accessible/xpcom/xpcAccessibilityService.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   3  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef mozilla_a11y_xpcAccessibilityService_h_
   6 #define mozilla_a11y_xpcAccessibilityService_h_
   7
   8 #include "nsIAccessibilityService.h"
   9 #include "nsITimer.h"
  10
  11 class xpcAccessibilityService : public nsIAccessibilityService {
  12  public:
  13   NS_DECL_ISUPPORTS
  14   NS_DECL_NSIACCESSIBILITYSERVICE
  15
  16   /**
  17    * Return true if xpc accessibility service is in use.
  18    */
  19   static bool IsInUse() {
  20     // When ref count goes down to 1 (held internally as a static reference),
  21     // it means that there are no more external references and thus it is not in
  22     // use.
  23     return gXPCAccessibilityService ? gXPCAccessibilityService->mRefCnt > 1
  24                                     : false;
  25   }
  26
  27  protected:
  28   virtual ~xpcAccessibilityService() {
  29     if (mShutdownTimer) {
  30       mShutdownTimer->Cancel();
  31       mShutdownTimer = nullptr;
  32     }
  33     gXPCAccessibilityService = nullptr;
  34   }
  35
  36  private:
  37   // xpcAccessibilityService creation is controlled by friend
  38   // NS_GetAccessibilityService, keep constructor private.
  39   xpcAccessibilityService() = default;
  40
  41   nsCOMPtr<nsITimer> mShutdownTimer;
  42
  43   /**
  44    * Reference for xpc accessibility service instance.
  45    */
  46   static xpcAccessibilityService* gXPCAccessibilityService;
  47
  48   /**
  49    * Used to shutdown nsAccessibilityService if xpcom accessible service is not
  50    * in use any more.
  51    */
  52   static void ShutdownCallback(nsITimer* aTimer, void* aClosure);
  53
  54   friend nsresult NS_GetAccessibilityService(nsIAccessibilityService** aResult);
  55 };
  56
  57 // for component registration
  58 // {3b265b69-f813-48ff-880d-d88d101af404}
  59 #define NS_ACCESSIBILITY_SERVICE_CID                 \
  60   {                                                  \
  61     0x3b265b69, 0xf813, 0x48ff, {                    \
  62       0x88, 0x0d, 0xd8, 0x8d, 0x10, 0x1a, 0xf4, 0x04 \
  63     }                                                \
  64   }
  65
  66 extern nsresult NS_GetAccessibilityService(nsIAccessibilityService** aResult);
  67
  68 #endif