gecko-dev/gfx/layers/d3d9/ThebesLayerD3D9.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * ***** 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 Mozilla Corporation code.
 *
 * The Initial Developer of the Original Code is Mozilla Foundation.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Bas Schouten <bschouten@mozilla.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either 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"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "ThebesLayerD3D9.h"
#include "gfxPlatform.h"

#include "gfxWindowsPlatform.h"
#include "gfxTeeSurface.h"
#include "gfxUtils.h"
#include "ReadbackProcessor.h"

namespace mozilla {
namespace layers {

ThebesLayerD3D9::ThebesLayerD3D9(LayerManagerD3D9 *aManager)
  : ThebesLayer(aManager, NULL)
  , LayerD3D9(aManager)
{
  mImplData = static_cast<LayerD3D9*>(this);
  aManager->deviceManager()->mLayersWithResources.AppendElement(this);
}

ThebesLayerD3D9::~ThebesLayerD3D9()
{
  if (mD3DManager) {
    mD3DManager->deviceManager()->mLayersWithResources.RemoveElement(this);
  }
}

/**
 * Retention threshold - amount of pixels intersection required to enable
 * layer content retention. This is a guesstimate. Profiling could be done to
 * figure out the optimal threshold.
 */
#define RETENTION_THRESHOLD 16384

void
ThebesLayerD3D9::InvalidateRegion(const nsIntRegion &aRegion)
{
  mValidRegion.Sub(mValidRegion, aRegion);
}

void
ThebesLayerD3D9::CopyRegion(IDirect3DTexture9* aSrc, const nsIntPoint &aSrcOffset,
                            IDirect3DTexture9* aDest, const nsIntPoint &aDestOffset,
                            const nsIntRegion &aCopyRegion, nsIntRegion* aValidRegion,
                            float aXRes, float aYRes)
{
  nsRefPtr<IDirect3DSurface9> srcSurface, dstSurface;
  aSrc->GetSurfaceLevel(0, getter_AddRefs(srcSurface));
  aDest->GetSurfaceLevel(0, getter_AddRefs(dstSurface));

  nsIntRegion retainedRegion;
  nsIntRegionRectIterator iter(aCopyRegion);
  const nsIntRect *r;
  while ((r = iter.Next())) {
    if (r->width * r->height > RETENTION_THRESHOLD) {
      RECT oldRect, newRect;

      // Calculate the retained rectangle's position on the old and the new
      // surface. We need to scale these rectangles since the visible
      // region is in unscaled units, and the texture size has been scaled.
      oldRect.left = UINT(floor((r->x - aSrcOffset.x) * aXRes));
      oldRect.top = UINT(floor((r->y - aSrcOffset.y) * aYRes));
      oldRect.right = oldRect.left + UINT(ceil(r->width * aXRes));
      oldRect.bottom = oldRect.top + UINT(ceil(r->height * aYRes));

      newRect.left = UINT(floor((r->x - aDestOffset.x) * aXRes));
      newRect.top = UINT(floor((r->y - aDestOffset.y) * aYRes));
      newRect.right = newRect.left + UINT(ceil(r->width * aXRes));
      newRect.bottom = newRect.top + UINT(ceil(r->height * aYRes));

      // Copy data from our old texture to the new one
      HRESULT hr = device()->
        StretchRect(srcSurface, &oldRect, dstSurface, &newRect, D3DTEXF_NONE);

      if (SUCCEEDED(hr)) {
        retainedRegion.Or(retainedRegion, *r);
      }
    }
  }

  // Areas which were valid and were retained are still valid
  aValidRegion->And(*aValidRegion, retainedRegion);
}

static PRUint64 RectArea(const nsIntRect& aRect)
{
  return aRect.width*PRUint64(aRect.height);
}

void
ThebesLayerD3D9::UpdateTextures(SurfaceMode aMode)
{
  nsIntRect visibleRect = mVisibleRegion.GetBounds();

  float xres, yres;
  GetDesiredResolutions(xres, yres);

