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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 mozilla_dom_TabContext_h
+#define mozilla_dom_TabContext_h
+
+#include "nsCOMPtr.h"
+#include "mozilla/BasePrincipal.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIWindowRoot.h"
+
+namespace mozilla::dom {
+
+class IPCTabContext;
+
+/**
+ * TabContext encapsulates information about an iframe.
+ *
+ * BrowserParent and BrowserChild both inherit from TabContext, and you can also
+ * have standalone TabContext objects.
+ *
+ * This class is immutable except by calling one of the protected
+ * SetTabContext*() methods (and those methods can only be called once). See
+ * also MutableTabContext.
+ */
+class TabContext {
+ public:
+ TabContext();
+
+ /* (The implicit copy-constructor and operator= are fine.) */
+
+ /**
+ * Generates IPCTabContext of type BrowserFrameIPCTabContext from this
+ * TabContext's information.
+ */
+ IPCTabContext AsIPCTabContext() const;
+
+ uint64_t ChromeOuterWindowID() const;
+
+ uint32_t MaxTouchPoints() const { return mMaxTouchPoints; }
+
+ protected:
+ friend class MaybeInvalidTabContext;
+
+ /**
+ * These protected mutator methods let you modify a TabContext once. Further
+ * attempts to modify a given TabContext will fail (the method will return
+ * false).
+ *
+ * These mutators will also fail if the TabContext was created with anything
+ * other than the no-args constructor.
+ */
+
+ /**
+ * Set this TabContext to match the given TabContext.
+ */
+ bool SetTabContext(const TabContext& aContext);
+
+ bool SetTabContext(uint64_t aChromeOuterWindowID, uint32_t aMaxTouchPoints);
+
+ /**
+ * Modify this TabContext to match the given TabContext. This is a special
+ * case triggered by nsFrameLoader::SwapWithOtherRemoteLoader which may have
+ * caused the owner content to change.
+ *
+ * This special case only allows the field `mChromeOuterWindowID` to be
+ * changed. If any other fields have changed, the update is ignored and
+ * returns false.
+ */
+ bool UpdateTabContextAfterSwap(const TabContext& aContext);
+
+ void SetMaxTouchPoints(uint32_t aMaxTouchPoints) {
+ mMaxTouchPoints = aMaxTouchPoints;
+ }
+
+ private:
+ /**
+ * Has this TabContext been initialized? If so, mutator methods will fail.
+ */
+ bool mInitialized;
+
+ /**
+ * The outerWindowID of the window hosting the remote frameloader.
+ */
+ uint64_t mChromeOuterWindowID;
+
+ /**
+ * Maximum number of touch points.
+ */
+ uint32_t mMaxTouchPoints;
+};
+
+/**
+ * MutableTabContext is the same as MaybeInvalidTabContext, except the mutation
+ * methods are public instead of protected. You can still only call these
+ * mutation methods once on a given object.
+ */
+class MutableTabContext : public TabContext {
+ public:
+ bool SetTabContext(const TabContext& aContext) {
+ return TabContext::SetTabContext(aContext);
+ }
+
+ bool SetTabContext(uint64_t aChromeOuterWindowID, uint32_t aMaxTouchPoints) {
+ return TabContext::SetTabContext(aChromeOuterWindowID, aMaxTouchPoints);
+ }
+};
+
+/**
+ * MaybeInvalidTabContext is a simple class that lets you transform an
+ * IPCTabContext into a TabContext.
+ *
+ * The issue is that an IPCTabContext is not necessarily valid. So to convert
+ * an IPCTabContext into a TabContext, you construct a MaybeInvalidTabContext,
+ * check whether it's valid, and, if so, read out your TabContext.
+ *
+ * Example usage:
+ *
+ * void UseTabContext(const TabContext& aTabContext);
+ *
+ * void CreateTab(const IPCTabContext& aContext) {
+ * MaybeInvalidTabContext tc(aContext);
+ * if (!tc.IsValid()) {
+ * NS_ERROR(nsPrintfCString("Got an invalid IPCTabContext: %s",
+ * tc.GetInvalidReason()));
+ * return;
+ * }
+ * UseTabContext(tc.GetTabContext());
+ * }
+ */
+class MaybeInvalidTabContext {
+ public:
+ /**
+ * This constructor copies the information in aContext and sets IsValid() as
+ * appropriate.
+ */
+ explicit MaybeInvalidTabContext(const IPCTabContext& aContext);
+
+ /**
+ * Was the IPCTabContext we received in our constructor valid?
+ */
+ bool IsValid();
+
+ /**
+ * If IsValid(), this function returns null. Otherwise, it returns a
+ * human-readable string indicating why the IPCTabContext passed to our
+ * constructor was not valid.
+ */
+ const char* GetInvalidReason();
+
+ /**
+ * If IsValid(), this function returns a reference to a TabContext
+ * corresponding to the IPCTabContext passed to our constructor. If
+ * !IsValid(), this function crashes.
+ */
+ const TabContext& GetTabContext();
+
+ private:
+ MaybeInvalidTabContext(const MaybeInvalidTabContext&) = delete;
+ MaybeInvalidTabContext& operator=(const MaybeInvalidTabContext&) = delete;
+
+ const char* mInvalidReason;
+ MutableTabContext mTabContext;
+};
+
+} // namespace mozilla::dom
+
+#endif