C++ DrawTarget::IsValid方法代碼示例

void
BasicPaintedLayer::Validate(LayerManager::DrawPaintedLayerCallback aCallback,
                           void* aCallbackData,
                           ReadbackProcessor* aReadback)
{
  if (!mContentClient) {
    // This client will have a null Forwarder, which means it will not have
    // a ContentHost on the other side.
    mContentClient = new ContentClientBasic(mBackend);
  }

  if (!BasicManager()->IsRetained()) {
    return;
  }

  nsTArray<ReadbackProcessor::Update> readbackUpdates;
  if (aReadback && UsedForReadback()) {
    aReadback->GetPaintedLayerUpdates(this, &readbackUpdates);
  }

  uint32_t flags = 0;
#ifndef MOZ_WIDGET_ANDROID
  if (BasicManager()->CompositorMightResample()) {
    flags |= RotatedContentBuffer::PAINT_WILL_RESAMPLE;
  }
  if (!(flags & RotatedContentBuffer::PAINT_WILL_RESAMPLE)) {
    if (MayResample()) {
      flags |= RotatedContentBuffer::PAINT_WILL_RESAMPLE;
    }
  }
#endif
  if (mDrawAtomically) {
    flags |= RotatedContentBuffer::PAINT_NO_ROTATION;
  }
  PaintState state =
    mContentClient->BeginPaintBuffer(this, flags);
  SubtractFromValidRegion(state.mRegionToInvalidate);

  DrawTarget* target = mContentClient->BorrowDrawTargetForPainting(state);
  if (target && target->IsValid()) {
    // The area that became invalid and is visible needs to be repainted
    // (this could be the whole visible area if our buffer switched
    // from RGB to RGBA, because we might need to repaint with
    // subpixel AA)
    state.mRegionToInvalidate.And(state.mRegionToInvalidate,
                                  GetLocalVisibleRegion().ToUnknownRegion());
    SetAntialiasingFlags(this, target);

    RenderTraceInvalidateStart(this, "FFFF00", state.mRegionToDraw.GetBounds());

    RefPtr<gfxContext> ctx = gfxContext::CreatePreservingTransformOrNull(target);
    MOZ_ASSERT(ctx); // already checked the target above

    PaintBuffer(ctx,
                state.mRegionToDraw, state.mRegionToDraw, state.mRegionToInvalidate,
                state.mDidSelfCopy,
                state.mClip,
                aCallback, aCallbackData);
    MOZ_LAYERS_LOG_IF_SHADOWABLE(this, ("Layer::Mutated(%p) PaintThebes", this));
    Mutated();
    ctx = nullptr;
    mContentClient->ReturnDrawTargetToBuffer(target);
    target = nullptr;

    RenderTraceInvalidateEnd(this, "FFFF00");
  } else {
    if (target) {
      mContentClient->ReturnDrawTargetToBuffer(target);
      target = nullptr;
    }

    // It's possible that state.mRegionToInvalidate is nonempty here,
    // if we are shrinking the valid region to nothing. So use mRegionToDraw
    // instead.
    NS_WARNING_ASSERTION(
      state.mRegionToDraw.IsEmpty(),
      "No context when we have something to draw, resource exhaustion?");
  }

  for (uint32_t i = 0; i < readbackUpdates.Length(); ++i) {
    ReadbackProcessor::Update& update = readbackUpdates[i];
    nsIntPoint offset = update.mLayer->GetBackgroundLayerOffset();
    RefPtr<DrawTarget> dt =
      update.mLayer->GetSink()->BeginUpdate(update.mUpdateRect + offset,
                                            update.mSequenceCounter);
    if (dt) {
      NS_ASSERTION(GetEffectiveOpacity() == 1.0, "Should only read back opaque layers");
      NS_ASSERTION(!GetMaskLayer(), "Should only read back layers without masks");
      dt->SetTransform(dt->GetTransform().PreTranslate(offset.x, offset.y));
      mContentClient->DrawTo(this, dt, 1.0, CompositionOp::OP_OVER,
                             nullptr, nullptr);
      update.mLayer->GetSink()->EndUpdate(update.mUpdateRect + offset);
    }
  }
}

/***
 * If we can, let's paint this ClientPaintedLayer's contents off the main thread.
 * The essential idea is that we ask the ContentClient for a DrawTarget and record
 * the moz2d commands. On the Paint Thread, we replay those commands to the
 * destination draw target. There are a couple of lifetime issues here though:
 *
 * 1) TextureClient owns the underlying buffer and DrawTarget. Because of this
 *    we have to keep the TextureClient and DrawTarget alive but trick the
 *    TextureClient into thinking it's already returned the DrawTarget
 *    since we iterate through different Rects to get DrawTargets*. If
 *    the TextureClient goes away, the DrawTarget and thus buffer can too.
 * 2) When ContentClient::EndPaint happens, it flushes the DrawTarget. We have
 *    to Reflush on the Paint Thread
 * 3) DrawTarget API is NOT thread safe. We get around this by recording
 *    on the main thread and painting on the paint thread. Logically,
 *    ClientLayerManager will force a flushed paint and block the main thread
 *    if we have another transaction. Thus we have a gap between when the main
 *    thread records, the paint thread paints, and we block the main thread
 *    from trying to paint again. The underlying API however is NOT thread safe.
 *  4) We have both "sync" and "async" OMTP. Sync OMTP means we paint on the main thread
 *     but block the main thread while the paint thread paints. Async OMTP doesn't block
 *     the main thread. Sync OMTP is only meant to be used as a debugging tool.
 */
bool
ClientPaintedLayer::PaintOffMainThread()
{
  mContentClient->BeginAsyncPaint();

  uint32_t flags = GetPaintFlags();

  PaintState state = mContentClient->BeginPaintBuffer(this, flags);
  if (!UpdatePaintRegion(state)) {
    return false;
  }

  bool didUpdate = false;
  RotatedContentBuffer::DrawIterator iter;

  // Debug Protip: Change to BorrowDrawTargetForPainting if using sync OMTP.
  while (RefPtr<CapturedPaintState> captureState =
          mContentClient->BorrowDrawTargetForRecording(state, &iter))
  {
    DrawTarget* target = captureState->mTarget;
    if (!target || !target->IsValid()) {
      if (target) {
        mContentClient->ReturnDrawTargetToBuffer(target);
      }
      continue;
    }

    RefPtr<DrawTargetCapture> captureDT =
      Factory::CreateCaptureDrawTarget(target->GetBackendType(),
                                       target->GetSize(),
                                       target->GetFormat());

    captureDT->SetTransform(captureState->mTargetTransform);
    SetAntialiasingFlags(this, captureDT);

    RefPtr<gfxContext> ctx = gfxContext::CreatePreservingTransformOrNull(captureDT);
    MOZ_ASSERT(ctx); // already checked the target above

    ClientManager()->GetPaintedLayerCallback()(this,
                                              ctx,
                                              iter.mDrawRegion,
                                              iter.mDrawRegion,
                                              state.mClip,
                                              state.mRegionToInvalidate,
                                              ClientManager()->GetPaintedLayerCallbackData());

    ctx = nullptr;

    captureState->mCapture = captureDT.forget();
    PaintThread::Get()->PaintContents(captureState,
                                      RotatedContentBuffer::PrepareDrawTargetForPainting);

    mContentClient->ReturnDrawTargetToBuffer(target);

    didUpdate = true;
  }
  mContentClient->EndPaint(nullptr);

  if (didUpdate) {
    UpdateContentClient(state);
  }
  return true;
}