software_renderer.cc

// Copyright 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/output/software_renderer.h"

#include "base/trace_event/trace_event.h"
#include "cc/base/math_util.h"
#include "cc/output/compositor_frame.h"
#include "cc/output/compositor_frame_ack.h"
#include "cc/output/compositor_frame_metadata.h"
#include "cc/output/copy_output_request.h"
#include "cc/output/output_surface.h"
#include "cc/output/render_surface_filters.h"
#include "cc/output/software_output_device.h"
#include "cc/quads/debug_border_draw_quad.h"
#include "cc/quads/picture_draw_quad.h"
#include "cc/quads/render_pass_draw_quad.h"
#include "cc/quads/solid_color_draw_quad.h"
#include "cc/quads/texture_draw_quad.h"
#include "cc/quads/tile_draw_quad.h"
#include "skia/ext/opacity_filter_canvas.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkColor.h"
#include "third_party/skia/include/core/SkImageFilter.h"
#include "third_party/skia/include/core/SkMatrix.h"
#include "third_party/skia/include/core/SkPath.h"
#include "third_party/skia/include/core/SkPoint.h"
#include "third_party/skia/include/core/SkShader.h"
#include "third_party/skia/include/effects/SkLayerRasterizer.h"
#include "ui/gfx/geometry/rect_conversions.h"
#include "ui/gfx/skia_util.h"
#include "ui/gfx/transform.h"

namespace cc {
namespace {

static inline bool IsScalarNearlyInteger(SkScalar scalar) {
  return SkScalarNearlyZero(scalar - SkScalarRoundToScalar(scalar));
}

bool IsScaleAndIntegerTranslate(const SkMatrix& matrix) {
  return IsScalarNearlyInteger(matrix[SkMatrix::kMTransX]) &&
         IsScalarNearlyInteger(matrix[SkMatrix::kMTransY]) &&
         SkScalarNearlyZero(matrix[SkMatrix::kMSkewX]) &&
         SkScalarNearlyZero(matrix[SkMatrix::kMSkewY]) &&
         SkScalarNearlyZero(matrix[SkMatrix::kMPersp0]) &&
         SkScalarNearlyZero(matrix[SkMatrix::kMPersp1]) &&
         SkScalarNearlyZero(matrix[SkMatrix::kMPersp2] - 1.0f);
}

}  // anonymous namespace

scoped_ptr<SoftwareRenderer> SoftwareRenderer::Create(
    RendererClient* client,
    const RendererSettings* settings,
    OutputSurface* output_surface,
    ResourceProvider* resource_provider) {
  return make_scoped_ptr(new SoftwareRenderer(
      client, settings, output_surface, resource_provider));
}

SoftwareRenderer::SoftwareRenderer(RendererClient* client,
                                   const RendererSettings* settings,
                                   OutputSurface* output_surface,
                                   ResourceProvider* resource_provider)
    : DirectRenderer(client, settings, output_surface, resource_provider),
      is_scissor_enabled_(false),
      is_backbuffer_discarded_(false),
      output_device_(output_surface->software_device()),
      current_canvas_(NULL) {
  if (resource_provider_) {
    capabilities_.max_texture_size = resource_provider_->max_texture_size();
    capabilities_.best_texture_format =
        resource_provider_->best_texture_format();
  }
  // The updater can access bitmaps while the SoftwareRenderer is using them.
  capabilities_.allow_partial_texture_updates = true;
  capabilities_.using_partial_swap = true;

  capabilities_.using_shared_memory_resources = true;

  capabilities_.allow_rasterize_on_demand = true;
}

SoftwareRenderer::~SoftwareRenderer() {}

const RendererCapabilitiesImpl& SoftwareRenderer::Capabilities() const {
  return capabilities_;
}

void SoftwareRenderer::BeginDrawingFrame(DrawingFrame* frame) {
  TRACE_EVENT0("cc", "SoftwareRenderer::BeginDrawingFrame");
  root_canvas_ = output_device_->BeginPaint(frame->root_damage_rect);
}

void SoftwareRenderer::FinishDrawingFrame(DrawingFrame* frame) {
  TRACE_EVENT0("cc", "SoftwareRenderer::FinishDrawingFrame");
  current_framebuffer_lock_ = nullptr;
  current_framebuffer_canvas_.clear();
  current_canvas_ = NULL;
  root_canvas_ = NULL;

