecko-dev/dom/canvas/TexUnpackBlob.cpp

/* -*- Mode: C++; tab-width: 20; 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/. */

#include "TexUnpackBlob.h"

#include "GLBlitHelper.h"
#include "GLContext.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/HTMLCanvasElement.h"
#include "mozilla/RefPtr.h"
#include "nsLayoutUtils.h"
#include "WebGLBuffer.h"
#include "WebGLContext.h"
#include "WebGLFormats.h"
#include "WebGLTexelConversions.h"
#include "WebGLTexture.h"

namespace mozilla {
namespace webgl {

static bool IsPIValidForDOM(const webgl::PackingInfo& pi) {
  // https://www.khronos.org/registry/webgl/specs/latest/2.0/#TEXTURE_TYPES_FORMATS_FROM_DOM_ELEMENTS_TABLE

  // Just check for invalid individual formats and types, not combinations.
  switch (pi.format) {
    case LOCAL_GL_RGB:
    case LOCAL_GL_RGBA:
    case LOCAL_GL_LUMINANCE_ALPHA:
    case LOCAL_GL_LUMINANCE:
    case LOCAL_GL_ALPHA:
    case LOCAL_GL_RED:
    case LOCAL_GL_RED_INTEGER:
    case LOCAL_GL_RG:
    case LOCAL_GL_RG_INTEGER:
    case LOCAL_GL_RGB_INTEGER:
    case LOCAL_GL_RGBA_INTEGER:
      break;

    case LOCAL_GL_SRGB:
    case LOCAL_GL_SRGB_ALPHA:
      // Allowed in WebGL1+EXT_srgb
      break;

    default:
      return false;
  }

  switch (pi.type) {
    case LOCAL_GL_UNSIGNED_BYTE:
    case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
    case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
    case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
    case LOCAL_GL_HALF_FLOAT:
    case LOCAL_GL_HALF_FLOAT_OES:
    case LOCAL_GL_FLOAT:
    case LOCAL_GL_UNSIGNED_INT_10F_11F_11F_REV:
      break;

    default:
      return false;
  }

  return true;
}

static bool ValidatePIForDOM(WebGLContext* webgl,
                             const webgl::PackingInfo& pi) {
  if (!IsPIValidForDOM(pi)) {
    webgl->ErrorInvalidValue("Format or type is invalid for DOM sources.");
    return false;
  }
  return true;
}

static WebGLTexelFormat FormatForPackingInfo(const PackingInfo& pi) {
  switch (pi.type) {
    case LOCAL_GL_UNSIGNED_BYTE:
      switch (pi.format) {
        case LOCAL_GL_RED:
        case LOCAL_GL_LUMINANCE:
        case LOCAL_GL_RED_INTEGER:
          return WebGLTexelFormat::R8;

        case LOCAL_GL_ALPHA:
          return WebGLTexelFormat::A8;

        case LOCAL_GL_LUMINANCE_ALPHA:
          return WebGLTexelFormat::RA8;

        case LOCAL_GL_RGB:
        case LOCAL_GL_RGB_INTEGER:
        case LOCAL_GL_SRGB:
          return WebGLTexelFormat::RGB8;

        case LOCAL_GL_RGBA:
        case LOCAL_GL_RGBA_INTEGER:
        case LOCAL_GL_SRGB_ALPHA:
          return WebGLTexelFormat::RGBA8;

        case LOCAL_GL_RG:
        case LOCAL_GL_RG_INTEGER:
          return WebGLTexelFormat::RG8;

        default:
          break;
      }
      break;

    case LOCAL_GL_UNSIGNED_SHORT_5_6_5:
      if (pi.format == LOCAL_GL_RGB) return WebGLTexelFormat::RGB565;
      break;

    case LOCAL_GL_UNSIGNED_SHORT_5_5_5_1:
      if (pi.format == LOCAL_GL_RGBA) return WebGLTexelFormat::RGBA5551;
      break;

    case LOCAL_GL_UNSIGNED_SHORT_4_4_4_4:
      if (pi.format == LOCAL_GL_RGBA) return WebGLTexelFormat::RGBA4444;
      break;

    case LOCAL_GL_HALF_FLOAT:
    case LOCAL_GL_HALF_FLOAT_OES:
      switch (pi.format) {
        case LOCAL_GL_RED:
        case LOCAL_GL_LUMINANCE:
          return WebGLTexelFormat::R16F;

