virtual nsIntRegion ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback,
                                            bool& aGeometryChanged)
  {
    ImageLayer* imageLayer = static_cast<ImageLayer*>(mLayer.get());
    
    if (!imageLayer->GetVisibleRegion().IsEqual(mVisibleRegion)) {
      aGeometryChanged = true;
      IntRect result = NewTransformedBounds();
      result = result.Union(OldTransformedBounds());
      return result;
    }

    ImageContainer* container = imageLayer->GetContainer();
    if (mContainer != container ||
        mFilter != imageLayer->GetFilter() ||
        mScaleToSize != imageLayer->GetScaleToSize() ||
        mScaleMode != imageLayer->GetScaleMode()) {
      aGeometryChanged = true;

      if (mIsMask) {
        // Mask layers have an empty visible region, so we have to
        // use the image size instead.
        IntSize size = container->GetCurrentSize();
        IntRect rect(0, 0, size.width, size.height);
        return TransformRect(rect, mLayer->GetLocalTransform());

      } else {
        return NewTransformedBounds();
      }
    }

    return IntRect();
  }
    virtual nsIntRect ComputeChangeInternal(NotifySubDocInvalidationFunc aCallback)
    {
        ImageLayer* image = static_cast<ImageLayer*>(mLayer);

        if (!image->GetVisibleRegion().IsEqual(mVisibleRegion)) {
            nsIntRect result = NewTransformedBounds();
            result = result.Union(OldTransformedBounds());
            return result;
        }

        if (mContainer != image->GetContainer() ||
                mFilter != image->GetFilter() ||
                mScaleToSize != image->GetScaleToSize() ||
                mScaleMode != image->GetScaleMode()) {
            return NewTransformedBounds();
        }

        return nsIntRect();
    }
示例#3
0
bool
HwcComposer2D::PrepareLayerList(Layer* aLayer,
                                const nsIntRect& aClip,
                                const Matrix& aParentTransform,
                                bool aFindSidebandStreams)
{
    // NB: we fall off this path whenever there are container layers
    // that require intermediate surfaces.  That means all the
    // GetEffective*() coordinates are relative to the framebuffer.

    bool fillColor = false;

    const nsIntRegion visibleRegion = aLayer->GetLocalVisibleRegion().ToUnknownRegion();
    if (visibleRegion.IsEmpty()) {
        return true;
    }

    uint8_t opacity = std::min(0xFF, (int)(aLayer->GetEffectiveOpacity() * 256.0));
    if (opacity == 0) {
        LOGD("%s Layer has zero opacity; skipping", aLayer->Name());
        return true;
    }

    if (!mHal->SupportTransparency() && opacity < 0xFF && !aFindSidebandStreams) {
        LOGD("%s Layer has planar semitransparency which is unsupported by hwcomposer", aLayer->Name());
        return false;
    }

    if (aLayer->GetMaskLayer() && !aFindSidebandStreams) {
        LOGD("%s Layer has MaskLayer which is unsupported by hwcomposer", aLayer->Name());
        return false;
    }

    nsIntRect clip;
    nsIntRect layerClip = aLayer->GetLocalClipRect().valueOr(ParentLayerIntRect()).ToUnknownRect();
    nsIntRect* layerClipPtr = aLayer->GetLocalClipRect() ? &layerClip : nullptr;
    if (!HwcUtils::CalculateClipRect(aParentTransform,
                                     layerClipPtr,
                                     aClip,
                                     &clip))
    {
        LOGD("%s Clip rect is empty. Skip layer", aLayer->Name());
        return true;
    }

    // HWC supports only the following 2D transformations:
    //
    // Scaling via the sourceCrop and displayFrame in HwcLayer
    // Translation via the sourceCrop and displayFrame in HwcLayer
    // Rotation (in square angles only) via the HWC_TRANSFORM_ROT_* flags
    // Reflection (horizontal and vertical) via the HWC_TRANSFORM_FLIP_* flags
    //
    // A 2D transform with PreservesAxisAlignedRectangles() has all the attributes
    // above
    Matrix layerTransform;
    if (!aLayer->GetEffectiveTransform().Is2D(&layerTransform) ||
        !layerTransform.PreservesAxisAlignedRectangles()) {
        LOGD("Layer EffectiveTransform has a 3D transform or a non-square angle rotation");
        return false;
    }

