layout/svg/base/src/nsSVGIntegrationUtils.cpp
author Daniel Holbert <dholbert@cs.stanford.edu>
Tue, 09 Nov 2010 21:50:29 -0800
changeset 57190 c7726ff56cbf49b5f93d901b712625d91a3afab3
parent 57000 15409ec3bf08282f95fb4dc3216df2c57fa69c81
child 57281 9b0f3c55849478630650fbec96a6395f7fd9b298
permissions -rw-r--r--
Bug 587336: Keep nsSVGIntegrationUtils::GetInvalidAreaForChangedSource from inadvertantly adding an observer relationship and potentially triggering an infinite loop a few stack-levels up. r=roc a=blocking-final+

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is the Mozilla SVG project.
 *
 * The Initial Developer of the Original Code is IBM Corporation.
 * Portions created by the Initial Developer are Copyright (C) 2005
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   rocallahan@mozilla.com
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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#include "nsSVGIntegrationUtils.h"

#include "nsSVGUtils.h"
#include "nsSVGEffects.h"
#include "nsRegion.h"
#include "nsLayoutUtils.h"
#include "nsDisplayList.h"
#include "nsSVGFilterPaintCallback.h"
#include "nsSVGFilterFrame.h"
#include "nsSVGClipPathFrame.h"
#include "nsSVGMaskFrame.h"
#include "gfxPlatform.h"
#include "gfxDrawable.h"
#include "nsSVGPaintServerFrame.h"

// ----------------------------------------------------------------------

PRBool
nsSVGIntegrationUtils::UsingEffectsForFrame(const nsIFrame* aFrame)
{
  const nsStyleSVGReset *style = aFrame->GetStyleSVGReset();
  return (style->mFilter || style->mClipPath || style->mMask) &&
          !aFrame->IsFrameOfType(nsIFrame::eSVG);
}

/* static */ nsRect
nsSVGIntegrationUtils::GetNonSVGUserSpace(nsIFrame* aFirst)
{
  NS_ASSERTION(!aFirst->GetPrevContinuation(), "Not first continuation");
  return nsLayoutUtils::GetAllInFlowRectsUnion(aFirst, aFirst);
}

static nsRect
GetPreEffectsOverflowRect(nsIFrame* aFrame)
{
  nsRect* r = static_cast<nsRect*>
    (aFrame->Properties().Get(nsIFrame::PreEffectsBBoxProperty()));
  if (r)
    return *r;
  return aFrame->GetVisualOverflowRect();
}

struct BBoxCollector : public nsLayoutUtils::BoxCallback {
  nsIFrame*     mReferenceFrame;
  nsIFrame*     mCurrentFrame;
  const nsRect& mCurrentFrameOverflowArea;
  nsRect        mResult;

  BBoxCollector(nsIFrame* aReferenceFrame, nsIFrame* aCurrentFrame,
                const nsRect& aCurrentFrameOverflowArea)
    : mReferenceFrame(aReferenceFrame), mCurrentFrame(aCurrentFrame),
      mCurrentFrameOverflowArea(aCurrentFrameOverflowArea) {}

  virtual void AddBox(nsIFrame* aFrame) {
    nsRect overflow = aFrame == mCurrentFrame ? mCurrentFrameOverflowArea
        : GetPreEffectsOverflowRect(aFrame);
    mResult.UnionRect(mResult, overflow + aFrame->GetOffsetTo(mReferenceFrame));
  }
};

static nsRect
GetSVGBBox(nsIFrame* aNonSVGFrame, nsIFrame* aCurrentFrame,
           const nsRect& aCurrentOverflow, const nsRect& aUserSpaceRect)
{
  NS_ASSERTION(!aNonSVGFrame->GetPrevContinuation(),
               "Need first continuation here");
  // Compute union of all overflow areas relative to 'first'.
  BBoxCollector collector(aNonSVGFrame, aCurrentFrame, aCurrentOverflow);
  nsLayoutUtils::GetAllInFlowBoxes(aNonSVGFrame, &collector);
  // Get it into "user space" for non-SVG frames
  return collector.mResult - aUserSpaceRect.TopLeft();
}

nsRect
nsSVGIntegrationUtils::ComputeFrameEffectsRect(nsIFrame* aFrame,
                                               const nsRect& aOverflowRect)
{
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aFrame);
  nsSVGEffects::EffectProperties effectProperties =
    nsSVGEffects::GetEffectProperties(firstFrame);
  nsSVGFilterFrame *filterFrame = effectProperties.mFilter ?
    effectProperties.mFilter->GetFilterFrame() : nsnull;
  if (!filterFrame)
    return aOverflowRect;