        case LOCAL_GL_ALPHA:
          return WebGLTexelFormat::A16F;
        case LOCAL_GL_LUMINANCE_ALPHA:
          return WebGLTexelFormat::RA16F;
        case LOCAL_GL_RG:
          return WebGLTexelFormat::RG16F;
        case LOCAL_GL_RGB:
          return WebGLTexelFormat::RGB16F;
        case LOCAL_GL_RGBA:
          return WebGLTexelFormat::RGBA16F;

        default:
          break;
      }
      break;

    case LOCAL_GL_FLOAT:
      switch (pi.format) {
        case LOCAL_GL_RED:
        case LOCAL_GL_LUMINANCE:
          return WebGLTexelFormat::R32F;

        case LOCAL_GL_ALPHA:
          return WebGLTexelFormat::A32F;
        case LOCAL_GL_LUMINANCE_ALPHA:
          return WebGLTexelFormat::RA32F;
        case LOCAL_GL_RG:
          return WebGLTexelFormat::RG32F;
        case LOCAL_GL_RGB:
          return WebGLTexelFormat::RGB32F;
        case LOCAL_GL_RGBA:
          return WebGLTexelFormat::RGBA32F;

        default:
          break;
      }
      break;

    case LOCAL_GL_UNSIGNED_INT_10F_11F_11F_REV:
      if (pi.format == LOCAL_GL_RGB) return WebGLTexelFormat::RGB11F11F10F;
      break;

    default:
      break;
  }

  return WebGLTexelFormat::FormatNotSupportingAnyConversion;
}

////////////////////

static bool ValidateUnpackPixels(WebGLContext* webgl, uint32_t fullRows,
                                 uint32_t tailPixels,
                                 webgl::TexUnpackBlob* blob) {
  if (!blob->mWidth || !blob->mHeight || !blob->mDepth) return true;

  const auto usedPixelsPerRow = CheckedUint32(blob->mSkipPixels) + blob->mWidth;
  if (!usedPixelsPerRow.isValid() ||
      usedPixelsPerRow.value() > blob->mRowLength) {
    webgl->ErrorInvalidOperation(
        "UNPACK_SKIP_PIXELS + width >"
        " UNPACK_ROW_LENGTH.");
    return false;
  }

  if (blob->mHeight > blob->mImageHeight) {
    webgl->ErrorInvalidOperation("height > UNPACK_IMAGE_HEIGHT.");
    return false;
  }

  //////

  // The spec doesn't bound SKIP_ROWS + height <= IMAGE_HEIGHT, unfortunately.
  auto skipFullRows = CheckedUint32(blob->mSkipImages) * blob->mImageHeight;
  skipFullRows += blob->mSkipRows;

  MOZ_ASSERT(blob->mDepth >= 1);
  MOZ_ASSERT(blob->mHeight >= 1);
  auto usedFullRows = CheckedUint32(blob->mDepth - 1) * blob->mImageHeight;
  usedFullRows +=
      blob->mHeight - 1;  // Full rows in the final image, excluding the tail.

  const auto fullRowsNeeded = skipFullRows + usedFullRows;
  if (!fullRowsNeeded.isValid()) {
    webgl->ErrorOutOfMemory("Invalid calculation for required row count.");
    return false;
  }

  if (fullRows > fullRowsNeeded.value()) return true;

  if (fullRows == fullRowsNeeded.value() &&
      tailPixels >= usedPixelsPerRow.value()) {
    blob->mNeedsExactUpload = true;
    return true;
  }

  webgl->ErrorInvalidOperation(
      "Desired upload requires more data than is"
      " available: (%u rows plus %u pixels needed, %u rows"
      " plus %u pixels available)",
      fullRowsNeeded.value(), usedPixelsPerRow.value(), fullRows, tailPixels);
  return false;
}

static bool ValidateUnpackBytes(WebGLContext* webgl,
                                const webgl::PackingInfo& pi,
                                size_t availByteCount,
                                webgl::TexUnpackBlob* blob) {
  if (!blob->mWidth || !blob->mHeight || !blob->mDepth) return true;

