accessible/base/AccessibleOrProxy.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_a11y_AccessibleOrProxy_h
   8 #define mozilla_a11y_AccessibleOrProxy_h
   9
  10 #include "mozilla/a11y/Accessible.h"
  11 #include "mozilla/a11y/ProxyAccessible.h"
  12 #include "mozilla/a11y/Role.h"
  13
  14 #include <stdint.h>
  15
  16 namespace mozilla {
  17 namespace a11y {
  18
  19 /**
  20  * This class stores an Accessible* or a ProxyAccessible* in a safe manner
  21  * with size sizeof(void*).
  22  */
  23 class AccessibleOrProxy {
  24  public:
  25   MOZ_IMPLICIT AccessibleOrProxy(Accessible* aAcc)
  26       : mBits(reinterpret_cast<uintptr_t>(aAcc)) {}
  27   MOZ_IMPLICIT AccessibleOrProxy(ProxyAccessible* aProxy)
  28       : mBits(aProxy ? (reinterpret_cast<uintptr_t>(aProxy) | IS_PROXY) : 0) {}
  29   MOZ_IMPLICIT AccessibleOrProxy(decltype(nullptr)) : mBits(0) {}
  30
  31   bool IsProxy() const { return mBits & IS_PROXY; }
  32   ProxyAccessible* AsProxy() const {
  33     if (IsProxy()) {
  34       return reinterpret_cast<ProxyAccessible*>(mBits & ~IS_PROXY);
  35     }
  36
  37     return nullptr;
  38   }
  39
  40   bool IsAccessible() const { return !IsProxy(); }
  41   Accessible* AsAccessible() const {
  42     if (IsAccessible()) {
  43       return reinterpret_cast<Accessible*>(mBits);
  44     }
  45
  46     return nullptr;
  47   }
  48
  49   bool IsNull() const { return mBits == 0; }
  50
  51   uint32_t ChildCount() const {
  52     if (IsProxy()) {
  53       return AsProxy()->ChildrenCount();
  54     }
  55
  56     return AsAccessible()->ChildCount();
  57   }
  58
  59   /**
  60    * Return the child object either an accessible or a proxied accessible at
  61    * the given index.
  62    */
  63   AccessibleOrProxy ChildAt(uint32_t aIdx) {
  64     if (IsProxy()) {
  65       return AsProxy()->ChildAt(aIdx);
  66     }
  67
  68     return AsAccessible()->GetChildAt(aIdx);
  69   }
  70
  71   /**
  72    * Return the first child object.
  73    */
  74   AccessibleOrProxy FirstChild() {
  75     if (IsProxy()) {
  76       return AsProxy()->FirstChild();
  77     }
  78
  79     return AsAccessible()->FirstChild();
  80   }
  81
  82   /**
  83    * Return the first child object.
  84    */
  85   AccessibleOrProxy LastChild() {
  86     if (IsProxy()) {
  87       return AsProxy()->LastChild();
  88     }
  89
  90     return AsAccessible()->LastChild();
  91   }
  92
  93   role Role() const {
  94     if (IsProxy()) {
  95       return AsProxy()->Role();
  96     }
  97
  98     return AsAccessible()->Role();
  99   }
 100
 101   AccessibleOrProxy Parent() const;
 102
 103   // XXX these are implementation details that ideally would not be exposed.
 104   uintptr_t Bits() const { return mBits; }
 105   void SetBits(uintptr_t aBits) { mBits = aBits; }
 106
 107  private:
 108   uintptr_t mBits;
 109   static const uintptr_t IS_PROXY = 0x1;
 110 };
 111
 112 }  // namespace a11y
 113 }  // namespace mozilla
 114
 115 #endif