    Matrix layerBufferTransform;
    if (!aLayer->GetEffectiveTransformForBuffer().Is2D(&layerBufferTransform) ||
        !layerBufferTransform.PreservesAxisAlignedRectangles()) {
        LOGD("Layer EffectiveTransformForBuffer has a 3D transform or a non-square angle rotation");
      return false;
    }

    if (ContainerLayer* container = aLayer->AsContainerLayer()) {
        if (container->UseIntermediateSurface() && !aFindSidebandStreams) {
            LOGD("Container layer needs intermediate surface");
            return false;
        }
        AutoTArray<Layer*, 12> children;
        container->SortChildrenBy3DZOrder(children);

        for (uint32_t i = 0; i < children.Length(); i++) {
            if (!PrepareLayerList(children[i], clip, layerTransform, aFindSidebandStreams) &&
                !aFindSidebandStreams) {
                return false;
            }
        }
        return true;
    }

    LayerRenderState state = aLayer->GetRenderState();

#if ANDROID_VERSION >= 21
    if (!state.GetGrallocBuffer() && !state.GetSidebandStream().IsValid()) {
#else
    if (!state.GetGrallocBuffer()) {
#endif
        if (aLayer->AsColorLayer() && mColorFill) {
            fillColor = true;
        } else {
            LOGD("%s Layer doesn't have a gralloc buffer", aLayer->Name());
            return false;
        }
    }

    nsIntRect visibleRect = visibleRegion.GetBounds();

    nsIntRect bufferRect;
    if (fillColor) {
        bufferRect = nsIntRect(visibleRect);
    } else {
        nsIntRect layerRect;
        if (state.mHasOwnOffset) {
            bufferRect = nsIntRect(state.mOffset.x, state.mOffset.y,
                                   state.mSize.width, state.mSize.height);
            layerRect = bufferRect;
        } else {
            //Since the buffer doesn't have its own offset, assign the whole
            //surface size as its buffer bounds
            bufferRect = nsIntRect(0, 0, state.mSize.width, state.mSize.height);
            layerRect = bufferRect;
            if (aLayer->GetType() == Layer::TYPE_IMAGE) {
                ImageLayer* imageLayer = static_cast<ImageLayer*>(aLayer);
                if(imageLayer->GetScaleMode() != ScaleMode::SCALE_NONE) {
                  layerRect = nsIntRect(0, 0, imageLayer->GetScaleToSize().width, imageLayer->GetScaleToSize().height);
                }
            }
        }
        // In some cases the visible rect assigned to the layer can be larger
        // than the layer's surface, e.g., an ImageLayer with a small Image
        // in it.
        visibleRect.IntersectRect(visibleRect, layerRect);
    }

    // Buffer rotation is not to be confused with the angled rotation done by a transform matrix
    // It's a fancy PaintedLayer feature used for scrolling
    if (state.BufferRotated()) {
        LOGD("%s Layer has a rotated buffer", aLayer->Name());
        return false;
    }

    const bool needsYFlip = state.OriginBottomLeft() ? true
                                                     : false;

    hwc_rect_t sourceCrop, displayFrame;
    if(!HwcUtils::PrepareLayerRects(visibleRect,
                          layerTransform,
                          layerBufferTransform,
                          clip,
                          bufferRect,
                          needsYFlip,
                          &(sourceCrop),
                          &(displayFrame)))
    {
        return true;
    }

    // OK!  We can compose this layer with hwc.
    int current = mList ? mList->numHwLayers : 0;