  const auto bytesPerPixel = webgl::BytesPerPixel(pi);
  const auto bytesPerRow = CheckedUint32(blob->mRowLength) * bytesPerPixel;
  const auto rowStride = RoundUpToMultipleOf(bytesPerRow, blob->mAlignment);

  const auto fullRows = availByteCount / rowStride;
  if (!fullRows.isValid()) {
    webgl->ErrorOutOfMemory("Unacceptable upload size calculated.");
    return false;
  }

  const auto bodyBytes = fullRows.value() * rowStride.value();
  const auto tailPixels = (availByteCount - bodyBytes) / bytesPerPixel;

  return ValidateUnpackPixels(webgl, fullRows.value(), tailPixels, blob);
}

////////////////////

static uint32_t ZeroOn2D(TexImageTarget target, uint32_t val) {
  return (IsTarget3D(target) ? val : 0);
}

static uint32_t FallbackOnZero(uint32_t val, uint32_t fallback) {
  return (val ? val : fallback);
}

TexUnpackBlob::TexUnpackBlob(const WebGLContext* webgl, TexImageTarget target,
                             uint32_t rowLength, uint32_t width,
                             uint32_t height, uint32_t depth,
                             gfxAlphaType srcAlphaType)
    : mAlignment(webgl->mPixelStore.mUnpackAlignment),
      mRowLength(rowLength),
      mImageHeight(FallbackOnZero(
          ZeroOn2D(target, webgl->mPixelStore.mUnpackImageHeight), height))

      ,
      mSkipPixels(webgl->mPixelStore.mUnpackSkipPixels),
      mSkipRows(webgl->mPixelStore.mUnpackSkipRows),
      mSkipImages(ZeroOn2D(target, webgl->mPixelStore.mUnpackSkipImages))

      ,
      mWidth(width),
      mHeight(height),
      mDepth(depth)

      ,
      mSrcAlphaType(srcAlphaType)

      ,
      mNeedsExactUpload(false) {
  MOZ_ASSERT_IF(!IsTarget3D(target), mDepth == 1);
}

static bool HasColorAndAlpha(const WebGLTexelFormat format) {
  switch (format) {
    case WebGLTexelFormat::RA8:
    case WebGLTexelFormat::RA16F:
    case WebGLTexelFormat::RA32F:
    case WebGLTexelFormat::RGBA8:
    case WebGLTexelFormat::RGBA5551:
    case WebGLTexelFormat::RGBA4444:
    case WebGLTexelFormat::RGBA16F:
    case WebGLTexelFormat::RGBA32F:
    case WebGLTexelFormat::BGRA8:
      return true;
    default:
      return false;
  }
}

bool TexUnpackBlob::ConvertIfNeeded(
    WebGLContext* webgl, const uint32_t rowLength, const uint32_t rowCount,
    WebGLTexelFormat srcFormat, const uint8_t* const srcBegin,
    const ptrdiff_t srcStride, WebGLTexelFormat dstFormat,
    const ptrdiff_t dstStride, const uint8_t** const out_begin,
    UniqueBuffer* const out_anchoredBuffer) const {
  MOZ_ASSERT(srcFormat != WebGLTexelFormat::FormatNotSupportingAnyConversion);
  MOZ_ASSERT(dstFormat != WebGLTexelFormat::FormatNotSupportingAnyConversion);

  *out_begin = srcBegin;

  if (!rowLength || !rowCount) return true;

  const auto srcIsPremult = (mSrcAlphaType == gfxAlphaType::Premult);
  const auto& dstIsPremult = webgl->mPixelStore.mPremultiplyAlpha;
  const auto fnHasPremultMismatch = [&]() {
    if (mSrcAlphaType == gfxAlphaType::Opaque) return false;

    if (!HasColorAndAlpha(srcFormat)) return false;

    return srcIsPremult != dstIsPremult;
  };

  const auto srcOrigin =
      (webgl->mPixelStore.mFlipY ? gl::OriginPos::TopLeft
                                 : gl::OriginPos::BottomLeft);
  const auto dstOrigin = gl::OriginPos::BottomLeft;

  if (srcFormat != dstFormat) {
    webgl->GeneratePerfWarning(
        "Conversion requires pixel reformatting. (%u->%u)", uint32_t(srcFormat),
        uint32_t(dstFormat));
  } else if (fnHasPremultMismatch()) {
    webgl->GeneratePerfWarning(
        "Conversion requires change in"
        " alpha-premultiplication.");
  } else if (srcOrigin != dstOrigin) {
    webgl->GeneratePerfWarning("Conversion requires y-flip.");
  } else if (srcStride != dstStride) {
    webgl->GeneratePerfWarning("Conversion requires change in stride. (%u->%u)",
                               uint32_t(srcStride), uint32_t(dstStride));
  } else {
    return true;
  }