  // XXX this isn't really right. We can't compute the correct filter
  // bbox until all aFrame's continuations have been reflowed.
  // but then it's too late to set the overflow areas for the earlier frames.
  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame);
  nsRect r = GetSVGBBox(firstFrame, aFrame, aOverflowRect, userSpaceRect);
  // r is relative to user space
  PRUint32 appUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
  nsIntRect p = r.ToOutsidePixels(appUnitsPerDevPixel);
  p = filterFrame->GetFilterBBox(firstFrame, &p);
  r = p.ToAppUnits(appUnitsPerDevPixel);
  // Make it relative to aFrame again
  return r + userSpaceRect.TopLeft() - aFrame->GetOffsetTo(firstFrame);
}

nsRect
nsSVGIntegrationUtils::GetInvalidAreaForChangedSource(nsIFrame* aFrame,
                                                      const nsRect& aInvalidRect)
{
  // Don't bother calling GetEffectProperties; the filter property should
  // already have been set up during reflow/ComputeFrameEffectsRect
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aFrame);
  nsSVGEffects::EffectProperties effectProperties =
    nsSVGEffects::GetEffectProperties(firstFrame);
  if (!effectProperties.mFilter)
    return aInvalidRect;

  nsSVGFilterProperty *prop = nsSVGEffects::GetFilterProperty(aFrame);
  if (!prop || !prop->IsInObserverList()) {
    return aInvalidRect;
  }

  nsSVGFilterFrame* filterFrame = prop->GetFilterFrame();
  if (!filterFrame) {
    // The frame is either not there or not currently available,
    // perhaps because we're in the middle of tearing stuff down.
    // Be conservative.
    return aFrame->GetVisualOverflowRect();
  }

  PRInt32 appUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame);
  nsPoint offset = aFrame->GetOffsetTo(firstFrame) - userSpaceRect.TopLeft();
  nsRect r = aInvalidRect + offset;
  nsIntRect p = r.ToOutsidePixels(appUnitsPerDevPixel);
  p = filterFrame->GetInvalidationBBox(firstFrame, p);
  r = p.ToAppUnits(appUnitsPerDevPixel);
  return r - offset;
}

nsRect
nsSVGIntegrationUtils::GetRequiredSourceForInvalidArea(nsIFrame* aFrame,
                                                       const nsRect& aDamageRect)
{
  // Don't bother calling GetEffectProperties; the filter property should
  // already have been set up during reflow/ComputeFrameEffectsRect
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aFrame);
  nsSVGFilterFrame* filterFrame =
    nsSVGEffects::GetFilterFrame(firstFrame);
  if (!filterFrame)
    return aDamageRect;
  
  PRInt32 appUnitsPerDevPixel = aFrame->PresContext()->AppUnitsPerDevPixel();
  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame);
  nsPoint offset = aFrame->GetOffsetTo(firstFrame) - userSpaceRect.TopLeft();
  nsRect r = aDamageRect + offset;
  nsIntRect p = r.ToOutsidePixels(appUnitsPerDevPixel);
  p = filterFrame->GetSourceForInvalidArea(firstFrame, p);
  r = p.ToAppUnits(appUnitsPerDevPixel);
  return r - offset;
}