  // If our resolution changed, we need new sized textures, delete the old ones.
  if (ResolutionChanged(xres, yres)) {
      mTexture = nsnull;
      mTextureOnWhite = nsnull;
  }

  if (HaveTextures(aMode)) {
    if (mTextureRect != visibleRect) {
      nsRefPtr<IDirect3DTexture9> oldTexture = mTexture;
      nsRefPtr<IDirect3DTexture9> oldTextureOnWhite = mTextureOnWhite;

      NS_ASSERTION(mTextureRect.Contains(mValidRegion.GetBounds()),
                   "How can we have valid data outside the texture?");
      nsIntRegion retainRegion;
      // The region we want to retain is the valid data that is inside
      // the new visible region
      retainRegion.And(mValidRegion, mVisibleRegion);

      CreateNewTextures(gfxIntSize(visibleRect.width, visibleRect.height), aMode);

      // If our texture creation failed this can mean a device reset is pending and we
      // should silently ignore the failure. In the future when device failures
      // are properly handled we should test for the type of failure and gracefully
      // handle different failures. See bug 569081.
      if (!HaveTextures(aMode)) {
        mValidRegion.SetEmpty();
      } else {
        CopyRegion(oldTexture, mTextureRect.TopLeft(), mTexture, visibleRect.TopLeft(),
                   retainRegion, &mValidRegion, xres, yres);
        if (aMode == SURFACE_COMPONENT_ALPHA) {
          CopyRegion(oldTextureOnWhite, mTextureRect.TopLeft(), mTextureOnWhite, visibleRect.TopLeft(),
                     retainRegion, &mValidRegion, xres, yres);
        }
      }

      mTextureRect = visibleRect;
    }
  } else {
    CreateNewTextures(gfxIntSize(visibleRect.width, visibleRect.height), aMode);
    mTextureRect = visibleRect;
    
    NS_ASSERTION(mValidRegion.IsEmpty(), "Someone forgot to empty the region");
  }
}

void
ThebesLayerD3D9::RenderVisibleRegion()
{
  nsIntRegionRectIterator iter(mVisibleRegion);

  const nsIntRect *iterRect;
  while ((iterRect = iter.Next())) {
    device()->SetVertexShaderConstantF(CBvLayerQuad,
                                       ShaderConstantRect(iterRect->x,
                                                          iterRect->y,
                                                          iterRect->width,
                                                          iterRect->height),
                                       1);

    device()->SetVertexShaderConstantF(CBvTextureCoords,
      ShaderConstantRect(
        (float)(iterRect->x - mTextureRect.x) / (float)mTextureRect.width,
        (float)(iterRect->y - mTextureRect.y) / (float)mTextureRect.height,
        (float)iterRect->width / (float)mTextureRect.width,
        (float)iterRect->height / (float)mTextureRect.height), 1);

    device()->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, 2);
  }
}

void
ThebesLayerD3D9::RenderThebesLayer(ReadbackProcessor* aReadback)
{
  if (mVisibleRegion.IsEmpty()) {
    return;
  }

  SurfaceMode mode = GetSurfaceMode();
  if (mode == SURFACE_COMPONENT_ALPHA &&
      (!mParent || !mParent->SupportsComponentAlphaChildren())) {
    mode = SURFACE_SINGLE_CHANNEL_ALPHA;
  }
  VerifyContentType(mode);
  UpdateTextures(mode);
  if (!HaveTextures(mode)) {
    NS_WARNING("Texture creation failed");
    return;
  }

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

  // Because updates to D3D9 ThebesLayers are rendered with the CPU, we don't
  // have to do readback from D3D9 surfaces. Instead we make sure that any area
  // needed for readback is included in the drawRegion we ask layout to render.
  // Then the readback areas we need can be copied out of the temporary
  // destinationSurface in DrawRegion.
  nsIntRegion drawRegion;
  drawRegion.Sub(mVisibleRegion, mValidRegion);
  drawRegion.Or(drawRegion, readbackRegion);
  // NS_ASSERTION(mVisibleRegion.Contains(region), "Bad readback region!");

  if (!drawRegion.IsEmpty()) {
    LayerManagerD3D9::CallbackInfo cbInfo = mD3DManager->GetCallbackInfo();
    if (!cbInfo.Callback) {
      NS_ERROR("D3D9 should never need to update ThebesLayers in an empty transaction");
      return;
    }

