C++ DrawTarget::GetSize方法代碼示例

void
GradientStopsView::UpdateView()
{
  DrawTarget *dt = ui->dtWidget->GetDT();

  dt->FillRect(Rect(0, 0, 100000, 100000), ColorPattern(Color(0.5f, 0.5f, 0.5f, 1.0f)));

  RefPtr<GradientStops> stops = mTranslator->LookupGradientStops(mRefPtr);

  ui->listWidget->clear();
  if (!stops) {
    dt->Flush();
    ui->dtWidget->redraw();
    ui->listWidget->addItem("Dead");
    return;
  }

  IntSize dstSize = dt->GetSize();

  RefPtr<DrawTarget> tmpdt = dt->CreateSimilarDrawTarget(IntSize(20, 20), SurfaceFormat::B8G8R8X8);
  tmpdt->FillRect(Rect(0, 0, 10, 10), ColorPattern(Color(1.0f, 1.0f, 1.0f)));
  tmpdt->FillRect(Rect(10, 10, 10, 10), ColorPattern(Color(1.0f, 1.0f, 1.0f)));
  tmpdt->FillRect(Rect(10, 0, 10, 10), ColorPattern(Color(0.7f, 0.7f, 0.7f)));
  tmpdt->FillRect(Rect(0, 10, 10, 10), ColorPattern(Color(0.7f, 0.7f, 0.7f)));
  RefPtr<SourceSurface> src = tmpdt->Snapshot();
  tmpdt = NULL;

  Rect dstRect(0, 0, dstSize.width, dstSize.height);
  dt->FillRect(dstRect, SurfacePattern(src, ExtendMode::REPEAT));

  dt->FillRect(dstRect, LinearGradientPattern(Point(0, dstSize.height / 2), Point(dstSize.width, dstSize.height / 2), stops));

  dt->Flush();
  ui->dtWidget->redraw();
}

/***
 * 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;
}