    // Do not compose any layer below full-screen Opaque layer
    // Note: It can be generalized to non-fullscreen Opaque layers.
    bool isOpaque = opacity == 0xFF &&
        (state.mFlags & LayerRenderStateFlags::OPAQUE);
    // Currently we perform opacity calculation using the *bounds* of the layer.
    // We can only make this assumption if we're not dealing with a complex visible region.
    bool isSimpleVisibleRegion = visibleRegion.Contains(visibleRect);
    if (current && isOpaque && isSimpleVisibleRegion) {
        nsIntRect displayRect = nsIntRect(displayFrame.left, displayFrame.top,
            displayFrame.right - displayFrame.left, displayFrame.bottom - displayFrame.top);
        if (displayRect.Contains(mScreenRect)) {
            // In z-order, all previous layers are below
            // the current layer. We can ignore them now.
            mList->numHwLayers = current = 0;
            mHwcLayerMap.Clear();
        }
    }

    if (!mList || current >= mMaxLayerCount) {
        if (!ReallocLayerList() || current >= mMaxLayerCount) {
            LOGE("PrepareLayerList failed! Could not increase the maximum layer count");
            return false;
        }
    }

    HwcLayer& hwcLayer = mList->hwLayers[current];
    hwcLayer.displayFrame = displayFrame;
    mHal->SetCrop(hwcLayer, sourceCrop);
    buffer_handle_t handle = nullptr;
#if ANDROID_VERSION >= 21
    if (state.GetSidebandStream().IsValid()) {
        handle = state.GetSidebandStream().GetRawNativeHandle();
    } else if (state.GetGrallocBuffer()) {
        handle = state.GetGrallocBuffer()->getNativeBuffer()->handle;
    }
#else
    if (state.GetGrallocBuffer()) {
        handle = state.GetGrallocBuffer()->getNativeBuffer()->handle;
    }
#endif
    hwcLayer.handle = handle;

    hwcLayer.flags = 0;
    hwcLayer.hints = 0;
    hwcLayer.blending = isOpaque ? HWC_BLENDING_NONE : HWC_BLENDING_PREMULT;
#if ANDROID_VERSION >= 17
    hwcLayer.compositionType = HWC_FRAMEBUFFER;
#if ANDROID_VERSION >= 21
    if (state.GetSidebandStream().IsValid()) {
        hwcLayer.compositionType = HWC_SIDEBAND;
    }
#endif
    hwcLayer.acquireFenceFd = -1;
    hwcLayer.releaseFenceFd = -1;
#if ANDROID_VERSION >= 18
    hwcLayer.planeAlpha = opacity;
#endif
#else
    hwcLayer.compositionType = HwcUtils::HWC_USE_COPYBIT;
#endif

    if (!fillColor) {
        if (state.FormatRBSwapped()) {
            if (!mRBSwapSupport) {
                LOGD("No R/B swap support in H/W Composer");
                return false;
            }
            hwcLayer.flags |= HwcUtils::HWC_FORMAT_RB_SWAP;
        }