    DrawRegion(drawRegion, mode, readbackUpdates);

    mValidRegion = mVisibleRegion;
  }

  SetShaderTransformAndOpacity();

  if (mode == SURFACE_COMPONENT_ALPHA) {
    mD3DManager->SetShaderMode(DeviceManagerD3D9::COMPONENTLAYERPASS1);
    device()->SetTexture(0, mTexture);
    device()->SetTexture(1, mTextureOnWhite);
    device()->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ZERO);
    device()->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCCOLOR);
    RenderVisibleRegion();

    mD3DManager->SetShaderMode(DeviceManagerD3D9::COMPONENTLAYERPASS2);
    device()->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ONE);
    device()->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_ONE);
    RenderVisibleRegion();

    // Restore defaults
    device()->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ONE);
    device()->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
    device()->SetTexture(1, NULL);
  } else {
    mD3DManager->SetShaderMode(DeviceManagerD3D9::RGBALAYER);
    device()->SetTexture(0, mTexture);
    RenderVisibleRegion();
  }

  // Set back to default.
  device()->SetVertexShaderConstantF(CBvTextureCoords,
                                     ShaderConstantRect(0, 0, 1.0f, 1.0f),
                                     1);
}

void
ThebesLayerD3D9::CleanResources()
{
  mTexture = nsnull;
  mTextureOnWhite = nsnull;
  mValidRegion.SetEmpty();
}

void
ThebesLayerD3D9::LayerManagerDestroyed()
{
  mD3DManager->deviceManager()->mLayersWithResources.RemoveElement(this);
  mD3DManager = nsnull;
}

Layer*
ThebesLayerD3D9::GetLayer()
{
  return this;
}

PRBool
ThebesLayerD3D9::IsEmpty()
{
  return !mTexture;
}

void
ThebesLayerD3D9::VerifyContentType(SurfaceMode aMode)
{
  if (!mTexture)
    return;

  D3DSURFACE_DESC desc;
  mTexture->GetLevelDesc(0, &desc);

  switch (aMode) {
  case SURFACE_OPAQUE:
    if (desc.Format == D3DFMT_X8R8G8B8 && !mTextureOnWhite)
      return;
    break;

  case SURFACE_SINGLE_CHANNEL_ALPHA:
    if (desc.Format == D3DFMT_A8R8G8B8 && !mTextureOnWhite)
      return;
    break;

  case SURFACE_COMPONENT_ALPHA:
    if (mTextureOnWhite) {
      NS_ASSERTION(desc.Format == D3DFMT_X8R8G8B8, "Wrong format for component alpha texture");
      return;
    }
    break;
  }

  // The new format isn't compatible with the old texture(s), toss out the old
  // texture(s).
  mTexture = nsnull;
  mTextureOnWhite = nsnull;
  mValidRegion.SetEmpty();
}

class OpaqueRenderer {
public:
  OpaqueRenderer(const nsIntRegion& aUpdateRegion) :
    mUpdateRegion(aUpdateRegion), mDC(NULL) {}
  ~OpaqueRenderer() { End(); }
  already_AddRefed<gfxWindowsSurface> Begin(LayerD3D9* aLayer, float aXRes, float aYRes);
  void End();
  IDirect3DTexture9* GetTexture() { return mTmpTexture; }

private:
  const nsIntRegion& mUpdateRegion;
  nsRefPtr<IDirect3DTexture9> mTmpTexture;
  nsRefPtr<IDirect3DSurface9> mSurface;
  HDC mDC;
};

already_AddRefed<gfxWindowsSurface>
OpaqueRenderer::Begin(LayerD3D9* aLayer, float aXRes, float aYRes)
{
  nsIntRect bounds = mUpdateRegion.GetBounds();
  gfxIntSize scaledSize;
  scaledSize.width = PRInt32(ceil(bounds.width * aXRes));
  scaledSize.height = PRInt32(ceil(bounds.height * aYRes));