PRBool
nsSVGIntegrationUtils::HitTestFrameForEffects(nsIFrame* aFrame, const nsPoint& aPt)
{
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aFrame);
  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame);
  // get point relative to userSpaceRect
  nsPoint pt = aPt + aFrame->GetOffsetTo(firstFrame) - userSpaceRect.TopLeft();
  return nsSVGUtils::HitTestClip(firstFrame, pt);
}

class RegularFramePaintCallback : public nsSVGFilterPaintCallback
{
public:
  RegularFramePaintCallback(nsDisplayListBuilder* aBuilder,
                            nsDisplayList* aInnerList,
                            nsIFrame* aFrame,
                            const nsPoint& aOffset)
    : mBuilder(aBuilder), mInnerList(aInnerList), mFrame(aFrame),
      mOffset(aOffset) {}

  virtual void Paint(nsSVGRenderState *aContext, nsIFrame *aTarget,
                     const nsIntRect* aDirtyRect)
  {
    nsIRenderingContext* ctx = aContext->GetRenderingContext(aTarget);
    nsIRenderingContext::AutoPushTranslation push(ctx, -mOffset.x, -mOffset.y);
    mInnerList->PaintForFrame(mBuilder, ctx, mFrame, nsDisplayList::PAINT_DEFAULT);
  }

private:
  nsDisplayListBuilder* mBuilder;
  nsDisplayList* mInnerList;
  nsIFrame* mFrame;
  nsPoint mOffset;
};

void
nsSVGIntegrationUtils::PaintFramesWithEffects(nsIRenderingContext* aCtx,
                                              nsIFrame* aEffectsFrame,
                                              const nsRect& aDirtyRect,
                                              nsDisplayListBuilder* aBuilder,
                                              nsDisplayList* aInnerList)
{
#ifdef DEBUG
  nsISVGChildFrame *svgChildFrame = do_QueryFrame(aEffectsFrame);
  NS_ASSERTION(!svgChildFrame, "Should never be called on an SVG frame");
#endif

  float opacity = aEffectsFrame->GetStyleDisplay()->mOpacity;
  if (opacity == 0.0f)
    return;

  /* Properties are added lazily and may have been removed by a restyle,
     so make sure all applicable ones are set again. */
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aEffectsFrame);
  nsSVGEffects::EffectProperties effectProperties =
    nsSVGEffects::GetEffectProperties(firstFrame);

  /* SVG defines the following rendering model:
   *
   *  1. Render geometry
   *  2. Apply filter
   *  3. Apply clipping, masking, group opacity
   *
   * We follow this, but perform a couple of optimizations:
   *
   * + Use cairo's clipPath when representable natively (single object
   *   clip region).
   *
   * + Merge opacity and masking if both used together.
   */

  PRBool isOK = PR_TRUE;
  nsSVGClipPathFrame *clipPathFrame = effectProperties.GetClipPathFrame(&isOK);
  nsSVGFilterFrame *filterFrame = effectProperties.GetFilterFrame(&isOK);
  nsSVGMaskFrame *maskFrame = effectProperties.GetMaskFrame(&isOK);

  PRBool isTrivialClip = clipPathFrame ? clipPathFrame->IsTrivial() : PR_TRUE;

  if (!isOK) {
    // Some resource is missing. We shouldn't paint anything.
    return;
  }

  gfxContext* gfx = aCtx->ThebesContext();
  gfxMatrix savedCTM = gfx->CurrentMatrix();
  nsSVGRenderState svgContext(aCtx);

  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame) + aBuilder->ToReferenceFrame(firstFrame);
  PRInt32 appUnitsPerDevPixel = aEffectsFrame->PresContext()->AppUnitsPerDevPixel();
  userSpaceRect = userSpaceRect.ToNearestPixels(appUnitsPerDevPixel).ToAppUnits(appUnitsPerDevPixel);
  aCtx->Translate(userSpaceRect.x, userSpaceRect.y);

  gfxMatrix matrix = GetInitialMatrix(aEffectsFrame);

  PRBool complexEffects = PR_FALSE;
  /* Check if we need to do additional operations on this child's
   * rendering, which necessitates rendering into another surface. */
  if (opacity != 1.0f || maskFrame || (clipPathFrame && !isTrivialClip)) {
    complexEffects = PR_TRUE;
    gfx->Save();
    aCtx->SetClipRect(aEffectsFrame->GetVisualOverflowRect(),
                      nsClipCombine_kIntersect);
    gfx->PushGroup(gfxASurface::CONTENT_COLOR_ALPHA);
  }

