C++ DrawTarget類代碼示例

CGContextRef
gfxQuartzNativeDrawing::BeginNativeDrawing()
{
  NS_ASSERTION(!mCGContext, "BeginNativeDrawing called when drawing already in progress");

  if (mContext->IsCairo()) {
    // We're past that now. Any callers that still supply a Cairo context
    // don't deserve native theming.
    NS_WARNING("gfxQuartzNativeDrawing being used with a gfxContext that is not backed by a DrawTarget");
    return nullptr;
  }

  DrawTarget *dt = mContext->GetDrawTarget();
  if (dt->GetBackendType() != BackendType::COREGRAPHICS || dt->IsDualDrawTarget()) {
    IntSize backingSize(NSToIntFloor(mNativeRect.width * mBackingScale),
                        NSToIntFloor(mNativeRect.height * mBackingScale));

    if (backingSize.IsEmpty()) {
      return nullptr;
    }

    mDrawTarget = Factory::CreateDrawTarget(BackendType::COREGRAPHICS, backingSize, SurfaceFormat::B8G8R8A8);

    Matrix transform;
    transform.Scale(mBackingScale, mBackingScale);
    transform.Translate(-mNativeRect.x, -mNativeRect.y);

    mDrawTarget->SetTransform(transform);
    dt = mDrawTarget;
  }

  mCGContext = mBorrowedContext.Init(dt);
  MOZ_ASSERT(mCGContext);
  return mCGContext;
}

void 
ClientLayerManager::MakeSnapshotIfRequired()
{
  if (!mShadowTarget) {
    return;
  }
  if (mWidget) {
    if (CompositorChild* remoteRenderer = GetRemoteRenderer()) {
      nsIntRect bounds;
      mWidget->GetBounds(bounds);
      IntSize widgetSize = bounds.Size().ToIntSize();
      SurfaceDescriptor inSnapshot, snapshot;
      if (mForwarder->AllocSurfaceDescriptor(widgetSize,
                                             gfxContentType::COLOR_ALPHA,
                                             &inSnapshot) &&
          // The compositor will usually reuse |snapshot| and return
          // it through |outSnapshot|, but if it doesn't, it's
          // responsible for freeing |snapshot|.
          remoteRenderer->SendMakeSnapshot(inSnapshot, &snapshot)) {
        RefPtr<DataSourceSurface> surf = GetSurfaceForDescriptor(snapshot);
        DrawTarget* dt = mShadowTarget->GetDrawTarget();
        Rect widgetRect(Point(0, 0), Size(widgetSize.width, widgetSize.height));
        dt->DrawSurface(surf, widgetRect, widgetRect,
                        DrawSurfaceOptions(),
                        DrawOptions(1.0f, CompositionOp::OP_OVER));
      }
      if (IsSurfaceDescriptorValid(snapshot)) {
        mForwarder->DestroySharedSurface(&snapshot);
      }
    }
  }
  mShadowTarget = nullptr;
}

static void
RepeatOrStretchSurface(DrawTarget& aDT, SourceSurface* aSurface,
                       const Rect& aDest, const Rect& aSrc, Rect& aSkipRect)
{
  if (aSkipRect.Contains(aDest)) {
    return;
  }

  if ((!aDT.GetTransform().IsRectilinear() &&
       aDT.GetBackendType() != BackendType::CAIRO) ||
      (aDT.GetBackendType() == BackendType::DIRECT2D)) {
    // Use stretching if possible, since it leads to less seams when the
    // destination is transformed. However, don't do this if we're using cairo,
    // because if cairo is using pixman it won't render anything for large
    // stretch factors because pixman's internal fixed point precision is not
    // high enough to handle those scale factors.
    // Calling FillRect on a D2D backend with a repeating pattern is much slower
    // than DrawSurface, so special case the D2D backend here.
    aDT.DrawSurface(aSurface, aDest, aSrc);
    return;
  }

