cc/resources/picture_pile_impl.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 <algorithm>
#include <limits>
#include <set>

#include "base/trace_event/trace_event.h"
#include "cc/base/region.h"
#include "cc/debug/debug_colors.h"
#include "cc/resources/picture_pile_impl.h"
#include "cc/resources/raster_source_helper.h"
#include "skia/ext/analysis_canvas.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkPictureRecorder.h"
#include "ui/gfx/geometry/rect_conversions.h"

namespace cc {

scoped_refptr<PicturePileImpl> PicturePileImpl::CreateFromPicturePile(
    const PicturePile* other,
    bool can_use_lcd_text) {
  return make_scoped_refptr(new PicturePileImpl(other, can_use_lcd_text));
}

PicturePileImpl::PicturePileImpl()
    : background_color_(SK_ColorTRANSPARENT),
      requires_clear_(true),
      can_use_lcd_text_(true),
      is_solid_color_(false),
      solid_color_(SK_ColorTRANSPARENT),
      has_any_recordings_(false),
      clear_canvas_with_debug_color_(false),
      min_contents_scale_(0.f),
      slow_down_raster_scale_factor_for_debug_(0),
      should_attempt_to_use_distance_field_text_(false) {
}

PicturePileImpl::PicturePileImpl(const PicturePile* other,
                                 bool can_use_lcd_text)
    : picture_map_(other->picture_map_),
      tiling_(other->tiling_),
      background_color_(other->background_color_),
      requires_clear_(other->requires_clear_),
      can_use_lcd_text_(can_use_lcd_text),
      is_solid_color_(other->is_solid_color_),
      solid_color_(other->solid_color_),
      recorded_viewport_(other->recorded_viewport_),
      has_any_recordings_(other->has_any_recordings_),
      clear_canvas_with_debug_color_(other->clear_canvas_with_debug_color_),
      min_contents_scale_(other->min_contents_scale_),
      slow_down_raster_scale_factor_for_debug_(
          other->slow_down_raster_scale_factor_for_debug_),
      should_attempt_to_use_distance_field_text_(false) {
}

PicturePileImpl::PicturePileImpl(const PicturePileImpl* other,
                                 bool can_use_lcd_text)
    : picture_map_(other->picture_map_),
      tiling_(other->tiling_),
      background_color_(other->background_color_),
      requires_clear_(other->requires_clear_),
      can_use_lcd_text_(can_use_lcd_text),
      is_solid_color_(other->is_solid_color_),
      solid_color_(other->solid_color_),
      recorded_viewport_(other->recorded_viewport_),
      has_any_recordings_(other->has_any_recordings_),
      clear_canvas_with_debug_color_(other->clear_canvas_with_debug_color_),
      min_contents_scale_(other->min_contents_scale_),
      slow_down_raster_scale_factor_for_debug_(
          other->slow_down_raster_scale_factor_for_debug_),
      should_attempt_to_use_distance_field_text_(
          other->should_attempt_to_use_distance_field_text_) {
}

PicturePileImpl::~PicturePileImpl() {
}

void PicturePileImpl::PlaybackToSharedCanvas(SkCanvas* canvas,
                                             const gfx::Rect& canvas_rect,
                                             float contents_scale) const {
  RasterCommon(canvas,
               NULL,
               canvas_rect,
               contents_scale,
               false);
}

void PicturePileImpl::RasterForAnalysis(skia::AnalysisCanvas* canvas,
                                        const gfx::Rect& canvas_rect,
                                        float contents_scale) const {
  RasterCommon(canvas, canvas, canvas_rect, contents_scale, true);
}

void PicturePileImpl::PlaybackToCanvas(SkCanvas* canvas,
                                       const gfx::Rect& canvas_rect,
                                       float contents_scale) const {
  RasterSourceHelper::PrepareForPlaybackToCanvas(
      canvas, canvas_rect, gfx::Rect(tiling_.tiling_size()), contents_scale,
      background_color_, clear_canvas_with_debug_color_, requires_clear_);
  RasterCommon(canvas,
               NULL,
               canvas_rect,
               contents_scale,
               false);
}

void PicturePileImpl::CoalesceRasters(const gfx::Rect& canvas_rect,
                                      const gfx::Rect& content_rect,
                                      float contents_scale,
                                      PictureRegionMap* results) const {
  DCHECK(results);
  // Rasterize the collection of relevant picture piles.
  gfx::Rect layer_rect = gfx::ScaleToEnclosingRect(
      content_rect, 1.f / contents_scale);