  /* If this frame has only a trivial clipPath, set up cairo's clipping now so
   * we can just do normal painting and get it clipped appropriately.
   */
  if (clipPathFrame && isTrivialClip) {
    gfx->Save();
    clipPathFrame->ClipPaint(&svgContext, aEffectsFrame, matrix);
  }

  /* Paint the child */
  if (filterFrame) {
    RegularFramePaintCallback paint(aBuilder, aInnerList, aEffectsFrame,
                                    userSpaceRect.TopLeft());
    nsIntRect r = (aDirtyRect - userSpaceRect.TopLeft()).ToOutsidePixels(appUnitsPerDevPixel);
    filterFrame->FilterPaint(&svgContext, aEffectsFrame, &paint, &r);
  } else {
    gfx->SetMatrix(savedCTM);
    aInnerList->PaintForFrame(aBuilder, aCtx, aEffectsFrame,
                              nsDisplayList::PAINT_DEFAULT);
    aCtx->Translate(userSpaceRect.x, userSpaceRect.y);
  }

  if (clipPathFrame && isTrivialClip) {
    gfx->Restore();
  }

  /* No more effects, we're done. */
  if (!complexEffects) {
    gfx->SetMatrix(savedCTM);
    return;
  }

  gfx->PopGroupToSource();

  nsRefPtr<gfxPattern> maskSurface =
    maskFrame ? maskFrame->ComputeMaskAlpha(&svgContext, aEffectsFrame,
                                            matrix, opacity) : nsnull;

  nsRefPtr<gfxPattern> clipMaskSurface;
  if (clipPathFrame && !isTrivialClip) {
    gfx->PushGroup(gfxASurface::CONTENT_COLOR_ALPHA);

    nsresult rv = clipPathFrame->ClipPaint(&svgContext, aEffectsFrame, matrix);
    clipMaskSurface = gfx->PopGroup();

    if (NS_SUCCEEDED(rv) && clipMaskSurface) {
      // Still more set after clipping, so clip to another surface
      if (maskSurface || opacity != 1.0f) {
        gfx->PushGroup(gfxASurface::CONTENT_COLOR_ALPHA);
        gfx->Mask(clipMaskSurface);
        gfx->PopGroupToSource();
      } else {
        gfx->Mask(clipMaskSurface);
      }
    }
  }

  if (maskSurface) {
    gfx->Mask(maskSurface);
  } else if (opacity != 1.0f) {
    gfx->Paint(opacity);
  }

  gfx->Restore();
  gfx->SetMatrix(savedCTM);
}

gfxMatrix
nsSVGIntegrationUtils::GetInitialMatrix(nsIFrame* aNonSVGFrame)
{
  NS_ASSERTION(!aNonSVGFrame->IsFrameOfType(nsIFrame::eSVG),
               "SVG frames should not get here");
  PRInt32 appUnitsPerDevPixel = aNonSVGFrame->PresContext()->AppUnitsPerDevPixel();
  float devPxPerCSSPx =
    1 / nsPresContext::AppUnitsToFloatCSSPixels(appUnitsPerDevPixel);

  return gfxMatrix(devPxPerCSSPx, 0.0,
                   0.0, devPxPerCSSPx,
                   0.0, 0.0);
}

gfxRect
nsSVGIntegrationUtils::GetSVGRectForNonSVGFrame(nsIFrame* aNonSVGFrame)
{
  NS_ASSERTION(!aNonSVGFrame->IsFrameOfType(nsIFrame::eSVG),
               "SVG frames should not get here");
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aNonSVGFrame);
  nsRect r = GetNonSVGUserSpace(firstFrame);
  nsPresContext* presContext = firstFrame->PresContext();
  return gfxRect(0, 0, presContext->AppUnitsToFloatCSSPixels(r.width),
                       presContext->AppUnitsToFloatCSSPixels(r.height));
}