  SurfacePattern pattern(aSurface, ExtendMode::REPEAT,
                         Matrix::Translation(aDest.TopLeft() - aSrc.TopLeft()),
                         Filter::GOOD, RoundedToInt(aSrc));
  aDT.FillRect(aDest, pattern);
}

void
ClientLayerManager::MakeSnapshotIfRequired()
{
  if (!mShadowTarget) {
    return;
  }
  if (mWidget) {
    if (CompositorChild* remoteRenderer = GetRemoteRenderer()) {
      nsIntRect bounds = ToOutsideIntRect(mShadowTarget->GetClipExtents());
      SurfaceDescriptor inSnapshot;
      if (!bounds.IsEmpty() &&
          mForwarder->AllocSurfaceDescriptor(bounds.Size().ToIntSize(),
                                             gfxContentType::COLOR_ALPHA,
                                             &inSnapshot) &&
          remoteRenderer->SendMakeSnapshot(inSnapshot, bounds)) {
        RefPtr<DataSourceSurface> surf = GetSurfaceForDescriptor(inSnapshot);
        DrawTarget* dt = mShadowTarget->GetDrawTarget();
        Rect dstRect(bounds.x, bounds.y, bounds.width, bounds.height);
        Rect srcRect(0, 0, bounds.width, bounds.height);
        dt->DrawSurface(surf, dstRect, srcRect,
                        DrawSurfaceOptions(),
                        DrawOptions(1.0f, CompositionOp::OP_OVER));
      }
      mForwarder->DestroySharedSurface(&inSnapshot);
    }
  }
  mShadowTarget = nullptr;
}

void nsCaret::PaintCaret(DrawTarget& aDrawTarget,
                         nsIFrame* aForFrame,
                         const nsPoint &aOffset)
{
  int32_t contentOffset;
  nsIFrame* frame = GetFrameAndOffset(GetSelectionInternal(),
    mOverrideContent, mOverrideOffset, &contentOffset);
  if (!frame) {
    return;
  }
  NS_ASSERTION(frame == aForFrame, "We're referring different frame");

  int32_t appUnitsPerDevPixel = frame->PresContext()->AppUnitsPerDevPixel();

  nsRect caretRect;
  nsRect hookRect;
  ComputeCaretRects(frame, contentOffset, &caretRect, &hookRect);

  Rect devPxCaretRect =
    NSRectToSnappedRect(caretRect + aOffset, appUnitsPerDevPixel, aDrawTarget);
  Rect devPxHookRect =
    NSRectToSnappedRect(hookRect + aOffset, appUnitsPerDevPixel, aDrawTarget);
  ColorPattern color(ToDeviceColor(frame->GetCaretColorAt(contentOffset)));

  aDrawTarget.FillRect(devPxCaretRect, color);
  if (!hookRect.IsEmpty()) {
    aDrawTarget.FillRect(devPxHookRect, color);
  }
}

already_AddRefed<Path>
nsSVGPathGeometryElement::GetOrBuildPath(const DrawTarget& aDrawTarget,
                                         FillRule aFillRule)
{
  // We only cache the path if it matches the backend used for screen painting:
  bool cacheable  = aDrawTarget.GetBackendType() ==
                    gfxPlatform::GetPlatform()->GetDefaultContentBackend();

  // Checking for and returning mCachedPath before checking the pref means
  // that the pref is only live on page reload (or app restart for SVG in
  // chrome). The benefit is that we avoid causing a CPU memory cache miss by
  // looking at the global variable that the pref's stored in.
  if (cacheable && mCachedPath) {
    if (aDrawTarget.GetBackendType() == mCachedPath->GetBackendType()) {
      RefPtr<Path> path(mCachedPath);
      return path.forget();
    }
  }
  RefPtr<PathBuilder> builder = aDrawTarget.CreatePathBuilder(aFillRule);
  RefPtr<Path> path = BuildPath(builder);
  if (cacheable && NS_SVGPathCachingEnabled()) {
    mCachedPath = path;
  }
  return path.forget();
}

  virtual void ProcessReadback(gfx::DataSourceSurface *aSourceSurface)
  {
    SourceRotatedBuffer rotBuffer(aSourceSurface, nullptr, mBufferRect, mBufferRotation);

    for (uint32_t i = 0; i < mReadbackUpdates.Length(); ++i) {
      ReadbackProcessor::Update& update = mReadbackUpdates[i];
      nsIntPoint offset = update.mLayer->GetBackgroundLayerOffset();