  ////

  const auto dstTotalBytes = CheckedUint32(rowCount) * dstStride;
  if (!dstTotalBytes.isValid()) {
    webgl->ErrorOutOfMemory("Calculation failed.");
    return false;
  }

  UniqueBuffer dstBuffer = calloc(1u, (size_t)dstTotalBytes.value());
  if (!dstBuffer.get()) {
    webgl->ErrorOutOfMemory("Failed to allocate dest buffer.");
    return false;
  }
  const auto dstBegin = static_cast<uint8_t*>(dstBuffer.get());

  ////

  // And go!:
  bool wasTrivial;
  if (!ConvertImage(rowLength, rowCount, srcBegin, srcStride, srcOrigin,
                    srcFormat, srcIsPremult, dstBegin, dstStride, dstOrigin,
                    dstFormat, dstIsPremult, &wasTrivial)) {
    webgl->ErrorImplementationBug("ConvertImage failed.");
    return false;
  }

  *out_begin = dstBegin;
  *out_anchoredBuffer = std::move(dstBuffer);
  return true;
}

static GLenum DoTexOrSubImage(bool isSubImage, gl::GLContext* gl,
                              TexImageTarget target, GLint level,
                              const DriverUnpackInfo* dui, GLint xOffset,
                              GLint yOffset, GLint zOffset, GLsizei width,
                              GLsizei height, GLsizei depth, const void* data) {
  if (isSubImage) {
    return DoTexSubImage(gl, target, level, xOffset, yOffset, zOffset, width,
                         height, depth, dui->ToPacking(), data);
  } else {
    return DoTexImage(gl, target, level, dui, width, height, depth, data);
  }
}

//////////////////////////////////////////////////////////////////////////////////////////
// TexUnpackBytes

TexUnpackBytes::TexUnpackBytes(const WebGLContext* webgl, TexImageTarget target,
                               uint32_t width, uint32_t height, uint32_t depth,
                               bool isClientData, const uint8_t* ptr,
                               size_t availBytes)
    : TexUnpackBlob(webgl, target,
                    FallbackOnZero(webgl->mPixelStore.mUnpackRowLength, width),
                    width, height, depth, gfxAlphaType::NonPremult),
      mIsClientData(isClientData),
      mPtr(ptr),
      mAvailBytes(availBytes) {}

bool TexUnpackBytes::Validate(WebGLContext* webgl,
                              const webgl::PackingInfo& pi) {
  if (mIsClientData && !mPtr) return true;

  return ValidateUnpackBytes(webgl, pi, mAvailBytes, this);
}

bool TexUnpackBytes::TexOrSubImage(bool isSubImage, bool needsRespec,
                                   WebGLTexture* tex, TexImageTarget target,
                                   GLint level,
                                   const webgl::DriverUnpackInfo* dui,
                                   GLint xOffset, GLint yOffset, GLint zOffset,
                                   const webgl::PackingInfo& pi,
                                   GLenum* const out_error) const {
  WebGLContext* webgl = tex->mContext;

  const auto format = FormatForPackingInfo(pi);
  const auto bytesPerPixel = webgl::BytesPerPixel(pi);

  const uint8_t* uploadPtr = mPtr;
  UniqueBuffer tempBuffer;

  do {
    if (!mIsClientData || !mPtr) break;

    if (!webgl->mPixelStore.mFlipY && !webgl->mPixelStore.mPremultiplyAlpha) {
      break;
    }

    if (webgl->mPixelStore.mUnpackImageHeight ||
        webgl->mPixelStore.mUnpackSkipImages ||
        webgl->mPixelStore.mUnpackRowLength ||
        webgl->mPixelStore.mUnpackSkipRows ||
        webgl->mPixelStore.mUnpackSkipPixels) {
      webgl->ErrorInvalidOperation(
          "Non-DOM-Element uploads with alpha-premult"
          " or y-flip do not support subrect selection.");
      return false;
    }

    webgl->GenerateWarning(
        "Alpha-premult and y-flip are deprecated for"
        " non-DOM-Element uploads.");

    const uint32_t rowLength = mWidth;
    const uint32_t rowCount = mHeight * mDepth;
    const auto stride =
        RoundUpToMultipleOf(rowLength * bytesPerPixel, mAlignment);
    if (!ConvertIfNeeded(webgl, rowLength, rowCount, format, mPtr, stride,
                         format, stride, &uploadPtr, &tempBuffer)) {
      return false;
    }
  } while (false);

