cc/playback/display_list_recording_source.cc

// Copyright 2014 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/playback/display_list_recording_source.h"

#include <algorithm>

#include "base/numerics/safe_math.h"
#include "cc/base/histograms.h"
#include "cc/base/region.h"
#include "cc/layers/content_layer_client.h"
#include "cc/playback/display_item_list.h"
#include "cc/playback/display_list_raster_source.h"
#include "skia/ext/analysis_canvas.h"

namespace {

// Layout pixel buffer around the visible layer rect to record.  Any base
// picture that intersects the visible layer rect expanded by this distance
// will be recorded.
const int kPixelDistanceToRecord = 4000;

// This is the distance, in layer space, by which the recorded viewport has to
// change before causing a paint of the new content. For example, it means
// that one has to scroll a very large page by 512 pixels before we will
// re-record a new DisplayItemList for an updated recorded viewport.
const int kMinimumDistanceBeforeUpdatingRecordedViewport = 512;

#ifdef NDEBUG
const bool kDefaultClearCanvasSetting = false;
#else
const bool kDefaultClearCanvasSetting = true;
#endif

DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
    ScopedDisplayListRecordingSourceUpdateTimer,
    "Compositing.%s.DisplayListRecordingSource.UpdateUs",
    "Compositing.%s.DisplayListRecordingSource.UpdateInvalidatedAreaPerMs");

}  // namespace

namespace cc {

DisplayListRecordingSource::DisplayListRecordingSource()
    : slow_down_raster_scale_factor_for_debug_(0),
      generate_discardable_images_metadata_(false),
      requires_clear_(false),
      is_solid_color_(false),
      clear_canvas_with_debug_color_(kDefaultClearCanvasSetting),
      solid_color_(SK_ColorTRANSPARENT),
      background_color_(SK_ColorTRANSPARENT),
      pixel_record_distance_(kPixelDistanceToRecord),
      painter_reported_memory_usage_(0) {}

DisplayListRecordingSource::~DisplayListRecordingSource() {
}

// This method only really makes sense to call if the size of the layer didn't
// change.
bool DisplayListRecordingSource::ExposesEnoughNewArea(
    const gfx::Rect& current_recorded_viewport,
    const gfx::Rect& potential_new_recorded_viewport,
    const gfx::Size& layer_size) {
  // If both are empty, nothing to do.
  if (current_recorded_viewport.IsEmpty() &&
      potential_new_recorded_viewport.IsEmpty())
    return false;

  // Re-record when going from empty to not-empty, to cover cases where
  // the layer is recorded for the first time, or otherwise becomes visible.
  if (current_recorded_viewport.IsEmpty())
    return true;

  // Re-record if the new viewport includes area outside of a skirt around the
  // existing viewport.
  gfx::Rect expanded_viewport(current_recorded_viewport);
  expanded_viewport.Inset(-kMinimumDistanceBeforeUpdatingRecordedViewport,
                          -kMinimumDistanceBeforeUpdatingRecordedViewport);
  if (!expanded_viewport.Contains(potential_new_recorded_viewport))
    return true;

  // Even if the new viewport doesn't include enough new area to satisfy the
  // condition above, re-record anyway if touches a layer edge not touched by
  // the existing viewport. Viewports are clipped to layer boundaries, so if the
  // new viewport touches a layer edge not touched by the existing viewport,
  // the new viewport must expose new area that touches this layer edge. Since
  // this new area touches a layer edge, it's impossible to expose more area in
  // that direction, so recording cannot be deferred until the exposed new area
  // satisfies the condition above.
  if (potential_new_recorded_viewport.x() == 0 &&
      current_recorded_viewport.x() != 0)
    return true;
  if (potential_new_recorded_viewport.y() == 0 &&
      current_recorded_viewport.y() != 0)
    return true;
  if (potential_new_recorded_viewport.right() == layer_size.width() &&
      current_recorded_viewport.right() != layer_size.width())
    return true;
  if (potential_new_recorded_viewport.bottom() == layer_size.height() &&
      current_recorded_viewport.bottom() != layer_size.height())
    return true;

  return false;
}

bool DisplayListRecordingSource::UpdateAndExpandInvalidation(
    ContentLayerClient* painter,
    Region* invalidation,
    const gfx::Size& layer_size,
    const gfx::Rect& visible_layer_rect,
    int frame_number,
    RecordingMode recording_mode) {
  ScopedDisplayListRecordingSourceUpdateTimer timer;
  bool updated = false;

  if (size_ != layer_size) {
    size_ = layer_size;
    updated = true;
  }

  // The recorded viewport is the visible layer rect, expanded
  // by the pixel record distance, up to a maximum of the total
  // layer size.
  gfx::Rect potential_new_recorded_viewport = visible_layer_rect;
  potential_new_recorded_viewport.Inset(-pixel_record_distance_,
                                        -pixel_record_distance_);
  potential_new_recorded_viewport.Intersect(gfx::Rect(GetSize()));

  if (updated ||
      ExposesEnoughNewArea(recorded_viewport_, potential_new_recorded_viewport,
                           GetSize())) {
    gfx::Rect old_recorded_viewport = recorded_viewport_;
    recorded_viewport_ = potential_new_recorded_viewport;