  output_device_->EndPaint();
}

void SoftwareRenderer::SwapBuffers(const CompositorFrameMetadata& metadata) {
  TRACE_EVENT0("cc,benchmark", "SoftwareRenderer::SwapBuffers");
  CompositorFrame compositor_frame;
  compositor_frame.metadata = metadata;
  output_surface_->SwapBuffers(&compositor_frame);
}

bool SoftwareRenderer::FlippedFramebuffer(const DrawingFrame* frame) const {
  return false;
}

void SoftwareRenderer::EnsureScissorTestEnabled() {
  is_scissor_enabled_ = true;
  SetClipRect(scissor_rect_);
}

void SoftwareRenderer::EnsureScissorTestDisabled() {
  // There is no explicit notion of enabling/disabling scissoring in software
  // rendering, but the underlying effect we want is to clear any existing
  // clipRect on the current SkCanvas. This is done by setting clipRect to
  // the viewport's dimensions.
  if (!current_canvas_)
    return;
  is_scissor_enabled_ = false;
  SkISize size = current_canvas_->getDeviceSize();
  SetClipRect(gfx::Rect(size.width(), size.height()));
}

void SoftwareRenderer::Finish() {}

void SoftwareRenderer::BindFramebufferToOutputSurface(DrawingFrame* frame) {
  DCHECK(!output_surface_->HasExternalStencilTest());
  current_framebuffer_lock_ = nullptr;
  current_framebuffer_canvas_.clear();
  current_canvas_ = root_canvas_;
}

bool SoftwareRenderer::BindFramebufferToTexture(
    DrawingFrame* frame,
    const ScopedResource* texture,
    const gfx::Rect& target_rect) {
  DCHECK(texture->id());

  // Explicitly release lock, otherwise we can crash when try to lock
  // same texture again.
  current_framebuffer_lock_ = nullptr;
  current_framebuffer_lock_ = make_scoped_ptr(
      new ResourceProvider::ScopedWriteLockSoftware(
          resource_provider_, texture->id()));
  current_framebuffer_canvas_ =
      skia::AdoptRef(new SkCanvas(current_framebuffer_lock_->sk_bitmap()));
  current_canvas_ = current_framebuffer_canvas_.get();
  return true;
}

void SoftwareRenderer::SetScissorTestRect(const gfx::Rect& scissor_rect) {
  is_scissor_enabled_ = true;
  scissor_rect_ = scissor_rect;
  SetClipRect(scissor_rect);
}

void SoftwareRenderer::SetClipRect(const gfx::Rect& rect) {
  if (!current_canvas_)
    return;
  // Skia applies the current matrix to clip rects so we reset it temporary.
  SkMatrix current_matrix = current_canvas_->getTotalMatrix();
  current_canvas_->resetMatrix();
  current_canvas_->clipRect(gfx::RectToSkRect(rect), SkRegion::kReplace_Op);
  current_canvas_->setMatrix(current_matrix);
}

void SoftwareRenderer::ClearCanvas(SkColor color) {
  if (!current_canvas_)
    return;
  // SkCanvas::clear doesn't respect the current clipping region
  // so we SkCanvas::drawColor instead if scissoring is active.
  if (is_scissor_enabled_)
    current_canvas_->drawColor(color, SkXfermode::kSrc_Mode);
  else
    current_canvas_->clear(color);
}

void SoftwareRenderer::ClearFramebuffer(DrawingFrame* frame) {
  if (frame->current_render_pass->has_transparent_background) {
    ClearCanvas(SkColorSetARGB(0, 0, 0, 0));
  } else {
#ifndef NDEBUG
    // On DEBUG builds, opaque render passes are cleared to blue
    // to easily see regions that were not drawn on the screen.
    ClearCanvas(SkColorSetARGB(255, 0, 0, 255));
#endif
  }
}

void SoftwareRenderer::PrepareSurfaceForPass(
    DrawingFrame* frame,
    SurfaceInitializationMode initialization_mode,
    const gfx::Rect& render_pass_scissor) {
  switch (initialization_mode) {
    case SURFACE_INITIALIZATION_MODE_PRESERVE:
      EnsureScissorTestDisabled();
      return;
    case SURFACE_INITIALIZATION_MODE_FULL_SURFACE_CLEAR:
      EnsureScissorTestDisabled();
      ClearFramebuffer(frame);
      break;
    case SURFACE_INITIALIZATION_MODE_SCISSORED_CLEAR:
      SetScissorTestRect(render_pass_scissor);
      ClearFramebuffer(frame);
      break;
  }
}

bool SoftwareRenderer::IsSoftwareResource(ResourceId resource_id) const {
  switch (resource_provider_->GetResourceType(resource_id)) {
    case ResourceProvider::RESOURCE_TYPE_GL_TEXTURE:
      return false;
    case ResourceProvider::RESOURCE_TYPE_BITMAP:
      return true;
  }

