gecko-dev/layout/painting/DisplayListChecker.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "DisplayListChecker.h"

#include "nsDisplayList.h"

namespace mozilla {

class DisplayItemBlueprint;

// Stack node used during tree visits, to store the path to a display item.
struct DisplayItemBlueprintStack
{
  const DisplayItemBlueprintStack* mPrevious;
  const DisplayItemBlueprint* mItem;
  // Output stack to aSs, with format "name#index > ... > name#index".
  // Returns true if anything was output, false if empty.
  bool Output(std::stringstream& aSs) const;
};

// Object representing a list of display items (either the top of the tree, or
// an item's children), with just enough information to compare with another
// tree and output useful debugging information.
class DisplayListBlueprint
{
public:
  DisplayListBlueprint(nsDisplayList* aList, const char* aName)
    : DisplayListBlueprint(aList, 0, aName)
  {
  }

  DisplayListBlueprint(nsDisplayList* aList,
                       const char* aName,
                       unsigned& aIndex)
  {
    processChildren(aList, aName, aIndex);
  }

  // Find a display item with the given frame and per-frame key.
  // Returns empty string if not found.
  std::string Find(const nsIFrame* aFrame, uint32_t aPerFrameKey) const
  {
    const DisplayItemBlueprintStack stack{ nullptr, nullptr };
    return Find(aFrame, aPerFrameKey, stack);
  }

  std::string Find(const nsIFrame* aFrame,
                   uint32_t aPerFrameKey,
                   const DisplayItemBlueprintStack& aStack) const;

  // Compare this list with another one, output differences between the two
  // into aDiff.
  // Differences include: Display items from one tree for which a corresponding
  // item (same frame and per-frame key) cannot be found under corresponding
  // parent items.
  // Returns true if trees are similar, false if different.
  bool CompareList(const DisplayListBlueprint& aOther,
                   std::stringstream& aDiff) const
  {
    const DisplayItemBlueprintStack stack{ nullptr, nullptr };
    const bool ab = CompareList(*this, aOther, aOther, aDiff, stack, stack);
    const bool ba =
      aOther.CompareList(aOther, *this, *this, aDiff, stack, stack);
    return ab && ba;
  }

  bool CompareList(const DisplayListBlueprint& aRoot,
                   const DisplayListBlueprint& aOther,
                   const DisplayListBlueprint& aOtherRoot,
                   std::stringstream& aDiff,
                   const DisplayItemBlueprintStack& aStack,
                   const DisplayItemBlueprintStack& aStackOther) const;

  // Output this tree to aSs.
  void Dump(std::stringstream& aSs) const { Dump(aSs, 0); }

  void Dump(std::stringstream& aSs, unsigned aDepth) const;

private:
  // Only used by first constructor, to call the 2nd constructor with an index
  // variable on the stack.
  DisplayListBlueprint(nsDisplayList* aList, unsigned aIndex, const char* aName)
    : DisplayListBlueprint(aList, aName, aIndex)
  {
  }

  void processChildren(nsDisplayList* aList,
                       const char* aName,
                       unsigned& aIndex);

  std::vector<DisplayItemBlueprint> mItems;
};

// Object representing one display item, with just enough information to
// compare with another item and output useful debugging information.
class DisplayItemBlueprint
{
public:
  DisplayItemBlueprint(nsDisplayItem& aItem,
                       const char* aName,
                       unsigned& aIndex)
    : mListName(aName)
    , mIndex(++aIndex)
    , mIndexString(WriteIndex(aName, aIndex))
    , mIndexStringFW(WriteIndexFW(aName, aIndex))
    , mDisplayItemPointer(WriteDisplayItemPointer(aItem))
    , mDescription(WriteDescription(aName, aIndex, aItem))
    , mFrame(aItem.HasDeletedFrame() ? nullptr : aItem.Frame())
    , mPerFrameKey(aItem.GetPerFrameKey())
    , mChildren(aItem.GetChildren(), aName, aIndex)
  {
  }