  // Make sure pictures don't overlap by keeping track of previous right/bottom.
  int min_content_left = -1;
  int min_content_top = -1;
  int last_row_index = -1;
  int last_col_index = -1;
  gfx::Rect last_content_rect;

  // Coalesce rasters of the same picture into different rects:
  //  - Compute the clip of each of the pile chunks,
  //  - Subtract it from the canvas rect to get difference region
  //  - Later, use the difference region to subtract each of the comprising
  //    rects from the canvas.
  // Note that in essence, we're trying to mimic clipRegion with intersect op
  // that also respects the current canvas transform and clip. In order to use
  // the canvas transform, we must stick to clipRect operations (clipRegion
  // ignores the transform). Intersect then can be written as subtracting the
  // negation of the region we're trying to intersect. Luckily, we know that all
  // of the rects will have to fit into |content_rect|, so we can start with
  // that and subtract chunk rects to get the region that we need to subtract
  // from the canvas. Then, we can use clipRect with difference op to subtract
  // each rect in the region.
  bool include_borders = true;
  for (TilingData::Iterator tile_iter(&tiling_, layer_rect, include_borders);
       tile_iter;
       ++tile_iter) {
    PictureMap::const_iterator map_iter = picture_map_.find(tile_iter.index());
    if (map_iter == picture_map_.end())
      continue;
    const PictureInfo& info = map_iter->second;
    const Picture* picture = info.GetPicture();
    if (!picture)
      continue;

    // This is intentionally *enclosed* rect, so that the clip is aligned on
    // integral post-scale content pixels and does not extend past the edges
    // of the picture chunk's layer rect.  The min_contents_scale enforces that
    // enough buffer pixels have been added such that the enclosed rect
    // encompasses all invalidated pixels at any larger scale level.
    gfx::Rect chunk_rect = PaddedRect(tile_iter.index());
    gfx::Rect content_clip =
        gfx::ScaleToEnclosedRect(chunk_rect, contents_scale);
    DCHECK(!content_clip.IsEmpty()) << "Layer rect: "
                                    << picture->LayerRect().ToString()
                                    << "Contents scale: " << contents_scale;
    content_clip.Intersect(canvas_rect);

    // Make sure iterator goes top->bottom.
    DCHECK_GE(tile_iter.index_y(), last_row_index);
    if (tile_iter.index_y() > last_row_index) {
      // First tile in a new row.
      min_content_left = content_clip.x();
      min_content_top = last_content_rect.bottom();
    } else {
      // Make sure iterator goes left->right.
      DCHECK_GT(tile_iter.index_x(), last_col_index);
      min_content_left = last_content_rect.right();
      min_content_top = last_content_rect.y();
    }

    last_col_index = tile_iter.index_x();
    last_row_index = tile_iter.index_y();

    // Only inset if the content_clip is less than then previous min.
    int inset_left = std::max(0, min_content_left - content_clip.x());
    int inset_top = std::max(0, min_content_top - content_clip.y());
    content_clip.Inset(inset_left, inset_top, 0, 0);

    PictureRegionMap::iterator it = results->find(picture);
    Region* clip_region;
    if (it == results->end()) {
      // The clip for a set of coalesced pictures starts out clipping the entire
      // canvas.  Each picture added to the set must subtract its own bounds
      // from the clip region, poking a hole so that the picture is unclipped.
      clip_region = &(*results)[picture];
      *clip_region = canvas_rect;
    } else {
      clip_region = &it->second;
    }

    DCHECK(clip_region->Contains(content_clip))
        << "Content clips should not overlap.";
    clip_region->Subtract(content_clip);
    last_content_rect = content_clip;
  }
}

void PicturePileImpl::RasterCommon(
    SkCanvas* canvas,
    SkDrawPictureCallback* callback,
    const gfx::Rect& canvas_rect,
    float contents_scale,
    bool is_analysis) const {
  DCHECK(contents_scale >= min_contents_scale_);

  canvas->translate(-canvas_rect.x(), -canvas_rect.y());
  gfx::Rect content_tiling_rect = gfx::ToEnclosingRect(
      gfx::ScaleRect(gfx::Rect(tiling_.tiling_size()), contents_scale));
  content_tiling_rect.Intersect(canvas_rect);

  canvas->clipRect(gfx::RectToSkRect(content_tiling_rect),
                   SkRegion::kIntersect_Op);

  PictureRegionMap picture_region_map;
  CoalesceRasters(
      canvas_rect, content_tiling_rect, contents_scale, &picture_region_map);