  LOG(FATAL) << "Invalid resource type.";
  return false;
}

void SoftwareRenderer::DoDrawQuad(DrawingFrame* frame,
                                  const DrawQuad* quad,
                                  const gfx::QuadF* draw_region) {
  if (!current_canvas_)
    return;
  if (draw_region) {
    current_canvas_->save();
  }

  TRACE_EVENT0("cc", "SoftwareRenderer::DoDrawQuad");
  gfx::Transform quad_rect_matrix;
  QuadRectTransform(&quad_rect_matrix,
                    quad->shared_quad_state->quad_to_target_transform,
                    gfx::RectF(quad->rect));
  gfx::Transform contents_device_transform =
      frame->window_matrix * frame->projection_matrix * quad_rect_matrix;
  contents_device_transform.FlattenTo2d();
  SkMatrix sk_device_matrix;
  gfx::TransformToFlattenedSkMatrix(contents_device_transform,
                                    &sk_device_matrix);
  current_canvas_->setMatrix(sk_device_matrix);

  current_paint_.reset();
  if (settings_->force_antialiasing ||
      !IsScaleAndIntegerTranslate(sk_device_matrix)) {
    // TODO(danakj): Until we can enable AA only on exterior edges of the
    // layer, disable AA if any interior edges are present. crbug.com/248175
    bool all_four_edges_are_exterior = quad->IsTopEdge() &&
                                       quad->IsLeftEdge() &&
                                       quad->IsBottomEdge() &&
                                       quad->IsRightEdge();
    if (settings_->allow_antialiasing &&
        (settings_->force_antialiasing || all_four_edges_are_exterior))
      current_paint_.setAntiAlias(true);
    current_paint_.setFilterQuality(kLow_SkFilterQuality);
  }

  if (quad->ShouldDrawWithBlending() ||
      quad->shared_quad_state->blend_mode != SkXfermode::kSrcOver_Mode) {
    current_paint_.setAlpha(quad->shared_quad_state->opacity * 255);
    current_paint_.setXfermodeMode(quad->shared_quad_state->blend_mode);
  } else {
    current_paint_.setXfermodeMode(SkXfermode::kSrc_Mode);
  }

  if (draw_region) {
    gfx::QuadF local_draw_region(*draw_region);
    SkPath draw_region_clip_path;
    local_draw_region -=
        gfx::Vector2dF(quad->visible_rect.x(), quad->visible_rect.y());
    local_draw_region.Scale(1.0f / quad->visible_rect.width(),
                            1.0f / quad->visible_rect.height());
    local_draw_region -= gfx::Vector2dF(0.5f, 0.5f);

    SkPoint clip_points[4];
    QuadFToSkPoints(local_draw_region, clip_points);
    draw_region_clip_path.addPoly(clip_points, 4, true);

    current_canvas_->clipPath(draw_region_clip_path, SkRegion::kIntersect_Op,
                              false);
  }

  switch (quad->material) {
    case DrawQuad::DEBUG_BORDER:
      DrawDebugBorderQuad(frame, DebugBorderDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::PICTURE_CONTENT:
      DrawPictureQuad(frame, PictureDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::RENDER_PASS:
      DrawRenderPassQuad(frame, RenderPassDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::SOLID_COLOR:
      DrawSolidColorQuad(frame, SolidColorDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::TEXTURE_CONTENT:
      DrawTextureQuad(frame, TextureDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::TILED_CONTENT:
      DrawTileQuad(frame, TileDrawQuad::MaterialCast(quad));
      break;
    case DrawQuad::SURFACE_CONTENT:
      // Surface content should be fully resolved to other quad types before
      // reaching a direct renderer.
      NOTREACHED();
      break;
    case DrawQuad::INVALID:
    case DrawQuad::IO_SURFACE_CONTENT:
    case DrawQuad::YUV_VIDEO_CONTENT:
    case DrawQuad::STREAM_VIDEO_CONTENT:
      DrawUnsupportedQuad(frame, quad);
      NOTREACHED();
      break;
  }