  // Compare this item with another one, based on frame and per-frame key.
  // Not recursive! I.e., children are not examined.
  bool CompareItem(const DisplayItemBlueprint& aOther,
                   std::stringstream& aDiff) const
  {
    return mFrame == aOther.mFrame && mPerFrameKey == aOther.mPerFrameKey;
  }

  void Dump(std::stringstream& aSs, unsigned aDepth) const;

  const char* mListName;
  const unsigned mIndex;
  const std::string mIndexString;
  const std::string mIndexStringFW;
  const std::string mDisplayItemPointer;
  const std::string mDescription;

  // For pointer comparison only, do not dereference!
  const nsIFrame* const mFrame;
  const uint32_t mPerFrameKey;

  const DisplayListBlueprint mChildren;

private:
  static std::string WriteIndex(const char* aName, unsigned aIndex)
  {
    return nsPrintfCString("%s#%u", aName, aIndex).get();
  }

  static std::string WriteIndexFW(const char* aName, unsigned aIndex)
  {
    return nsPrintfCString("%s#%4u", aName, aIndex).get();
  }

  static std::string WriteDisplayItemPointer(nsDisplayItem& aItem)
  {
    return nsPrintfCString("0x%p", &aItem).get();
  }

  static std::string WriteDescription(const char* aName,
                                      unsigned aIndex,
                                      nsDisplayItem& aItem)
  {
    if (aItem.HasDeletedFrame()) {
      return nsPrintfCString(
               "%s %s#%u 0x%p f=0x0", aItem.Name(), aName, aIndex, &aItem)
        .get();
    }

    const nsIFrame* f = aItem.Frame();
    nsAutoString contentData;
#ifdef DEBUG_FRAME_DUMP
    f->GetFrameName(contentData);
#endif
    nsIContent* content = f->GetContent();
    if (content) {
      nsString tmp;
      if (content->GetID()) {
        content->GetID()->ToString(tmp);
        contentData.AppendLiteral(" id:");
        contentData.Append(tmp);
      }
      const nsAttrValue* classes =
        content->IsElement() ? content->AsElement()->GetClasses() : nullptr;
      if (classes) {
        classes->ToString(tmp);
        contentData.AppendLiteral(" class:");
        contentData.Append(tmp);
      }
    }
    return nsPrintfCString("%s %s#%u p=0x%p f=0x%p(%s) key=%" PRIu32,
                           aItem.Name(),
                           aName,
                           aIndex,
                           &aItem,
                           f,
                           NS_ConvertUTF16toUTF8(contentData).get(),
                           aItem.GetPerFrameKey())
      .get();
  }
};

void
DisplayListBlueprint::processChildren(nsDisplayList* aList,
                                      const char* aName,
                                      unsigned& aIndex)
{
  if (!aList) {
    return;
  }
  const uint32_t n = aList->Count();
  if (n == 0) {
    return;
  }
  mItems.reserve(n);
  for (nsDisplayItem* item = aList->GetBottom(); item;
       item = item->GetAbove()) {
    mItems.emplace_back(*item, aName, aIndex);
  }
  MOZ_ASSERT(mItems.size() == n);
}

bool
DisplayItemBlueprintStack::Output(std::stringstream& aSs) const
{
  const bool output = mPrevious ? mPrevious->Output(aSs) : false;
  if (mItem) {
    if (output) {
      aSs << " > ";
    }
    aSs << mItem->mIndexString;
    return true;
  }
  return output;
}

std::string
DisplayListBlueprint::Find(const nsIFrame* aFrame,
                           uint32_t aPerFrameKey,
                           const DisplayItemBlueprintStack& aStack) const
{
  for (const DisplayItemBlueprint& item : mItems) {
    if (item.mFrame == aFrame && item.mPerFrameKey == aPerFrameKey) {
      std::stringstream ss;
      if (aStack.Output(ss)) {
        ss << " > ";
      }
      ss << item.mDescription;
      return ss.str();
    }
    const DisplayItemBlueprintStack stack = { &aStack, &item };
    std::string s = item.mChildren.Find(aFrame, aPerFrameKey, stack);
    if (!s.empty()) {
      return s;
    }
  }
  return "";
}