#ifndef NDEBUG
  Region total_clip;
#endif  // NDEBUG

  // Iterate the coalesced map and use each picture's region
  // to clip the canvas.
  for (PictureRegionMap::iterator it = picture_region_map.begin();
       it != picture_region_map.end();
       ++it) {
    const Picture* picture = it->first;
    Region negated_clip_region = it->second;

#ifndef NDEBUG
    Region positive_clip = content_tiling_rect;
    positive_clip.Subtract(negated_clip_region);
    // Make sure we never rasterize the same region twice.
    DCHECK(!total_clip.Intersects(positive_clip));
    total_clip.Union(positive_clip);
#endif  // NDEBUG

    int repeat_count = std::max(1, slow_down_raster_scale_factor_for_debug_);

    for (int j = 0; j < repeat_count; ++j)
      picture->Raster(canvas, callback, negated_clip_region, contents_scale);
  }

#ifndef NDEBUG
  // Fill the clip with debug color. This allows us to
  // distinguish between non painted areas and problems with missing
  // pictures.
  SkPaint paint;
  for (Region::Iterator it(total_clip); it.has_rect(); it.next())
    canvas->clipRect(gfx::RectToSkRect(it.rect()), SkRegion::kDifference_Op);
  paint.setColor(DebugColors::MissingPictureFillColor());
  paint.setXfermodeMode(SkXfermode::kSrc_Mode);
  canvas->drawPaint(paint);
#endif  // NDEBUG
}

skia::RefPtr<SkPicture> PicturePileImpl::GetFlattenedPicture() {
  TRACE_EVENT0("cc", "PicturePileImpl::GetFlattenedPicture");

  gfx::Rect tiling_rect(tiling_.tiling_size());
  SkPictureRecorder recorder;
  SkCanvas* canvas =
      recorder.beginRecording(tiling_rect.width(), tiling_rect.height());
  if (!tiling_rect.IsEmpty())
    PlaybackToCanvas(canvas, tiling_rect, 1.0);
  skia::RefPtr<SkPicture> picture = skia::AdoptRef(recorder.endRecording());

  return picture;
}

size_t PicturePileImpl::GetPictureMemoryUsage() const {
  // Place all pictures in a set to de-dupe.
  size_t total_size = 0;
  std::set<const Picture*> pictures_seen;
  for (const auto& map_value : picture_map_) {
    const Picture* picture = map_value.second.GetPicture();
    if (picture && pictures_seen.insert(picture).second)
      total_size += picture->ApproximateMemoryUsage();
  }

  return total_size;
}

void PicturePileImpl::PerformSolidColorAnalysis(
    const gfx::Rect& content_rect,
    float contents_scale,
    RasterSource::SolidColorAnalysis* analysis) const {
  DCHECK(analysis);
  TRACE_EVENT0("cc", "PicturePileImpl::PerformSolidColorAnalysis");

  gfx::Rect layer_rect = gfx::ScaleToEnclosingRect(
      content_rect, 1.0f / contents_scale);

  layer_rect.Intersect(gfx::Rect(tiling_.tiling_size()));

  skia::AnalysisCanvas canvas(layer_rect.width(), layer_rect.height());

  RasterForAnalysis(&canvas, layer_rect, 1.0f);

  analysis->is_solid_color = canvas.GetColorIfSolid(&analysis->solid_color);
}

void PicturePileImpl::GatherPixelRefs(
    const gfx::Rect& content_rect,
    float contents_scale,
    std::vector<SkPixelRef*>* pixel_refs) const {
  DCHECK_EQ(0u, pixel_refs->size());
  for (PixelRefIterator iter(content_rect, contents_scale, this); iter;
       ++iter) {
    pixel_refs->push_back(*iter);
  }
}

bool PicturePileImpl::CoversRect(const gfx::Rect& content_rect,
                                 float contents_scale) const {
  if (tiling_.tiling_size().IsEmpty())
    return false;
  gfx::Rect layer_rect =
      gfx::ScaleToEnclosingRect(content_rect, 1.f / contents_scale);
  layer_rect.Intersect(gfx::Rect(tiling_.tiling_size()));