  current_canvas_->resetMatrix();
  if (draw_region) {
    current_canvas_->restore();
  }
}

void SoftwareRenderer::DrawDebugBorderQuad(const DrawingFrame* frame,
                                           const DebugBorderDrawQuad* quad) {
  // We need to apply the matrix manually to have pixel-sized stroke width.
  SkPoint vertices[4];
  gfx::RectFToSkRect(QuadVertexRect()).toQuad(vertices);
  SkPoint transformed_vertices[4];
  current_canvas_->getTotalMatrix().mapPoints(transformed_vertices,
                                              vertices,
                                              4);
  current_canvas_->resetMatrix();

  current_paint_.setColor(quad->color);
  current_paint_.setAlpha(quad->shared_quad_state->opacity *
                          SkColorGetA(quad->color));
  current_paint_.setStyle(SkPaint::kStroke_Style);
  current_paint_.setStrokeWidth(quad->width);
  current_canvas_->drawPoints(SkCanvas::kPolygon_PointMode,
                              4, transformed_vertices, current_paint_);
}

void SoftwareRenderer::DrawPictureQuad(const DrawingFrame* frame,
                                       const PictureDrawQuad* quad) {
  SkMatrix content_matrix;
  content_matrix.setRectToRect(
      gfx::RectFToSkRect(quad->tex_coord_rect),
      gfx::RectFToSkRect(QuadVertexRect()),
      SkMatrix::kFill_ScaleToFit);
  current_canvas_->concat(content_matrix);

  const bool needs_transparency =
      SkScalarRoundToInt(quad->shared_quad_state->opacity * 255) < 255;
  const bool disable_image_filtering =
      frame->disable_picture_quad_image_filtering || quad->nearest_neighbor;

  TRACE_EVENT0("cc", "SoftwareRenderer::DrawPictureQuad");

  if (needs_transparency || disable_image_filtering) {
    // TODO(aelias): This isn't correct in all cases. We should detect these
    // cases and fall back to a persistent bitmap backing
    // (http://crbug.com/280374).
    skia::OpacityFilterCanvas filtered_canvas(current_canvas_,
                                              quad->shared_quad_state->opacity,
                                              disable_image_filtering);
    quad->raster_source->PlaybackToSharedCanvas(
        &filtered_canvas, quad->content_rect, quad->contents_scale);
  } else {
    quad->raster_source->PlaybackToSharedCanvas(
        current_canvas_, quad->content_rect, quad->contents_scale);
  }
}

void SoftwareRenderer::DrawSolidColorQuad(const DrawingFrame* frame,
                                          const SolidColorDrawQuad* quad) {
  gfx::RectF visible_quad_vertex_rect = MathUtil::ScaleRectProportional(
      QuadVertexRect(), gfx::RectF(quad->rect), gfx::RectF(quad->visible_rect));
  current_paint_.setColor(quad->color);
  current_paint_.setAlpha(quad->shared_quad_state->opacity *
                          SkColorGetA(quad->color));
  current_canvas_->drawRect(gfx::RectFToSkRect(visible_quad_vertex_rect),
                            current_paint_);
}

void SoftwareRenderer::DrawTextureQuad(const DrawingFrame* frame,
                                       const TextureDrawQuad* quad) {
  if (!IsSoftwareResource(quad->resource_id())) {
    DrawUnsupportedQuad(frame, quad);
    return;
  }

  // TODO(skaslev): Add support for non-premultiplied alpha.
  ResourceProvider::ScopedReadLockSoftware lock(resource_provider_,
                                                quad->resource_id());
  if (!lock.valid())
    return;
  const SkBitmap* bitmap = lock.sk_bitmap();
  gfx::RectF uv_rect = gfx::ScaleRect(gfx::BoundingRect(quad->uv_top_left,
                                                        quad->uv_bottom_right),
                                      bitmap->width(),
                                      bitmap->height());
  gfx::RectF visible_uv_rect = MathUtil::ScaleRectProportional(
      uv_rect, gfx::RectF(quad->rect), gfx::RectF(quad->visible_rect));
  SkRect sk_uv_rect = gfx::RectFToSkRect(visible_uv_rect);
  gfx::RectF visible_quad_vertex_rect = MathUtil::ScaleRectProportional(
      QuadVertexRect(), gfx::RectF(quad->rect), gfx::RectF(quad->visible_rect));
  SkRect quad_rect = gfx::RectFToSkRect(visible_quad_vertex_rect);