bool
DisplayListBlueprint::CompareList(
  const DisplayListBlueprint& aRoot,
  const DisplayListBlueprint& aOther,
  const DisplayListBlueprint& aOtherRoot,
  std::stringstream& aDiff,
  const DisplayItemBlueprintStack& aStack,
  const DisplayItemBlueprintStack& aStackOther) const
{
  bool same = true;
  for (const DisplayItemBlueprint& itemBefore : mItems) {
    bool found = false;
    for (const DisplayItemBlueprint& itemAfter : aOther.mItems) {
      if (itemBefore.CompareItem(itemAfter, aDiff)) {
        found = true;

        const DisplayItemBlueprintStack stack = { &aStack, &itemBefore };
        const DisplayItemBlueprintStack stackOther = { &aStackOther,
                                                       &itemAfter };
        if (!itemBefore.mChildren.CompareList(aRoot,
                                              itemAfter.mChildren,
                                              aOtherRoot,
                                              aDiff,
                                              stack,
                                              stackOther)) {
          same = false;
        }
        break;
      }
    }
    if (!found) {
      same = false;
      aDiff << "\n";
      if (aStack.Output(aDiff)) {
        aDiff << " > ";
      }
      aDiff << itemBefore.mDescription;
      aDiff << "\n * Cannot find corresponding item under ";
      if (!aStackOther.Output(aDiff)) {
        if (!aOtherRoot.mItems.empty()) {
          aDiff << aOtherRoot.mItems[0].mListName;
        } else {
          aDiff << "other root";
        }
      }
      std::string elsewhere =
        aOtherRoot.Find(itemBefore.mFrame, itemBefore.mPerFrameKey);
      if (!elsewhere.empty()) {
        aDiff << "\n * But found: " << elsewhere;
      }
    }
  }
  return same;
}

void
DisplayListBlueprint::Dump(std::stringstream& aSs, unsigned aDepth) const
{
  for (const DisplayItemBlueprint& item : mItems) {
    item.Dump(aSs, aDepth);
  }
}

void
DisplayItemBlueprint::Dump(std::stringstream& aSs, unsigned aDepth) const
{
  aSs << "\n" << mIndexStringFW << " ";
  for (unsigned i = 0; i < aDepth; ++i) {
    aSs << "  ";
  }
  aSs << mDescription;
  mChildren.Dump(aSs, aDepth + 1);
}

DisplayListChecker::DisplayListChecker()
  : mBlueprint(nullptr)
{
}

DisplayListChecker::DisplayListChecker(nsDisplayList* aList, const char* aName)
  : mBlueprint(MakeUnique<DisplayListBlueprint>(aList, aName))
{
}

DisplayListChecker::~DisplayListChecker() = default;

void
DisplayListChecker::Set(nsDisplayList* aList, const char* aName)
{
  mBlueprint = MakeUnique<DisplayListBlueprint>(aList, aName);
}

// Compare this list with another one, output differences between the two
// into aDiff.
// Differences include: Display items from one tree for which a corresponding
// item (same frame and per-frame key) cannot be found under corresponding
// parent items.
// Returns true if trees are similar, false if different.
bool
DisplayListChecker::CompareList(const DisplayListChecker& aOther,
                                std::stringstream& aDiff) const
{
  MOZ_ASSERT(mBlueprint);
  MOZ_ASSERT(aOther.mBlueprint);
  return mBlueprint->CompareList(*aOther.mBlueprint, aDiff);
}

void
DisplayListChecker::Dump(std::stringstream& aSs) const
{
  MOZ_ASSERT(mBlueprint);
  mBlueprint->Dump(aSs);
}

} // namespace mozilla