        // Translation and scaling have been addressed in PrepareLayerRects().
        // Given the above and that we checked for PreservesAxisAlignedRectangles()
        // the only possible transformations left to address are
        // square angle rotation and horizontal/vertical reflection.
        //
        // The rotation and reflection permutations total 16 but can be
        // reduced to 8 transformations after eliminating redundancies.
        //
        // All matrices represented here are in the form
        //
        // | xx  xy |
        // | yx  yy |
        //
        // And ignore scaling.
        //
        // Reflection is applied before rotation
        gfx::Matrix rotation = layerTransform;
        // Compute fuzzy zero like PreservesAxisAlignedRectangles()
        if (fabs(rotation._11) < 1e-6) {
            if (rotation._21 < 0) {
                if (rotation._12 > 0) {
                    // 90 degree rotation
                    //
                    // |  0  -1  |
                    // |  1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90;
                    LOGD("Layer rotated 90 degrees");
                }
                else {
                    // Horizontal reflection then 90 degree rotation
                    //
                    // |  0  -1  | | -1   0  | = |  0  -1  |
                    // |  1   0  | |  0   1  |   | -1   0  |
                    //
                    // same as vertical reflection then 270 degree rotation
                    //
                    // |  0   1  | |  1   0  | = |  0  -1  |
                    // | -1   0  | |  0  -1  |   | -1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90 | HWC_TRANSFORM_FLIP_H;
                    LOGD("Layer vertically reflected then rotated 270 degrees");
                }
            } else {
                if (rotation._12 < 0) {
                    // 270 degree rotation
                    //
                    // |  0   1  |
                    // | -1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_270;
                    LOGD("Layer rotated 270 degrees");
                }
                else {
                    // Vertical reflection then 90 degree rotation
                    //
                    // |  0   1  | | -1   0  | = |  0   1  |
                    // | -1   0  | |  0   1  |   |  1   0  |
                    //
                    // Same as horizontal reflection then 270 degree rotation
                    //
                    // |  0  -1  | |  1   0  | = |  0   1  |
                    // |  1   0  | |  0  -1  |   |  1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90 | HWC_TRANSFORM_FLIP_V;
                    LOGD("Layer horizontally reflected then rotated 270 degrees");
                }
            }
        } else if (rotation._11 < 0) {
            if (rotation._22 > 0) {
                // Horizontal reflection
                //
                // | -1   0  |
                // |  0   1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_FLIP_H;
                LOGD("Layer rotated 180 degrees");
            }
            else {
                // 180 degree rotation
                //
                // | -1   0  |
                // |  0  -1  |
                //
                // Same as horizontal and vertical reflection
                //
                // | -1   0  | |  1   0  | = | -1   0  |
                // |  0   1  | |  0  -1  |   |  0  -1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_ROT_180;
                LOGD("Layer rotated 180 degrees");
            }
        } else {
            if (rotation._22 < 0) {
                // Vertical reflection
                //
                // |  1   0  |
                // |  0  -1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_FLIP_V;
                LOGD("Layer rotated 180 degrees");
            }
            else {
                // No rotation or reflection
                //
                // |  1   0  |
                // |  0   1  |
                //
                hwcLayer.transform = 0;
            }
        }

        const bool needsYFlip = state.OriginBottomLeft() ? true
                                                         : false;

        if (needsYFlip) {
           // Invert vertical reflection flag if it was already set
           hwcLayer.transform ^= HWC_TRANSFORM_FLIP_V;
        }
        hwc_region_t region;
        if (visibleRegion.GetNumRects() > 1) {
            mVisibleRegions.push_back(HwcUtils::RectVector());
            HwcUtils::RectVector* visibleRects = &(mVisibleRegions.back());
            bool isVisible = false;
            if(!HwcUtils::PrepareVisibleRegion(visibleRegion,
                                     layerTransform,
                                     layerBufferTransform,
                                     clip,
                                     bufferRect,
                                     visibleRects,
                                     isVisible)) {
                LOGD("A region of layer is too small to be rendered by HWC");
                return false;
            }
            if (!isVisible) {
                // Layer is not visible, no need to render it
                return true;
            }
            region.numRects = visibleRects->size();
            region.rects = &((*visibleRects)[0]);
        } else {
            region.numRects = 1;
            region.rects = &(hwcLayer.displayFrame);
        }
        hwcLayer.visibleRegionScreen = region;
    } else {
        hwcLayer.flags |= HwcUtils::HWC_COLOR_FILL;
        ColorLayer* colorLayer = aLayer->AsColorLayer();
        if (colorLayer->GetColor().a < 1.0) {
            LOGD("Color layer has semitransparency which is unsupported");
            return false;
        }
        hwcLayer.transform = colorLayer->GetColor().ToABGR();
    }

#if ANDROID_VERSION >= 21
    if (aFindSidebandStreams && hwcLayer.compositionType == HWC_SIDEBAND) {
        mCachedSidebandLayers.AppendElement(hwcLayer);
    }
#endif

    mHwcLayerMap.AppendElement(static_cast<LayerComposite*>(aLayer->ImplData()));
    mList->numHwLayers++;
    return true;
}