  HRESULT hr = aLayer->device()->
      CreateTexture(scaledSize.width, scaledSize.height, 1, 0, D3DFMT_X8R8G8B8,
                    D3DPOOL_SYSTEMMEM, getter_AddRefs(mTmpTexture), NULL);

  if (FAILED(hr)) {
    aLayer->ReportFailure(NS_LITERAL_CSTRING("Failed to create temporary texture in system memory."), hr);
    return nsnull;
  }

  hr = mTmpTexture->GetSurfaceLevel(0, getter_AddRefs(mSurface));

  if (FAILED(hr)) {
    // Uh-oh, bail.
    NS_WARNING("Failed to get texture surface level.");
    return nsnull;
  }

  hr = mSurface->GetDC(&mDC);
  if (FAILED(hr)) {
    NS_WARNING("Failed to get device context for texture surface.");
    return nsnull;
  }

  nsRefPtr<gfxWindowsSurface> result = new gfxWindowsSurface(mDC);
  return result.forget();
}

void
OpaqueRenderer::End()
{
  if (mSurface && mDC) {
    mSurface->ReleaseDC(mDC);
    mSurface = NULL;
    mDC = NULL;
  }
}

static void
FillSurface(gfxASurface* aSurface, const nsIntRegion& aRegion,
            const nsIntPoint& aOffset, const gfxRGBA& aColor,
            float aXRes, float aYRes)
{
  nsRefPtr<gfxContext> ctx = new gfxContext(aSurface);
  ctx->Scale(aXRes, aYRes);
  ctx->Translate(-gfxPoint(aOffset.x, aOffset.y));
  gfxUtils::ClipToRegion(ctx, aRegion);
  ctx->SetColor(aColor);
  ctx->Paint();
}

void
ThebesLayerD3D9::DrawRegion(nsIntRegion &aRegion, SurfaceMode aMode,
                            const nsTArray<ReadbackProcessor::Update>& aReadbackUpdates)
{
  HRESULT hr;
  nsIntRect visibleRect = mVisibleRegion.GetBounds();
  float xres, yres;
  GetDesiredResolutions(xres, yres);

  nsRefPtr<gfxASurface> destinationSurface;
  nsIntRect bounds = aRegion.GetBounds();
  gfxIntSize scaledSize;
  scaledSize.width = PRInt32(ceil(bounds.width * xres));
  scaledSize.height = PRInt32(ceil(bounds.height * yres));
  nsRefPtr<IDirect3DTexture9> tmpTexture;
  OpaqueRenderer opaqueRenderer(aRegion);
  OpaqueRenderer opaqueRendererOnWhite(aRegion);

  switch (aMode)
  {
    case SURFACE_OPAQUE:
      destinationSurface = opaqueRenderer.Begin(this, xres, yres);
      break;

    case SURFACE_SINGLE_CHANNEL_ALPHA: {
      hr = device()->CreateTexture(scaledSize.width, scaledSize.height, 1,
                                   0, D3DFMT_A8R8G8B8,
                                   D3DPOOL_SYSTEMMEM, getter_AddRefs(tmpTexture), NULL);

      if (FAILED(hr)) {
        ReportFailure(NS_LITERAL_CSTRING("Failed to create temporary texture in system memory."), hr);
        return;
      }