  // Common case inside of viewport to avoid the slower map lookups.
  if (recorded_viewport_.Contains(layer_rect)) {
    // Sanity check that there are no false positives in recorded_viewport_.
    DCHECK(CanRasterSlowTileCheck(layer_rect));
    return true;
  }

  return CanRasterSlowTileCheck(layer_rect);
}

gfx::Size PicturePileImpl::GetSize() const {
  return tiling_.tiling_size();
}

bool PicturePileImpl::IsSolidColor() const {
  return is_solid_color_;
}

SkColor PicturePileImpl::GetSolidColor() const {
  DCHECK(IsSolidColor());
  return solid_color_;
}

bool PicturePileImpl::HasRecordings() const {
  return has_any_recordings_;
}

gfx::Rect PicturePileImpl::PaddedRect(const PictureMapKey& key) const {
  gfx::Rect padded_rect = tiling_.TileBounds(key.first, key.second);
  padded_rect.Inset(-buffer_pixels(), -buffer_pixels(), -buffer_pixels(),
                    -buffer_pixels());
  return padded_rect;
}

bool PicturePileImpl::CanRasterSlowTileCheck(
    const gfx::Rect& layer_rect) const {
  bool include_borders = false;
  for (TilingData::Iterator tile_iter(&tiling_, layer_rect, include_borders);
       tile_iter; ++tile_iter) {
    PictureMap::const_iterator map_iter = picture_map_.find(tile_iter.index());
    if (map_iter == picture_map_.end())
      return false;
    if (!map_iter->second.GetPicture())
      return false;
  }
  return true;
}

void PicturePileImpl::SetShouldAttemptToUseDistanceFieldText() {
  should_attempt_to_use_distance_field_text_ = true;
}

bool PicturePileImpl::ShouldAttemptToUseDistanceFieldText() const {
  return should_attempt_to_use_distance_field_text_;
}

void PicturePileImpl::AsValueInto(
    base::trace_event::TracedValue* pictures) const {
  gfx::Rect tiling_rect(tiling_.tiling_size());
  std::set<const void*> appended_pictures;
  bool include_borders = true;
  for (TilingData::Iterator tile_iter(&tiling_, tiling_rect, include_borders);
       tile_iter; ++tile_iter) {
    PictureMap::const_iterator map_iter = picture_map_.find(tile_iter.index());
    if (map_iter == picture_map_.end())
      continue;

    const Picture* picture = map_iter->second.GetPicture();
    if (picture && (appended_pictures.count(picture) == 0)) {
      appended_pictures.insert(picture);
      TracedValue::AppendIDRef(picture, pictures);
    }
  }
}

bool PicturePileImpl::CanUseLCDText() const {
  return can_use_lcd_text_;
}

scoped_refptr<RasterSource> PicturePileImpl::CreateCloneWithoutLCDText() const {
  DCHECK(CanUseLCDText());
  bool can_use_lcd_text = false;
  return scoped_refptr<RasterSource>(
      new PicturePileImpl(this, can_use_lcd_text));
}

PicturePileImpl::PixelRefIterator::PixelRefIterator(
    const gfx::Rect& content_rect,
    float contents_scale,
    const PicturePileImpl* picture_pile)
    : picture_pile_(picture_pile),
      layer_rect_(
          gfx::ScaleToEnclosingRect(content_rect, 1.f / contents_scale)),
      tile_iterator_(&picture_pile_->tiling_,
                     layer_rect_,
                     false /* include_borders */) {
  // Early out if there isn't a single tile.
  if (!tile_iterator_)
    return;

  AdvanceToTilePictureWithPixelRefs();
}

PicturePileImpl::PixelRefIterator::~PixelRefIterator() {
}

PicturePileImpl::PixelRefIterator&
    PicturePileImpl::PixelRefIterator::operator++() {
  ++pixel_ref_iterator_;
  if (pixel_ref_iterator_)
    return *this;

  ++tile_iterator_;
  AdvanceToTilePictureWithPixelRefs();
  return *this;
}

void PicturePileImpl::PixelRefIterator::AdvanceToTilePictureWithPixelRefs() {
  for (; tile_iterator_; ++tile_iterator_) {
    PictureMap::const_iterator it =
        picture_pile_->picture_map_.find(tile_iterator_.index());
    if (it == picture_pile_->picture_map_.end())
      continue;

    const Picture* picture = it->second.GetPicture();
    if (!picture || (processed_pictures_.count(picture) != 0) ||
        !picture->WillPlayBackBitmaps())
      continue;

    processed_pictures_.insert(picture);
    pixel_ref_iterator_ = Picture::PixelRefIterator(layer_rect_, picture);
    if (pixel_ref_iterator_)
      break;
  }
}

void PicturePileImpl::DidBeginTracing() {
  std::set<const void*> processed_pictures;
  for (const auto& map_pair : picture_map_) {
    const Picture* picture = map_pair.second.GetPicture();
    if (picture && (processed_pictures.count(picture) == 0)) {
      picture->EmitTraceSnapshot();
      processed_pictures.insert(picture);
    }
  }
}

}  // namespace cc