editor/libeditor/ManualNAC.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef mozilla_ManualNAC_h
   7 #define mozilla_ManualNAC_h
   8
   9 #include "mozilla/dom/Element.h"
  10 #include "mozilla/RefPtr.h"
  11
  12 namespace mozilla {
  13
  14 // 16 seems to be the maximum number of manual Native Anonymous Content (NAC)
  15 // nodes that editor creates for a given element.
  16 //
  17 // These need to be manually removed by the machinery that sets the NAC,
  18 // otherwise we'll leak.
  19 using ManualNACArray = AutoTArray<RefPtr<dom::Element>, 16>;
  20
  21 /**
  22  * Smart pointer class to own "manual" Native Anonymous Content, and perform
  23  * the necessary registration and deregistration on the parent element.
  24  */
  25 class ManualNACPtr final {
  26  public:
  27   ManualNACPtr() = default;
  28   MOZ_IMPLICIT ManualNACPtr(decltype(nullptr)) {}
  29   explicit ManualNACPtr(already_AddRefed<dom::Element> aNewNAC)
  30       : mPtr(aNewNAC) {
  31     if (!mPtr) {
  32       return;
  33     }
  34
  35     // Record the NAC on the element, so that AllChildrenIterator can find it.
  36     nsIContent* parentContent = mPtr->GetParent();
  37     auto nac = static_cast<ManualNACArray*>(
  38         parentContent->GetProperty(nsGkAtoms::manualNACProperty));
  39     if (!nac) {
  40       nac = new ManualNACArray();
  41       parentContent->SetProperty(nsGkAtoms::manualNACProperty, nac,
  42                                  nsINode::DeleteProperty<ManualNACArray>);
  43     }
  44     nac->AppendElement(mPtr);
  45   }
  46
  47   // We use move semantics, and delete the copy-constructor and operator=.
  48   ManualNACPtr(ManualNACPtr&& aOther) : mPtr(std::move(aOther.mPtr)) {}
  49   ManualNACPtr(ManualNACPtr& aOther) = delete;
  50   ManualNACPtr& operator=(ManualNACPtr&& aOther) {
  51     mPtr = std::move(aOther.mPtr);
  52     return *this;
  53   }
  54   ManualNACPtr& operator=(ManualNACPtr& aOther) = delete;
  55
  56   ~ManualNACPtr() { Reset(); }
  57
  58   void Reset() {
  59     if (!mPtr) {
  60       return;
  61     }
  62
  63     RefPtr<dom::Element> ptr = std::move(mPtr);
  64     RemoveContentFromNACArray(ptr);
  65   }
  66
  67   static bool IsManualNAC(nsIContent* aAnonContent) {
  68     MOZ_ASSERT(aAnonContent->IsRootOfNativeAnonymousSubtree());
  69     MOZ_ASSERT(aAnonContent->IsInComposedDoc());
  70
  71     auto* nac = static_cast<ManualNACArray*>(
  72         aAnonContent->GetParent()->GetProperty(nsGkAtoms::manualNACProperty));
  73     return nac && nac->Contains(aAnonContent);
  74   }
  75
  76   static void RemoveContentFromNACArray(nsIContent* aAnonymousContent) {
  77     nsIContent* parentContent = aAnonymousContent->GetParent();
  78     if (!parentContent) {
  79       NS_WARNING("Potentially leaking manual NAC");
  80       return;
  81     }
  82
  83     // Remove reference from the parent element.
  84     auto* nac = static_cast<ManualNACArray*>(
  85         parentContent->GetProperty(nsGkAtoms::manualNACProperty));
  86     // Document::AdoptNode might remove all properties before destroying editor.
  87     // So we have to consider that NAC could be already removed.
  88     if (nac) {
  89       nac->RemoveElement(aAnonymousContent);
  90       if (nac->IsEmpty()) {
  91         parentContent->RemoveProperty(nsGkAtoms::manualNACProperty);
  92       }
  93     }
  94
  95     aAnonymousContent->UnbindFromTree();
  96   }
  97
  98   dom::Element* get() const { return mPtr.get(); }
  99   dom::Element* operator->() const { return get(); }
 100   operator dom::Element*() const& { return get(); }
 101
 102  private:
 103   RefPtr<dom::Element> mPtr;
 104 };
 105
 106 }  // namespace mozilla
 107
 108 inline void ImplCycleCollectionUnlink(mozilla::ManualNACPtr& field) {
 109   field.Reset();
 110 }
 111
 112 inline void ImplCycleCollectionTraverse(
 113     nsCycleCollectionTraversalCallback& callback,
 114     const mozilla::ManualNACPtr& field, const char* name, uint32_t flags = 0) {
 115   CycleCollectionNoteChild(callback, field.get(), name, flags);
 116 }
 117
 118 #endif  // #ifndef mozilla_ManualNAC_h