  if (quad->y_flipped)
    current_canvas_->scale(1, -1);

  bool blend_background = quad->background_color != SK_ColorTRANSPARENT &&
                          !bitmap->isOpaque();
  bool needs_layer = blend_background && (current_paint_.getAlpha() != 0xFF);
  if (needs_layer) {
    current_canvas_->saveLayerAlpha(&quad_rect, current_paint_.getAlpha());
    current_paint_.setAlpha(0xFF);
  }
  if (blend_background) {
    SkPaint background_paint;
    background_paint.setColor(quad->background_color);
    current_canvas_->drawRect(quad_rect, background_paint);
  }
  current_paint_.setFilterQuality(
      quad->nearest_neighbor ? kNone_SkFilterQuality : kLow_SkFilterQuality);
  current_canvas_->drawBitmapRect(*bitmap, sk_uv_rect, quad_rect,
                                  &current_paint_);
  if (needs_layer)
    current_canvas_->restore();
}

void SoftwareRenderer::DrawTileQuad(const DrawingFrame* frame,
                                    const TileDrawQuad* quad) {
  // |resource_provider_| can be NULL in resourceless software draws, which
  // should never produce tile quads in the first place.
  DCHECK(resource_provider_);
  DCHECK(IsSoftwareResource(quad->resource_id()));

  ResourceProvider::ScopedReadLockSoftware lock(resource_provider_,
                                                quad->resource_id());
  if (!lock.valid())
    return;

  gfx::RectF visible_tex_coord_rect = MathUtil::ScaleRectProportional(
      quad->tex_coord_rect, gfx::RectF(quad->rect),
      gfx::RectF(quad->visible_rect));
  gfx::RectF visible_quad_vertex_rect = MathUtil::ScaleRectProportional(
      QuadVertexRect(), gfx::RectF(quad->rect), gfx::RectF(quad->visible_rect));

  SkRect uv_rect = gfx::RectFToSkRect(visible_tex_coord_rect);
  current_paint_.setFilterQuality(
      quad->nearest_neighbor ? kNone_SkFilterQuality : kLow_SkFilterQuality);
  current_canvas_->drawBitmapRect(*lock.sk_bitmap(), uv_rect,
                                  gfx::RectFToSkRect(visible_quad_vertex_rect),
                                  &current_paint_);
}

void SoftwareRenderer::DrawRenderPassQuad(const DrawingFrame* frame,
                                          const RenderPassDrawQuad* quad) {
  ScopedResource* content_texture =
      render_pass_textures_.get(quad->render_pass_id);
  DCHECK(content_texture);
  DCHECK(content_texture->id());
  DCHECK(IsSoftwareResource(content_texture->id()));

  ResourceProvider::ScopedReadLockSoftware lock(resource_provider_,
                                                content_texture->id());
  if (!lock.valid())
    return;

  SkRect dest_rect = gfx::RectFToSkRect(QuadVertexRect());
  SkRect dest_visible_rect = gfx::RectFToSkRect(
      MathUtil::ScaleRectProportional(QuadVertexRect(), gfx::RectF(quad->rect),
                                      gfx::RectF(quad->visible_rect)));
  SkRect content_rect = SkRect::MakeWH(quad->rect.width(), quad->rect.height());

  SkMatrix content_mat;
  content_mat.setRectToRect(content_rect, dest_rect,
                            SkMatrix::kFill_ScaleToFit);

  const SkBitmap* content = lock.sk_bitmap();

  SkBitmap filter_bitmap;
  if (!quad->filters.IsEmpty()) {
    skia::RefPtr<SkImageFilter> filter = RenderSurfaceFilters::BuildImageFilter(
        quad->filters, gfx::SizeF(content_texture->size()));
    // TODO(ajuma): Apply the filter in the same pass as the content where
    // possible (e.g. when there's no origin offset). See crbug.com/308201.
    filter_bitmap = ApplyImageFilter(filter.get(), quad, content);
  }

  skia::RefPtr<SkShader> shader;
  if (filter_bitmap.isNull()) {
    shader = skia::AdoptRef(
        SkShader::CreateBitmapShader(*content, SkShader::kClamp_TileMode,
                                     SkShader::kClamp_TileMode, &content_mat));
  } else {
    shader = skia::AdoptRef(
        SkShader::CreateBitmapShader(filter_bitmap, SkShader::kClamp_TileMode,
                                     SkShader::kClamp_TileMode, &content_mat));
  }

  scoped_ptr<ResourceProvider::ScopedReadLockSoftware> mask_lock;
  if (quad->mask_resource_id()) {
    mask_lock = scoped_ptr<ResourceProvider::ScopedReadLockSoftware>(
        new ResourceProvider::ScopedReadLockSoftware(resource_provider_,
                                                     quad->mask_resource_id()));

    if (!mask_lock->valid())
      return;

    const SkBitmap* mask = mask_lock->sk_bitmap();