  //////

  const auto& gl = webgl->gl;

  bool useParanoidHandling = false;
  if (mNeedsExactUpload && webgl->mBoundPixelUnpackBuffer) {
    webgl->GenerateWarning(
        "Uploads from a buffer with a final row with a byte"
        " count smaller than the row stride can incur extra"
        " overhead.");

    if (gl->WorkAroundDriverBugs()) {
      useParanoidHandling |= (gl->Vendor() == gl::GLVendor::NVIDIA);
    }
  }

  if (!useParanoidHandling) {
    if (webgl->mBoundPixelUnpackBuffer) {
      gl->fBindBuffer(LOCAL_GL_PIXEL_UNPACK_BUFFER,
                      webgl->mBoundPixelUnpackBuffer->mGLName);
    }

    *out_error =
        DoTexOrSubImage(isSubImage, gl, target, level, dui, xOffset, yOffset,
                        zOffset, mWidth, mHeight, mDepth, uploadPtr);

    if (webgl->mBoundPixelUnpackBuffer) {
      gl->fBindBuffer(LOCAL_GL_PIXEL_UNPACK_BUFFER, 0);
    }
    return true;
  }

  //////

  MOZ_ASSERT(webgl->mBoundPixelUnpackBuffer);

  if (!isSubImage) {
    // Alloc first to catch OOMs.
    AssertUintParamCorrect(gl, LOCAL_GL_PIXEL_UNPACK_BUFFER, 0);
    *out_error =
        DoTexOrSubImage(false, gl, target, level, dui, xOffset, yOffset,
                        zOffset, mWidth, mHeight, mDepth, nullptr);
    if (*out_error) return true;
  }

  const ScopedLazyBind bindPBO(gl, LOCAL_GL_PIXEL_UNPACK_BUFFER,
                               webgl->mBoundPixelUnpackBuffer);

  //////

  // Make our sometimes-implicit values explicit. Also this keeps them constant
  // when we ask for height=mHeight-1 and such.
  gl->fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, mRowLength);
  gl->fPixelStorei(LOCAL_GL_UNPACK_IMAGE_HEIGHT, mImageHeight);

  if (mDepth > 1) {
    *out_error =
        DoTexOrSubImage(true, gl, target, level, dui, xOffset, yOffset, zOffset,
                        mWidth, mHeight, mDepth - 1, uploadPtr);
  }

  // Skip the images we uploaded.
  gl->fPixelStorei(LOCAL_GL_UNPACK_SKIP_IMAGES, mSkipImages + mDepth - 1);

  if (mHeight > 1) {
    *out_error = DoTexOrSubImage(true, gl, target, level, dui, xOffset, yOffset,
                                 zOffset + mDepth - 1, mWidth, mHeight - 1, 1,
                                 uploadPtr);
  }

  const auto totalSkipRows =
      CheckedUint32(mSkipImages) * mImageHeight + mSkipRows;
  const auto totalFullRows =
      CheckedUint32(mDepth - 1) * mImageHeight + mHeight - 1;
  const auto tailOffsetRows = totalSkipRows + totalFullRows;

  const auto bytesPerRow = CheckedUint32(mRowLength) * bytesPerPixel;
  const auto rowStride = RoundUpToMultipleOf(bytesPerRow, mAlignment);
  if (!rowStride.isValid()) {
    MOZ_CRASH("Should be checked earlier.");
  }
  const auto tailOffsetBytes = tailOffsetRows * rowStride;

  uploadPtr += tailOffsetBytes.value();

  //////

  gl->fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, 1);    // No stride padding.
  gl->fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, 0);   // No padding in general.
  gl->fPixelStorei(LOCAL_GL_UNPACK_SKIP_IMAGES, 0);  // Don't skip images,
  gl->fPixelStorei(LOCAL_GL_UNPACK_SKIP_ROWS,
                   0);  // or rows.
                        // Keep skipping pixels though!