      ReadbackSink* sink = update.mLayer->GetSink();

      if (!sink) {
        continue;
      }

      if (!aSourceSurface) {
        sink->SetUnknown(update.mSequenceCounter);
        continue;
      }

      nsRefPtr<gfxContext> ctx =
        sink->BeginUpdate(update.mUpdateRect + offset, update.mSequenceCounter);

      if (!ctx) {
        continue;
      }

      DrawTarget* dt = ctx->GetDrawTarget();
      dt->SetTransform(Matrix::Translation(offset.x, offset.y));

      rotBuffer.DrawBufferWithRotation(dt, RotatedBuffer::BUFFER_BLACK);

      update.mLayer->GetSink()->EndUpdate(ctx, update.mUpdateRect + offset);
    }
  }

void
StrokeSnappedEdgesOfRect(const Rect& aRect, DrawTarget& aDrawTarget,
                        const ColorPattern& aColor,
                        const StrokeOptions& aStrokeOptions)
{
  if (aRect.IsEmpty()) {
    return;
  }

  Point p1 = aRect.TopLeft();
  Point p2 = aRect.BottomLeft();
  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget);
  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);

  p1 = aRect.BottomLeft();
  p2 = aRect.BottomRight();
  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget);
  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);

  p1 = aRect.TopLeft();
  p2 = aRect.TopRight();
  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget);
  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);

  p1 = aRect.TopRight();
  p2 = aRect.BottomRight();
  SnapLineToDevicePixelsForStroking(p1, p2, aDrawTarget);
  aDrawTarget.StrokeLine(p1, p2, aColor, aStrokeOptions);
}

/***
 * Blur an inset box shadow by doing:
 * 1) Create a minimal box shadow path that creates a frame.
 * 2) Draw the box shadow portion over the destination surface.
 * 3) The "inset" part is created by a clip rect that properly clips
 *    the alpha mask so that it has clean edges. We still create the full
 *    proper alpha mask, but let the clip deal with the clean edges.
 *
 * All parameters should already be in device pixels.
 */
void
gfxAlphaBoxBlur::BlurInsetBox(gfxContext* aDestinationCtx,
                              const Rect aDestinationRect,
                              const Rect aShadowClipRect,
                              const gfxIntSize aBlurRadius,
                              const gfxIntSize aSpreadRadius,
                              const Color& aShadowColor,
                              bool aHasBorderRadius,
                              const RectCornerRadii& aInnerClipRadii,
                              const Rect aSkipRect)
{
  if ((aBlurRadius.width <= 0 && aBlurRadius.height <= 0)) {
    // The outer path must be rounded out
    // If not blurring, we're done now.
    Rect pathRect(aDestinationRect);
    pathRect.RoundOut();
    FillDestinationPath(aDestinationCtx, pathRect, aShadowClipRect,
        aShadowColor, aHasBorderRadius, aInnerClipRadii);
    return;
  }

  DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();
  Rect outerRect;
  Rect innerRect;
  Margin pathMargins;
  ComputeRectsForInsetBoxShadow(aBlurRadius, aSpreadRadius,
                                aDestinationRect, aShadowClipRect,
                                outerRect, innerRect,
                                pathMargins);
  IntPoint topLeft;
  RefPtr<SourceSurface> minInsetBlur = GetInsetBlur(outerRect, innerRect,
                                                    aBlurRadius, aSpreadRadius,
                                                    aInnerClipRadii, aShadowColor,
                                                    aHasBorderRadius,
                                                    topLeft, aDestinationCtx);
  if (!minInsetBlur) {
    return;
  }

  Rect destRectOuter(aDestinationRect);
  destRectOuter.RoundIn();
  Rect destRectInner(destRectOuter);
  destRectInner.Deflate(pathMargins);