      // XXX - We may consider retaining a SYSTEMMEM texture texture the size
      // of our DEFAULT texture and then use UpdateTexture and add dirty rects
      // to update in a single call.
      nsRefPtr<gfxWindowsSurface> dest = new gfxWindowsSurface(
          gfxIntSize(bounds.width, bounds.height), gfxASurface::ImageFormatARGB32);
      // If the contents of this layer don't require component alpha in the
      // end of rendering, it's safe to enable Cleartype since all the Cleartype
      // glyphs must be over (or under) opaque pixels.
      dest->SetSubpixelAntialiasingEnabled(!(mContentFlags & CONTENT_COMPONENT_ALPHA));
      destinationSurface = dest.forget();
      break;
    }

    case SURFACE_COMPONENT_ALPHA: {
      nsRefPtr<gfxWindowsSurface> onBlack = opaqueRenderer.Begin(this, xres, yres);
      nsRefPtr<gfxWindowsSurface> onWhite = opaqueRendererOnWhite.Begin(this, xres, yres);
      if (onBlack && onWhite) {
        FillSurface(onBlack, aRegion, bounds.TopLeft(), gfxRGBA(0.0, 0.0, 0.0, 1.0), xres, yres);
        FillSurface(onWhite, aRegion, bounds.TopLeft(), gfxRGBA(1.0, 1.0, 1.0, 1.0), xres, yres);
        gfxASurface* surfaces[2] = { onBlack.get(), onWhite.get() };
        destinationSurface = new gfxTeeSurface(surfaces, NS_ARRAY_LENGTH(surfaces));
        // Using this surface as a source will likely go horribly wrong, since
        // only the onBlack surface will really be used, so alpha information will
        // be incorrect.
        destinationSurface->SetAllowUseAsSource(PR_FALSE);
      }
      break;
    }
  }

  if (!destinationSurface)
    return;

  nsRefPtr<gfxContext> context = new gfxContext(destinationSurface);
  // Draw content scaled at our current resolution.
  context->Scale(xres, yres);
  context->Translate(gfxPoint(-bounds.x, -bounds.y));
  aRegion.ExtendForScaling(xres, yres);
  LayerManagerD3D9::CallbackInfo cbInfo = mD3DManager->GetCallbackInfo();
  cbInfo.Callback(this, context, aRegion, nsIntRegion(), cbInfo.CallbackData);

  for (PRUint32 i = 0; i < aReadbackUpdates.Length(); ++i) {
    NS_ASSERTION(aMode == SURFACE_OPAQUE,
                 "Transparent surfaces should not be used for readback");
    const ReadbackProcessor::Update& update = aReadbackUpdates[i];
    nsIntPoint offset = update.mLayer->GetBackgroundLayerOffset();
    nsRefPtr<gfxContext> ctx =
        update.mLayer->GetSink()->BeginUpdate(update.mUpdateRect + offset,
                                              update.mSequenceCounter);
    if (ctx) {
      ctx->Translate(gfxPoint(offset.x, offset.y));
      ctx->SetSource(destinationSurface, gfxPoint(bounds.x, bounds.y));
      ctx->Paint();
      update.mLayer->GetSink()->EndUpdate(ctx, update.mUpdateRect + offset);
    }
  }

  nsAutoTArray<IDirect3DTexture9*,2> srcTextures;
  nsAutoTArray<IDirect3DTexture9*,2> destTextures;
  switch (aMode)
  {
    case SURFACE_OPAQUE:
      opaqueRenderer.End();
      srcTextures.AppendElement(opaqueRenderer.GetTexture());
      destTextures.AppendElement(mTexture);
      break;

    case SURFACE_SINGLE_CHANNEL_ALPHA: {
      D3DLOCKED_RECT r;
      tmpTexture->LockRect(0, &r, NULL, 0);

      nsRefPtr<gfxImageSurface> imgSurface =
        new gfxImageSurface((unsigned char *)r.pBits,
                            scaledSize,
                            r.Pitch,
                            gfxASurface::ImageFormatARGB32);

      if (destinationSurface) {
        nsRefPtr<gfxContext> context = new gfxContext(imgSurface);
        context->SetSource(destinationSurface);
        context->SetOperator(gfxContext::OPERATOR_SOURCE);
        context->Paint();
      }

      imgSurface = NULL;

      tmpTexture->UnlockRect(0);

      srcTextures.AppendElement(tmpTexture);
      destTextures.AppendElement(mTexture);
      break;
    }

    case SURFACE_COMPONENT_ALPHA: {
      opaqueRenderer.End();
      opaqueRendererOnWhite.End();
      srcTextures.AppendElement(opaqueRenderer.GetTexture());
      destTextures.AppendElement(mTexture);
      srcTextures.AppendElement(opaqueRendererOnWhite.GetTexture());
      destTextures.AppendElement(mTextureOnWhite);
      break;
    }
  }
  NS_ASSERTION(srcTextures.Length() == destTextures.Length(), "Mismatched lengths");