    // Scale normalized uv rect into absolute texel coordinates.
    SkRect mask_rect =
        gfx::RectFToSkRect(gfx::ScaleRect(quad->MaskUVRect(),
                                          quad->mask_texture_size.width(),
                                          quad->mask_texture_size.height()));

    SkMatrix mask_mat;
    mask_mat.setRectToRect(mask_rect, dest_rect, SkMatrix::kFill_ScaleToFit);

    skia::RefPtr<SkShader> mask_shader = skia::AdoptRef(
        SkShader::CreateBitmapShader(*mask, SkShader::kClamp_TileMode,
                                     SkShader::kClamp_TileMode, &mask_mat));

    SkPaint mask_paint;
    mask_paint.setShader(mask_shader.get());

    SkLayerRasterizer::Builder builder;
    builder.addLayer(mask_paint);

    skia::RefPtr<SkLayerRasterizer> mask_rasterizer =
        skia::AdoptRef(builder.detachRasterizer());

    current_paint_.setRasterizer(mask_rasterizer.get());
  }

  // If we have a background filter shader, render its results first.
  skia::RefPtr<SkShader> background_filter_shader =
      GetBackgroundFilterShader(frame, quad, SkShader::kClamp_TileMode);
  if (background_filter_shader) {
    SkPaint paint;
    paint.setShader(background_filter_shader.get());
    paint.setRasterizer(current_paint_.getRasterizer());
    current_canvas_->drawRect(dest_visible_rect, paint);
  }
  current_paint_.setShader(shader.get());
  current_canvas_->drawRect(dest_visible_rect, current_paint_);
}

void SoftwareRenderer::DrawUnsupportedQuad(const DrawingFrame* frame,
                                           const DrawQuad* quad) {
#ifdef NDEBUG
  current_paint_.setColor(SK_ColorWHITE);
#else
  current_paint_.setColor(SK_ColorMAGENTA);
#endif
  current_paint_.setAlpha(quad->shared_quad_state->opacity * 255);
  current_canvas_->drawRect(gfx::RectFToSkRect(QuadVertexRect()),
                            current_paint_);
}

void SoftwareRenderer::CopyCurrentRenderPassToBitmap(
    DrawingFrame* frame,
    scoped_ptr<CopyOutputRequest> request) {
  gfx::Rect copy_rect = frame->current_render_pass->output_rect;
  if (request->has_area())
    copy_rect.Intersect(request->area());
  gfx::Rect window_copy_rect = MoveFromDrawToWindowSpace(frame, copy_rect);

  scoped_ptr<SkBitmap> bitmap(new SkBitmap);
  bitmap->setInfo(SkImageInfo::MakeN32Premul(window_copy_rect.width(),
                                             window_copy_rect.height()));
  current_canvas_->readPixels(
      bitmap.get(), window_copy_rect.x(), window_copy_rect.y());

  request->SendBitmapResult(bitmap.Pass());
}

void SoftwareRenderer::DiscardBackbuffer() {
  if (is_backbuffer_discarded_)
    return;

  output_surface_->DiscardBackbuffer();

  is_backbuffer_discarded_ = true;

  // Damage tracker needs a full reset every time framebuffer is discarded.
  client_->SetFullRootLayerDamage();
}

void SoftwareRenderer::EnsureBackbuffer() {
  if (!is_backbuffer_discarded_)
    return;

  output_surface_->EnsureBackbuffer();
  is_backbuffer_discarded_ = false;
}

void SoftwareRenderer::DidChangeVisibility() {
  if (visible())
    EnsureBackbuffer();
  else
    DiscardBackbuffer();
}

bool SoftwareRenderer::ShouldApplyBackgroundFilters(
    const RenderPassDrawQuad* quad) const {
  if (quad->background_filters.IsEmpty())
    return false;

