flow/layers/display_list_layer.cc

// Copyright 2013 The Flutter 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 "flutter/flow/layers/display_list_layer.h"

#include "flutter/flow/display_list_canvas.h"

namespace flutter {

DisplayListLayer::DisplayListLayer(const SkPoint& offset,
                                   SkiaGPUObject<DisplayList> display_list,
                                   bool is_complex,
                                   bool will_change)
    : offset_(offset),
      display_list_(std::move(display_list)),
      is_complex_(is_complex),
      will_change_(will_change) {}

#ifdef FLUTTER_ENABLE_DIFF_CONTEXT

bool DisplayListLayer::IsReplacing(DiffContext* context,
                                   const Layer* layer) const {
  // Only return true for identical display lists; This way
  // ContainerLayer::DiffChildren can detect when a display list layer
  // got inserted between other display list layers
  auto old_layer = layer->as_display_list_layer();
  return old_layer != nullptr && offset_ == old_layer->offset_ &&
         Compare(context->statistics(), this, old_layer);
}

void DisplayListLayer::Diff(DiffContext* context, const Layer* old_layer) {
  DiffContext::AutoSubtreeRestore subtree(context);
  if (!context->IsSubtreeDirty()) {
#ifndef NDEBUG
    FML_DCHECK(old_layer);
    auto prev = old_layer->as_display_list_layer();
    DiffContext::Statistics dummy_statistics;
    // IsReplacing has already determined that the display list is same
    FML_DCHECK(prev->offset_ == offset_ &&
               Compare(dummy_statistics, this, prev));
#endif
  }
  context->PushTransform(SkMatrix::Translate(offset_.x(), offset_.y()));
#ifndef SUPPORT_FRACTIONAL_TRANSLATION
  context->SetTransform(
      RasterCache::GetIntegralTransCTM(context->GetTransform()));
#endif
  context->AddLayerBounds(display_list()->bounds());
  context->SetLayerPaintRegion(this, context->CurrentSubtreeRegion());
}

bool DisplayListLayer::Compare(DiffContext::Statistics& statistics,
                               const DisplayListLayer* l1,
                               const DisplayListLayer* l2) {
  const auto& dl1 = l1->display_list_.skia_object();
  const auto& dl2 = l2->display_list_.skia_object();
  if (dl1.get() == dl2.get()) {
    statistics.AddSameInstancePicture();
    return true;
  }
  const auto op_cnt_1 = dl1->op_count();
  const auto op_cnt_2 = dl2->op_count();
  const auto op_bytes_1 = dl1->bytes();
  const auto op_bytes_2 = dl2->bytes();
  if (op_cnt_1 != op_cnt_2 || op_bytes_1 != op_bytes_2 ||
      dl1->bounds() != dl2->bounds()) {
    statistics.AddNewPicture();
    return false;
  }

  if (op_bytes_1 > kMaxBytesToCompare) {
    statistics.AddPictureTooComplexToCompare();
    return false;
  }

  statistics.AddDeepComparePicture();

  auto res = dl1->Equals(*dl2);
  if (res) {
    statistics.AddDifferentInstanceButEqualPicture();
  } else {
    statistics.AddNewPicture();
  }
  return res;
}

#endif  // FLUTTER_ENABLE_DIFF_CONTEXT

void DisplayListLayer::Preroll(PrerollContext* context,
                               const SkMatrix& matrix) {
  TRACE_EVENT0("flutter", "DisplayListLayer::Preroll");

  DisplayList* disp_list = display_list();

  if (auto* cache = context->raster_cache) {
    TRACE_EVENT0("flutter", "DisplayListLayer::RasterCache (Preroll)");
    cache->Prepare(context, disp_list, is_complex_, will_change_, matrix,
                   offset_);
  }

  SkRect bounds = disp_list->bounds().makeOffset(offset_.x(), offset_.y());
  set_paint_bounds(bounds);
}

void DisplayListLayer::Paint(PaintContext& context) const {
  TRACE_EVENT0("flutter", "DisplayListLayer::Paint");
  FML_DCHECK(display_list_.skia_object());
  FML_DCHECK(needs_painting(context));

  SkAutoCanvasRestore save(context.leaf_nodes_canvas, true);
  context.leaf_nodes_canvas->translate(offset_.x(), offset_.y());
#ifndef SUPPORT_FRACTIONAL_TRANSLATION
  context.leaf_nodes_canvas->setMatrix(RasterCache::GetIntegralTransCTM(
      context.leaf_nodes_canvas->getTotalMatrix()));
#endif

  if (context.raster_cache &&
      context.raster_cache->Draw(*display_list(), *context.leaf_nodes_canvas)) {
    TRACE_EVENT_INSTANT0("flutter", "raster cache hit");
    return;
  }

  display_list()->RenderTo(context.leaf_nodes_canvas);
}

}  // namespace flutter