  Rect srcRectOuter(outerRect);
  srcRectOuter.MoveBy(abs(topLeft.x), abs(topLeft.y));
  Rect srcRectInner(srcRectOuter);
  srcRectInner.Deflate(pathMargins);

  if (srcRectOuter.IsEqualInterior(srcRectInner)) {
    destDrawTarget->DrawSurface(minInsetBlur, destRectOuter, srcRectOuter);
  } else {
    DrawBoxShadows(*destDrawTarget, minInsetBlur,
                   destRectOuter, destRectInner,
                   srcRectOuter, srcRectInner,
                   aSkipRect);
 }
}

void
gfxContext::PushGroupAndCopyBackground(gfxContentType content)
{
  IntRect clipExtents;
  if (mDT->GetFormat() != SurfaceFormat::B8G8R8X8) {
    gfxRect clipRect = GetRoundOutDeviceClipExtents(this);
    clipExtents = IntRect(clipRect.x, clipRect.y, clipRect.width, clipRect.height);
  }
  if ((mDT->GetFormat() == SurfaceFormat::B8G8R8X8 ||
       mDT->GetOpaqueRect().Contains(clipExtents)) &&
      !mDT->GetUserData(&sDontUseAsSourceKey)) {
    DrawTarget *oldDT = mDT;
    RefPtr<SourceSurface> source = mDT->Snapshot();
    Point oldDeviceOffset = CurrentState().deviceOffset;

    PushNewDT(gfxContentType::COLOR);

    if (oldDT == mDT) {
      // Creating new DT failed.
      return;
    }

    Point offset = CurrentState().deviceOffset - oldDeviceOffset;
    Rect surfRect(0, 0, Float(mDT->GetSize().width), Float(mDT->GetSize().height));
    Rect sourceRect = surfRect + offset;

    mDT->SetTransform(Matrix());

    // XXX: It's really sad that we have to do this (for performance).
    // Once DrawTarget gets a PushLayer API we can implement this within
    // DrawTargetTiled.
    if (source->GetType() == SurfaceType::TILED) {
      SnapshotTiled *sourceTiled = static_cast<SnapshotTiled*>(source.get());
      for (uint32_t i = 0; i < sourceTiled->mSnapshots.size(); i++) {
        Rect tileSourceRect = sourceRect.Intersect(Rect(sourceTiled->mOrigins[i].x,
                                                        sourceTiled->mOrigins[i].y,
                                                        sourceTiled->mSnapshots[i]->GetSize().width,
                                                        sourceTiled->mSnapshots[i]->GetSize().height));

        if (tileSourceRect.IsEmpty()) {
          continue;
        }
        Rect tileDestRect = tileSourceRect - offset;
        tileSourceRect -= sourceTiled->mOrigins[i];

        mDT->DrawSurface(sourceTiled->mSnapshots[i], tileDestRect, tileSourceRect);
      }
    } else {
      mDT->DrawSurface(source, surfRect, sourceRect);
    }
    mDT->SetOpaqueRect(oldDT->GetOpaqueRect());

    PushClipsToDT(mDT);
    mDT->SetTransform(GetDTTransform());
    return;
  }
  PushGroup(content);
}

DrawTarget*
ContentClientIncremental::BorrowDrawTargetForPainting(const PaintState& aPaintState,
        RotatedContentBuffer::DrawIterator* aIter)
{
    if (aPaintState.mMode == SurfaceMode::SURFACE_NONE) {
        return nullptr;
    }

    if (aIter) {
        if (aIter->mCount++ > 0) {
            return nullptr;
        }
        aIter->mDrawRegion = aPaintState.mRegionToDraw;
    }

    DrawTarget* result = nullptr;

    nsIntRect drawBounds = aPaintState.mRegionToDraw.GetBounds();
    MOZ_ASSERT(!mLoanedDrawTarget);

    // BeginUpdate is allowed to modify the given region,
    // if it wants more to be repainted than we request.
    if (aPaintState.mMode == SurfaceMode::SURFACE_COMPONENT_ALPHA) {
        nsIntRegion drawRegionCopy = aPaintState.mRegionToDraw;
        RefPtr<DrawTarget> onBlack = GetUpdateSurface(BUFFER_BLACK, drawRegionCopy);
        RefPtr<DrawTarget> onWhite = GetUpdateSurface(BUFFER_WHITE, aPaintState.mRegionToDraw);
        if (onBlack && onWhite) {
            NS_ASSERTION(aPaintState.mRegionToDraw == drawRegionCopy,
                         "BeginUpdate should always modify the draw region in the same way!");
            FillSurface(onBlack, aPaintState.mRegionToDraw, nsIntPoint(drawBounds.x, drawBounds.y), gfxRGBA(0.0, 0.0, 0.0, 1.0));
            FillSurface(onWhite, aPaintState.mRegionToDraw, nsIntPoint(drawBounds.x, drawBounds.y), gfxRGBA(1.0, 1.0, 1.0, 1.0));
            mLoanedDrawTarget = Factory::CreateDualDrawTarget(onBlack, onWhite);
        } else {
            mLoanedDrawTarget = nullptr;
        }
    } else {
        mLoanedDrawTarget = GetUpdateSurface(BUFFER_BLACK, aPaintState.mRegionToDraw);
    }
    if (!mLoanedDrawTarget) {
        NS_WARNING("unable to get context for update");
        return nullptr;
    }