  // TODO(hendrikw): Look into allowing background filters to see pixels from
  // other render targets.  See crbug.com/314867.

  return true;
}

SkBitmap SoftwareRenderer::ApplyImageFilter(SkImageFilter* filter,
                                            const RenderPassDrawQuad* quad,
                                            const SkBitmap* to_filter) const {
  if (!filter)
    return SkBitmap();

  SkBitmap filter_bitmap;
  if (filter_bitmap.tryAllocPixels(SkImageInfo::MakeN32Premul(
          to_filter->width(), to_filter->height()))) {
    SkCanvas canvas(filter_bitmap);
    SkPaint paint;
    paint.setImageFilter(filter);
    canvas.clear(SK_ColorTRANSPARENT);
    canvas.translate(SkIntToScalar(-quad->rect.origin().x()),
                     SkIntToScalar(-quad->rect.origin().y()));
    canvas.scale(quad->filters_scale.x(), quad->filters_scale.y());
    canvas.drawSprite(*to_filter, 0, 0, &paint);
  }
  return filter_bitmap;
}

SkBitmap SoftwareRenderer::GetBackdropBitmap(
    const gfx::Rect& bounding_rect) const {
  SkBitmap bitmap;
  bitmap.setInfo(SkImageInfo::MakeN32Premul(bounding_rect.width(),
                                            bounding_rect.height()));
  current_canvas_->readPixels(&bitmap, bounding_rect.x(), bounding_rect.y());
  return bitmap;
}

gfx::Rect SoftwareRenderer::GetBackdropBoundingBoxForRenderPassQuad(
    const DrawingFrame* frame,
    const RenderPassDrawQuad* quad,
    const gfx::Transform& contents_device_transform) const {
  DCHECK(ShouldApplyBackgroundFilters(quad));
  gfx::Rect backdrop_rect = gfx::ToEnclosingRect(
      MathUtil::MapClippedRect(contents_device_transform, QuadVertexRect()));

  int top, right, bottom, left;
  quad->background_filters.GetOutsets(&top, &right, &bottom, &left);
  backdrop_rect.Inset(-left, -top, -right, -bottom);

  backdrop_rect.Intersect(MoveFromDrawToWindowSpace(
      frame, frame->current_render_pass->output_rect));

  return backdrop_rect;
}

skia::RefPtr<SkShader> SoftwareRenderer::GetBackgroundFilterShader(
    const DrawingFrame* frame,
    const RenderPassDrawQuad* quad,
    SkShader::TileMode content_tile_mode) const {
  if (!ShouldApplyBackgroundFilters(quad))
    return skia::RefPtr<SkShader>();

  gfx::Transform quad_rect_matrix;
  QuadRectTransform(&quad_rect_matrix,
                    quad->shared_quad_state->quad_to_target_transform,
                    gfx::RectF(quad->rect));
  gfx::Transform contents_device_transform =
      frame->window_matrix * frame->projection_matrix * quad_rect_matrix;
  contents_device_transform.FlattenTo2d();

  gfx::Rect backdrop_rect = GetBackdropBoundingBoxForRenderPassQuad(
      frame, quad, contents_device_transform);

  // Figure out the transformations to move it back to pixel space.
  gfx::Transform contents_device_transform_inverse;
  if (!contents_device_transform.GetInverse(&contents_device_transform_inverse))
    return skia::RefPtr<SkShader>();

  SkMatrix filter_backdrop_transform =
      contents_device_transform_inverse.matrix();
  filter_backdrop_transform.preTranslate(backdrop_rect.x(), backdrop_rect.y());

  // Draw what's behind, and apply the filter to it.
  SkBitmap backdrop_bitmap = GetBackdropBitmap(backdrop_rect);

  skia::RefPtr<SkImageFilter> filter = RenderSurfaceFilters::BuildImageFilter(
      quad->background_filters,
      gfx::SizeF(backdrop_bitmap.width(), backdrop_bitmap.height()));
  SkBitmap filter_backdrop_bitmap =
      ApplyImageFilter(filter.get(), quad, &backdrop_bitmap);

  if (filter_backdrop_bitmap.empty())
    return skia::RefPtr<SkShader>();

  return skia::AdoptRef(SkShader::CreateBitmapShader(
      filter_backdrop_bitmap, content_tile_mode, content_tile_mode,
      &filter_backdrop_transform));
}

}  // namespace cc