display_list/display_list.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 <type_traits>

#include "flutter/display_list/display_list.h"
#include "flutter/display_list/display_list_canvas_dispatcher.h"
#include "flutter/display_list/display_list_ops.h"
#include "flutter/display_list/display_list_utils.h"

namespace flutter {

const SaveLayerOptions SaveLayerOptions::kNoAttributes = SaveLayerOptions();
const SaveLayerOptions SaveLayerOptions::kWithAttributes =
    kNoAttributes.with_renders_with_attributes();

const SkSamplingOptions DisplayList::NearestSampling =
    SkSamplingOptions(SkFilterMode::kNearest, SkMipmapMode::kNone);
const SkSamplingOptions DisplayList::LinearSampling =
    SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kNone);
const SkSamplingOptions DisplayList::MipmapSampling =
    SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear);
const SkSamplingOptions DisplayList::CubicSampling =
    SkSamplingOptions(SkCubicResampler{1 / 3.0f, 1 / 3.0f});

DisplayList::DisplayList()
    : byte_count_(0),
      op_count_(0),
      nested_byte_count_(0),
      nested_op_count_(0),
      unique_id_(0),
      bounds_({0, 0, 0, 0}),
      bounds_cull_({0, 0, 0, 0}),
      can_apply_group_opacity_(true) {}

DisplayList::DisplayList(uint8_t* ptr,
                         size_t byte_count,
                         unsigned int op_count,
                         size_t nested_byte_count,
                         unsigned int nested_op_count,
                         const SkRect& cull_rect,
                         bool can_apply_group_opacity)
    : storage_(ptr),
      byte_count_(byte_count),
      op_count_(op_count),
      nested_byte_count_(nested_byte_count),
      nested_op_count_(nested_op_count),
      bounds_({0, 0, -1, -1}),
      bounds_cull_(cull_rect),
      can_apply_group_opacity_(can_apply_group_opacity) {
  static std::atomic<uint32_t> nextID{1};
  do {
    unique_id_ = nextID.fetch_add(+1, std::memory_order_relaxed);
  } while (unique_id_ == 0);
}

DisplayList::~DisplayList() {
  uint8_t* ptr = storage_.get();
  DisposeOps(ptr, ptr + byte_count_);
}

void DisplayList::ComputeBounds() {
  DisplayListBoundsCalculator calculator(&bounds_cull_);
  Dispatch(calculator);
  bounds_ = calculator.bounds();
}

void DisplayList::Dispatch(Dispatcher& dispatcher,
                           uint8_t* ptr,
                           uint8_t* end) const {
  while (ptr < end) {
    auto op = reinterpret_cast<const DLOp*>(ptr);
    ptr += op->size;
    FML_DCHECK(ptr <= end);
    switch (op->type) {
#define DL_OP_DISPATCH(name)                                \
  case DisplayListOpType::k##name:                          \
    static_cast<const name##Op*>(op)->dispatch(dispatcher); \
    break;

      FOR_EACH_DISPLAY_LIST_OP(DL_OP_DISPATCH)

#undef DL_OP_DISPATCH

      default:
        FML_DCHECK(false);
        return;
    }
  }
}

void DisplayList::DisposeOps(uint8_t* ptr, uint8_t* end) {
  while (ptr < end) {
    auto op = reinterpret_cast<const DLOp*>(ptr);
    ptr += op->size;
    FML_DCHECK(ptr <= end);
    switch (op->type) {
#define DL_OP_DISPOSE(name)                            \
  case DisplayListOpType::k##name:                     \
    if (!std::is_trivially_destructible_v<name##Op>) { \
      static_cast<const name##Op*>(op)->~name##Op();   \
    }                                                  \
    break;

      FOR_EACH_DISPLAY_LIST_OP(DL_OP_DISPOSE)

#undef DL_OP_DISPOSE

      default:
        FML_DCHECK(false);
        return;
    }
  }
}

static bool CompareOps(uint8_t* ptrA,
                       uint8_t* endA,
                       uint8_t* ptrB,
                       uint8_t* endB) {
  // These conditions are checked by the caller...
  FML_DCHECK((endA - ptrA) == (endB - ptrB));
  FML_DCHECK(ptrA != ptrB);
  uint8_t* bulkStartA = ptrA;
  uint8_t* bulkStartB = ptrB;
  while (ptrA < endA && ptrB < endB) {
    auto opA = reinterpret_cast<const DLOp*>(ptrA);
    auto opB = reinterpret_cast<const DLOp*>(ptrB);
    if (opA->type != opB->type || opA->size != opB->size) {
      return false;
    }
    ptrA += opA->size;
    ptrB += opB->size;
    FML_DCHECK(ptrA <= endA);
    FML_DCHECK(ptrB <= endB);
    DisplayListCompare result;
    switch (opA->type) {
#define DL_OP_EQUALS(name)                              \
  case DisplayListOpType::k##name:                      \
    result = static_cast<const name##Op*>(opA)->equals( \
        static_cast<const name##Op*>(opB));             \
    break;

      FOR_EACH_DISPLAY_LIST_OP(DL_OP_EQUALS)

#undef DL_OP_EQUALS

      default:
        FML_DCHECK(false);
        return false;
    }
    switch (result) {
      case DisplayListCompare::kNotEqual:
        return false;
      case DisplayListCompare::kUseBulkCompare:
        break;
      case DisplayListCompare::kEqual:
        // Check if we have a backlog of bytes to bulk compare and then
        // reset the bulk compare pointers to the address following this op
        auto bulkBytes = reinterpret_cast<const uint8_t*>(opA) - bulkStartA;
        if (bulkBytes > 0) {
          if (memcmp(bulkStartA, bulkStartB, bulkBytes) != 0) {
            return false;
          }
        }
        bulkStartA = ptrA;
        bulkStartB = ptrB;
        break;
    }
  }
  if (ptrA != endA || ptrB != endB) {
    return false;
  }
  if (bulkStartA < ptrA) {
    // Perform a final bulk compare if we have remaining bytes waiting
    if (memcmp(bulkStartA, bulkStartB, ptrA - bulkStartA) != 0) {
      return false;
    }
  }
  return true;
}

void DisplayList::RenderTo(SkCanvas* canvas, SkScalar opacity) const {
  DisplayListCanvasDispatcher dispatcher(canvas, opacity);
  Dispatch(dispatcher);
}

bool DisplayList::Equals(const DisplayList& other) const {
  if (byte_count_ != other.byte_count_ || op_count_ != other.op_count_) {
    return false;
  }
  uint8_t* ptr = storage_.get();
  uint8_t* o_ptr = other.storage_.get();
  if (ptr == o_ptr) {
    return true;
  }
  return CompareOps(ptr, ptr + byte_count_, o_ptr, o_ptr + other.byte_count_);
}

}  // namespace flutter