    result = mLoanedDrawTarget;
    mLoanedTransform = mLoanedDrawTarget->GetTransform();
    mLoanedTransform.Translate(-drawBounds.x, -drawBounds.y);
    result->SetTransform(mLoanedTransform);
    mLoanedTransform.Translate(drawBounds.x, drawBounds.y);

    if (mContentType == gfxContentType::COLOR_ALPHA) {
        gfxUtils::ClipToRegion(result, aPaintState.mRegionToDraw);
        nsIntRect bounds = aPaintState.mRegionToDraw.GetBounds();
        result->ClearRect(Rect(bounds.x, bounds.y, bounds.width, bounds.height));
    }

    return result;
}

static already_AddRefed<SourceSurface>
GetBlur(gfxContext* aDestinationCtx,
        const IntSize& aRectSize,
        const IntSize& aBlurRadius,
        const RectCornerRadii* aCornerRadii,
        const Color& aShadowColor,
        bool aMirrorCorners,
        IntMargin& aOutBlurMargin,
        IntMargin& aOutSlice,
        IntSize& aOutMinSize)
{
  if (!gBlurCache) {
    gBlurCache = new BlurCache();
  }

  IntSize minSize =
    ComputeMinSizeForShadowShape(aCornerRadii, aBlurRadius, aOutSlice, aRectSize);

  // We can get seams using the min size rect when drawing to the destination rect
  // if we have a non-pixel aligned destination transformation. In those cases,
  // fallback to just rendering the destination rect.
  Matrix destMatrix = ToMatrix(aDestinationCtx->CurrentMatrix());
  bool useDestRect = !destMatrix.IsRectilinear() || destMatrix.HasNonIntegerTranslation();
  if (useDestRect) {
    minSize = aRectSize;
  }
  aOutMinSize = minSize;

  DrawTarget* destDT = aDestinationCtx->GetDrawTarget();

  if (!useDestRect) {
    BlurCacheData* cached = gBlurCache->Lookup(minSize, aBlurRadius,
                                               aCornerRadii, aShadowColor,
                                               destDT->GetBackendType());
    if (cached) {
      // See CreateBoxShadow() for these values
      aOutBlurMargin = cached->mBlurMargin;
      RefPtr<SourceSurface> blur = cached->mBlur;
      return blur.forget();
    }
  }

  RefPtr<SourceSurface> boxShadow =
    CreateBoxShadow(destDT, minSize, aCornerRadii, aBlurRadius,
                    aShadowColor, aMirrorCorners, aOutBlurMargin);
  if (!boxShadow) {
    return nullptr;
  }

  if (!useDestRect) {
    CacheBlur(destDT, minSize, aBlurRadius, aCornerRadii, aShadowColor,
              aOutBlurMargin, boxShadow);
  }
  return boxShadow.forget();
}

/***
 * Blur an inset box shadow by doing:
 * 1) Create a minimal box shadow path that creates a frame.
 * 2) Draw the box shadow portion over the destination surface.
 * 3) The "inset" part is created by a clip rect that properly clips
 *    the alpha mask so that it has clean edges. We still create the full
 *    proper alpha mask, but let the clip deal with the clean edges.
 *
 * All parameters should already be in device pixels.
 */
void
gfxAlphaBoxBlur::BlurInsetBox(gfxContext* aDestinationCtx,
                              const Rect aDestinationRect,
                              const Rect aShadowClipRect,
                              const IntSize aBlurRadius,
                              const IntSize aSpreadRadius,
                              const Color& aShadowColor,
                              bool aHasBorderRadius,
                              const RectCornerRadii& aInnerClipRadii,
                              const Rect aSkipRect,
                              const Point aShadowOffset)
{
  DrawTarget* destDrawTarget = aDestinationCtx->GetDrawTarget();