gfxRect
nsSVGIntegrationUtils::GetSVGBBoxForNonSVGFrame(nsIFrame* aNonSVGFrame)
{
  NS_ASSERTION(!aNonSVGFrame->IsFrameOfType(nsIFrame::eSVG),
               "SVG frames should not get here");
  nsIFrame* firstFrame =
    nsLayoutUtils::GetFirstContinuationOrSpecialSibling(aNonSVGFrame);
  nsRect userSpaceRect = GetNonSVGUserSpace(firstFrame);
  nsRect r = GetSVGBBox(firstFrame, nsnull, nsRect(), userSpaceRect);
  gfxRect result(r.x, r.y, r.width, r.height);
  nsPresContext* presContext = aNonSVGFrame->PresContext();
  result.ScaleInverse(presContext->AppUnitsPerCSSPixel());
  return result;
}

class PaintFrameCallback : public gfxDrawingCallback {
public:
  PaintFrameCallback(nsIFrame* aFrame,
                     nsIFrame* aTarget,
                     const nsSize aPaintServerSize,
                     const gfxIntSize aRenderSize)
   : mFrame(aFrame)
   , mTarget(aTarget)
   , mPaintServerSize(aPaintServerSize)
   , mRenderSize(aRenderSize)
  {}
  virtual PRBool operator()(gfxContext* aContext,
                            const gfxRect& aFillRect,
                            const gfxPattern::GraphicsFilter& aFilter,
                            const gfxMatrix& aTransform);
private:
  nsIFrame* mFrame;
  nsIFrame* mTarget;
  nsSize mPaintServerSize;
  gfxIntSize mRenderSize;
};

PRBool
PaintFrameCallback::operator()(gfxContext* aContext,
                               const gfxRect& aFillRect,
                               const gfxPattern::GraphicsFilter& aFilter,
                               const gfxMatrix& aTransform)
{
  if (mFrame->GetStateBits() & NS_FRAME_DRAWING_AS_PAINTSERVER)
    return PR_FALSE;

  mFrame->AddStateBits(NS_FRAME_DRAWING_AS_PAINTSERVER);

  nsSVGRenderState renderState(aContext);
  aContext->Save();

  // Clip to aFillRect so that we don't paint outside.
  aContext->NewPath();
  aContext->Rectangle(aFillRect);
  aContext->Clip();
  gfxMatrix savedMatrix(aContext->CurrentMatrix());

  aContext->Multiply(gfxMatrix(aTransform).Invert());

  // nsLayoutUtils::PaintFrame will anchor its painting at mFrame. But we want
  // to have it anchored at the top left corner of the bounding box of all of
  // mFrame's continuations. So we add a translation transform.
  nsRect bbox = nsSVGIntegrationUtils::GetNonSVGUserSpace(mFrame);
  PRInt32 appUnitsPerDevPixel = mFrame->PresContext()->AppUnitsPerDevPixel();
  gfxPoint offset = gfxPoint(bbox.x, bbox.y) / appUnitsPerDevPixel;
  aContext->Multiply(gfxMatrix().Translate(-offset));

  gfxSize paintServerSize =
    gfxSize(mPaintServerSize.width, mPaintServerSize.height) /
      mFrame->PresContext()->AppUnitsPerDevPixel();

  // nsLayoutUtils::PaintFrame wants to render with paintServerSize, but we
  // want it to render with mRenderSize, so we need to set up a scale transform.
  gfxFloat scaleX = mRenderSize.width / paintServerSize.width;
  gfxFloat scaleY = mRenderSize.height / paintServerSize.height;
  gfxMatrix scaleMatrix = gfxMatrix().Scale(scaleX, scaleY);
  aContext->Multiply(scaleMatrix);