    // Invalidate newly-exposed and no-longer-exposed areas.
    Region newly_exposed_region(recorded_viewport_);
    newly_exposed_region.Subtract(old_recorded_viewport);
    invalidation->Union(newly_exposed_region);

    Region no_longer_exposed_region(old_recorded_viewport);
    no_longer_exposed_region.Subtract(recorded_viewport_);
    invalidation->Union(no_longer_exposed_region);

    updated = true;
  }

  // Count the area that is being invalidated.
  Region recorded_invalidation(*invalidation);
  recorded_invalidation.Intersect(recorded_viewport_);
  for (Region::Iterator it(recorded_invalidation); it.has_rect(); it.next()) {
    // gfx::Size::GetArea might overflow in this case, so use an explicit
    // CheckedNumeric instead.
    base::CheckedNumeric<int> checked_area = it.rect().size().width();
    checked_area *= it.rect().size().height();
    timer.AddArea(checked_area);
  }

  if (!updated && !invalidation->Intersects(recorded_viewport_))
    return false;

  ContentLayerClient::PaintingControlSetting painting_control =
      ContentLayerClient::PAINTING_BEHAVIOR_NORMAL;

  switch (recording_mode) {
    case RECORD_NORMALLY:
      // Already setup for normal recording.
      break;
    case RECORD_WITH_PAINTING_DISABLED:
      painting_control = ContentLayerClient::DISPLAY_LIST_PAINTING_DISABLED;
      break;
    case RECORD_WITH_CACHING_DISABLED:
      painting_control = ContentLayerClient::DISPLAY_LIST_CACHING_DISABLED;
      break;
    case RECORD_WITH_CONSTRUCTION_DISABLED:
      painting_control = ContentLayerClient::DISPLAY_LIST_CONSTRUCTION_DISABLED;
      break;
    case RECORD_WITH_SK_NULL_CANVAS:
    case RECORDING_MODE_COUNT:
      NOTREACHED();
  }

  // TODO(vmpstr): Add a slow_down_recording_scale_factor_for_debug_ to be able
  // to slow down recording.
  display_list_ =
      painter->PaintContentsToDisplayList(recorded_viewport_, painting_control);
  painter_reported_memory_usage_ = painter->GetApproximateUnsharedMemoryUsage();

  DetermineIfSolidColor();
  display_list_->EmitTraceSnapshot();
  if (generate_discardable_images_metadata_)
    display_list_->GenerateDiscardableImagesMetadata();

  return true;
}

gfx::Size DisplayListRecordingSource::GetSize() const {
  return size_;
}

void DisplayListRecordingSource::SetEmptyBounds() {
  size_ = gfx::Size();
  Clear();
}

void DisplayListRecordingSource::SetSlowdownRasterScaleFactor(int factor) {
  slow_down_raster_scale_factor_for_debug_ = factor;
}

void DisplayListRecordingSource::SetGenerateDiscardableImagesMetadata(
    bool generate_metadata) {
  generate_discardable_images_metadata_ = generate_metadata;
}

void DisplayListRecordingSource::SetBackgroundColor(SkColor background_color) {
  background_color_ = background_color;
}

void DisplayListRecordingSource::SetRequiresClear(bool requires_clear) {
  requires_clear_ = requires_clear;
}

bool DisplayListRecordingSource::IsSuitableForGpuRasterization() const {
  // The display list needs to be created (see: UpdateAndExpandInvalidation)
  // before checking for suitability. There are cases where an update will not
  // create a display list (e.g., if the size is empty). We return true in these
  // cases because the gpu suitability bit sticks false.
  return !display_list_ || display_list_->IsSuitableForGpuRasterization();
}

scoped_refptr<DisplayListRasterSource>
DisplayListRecordingSource::CreateRasterSource(bool can_use_lcd_text) const {
  return scoped_refptr<DisplayListRasterSource>(
      DisplayListRasterSource::CreateFromDisplayListRecordingSource(
          this, can_use_lcd_text));
}

void DisplayListRecordingSource::DetermineIfSolidColor() {
  DCHECK(display_list_);
  is_solid_color_ = false;
  solid_color_ = SK_ColorTRANSPARENT;

  if (!display_list_->ShouldBeAnalyzedForSolidColor())
    return;

  gfx::Size layer_size = GetSize();
  skia::AnalysisCanvas canvas(layer_size.width(), layer_size.height());
  display_list_->Raster(&canvas, nullptr, gfx::Rect(), 1.f);
  is_solid_color_ = canvas.GetColorIfSolid(&solid_color_);
}

void DisplayListRecordingSource::Clear() {
  recorded_viewport_ = gfx::Rect();
  display_list_ = nullptr;
  painter_reported_memory_usage_ = 0;
  is_solid_color_ = false;
}

}  // namespace cc