#if ANDROID_VERSION >= 17
bool
HwcComposer2D::TryHwComposition(nsScreenGonk* aScreen)
{
    DisplaySurface* dispSurface = aScreen->GetDisplaySurface();

    if (!(dispSurface && dispSurface->lastHandle)) {
        LOGD("H/W Composition failed. DispSurface not initialized.");
        return false;
    }

    // Add FB layer
    int idx = mList->numHwLayers++;
    if (idx >= mMaxLayerCount) {
        if (!ReallocLayerList() || idx >= mMaxLayerCount) {
            LOGE("TryHwComposition failed! Could not add FB layer");
            return false;
        }
    }

    Prepare(dispSurface->lastHandle, -1, aScreen);

    /* Possible composition paths, after hwc prepare:
    1. GPU Composition
    2. BLIT Composition
    3. Full OVERLAY Composition
    4. Partial OVERLAY Composition (GPU + OVERLAY) */

    bool gpuComposite = false;
    bool blitComposite = false;
    bool overlayComposite = true;

    for (int j=0; j < idx; j++) {
        if (mList->hwLayers[j].compositionType == HWC_FRAMEBUFFER ||
            mList->hwLayers[j].compositionType == HWC_BLIT) {
            // Full OVERLAY composition is not possible on this frame
            // It is either GPU / BLIT / partial OVERLAY composition.
            overlayComposite = false;
            break;
        }
    }

    if (!overlayComposite) {
        for (int k=0; k < idx; k++) {
            switch (mList->hwLayers[k].compositionType) {
                case HWC_FRAMEBUFFER:
                    gpuComposite = true;
                    break;
                case HWC_BLIT:
                    blitComposite = true;
                    break;
#if ANDROID_VERSION >= 21
                case HWC_SIDEBAND:
#endif
                case HWC_OVERLAY: {
                    // HWC will compose HWC_OVERLAY layers in partial
                    // Overlay Composition, set layer composition flag
                    // on mapped LayerComposite to skip GPU composition
                    mHwcLayerMap[k]->SetLayerComposited(true);

                    uint8_t opacity = std::min(0xFF, (int)(mHwcLayerMap[k]->GetLayer()->GetEffectiveOpacity() * 256.0));
                    if ((mList->hwLayers[k].hints & HWC_HINT_CLEAR_FB) &&
                        (opacity == 0xFF)) {
                        // Clear visible rect on FB with transparent pixels.
                        hwc_rect_t r = mList->hwLayers[k].displayFrame;
                        mHwcLayerMap[k]->SetClearRect(nsIntRect(r.left, r.top,
                                                                r.right - r.left,
                                                                r.bottom - r.top));
                    }
                    break;
                }
                default:
                    break;
            }
        }

        if (gpuComposite) {
            // GPU or partial OVERLAY Composition
            return false;
        } else if (blitComposite) {
            // BLIT Composition, flip DispSurface target
            GetGonkDisplay()->UpdateDispSurface(aScreen->GetEGLDisplay(), aScreen->GetEGLSurface());
            DisplaySurface* dispSurface = aScreen->GetDisplaySurface();
            if (!dispSurface) {
                LOGE("H/W Composition failed. NULL DispSurface.");
                return false;
            }
            mList->hwLayers[idx].handle = dispSurface->lastHandle;
            mList->hwLayers[idx].acquireFenceFd = dispSurface->GetPrevDispAcquireFd();
        }
    }

    // BLIT or full OVERLAY Composition
    return Commit(aScreen);
}
bool
HwcComposer2D::PrepareLayerList(Layer* aLayer,
                                const nsIntRect& aClip,
                                const Matrix& aParentTransform)
{
    // NB: we fall off this path whenever there are container layers
    // that require intermediate surfaces.  That means all the
    // GetEffective*() coordinates are relative to the framebuffer.