  // Draw.
  nsRect dirty(bbox.x, bbox.y, mPaintServerSize.width, mPaintServerSize.height);
  nsLayoutUtils::PaintFrame(renderState.GetRenderingContext(mTarget), mFrame,
                            dirty, NS_RGBA(0, 0, 0, 0),
                            nsLayoutUtils::PAINT_IN_TRANSFORM |
                            nsLayoutUtils::PAINT_ALL_CONTINUATIONS);

  aContext->SetMatrix(savedMatrix);
  aContext->Restore();

  mFrame->RemoveStateBits(NS_FRAME_DRAWING_AS_PAINTSERVER);

  return PR_TRUE;
}

static already_AddRefed<gfxDrawable>
DrawableFromPaintServer(nsIFrame*         aFrame,
                        nsIFrame*         aTarget,
                        const nsSize&     aPaintServerSize,
                        const gfxIntSize& aRenderSize)
{
  // aPaintServerSize is the size that would be filled when using
  // background-repeat:no-repeat and background-size:auto. For normal background
  // images, this would be the intrinsic size of the image; for gradients and
  // patterns this would be the whole target frame fill area.
  // aRenderSize is what we will be actually filling after accounting for
  // background-size.
  if (aFrame->IsFrameOfType(nsIFrame::eSVGPaintServer)) {
    // aFrame is either a pattern or a gradient. These fill the whole target
    // frame by default, so aPaintServerSize is the whole target background fill
    // area.
    nsSVGPaintServerFrame* server =
      static_cast<nsSVGPaintServerFrame*>(aFrame);

    gfxRect overrideBounds(0, 0,
                           aPaintServerSize.width, aPaintServerSize.height);
    overrideBounds.ScaleInverse(aFrame->PresContext()->AppUnitsPerDevPixel());
    nsRefPtr<gfxPattern> pattern =
      server->GetPaintServerPattern(aTarget, 1.0, &overrideBounds);

    if (!pattern)
      return nsnull;

    // pattern is now set up to fill aPaintServerSize. But we want it to
    // fill aRenderSize, so we need to add a scaling transform.
    // We couldn't just have set overrideBounds to aRenderSize - it would have
    // worked for gradients, but for patterns it would result in a different
    // pattern size.
    gfxFloat scaleX = overrideBounds.Width() / aRenderSize.width;
    gfxFloat scaleY = overrideBounds.Height() / aRenderSize.height;
    gfxMatrix scaleMatrix = gfxMatrix().Scale(scaleX, scaleY);
    pattern->SetMatrix(scaleMatrix.Multiply(pattern->GetMatrix()));
    nsRefPtr<gfxDrawable> drawable =
      new gfxPatternDrawable(pattern, aRenderSize);
    return drawable.forget();
  }

  // We don't want to paint into a surface as long as we don't need to, so we
  // set up a drawing callback.
  nsRefPtr<gfxDrawingCallback> cb =
    new PaintFrameCallback(aFrame, aTarget, aPaintServerSize, aRenderSize);
  nsRefPtr<gfxDrawable> drawable = new gfxCallbackDrawable(cb, aRenderSize);
  return drawable.forget();
}

/* static */ void
nsSVGIntegrationUtils::DrawPaintServer(nsIRenderingContext* aRenderingContext,
                                       nsIFrame*            aTarget,
                                       nsIFrame*            aPaintServer,
                                       gfxPattern::GraphicsFilter aFilter,
                                       const nsRect&        aDest,
                                       const nsRect&        aFill,
                                       const nsPoint&       aAnchor,
                                       const nsRect&        aDirty,
                                       const nsSize&        aPaintServerSize)
{
  if (aDest.IsEmpty() || aFill.IsEmpty())
    return;

  PRInt32 appUnitsPerDevPixel = aTarget->PresContext()->AppUnitsPerDevPixel();
  nsRect destSize = aDest - aDest.TopLeft();
  nsIntSize roundedOut = destSize.ToOutsidePixels(appUnitsPerDevPixel).Size();
  gfxIntSize imageSize(roundedOut.width, roundedOut.height);
  nsRefPtr<gfxDrawable> drawable =
    DrawableFromPaintServer(aPaintServer, aTarget, aPaintServerSize, imageSize);

  if (drawable) {
    nsLayoutUtils::DrawPixelSnapped(aRenderingContext, drawable, aFilter,
                                    aDest, aFill, aAnchor, aDirty);
  }
}