  // Blur inset shadows ALWAYS have a 0 spread radius.
  if ((aBlurRadius.width <= 0 && aBlurRadius.height <= 0)) {
    FillDestinationPath(aDestinationCtx, aDestinationRect, aShadowClipRect,
        aShadowColor, aHasBorderRadius, aInnerClipRadii);
    return;
  }

  IntMargin extendDest;
  IntMargin slice;
  bool didMoveOffset;
  RefPtr<SourceSurface> minInsetBlur = GetInsetBlur(extendDest, slice,
                                                    aDestinationRect, aShadowClipRect,
                                                    aBlurRadius, aSpreadRadius,
                                                    aInnerClipRadii, aShadowColor,
                                                    aHasBorderRadius, aShadowOffset,
                                                    didMoveOffset, destDrawTarget);
  if (!minInsetBlur) {
    return;
  }

  Rect srcOuter(Point(), Size(minInsetBlur->GetSize()));
  Rect srcInner = srcOuter;
  srcInner.Deflate(Margin(slice));

  Rect dstOuter(aDestinationRect);
  if (!didMoveOffset) {
    dstOuter.MoveBy(aShadowOffset);
  }
  dstOuter.Inflate(Margin(extendDest));
  Rect dstInner = dstOuter;
  dstInner.Deflate(Margin(slice));

  if (dstOuter.Size() == srcOuter.Size()) {
    destDrawTarget->DrawSurface(minInsetBlur, dstOuter, srcOuter);
  } else {
    DrawBoxShadows(*destDrawTarget, minInsetBlur,
                   dstOuter, dstInner,
                   srcOuter, srcInner,
                   aSkipRect);
  }
}

void
ClientLayerManager::MakeSnapshotIfRequired()
{
  if (!mShadowTarget) {
    return;
  }
  if (mWidget) {
    if (CompositorBridgeChild* remoteRenderer = GetRemoteRenderer()) {
      // The compositor doesn't draw to a different sized surface
      // when there's a rotation. Instead we rotate the result
      // when drawing into dt
      LayoutDeviceIntRect outerBounds;
      mWidget->GetBounds(outerBounds);

      IntRect bounds = ToOutsideIntRect(mShadowTarget->GetClipExtents());
      if (mTargetRotation) {
        bounds =
          RotateRect(bounds, outerBounds.ToUnknownRect(), mTargetRotation);
      }

      SurfaceDescriptor inSnapshot;
      if (!bounds.IsEmpty() &&
          mForwarder->AllocSurfaceDescriptor(bounds.Size(),
                                             gfxContentType::COLOR_ALPHA,
                                             &inSnapshot)) {

        // Make a copy of |inSnapshot| because the call to send it over IPC
        // will call forget() on the Shmem inside, and zero it out.
        SurfaceDescriptor outSnapshot = inSnapshot;

        if (remoteRenderer->SendMakeSnapshot(inSnapshot, bounds)) {
          RefPtr<DataSourceSurface> surf = GetSurfaceForDescriptor(outSnapshot);
          DrawTarget* dt = mShadowTarget->GetDrawTarget();

          Rect dstRect(bounds.x, bounds.y, bounds.width, bounds.height);
          Rect srcRect(0, 0, bounds.width, bounds.height);

          gfx::Matrix rotate =
            ComputeTransformForUnRotation(outerBounds.ToUnknownRect(),
                                          mTargetRotation);

          gfx::Matrix oldMatrix = dt->GetTransform();
          dt->SetTransform(rotate * oldMatrix);
          dt->DrawSurface(surf, dstRect, srcRect,
                          DrawSurfaceOptions(),
                          DrawOptions(1.0f, CompositionOp::OP_OVER));
          dt->SetTransform(oldMatrix);
        }
        mForwarder->DestroySurfaceDescriptor(&outSnapshot);
      }
    }
  }
  mShadowTarget = nullptr;
}

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();
}