widget/nsScreenManagerProxy.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 nsScreenManagerProxy_h
   7 #define nsScreenManagerProxy_h
   8
   9 #include "nsIScreenManager.h"
  10 #include "mozilla/dom/PScreenManagerChild.h"
  11 #include "mozilla/dom/TabChild.h"
  12 #include "ScreenProxy.h"
  13
  14 /**
  15  * The nsScreenManagerProxy is used by the content process to get
  16  * information about system screens. It uses the PScreenManager protocol
  17  * to communicate with a PScreenManagerParent to get this information,
  18  * and also caches the information it gets back.
  19  *
  20  * We cache both the system screen information that nsIScreenManagers
  21  * provide, as well as the nsIScreens that callers can query for.
  22  *
  23  * Both of these caches are invalidated on the next tick of the event
  24  * loop.
  25  */
  26 class nsScreenManagerProxy MOZ_FINAL : public nsIScreenManager,
  27                                        public mozilla::dom::PScreenManagerChild
  28 {
  29 public:
  30   nsScreenManagerProxy();
  31
  32   NS_DECL_ISUPPORTS
  33   NS_DECL_NSISCREENMANAGER
  34
  35 private:
  36   ~nsScreenManagerProxy() {};
  37
  38   bool EnsureCacheIsValid();
  39   void InvalidateCacheOnNextTick();
  40   void InvalidateCache();
  41
  42   uint32_t mNumberOfScreens;
  43   float mSystemDefaultScale;
  44   bool mCacheValid;
  45   bool mCacheWillInvalidate;
  46
  47   nsRefPtr<mozilla::widget::ScreenProxy> mPrimaryScreen;
  48
  49   // nsScreenManagerProxy caches the results to repeated calls to
  50   // ScreenForNativeWidget, which can be triggered indirectly by
  51   // web content using the DOM Screen API. This allows us to bypass
  52   // a lot of IPC traffic.
  53   //
  54   // The cache stores ScreenProxy's mapped to the TabChild that
  55   // asked for the ScreenForNativeWidget was called with via
  56   // ScreenCacheEntry's. The cache is cleared on the next tick of
  57   // the event loop.
  58   struct ScreenCacheEntry
  59   {
  60     nsRefPtr<mozilla::widget::ScreenProxy> mScreenProxy;
  61     nsRefPtr<mozilla::dom::TabChild> mTabChild;
  62   };
  63
  64   nsTArray<ScreenCacheEntry> mScreenCache;
  65 };
  66
  67 #endif // nsScreenManagerProxy_h