  *out_error = DoTexOrSubImage(true, gl, target, level, dui, xOffset,
                               yOffset + mHeight - 1, zOffset + mDepth - 1,
                               mWidth, 1, 1, uploadPtr);

  // Reset all our modified state.
  gl->fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                   webgl->mPixelStore.mUnpackAlignment);
  gl->fPixelStorei(LOCAL_GL_UNPACK_IMAGE_HEIGHT,
                   webgl->mPixelStore.mUnpackImageHeight);
  gl->fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH,
                   webgl->mPixelStore.mUnpackRowLength);
  gl->fPixelStorei(LOCAL_GL_UNPACK_SKIP_IMAGES,
                   webgl->mPixelStore.mUnpackSkipImages);
  gl->fPixelStorei(LOCAL_GL_UNPACK_SKIP_ROWS,
                   webgl->mPixelStore.mUnpackSkipRows);

  return true;
}

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// TexUnpackImage

TexUnpackImage::TexUnpackImage(const WebGLContext* webgl, TexImageTarget target,
                               uint32_t width, uint32_t height, uint32_t depth,
                               layers::Image* image, gfxAlphaType srcAlphaType)
    : TexUnpackBlob(webgl, target, image->GetSize().width, width, height, depth,
                    srcAlphaType),
      mImage(image) {}

TexUnpackImage::~TexUnpackImage() = default;

bool TexUnpackImage::Validate(WebGLContext* webgl,
                              const webgl::PackingInfo& pi) {
  if (!ValidatePIForDOM(webgl, pi)) return false;

  const auto fullRows = mImage->GetSize().height;
  return ValidateUnpackPixels(webgl, fullRows, 0, this);
}

bool TexUnpackImage::TexOrSubImage(bool isSubImage, bool needsRespec,
                                   WebGLTexture* tex, TexImageTarget target,
                                   GLint level,
                                   const webgl::DriverUnpackInfo* dui,
                                   GLint xOffset, GLint yOffset, GLint zOffset,
                                   const webgl::PackingInfo& pi,
                                   GLenum* const out_error) const {
  MOZ_ASSERT_IF(needsRespec, !isSubImage);

  WebGLContext* webgl = tex->mContext;

  gl::GLContext* gl = webgl->GL();

  if (needsRespec) {
    *out_error =
        DoTexOrSubImage(isSubImage, gl, target.get(), level, dui, xOffset,
                        yOffset, zOffset, mWidth, mHeight, mDepth, nullptr);
    if (*out_error) return true;
  }

  const char* fallbackReason;
  do {
    if (mDepth != 1) {
      fallbackReason = "depth is not 1";
      break;
    }
    if (xOffset != 0 || yOffset != 0 || zOffset != 0) {
      fallbackReason = "x/y/zOffset is not 0";
      break;
    }

    if (webgl->mPixelStore.mUnpackSkipPixels ||
        webgl->mPixelStore.mUnpackSkipRows ||
        webgl->mPixelStore.mUnpackSkipImages) {
      fallbackReason = "non-zero UNPACK_SKIP_* not yet supported";
      break;
    }

    const auto fnHasPremultMismatch = [&]() {
      if (mSrcAlphaType == gfxAlphaType::Opaque) return false;

      const bool srcIsPremult = (mSrcAlphaType == gfxAlphaType::Premult);
      const auto& dstIsPremult = webgl->mPixelStore.mPremultiplyAlpha;
      if (srcIsPremult == dstIsPremult) return false;

      if (dstIsPremult) {
        fallbackReason = "UNPACK_PREMULTIPLY_ALPHA_WEBGL is not true";
      } else {
        fallbackReason = "UNPACK_PREMULTIPLY_ALPHA_WEBGL is not false";
      }
      return true;
    };
    if (fnHasPremultMismatch()) break;

    if (dui->unpackFormat != LOCAL_GL_RGB &&
        dui->unpackFormat != LOCAL_GL_RGBA) {
      fallbackReason = "`format` is not RGB or RGBA";
      break;
    }

    if (dui->unpackType != LOCAL_GL_UNSIGNED_BYTE) {
      fallbackReason = "`type` is not UNSIGNED_BYTE";
      break;
    }

    gl::ScopedFramebuffer scopedFB(gl);
    gl::ScopedBindFramebuffer bindFB(gl, scopedFB.FB());