    bool fillColor = false;

    const nsIntRegion& visibleRegion = aLayer->GetEffectiveVisibleRegion();
    if (visibleRegion.IsEmpty()) {
        return true;
    }

    uint8_t opacity = std::min(0xFF, (int)(aLayer->GetEffectiveOpacity() * 256.0));
#if ANDROID_VERSION < 18
    if (opacity < 0xFF) {
        LOGD("%s Layer has planar semitransparency which is unsupported by hwcomposer", aLayer->Name());
        return false;
    }
#endif

    if (aLayer->GetMaskLayer()) {
      LOGD("%s Layer has MaskLayer which is unsupported by hwcomposer", aLayer->Name());
      return false;
    }

    nsIntRect clip;
    if (!HwcUtils::CalculateClipRect(aParentTransform,
                                     aLayer->GetEffectiveClipRect(),
                                     aClip,
                                     &clip))
    {
        LOGD("%s Clip rect is empty. Skip layer", aLayer->Name());
        return true;
    }

    // HWC supports only the following 2D transformations:
    //
    // Scaling via the sourceCrop and displayFrame in HwcLayer
    // Translation via the sourceCrop and displayFrame in HwcLayer
    // Rotation (in square angles only) via the HWC_TRANSFORM_ROT_* flags
    // Reflection (horizontal and vertical) via the HWC_TRANSFORM_FLIP_* flags
    //
    // A 2D transform with PreservesAxisAlignedRectangles() has all the attributes
    // above
    Matrix layerTransform;
    if (!aLayer->GetEffectiveTransform().Is2D(&layerTransform) ||
        !layerTransform.PreservesAxisAlignedRectangles()) {
        LOGD("Layer EffectiveTransform has a 3D transform or a non-square angle rotation");
        return false;
    }

    Matrix layerBufferTransform;
    if (!aLayer->GetEffectiveTransformForBuffer().Is2D(&layerBufferTransform) ||
        !layerBufferTransform.PreservesAxisAlignedRectangles()) {
        LOGD("Layer EffectiveTransformForBuffer has a 3D transform or a non-square angle rotation");
      return false;
    }

    if (ContainerLayer* container = aLayer->AsContainerLayer()) {
        if (container->UseIntermediateSurface()) {
            LOGD("Container layer needs intermediate surface");
            return false;
        }
        nsAutoTArray<Layer*, 12> children;
        container->SortChildrenBy3DZOrder(children);

        for (uint32_t i = 0; i < children.Length(); i++) {
            if (!PrepareLayerList(children[i], clip, layerTransform)) {
                return false;
            }
        }
        return true;
    }

    LayerRenderState state = aLayer->GetRenderState();

    if (!state.mSurface.get()) {
      if (aLayer->AsColorLayer() && mColorFill) {
        fillColor = true;
      } else {
          LOGD("%s Layer doesn't have a gralloc buffer", aLayer->Name());
          return false;
      }
    }

    nsIntRect visibleRect = visibleRegion.GetBounds();

    nsIntRect bufferRect;
    if (fillColor) {
        bufferRect = nsIntRect(visibleRect);
    } else {
        nsIntRect layerRect;
        if (state.mHasOwnOffset) {
            bufferRect = nsIntRect(state.mOffset.x, state.mOffset.y,
                                   state.mSize.width, state.mSize.height);
            layerRect = bufferRect;
        } else {
            //Since the buffer doesn't have its own offset, assign the whole
            //surface size as its buffer bounds
            bufferRect = nsIntRect(0, 0, state.mSize.width, state.mSize.height);
            layerRect = bufferRect;
            if (aLayer->GetType() == Layer::TYPE_IMAGE) {
                ImageLayer* imageLayer = static_cast<ImageLayer*>(aLayer);
                if(imageLayer->GetScaleMode() != ScaleMode::SCALE_NONE) {
                  layerRect = nsIntRect(0, 0, imageLayer->GetScaleToSize().width, imageLayer->GetScaleToSize().height);
                }
            }
        }
        // In some cases the visible rect assigned to the layer can be larger
        // than the layer's surface, e.g., an ImageLayer with a small Image
        // in it.
        visibleRect.IntersectRect(visibleRect, layerRect);
    }

