1 files changed, 67 insertions, 0 deletions
diff --git a/widget/nsScreenManagerProxy.h b/widget/nsScreenManagerProxy.h
new file mode 100644
index 0000000000..bcfa387a4c
--- /dev/null
+++ b/widget/nsScreenManagerProxy.h
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#ifndef nsScreenManagerProxy_h
+#define nsScreenManagerProxy_h
+
+#include "nsIScreenManager.h"
+#include "mozilla/dom/PScreenManagerChild.h"
+#include "mozilla/dom/TabChild.h"
+#include "ScreenProxy.h"
+
+/**
+ * The nsScreenManagerProxy is used by the content process to get
+ * information about system screens. It uses the PScreenManager protocol
+ * to communicate with a PScreenManagerParent to get this information,
+ * and also caches the information it gets back.
+ *
+ * We cache both the system screen information that nsIScreenManagers
+ * provide, as well as the nsIScreens that callers can query for.
+ *
+ * Both of these caches are invalidated on the next tick of the event
+ * loop.
+ */
+class nsScreenManagerProxy final : public nsIScreenManager,
+                                   public mozilla::dom::PScreenManagerChild
+{
+public:
+  nsScreenManagerProxy();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISCREENMANAGER
+
+private:
+  ~nsScreenManagerProxy() {};
+
+  bool EnsureCacheIsValid();
+  void InvalidateCacheOnNextTick();
+  void InvalidateCache();
+
+  uint32_t mNumberOfScreens;
+  float mSystemDefaultScale;
+  bool mCacheValid;
+  bool mCacheWillInvalidate;
+
+  RefPtr<mozilla::widget::ScreenProxy> mPrimaryScreen;
+
+  // nsScreenManagerProxy caches the results to repeated calls to
+  // ScreenForNativeWidget, which can be triggered indirectly by
+  // web content using the DOM Screen API. This allows us to bypass
+  // a lot of IPC traffic.
+  //
+  // The cache stores ScreenProxy's mapped to the TabChild that
+  // asked for the ScreenForNativeWidget was called with via
+  // ScreenCacheEntry's. The cache is cleared on the next tick of
+  // the event loop.
+  struct ScreenCacheEntry
+  {
+    RefPtr<mozilla::widget::ScreenProxy> mScreenProxy;
+    RefPtr<mozilla::dom::TabChild> mTabChild;
+  };
+
+  nsTArray<ScreenCacheEntry> mScreenCache;
+};
+
+#endif // nsScreenManagerProxy_h