    {
      gl::GLContext::LocalErrorScope errorScope(*gl);

      gl->fFramebufferTexture2D(LOCAL_GL_FRAMEBUFFER,
                                LOCAL_GL_COLOR_ATTACHMENT0, target.get(),
                                tex->mGLName, level);

      if (errorScope.GetError()) {
        fallbackReason = "bug: failed to attach to FB for blit";
        break;
      }
    }

    const GLenum status = gl->fCheckFramebufferStatus(LOCAL_GL_FRAMEBUFFER);
    if (status != LOCAL_GL_FRAMEBUFFER_COMPLETE) {
      fallbackReason = "bug: failed to confirm FB for blit";
      break;
    }

    const gfx::IntSize dstSize(mWidth, mHeight);
    const auto dstOrigin =
        (webgl->mPixelStore.mFlipY ? gl::OriginPos::TopLeft
                                   : gl::OriginPos::BottomLeft);
    if (!gl->BlitHelper()->BlitImageToFramebuffer(mImage, dstSize, dstOrigin)) {
      fallbackReason = "likely bug: failed to blit";
      break;
    }

    // Blitting was successful, so we're done!
    *out_error = 0;
    return true;
  } while (false);

  const nsPrintfCString perfMsg(
      "Failed to hit GPU-copy fast-path: %s (src type %u)", fallbackReason,
      uint32_t(mImage->GetFormat()));

  if (webgl->mPixelStore.mRequireFastPath) {
    webgl->ErrorInvalidOperation("%s", perfMsg.BeginReading());
    return false;
  }

  webgl->GeneratePerfWarning("%s Falling back to CPU upload.",
                             perfMsg.BeginReading());

  const RefPtr<gfx::SourceSurface> surf = mImage->GetAsSourceSurface();

  RefPtr<gfx::DataSourceSurface> dataSurf;
  if (surf) {
    // WARNING: OSX can lose our MakeCurrent here.
    dataSurf = surf->GetDataSurface();
  }
  if (!dataSurf) {
    webgl->ErrorOutOfMemory(
        "GetAsSourceSurface or GetDataSurface failed after"
        " blit failed for TexUnpackImage.");
    return false;
  }

  const TexUnpackSurface surfBlob(webgl, target, mWidth, mHeight, mDepth,
                                  dataSurf, mSrcAlphaType);

  return surfBlob.TexOrSubImage(isSubImage, needsRespec, tex, target, level,
                                dui, xOffset, yOffset, zOffset, pi, out_error);
}

////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////////
// TexUnpackSurface

TexUnpackSurface::TexUnpackSurface(const WebGLContext* webgl,
                                   TexImageTarget target, uint32_t width,
                                   uint32_t height, uint32_t depth,
                                   gfx::DataSourceSurface* surf,
                                   gfxAlphaType srcAlphaType)
    : TexUnpackBlob(webgl, target, surf->GetSize().width, width, height, depth,
                    srcAlphaType),
      mSurf(surf) {}

//////////

static bool GetFormatForSurf(gfx::SourceSurface* surf,
                             WebGLTexelFormat* const out_texelFormat,
                             uint8_t* const out_bpp) {
  const auto surfFormat = surf->GetFormat();
  switch (surfFormat) {
    case gfx::SurfaceFormat::B8G8R8A8:
      *out_texelFormat = WebGLTexelFormat::BGRA8;
      *out_bpp = 4;
      return true;

    case gfx::SurfaceFormat::B8G8R8X8:
      *out_texelFormat = WebGLTexelFormat::BGRX8;
      *out_bpp = 4;
      return true;

    case gfx::SurfaceFormat::R8G8B8A8:
      *out_texelFormat = WebGLTexelFormat::RGBA8;
      *out_bpp = 4;
      return true;

    case gfx::SurfaceFormat::R8G8B8X8:
      *out_texelFormat = WebGLTexelFormat::RGBX8;
      *out_bpp = 4;
      return true;

    case gfx::SurfaceFormat::R5G6B5_UINT16:
      *out_texelFormat = WebGLTexelFormat::RGB565;
      *out_bpp = 2;
      return true;