    // Buffer rotation is not to be confused with the angled rotation done by a transform matrix
    // It's a fancy PaintedLayer feature used for scrolling
    if (state.BufferRotated()) {
        LOGD("%s Layer has a rotated buffer", aLayer->Name());
        return false;
    }

    const bool needsYFlip = state.OriginBottomLeft() ? true
                                                     : false;

    hwc_rect_t sourceCrop, displayFrame;
    if(!HwcUtils::PrepareLayerRects(visibleRect,
                          layerTransform,
                          layerBufferTransform,
                          clip,
                          bufferRect,
                          needsYFlip,
                          &(sourceCrop),
                          &(displayFrame)))
    {
        return true;
    }

    // OK!  We can compose this layer with hwc.
    int current = mList ? mList->numHwLayers : 0;

    // Do not compose any layer below full-screen Opaque layer
    // Note: It can be generalized to non-fullscreen Opaque layers.
    bool isOpaque = opacity == 0xFF &&
        (state.mFlags & LayerRenderStateFlags::OPAQUE);
    // Currently we perform opacity calculation using the *bounds* of the layer.
    // We can only make this assumption if we're not dealing with a complex visible region.
    bool isSimpleVisibleRegion = visibleRegion.Contains(visibleRect);
    if (current && isOpaque && isSimpleVisibleRegion) {
        nsIntRect displayRect = nsIntRect(displayFrame.left, displayFrame.top,
            displayFrame.right - displayFrame.left, displayFrame.bottom - displayFrame.top);
        if (displayRect.Contains(mScreenRect)) {
            // In z-order, all previous layers are below
            // the current layer. We can ignore them now.
            mList->numHwLayers = current = 0;
            mHwcLayerMap.Clear();
        }
    }

    if (!mList || current >= mMaxLayerCount) {
        if (!ReallocLayerList() || current >= mMaxLayerCount) {
            LOGE("PrepareLayerList failed! Could not increase the maximum layer count");
            return false;
        }
    }

    HwcLayer& hwcLayer = mList->hwLayers[current];
    hwcLayer.displayFrame = displayFrame;
    setCrop(&hwcLayer, sourceCrop);
    buffer_handle_t handle = fillColor ? nullptr : state.mSurface->getNativeBuffer()->handle;
    hwcLayer.handle = handle;

    hwcLayer.flags = 0;
    hwcLayer.hints = 0;
    hwcLayer.blending = isOpaque ? HWC_BLENDING_NONE : HWC_BLENDING_PREMULT;
#if ANDROID_VERSION >= 17
    hwcLayer.compositionType = HWC_FRAMEBUFFER;

    hwcLayer.acquireFenceFd = -1;
    hwcLayer.releaseFenceFd = -1;
#if ANDROID_VERSION >= 18
    hwcLayer.planeAlpha = opacity;
#endif
#else
    hwcLayer.compositionType = HwcUtils::HWC_USE_COPYBIT;
#endif

    if (!fillColor) {
        if (state.FormatRBSwapped()) {
            if (!mRBSwapSupport) {
                LOGD("No R/B swap support in H/W Composer");
                return false;
            }
            hwcLayer.flags |= HwcUtils::HWC_FORMAT_RB_SWAP;
        }