  // Copy to the texture. We need to scale these rectangles since the visible
  // region is in unscaled units, and the texture sizes have been scaled.
  for (PRUint32 i = 0; i < srcTextures.Length(); ++i) {
    nsRefPtr<IDirect3DSurface9> srcSurface;
    nsRefPtr<IDirect3DSurface9> dstSurface;

    destTextures[i]->GetSurfaceLevel(0, getter_AddRefs(dstSurface));
    srcTextures[i]->GetSurfaceLevel(0, getter_AddRefs(srcSurface));

    nsIntRegionRectIterator iter(aRegion);
    const nsIntRect *iterRect;
    while ((iterRect = iter.Next())) {
      RECT rect;
      rect.left = UINT(floor((iterRect->x - bounds.x) * xres));
      rect.top = UINT(floor((iterRect->y - bounds.y) * yres));
      rect.right = rect.left +  UINT(ceil(iterRect->width * xres));
      rect.bottom = rect.top +  UINT(ceil(iterRect->height * yres));
      POINT point;
      point.x =  UINT(floor((iterRect->x - visibleRect.x) * xres));
      point.y =  UINT(floor((iterRect->y - visibleRect.y) * yres));
      device()->UpdateSurface(srcSurface, &rect, dstSurface, &point);
    }
  }
}

void
ThebesLayerD3D9::CreateNewTextures(const gfxIntSize &aSize,
                                   SurfaceMode aMode)
{
  if (aSize.width == 0 || aSize.height == 0) {
    // Nothing to do.
    return;
  }

  // Scale the requested size (in unscaled units) to the actual
  // texture size we require.
  gfxIntSize scaledSize;
  float xres, yres;
  GetDesiredResolutions(xres, yres);
  scaledSize.width = PRInt32(ceil(aSize.width * xres));
  scaledSize.height = PRInt32(ceil(aSize.height * yres));

  mTexture = nsnull;
  mTextureOnWhite = nsnull;
  device()->CreateTexture(scaledSize.width, scaledSize.height, 1,
                          D3DUSAGE_RENDERTARGET,
                          aMode != SURFACE_SINGLE_CHANNEL_ALPHA ? D3DFMT_X8R8G8B8 : D3DFMT_A8R8G8B8,
                          D3DPOOL_DEFAULT, getter_AddRefs(mTexture), NULL);
  if (aMode == SURFACE_COMPONENT_ALPHA) {
    device()->CreateTexture(scaledSize.width, scaledSize.height, 1,
                            D3DUSAGE_RENDERTARGET,
                            D3DFMT_X8R8G8B8,
                            D3DPOOL_DEFAULT, getter_AddRefs(mTextureOnWhite), NULL);
  }

  mXResolution = xres;
  mYResolution = yres;
}

void 
ThebesLayerD3D9::GetDesiredResolutions(float& aXRes, float& aYRes)
{
  const gfx3DMatrix& transform = GetLayer()->GetEffectiveTransform();
  gfxMatrix transform2d;
  if (transform.Is2D(&transform2d)) {     
    //Scale factors are normalized to a power of 2 to reduce the number of resolution changes
    gfxSize scale = transform2d.ScaleFactors(PR_TRUE);
    aXRes = gfxUtils::ClampToScaleFactor(scale.width);
    aYRes = gfxUtils::ClampToScaleFactor(scale.height);
  } else {
    aXRes = 1.0;
    aYRes = 1.0;
  }
}

bool 
ThebesLayerD3D9::ResolutionChanged(float aXRes, float aYRes)
{
  return aXRes != mXResolution ||
         aYRes != mYResolution;
}

} /* namespace layers */
} /* namespace mozilla */