    case gfx::SurfaceFormat::A8:
      *out_texelFormat = WebGLTexelFormat::A8;
      *out_bpp = 1;
      return true;

    case gfx::SurfaceFormat::YUV:
      // Ugh...
      NS_ERROR("We don't handle uploads from YUV sources yet.");
      // When we want to, check out gfx/ycbcr/YCbCrUtils.h. (specifically
      // GetYCbCrToRGBDestFormatAndSize and ConvertYCbCrToRGB)
      return false;

    default:
      return false;
  }
}

//////////

bool TexUnpackSurface::Validate(WebGLContext* webgl,
                                const webgl::PackingInfo& pi) {
  if (!ValidatePIForDOM(webgl, pi)) return false;

  const auto fullRows = mSurf->GetSize().height;
  return ValidateUnpackPixels(webgl, fullRows, 0, this);
}

bool TexUnpackSurface::TexOrSubImage(
    bool isSubImage, bool needsRespec, WebGLTexture* tex, TexImageTarget target,
    GLint level, const webgl::DriverUnpackInfo* dui, GLint xOffset,
    GLint yOffset, GLint zOffset, const webgl::PackingInfo& dstPI,
    GLenum* const out_error) const {
  const auto& webgl = tex->mContext;

  ////

  const auto rowLength = mSurf->GetSize().width;
  const auto rowCount = mSurf->GetSize().height;

  const auto& dstBPP = webgl::BytesPerPixel(dstPI);
  const auto dstFormat = FormatForPackingInfo(dstPI);

  ////

  WebGLTexelFormat srcFormat;
  uint8_t srcBPP;
  if (!GetFormatForSurf(mSurf, &srcFormat, &srcBPP)) {
    webgl->ErrorImplementationBug(
        "GetFormatForSurf failed for"
        " WebGLTexelFormat::%u.",
        uint32_t(mSurf->GetFormat()));
    return false;
  }

  gfx::DataSourceSurface::ScopedMap map(mSurf,
                                        gfx::DataSourceSurface::MapType::READ);
  if (!map.IsMapped()) {
    webgl->ErrorOutOfMemory("Failed to map source surface for upload.");
    return false;
  }

  const auto& srcBegin = map.GetData();
  const auto& srcStride = map.GetStride();

  ////

  const auto srcRowLengthBytes = rowLength * srcBPP;

  const uint8_t maxGLAlignment = 8;
  uint8_t srcAlignment = 1;
  for (; srcAlignment <= maxGLAlignment; srcAlignment *= 2) {
    const auto strideGuess =
        RoundUpToMultipleOf(srcRowLengthBytes, srcAlignment);
    if (strideGuess == srcStride) break;
  }
  const uint32_t dstAlignment =
      (srcAlignment > maxGLAlignment) ? 1 : srcAlignment;

  const auto dstRowLengthBytes = rowLength * dstBPP;
  const auto dstStride = RoundUpToMultipleOf(dstRowLengthBytes, dstAlignment);

  ////

  const uint8_t* dstBegin = srcBegin;
  UniqueBuffer tempBuffer;
  if (!ConvertIfNeeded(webgl, rowLength, rowCount, srcFormat, srcBegin,
                       srcStride, dstFormat, dstStride, &dstBegin,
                       &tempBuffer)) {
    return false;
  }

  ////

  const auto& gl = webgl->gl;
  if (!gl->MakeCurrent()) {
    *out_error = LOCAL_GL_CONTEXT_LOST;
    return true;
  }

  gl->fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT, dstAlignment);
  if (webgl->IsWebGL2()) {
    gl->fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH, rowLength);
  }

  *out_error =
      DoTexOrSubImage(isSubImage, gl, target.get(), level, dui, xOffset,
                      yOffset, zOffset, mWidth, mHeight, mDepth, dstBegin);

  gl->fPixelStorei(LOCAL_GL_UNPACK_ALIGNMENT,
                   webgl->mPixelStore.mUnpackAlignment);
  if (webgl->IsWebGL2()) {
    gl->fPixelStorei(LOCAL_GL_UNPACK_ROW_LENGTH,
                     webgl->mPixelStore.mUnpackRowLength);
  }

  return true;
}

}  // namespace webgl
}  // namespace mozilla