        // Translation and scaling have been addressed in PrepareLayerRects().
        // Given the above and that we checked for PreservesAxisAlignedRectangles()
        // the only possible transformations left to address are
        // square angle rotation and horizontal/vertical reflection.
        //
        // The rotation and reflection permutations total 16 but can be
        // reduced to 8 transformations after eliminating redundancies.
        //
        // All matrices represented here are in the form
        //
        // | xx  xy |
        // | yx  yy |
        //
        // And ignore scaling.
        //
        // Reflection is applied before rotation
        gfx::Matrix rotation = layerTransform;
        // Compute fuzzy zero like PreservesAxisAlignedRectangles()
        if (fabs(rotation._11) < 1e-6) {
            if (rotation._21 < 0) {
                if (rotation._12 > 0) {
                    // 90 degree rotation
                    //
                    // |  0  -1  |
                    // |  1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90;
                    LOGD("Layer rotated 90 degrees");
                }
                else {
                    // Horizontal reflection then 90 degree rotation
                    //
                    // |  0  -1  | | -1   0  | = |  0  -1  |
                    // |  1   0  | |  0   1  |   | -1   0  |
                    //
                    // same as vertical reflection then 270 degree rotation
                    //
                    // |  0   1  | |  1   0  | = |  0  -1  |
                    // | -1   0  | |  0  -1  |   | -1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90 | HWC_TRANSFORM_FLIP_H;
                    LOGD("Layer vertically reflected then rotated 270 degrees");
                }
            } else {
                if (rotation._12 < 0) {
                    // 270 degree rotation
                    //
                    // |  0   1  |
                    // | -1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_270;
                    LOGD("Layer rotated 270 degrees");
                }
                else {
                    // Vertical reflection then 90 degree rotation
                    //
                    // |  0   1  | | -1   0  | = |  0   1  |
                    // | -1   0  | |  0   1  |   |  1   0  |
                    //
                    // Same as horizontal reflection then 270 degree rotation
                    //
                    // |  0  -1  | |  1   0  | = |  0   1  |
                    // |  1   0  | |  0  -1  |   |  1   0  |
                    //
                    hwcLayer.transform = HWC_TRANSFORM_ROT_90 | HWC_TRANSFORM_FLIP_V;
                    LOGD("Layer horizontally reflected then rotated 270 degrees");
                }
            }
        } else if (rotation._11 < 0) {
            if (rotation._22 > 0) {
                // Horizontal reflection
                //
                // | -1   0  |
                // |  0   1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_FLIP_H;
                LOGD("Layer rotated 180 degrees");
            }
            else {
                // 180 degree rotation
                //
                // | -1   0  |
                // |  0  -1  |
                //
                // Same as horizontal and vertical reflection
                //
                // | -1   0  | |  1   0  | = | -1   0  |
                // |  0   1  | |  0  -1  |   |  0  -1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_ROT_180;
                LOGD("Layer rotated 180 degrees");
            }
        } else {
            if (rotation._22 < 0) {
                // Vertical reflection
                //
                // |  1   0  |
                // |  0  -1  |
                //
                hwcLayer.transform = HWC_TRANSFORM_FLIP_V;
                LOGD("Layer rotated 180 degrees");
            }
            else {
                // No rotation or reflection
                //
                // |  1   0  |
                // |  0   1  |
                //
                hwcLayer.transform = 0;
            }
        }

        const bool needsYFlip = state.OriginBottomLeft() ? true
                                                         : false;

        if (needsYFlip) {
           // Invert vertical reflection flag if it was already set
           hwcLayer.transform ^= HWC_TRANSFORM_FLIP_V;
        }
        hwc_region_t region;
        if (visibleRegion.GetNumRects() > 1) {
            mVisibleRegions.push_back(HwcUtils::RectVector());
            HwcUtils::RectVector* visibleRects = &(mVisibleRegions.back());
            if(!HwcUtils::PrepareVisibleRegion(visibleRegion,
                                     layerTransform,
                                     layerBufferTransform,
                                     clip,
                                     bufferRect,
                                     visibleRects)) {
                return true;
            }
            region.numRects = visibleRects->size();
            region.rects = &((*visibleRects)[0]);
        } else {
            region.numRects = 1;
            region.rects = &(hwcLayer.displayFrame);
        }
        hwcLayer.visibleRegionScreen = region;
    } else {
        hwcLayer.flags |= HwcUtils::HWC_COLOR_FILL;
        ColorLayer* colorLayer = aLayer->AsColorLayer();
        if (colorLayer->GetColor().a < 1.0) {
            LOGD("Color layer has semitransparency which is unsupported");
            return false;
        }
        hwcLayer.transform = colorLayer->GetColor().Packed();
    }

    mHwcLayerMap.AppendElement(static_cast<LayerComposite*>(aLayer->ImplData()));
    mList->numHwLayers++;
    return true;
}