Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 748 insertions, 0 deletions

diff --git a/xpfe/appshell/nsWindowMediator.cpp b/xpfe/appshell/nsWindowMediator.cpp
new file mode 100644
index 0000000000..2fb97c6f03
--- /dev/null
+++ b/xpfe/appshell/nsWindowMediator.cpp
@@ -0,0 +1,748 @@
+/* -*- 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/. */
+
+#include "nsCOMPtr.h"
+#include "nsEnumeratorUtils.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsUnicharUtils.h"
+#include "nsTArray.h"
+#include "nsIBaseWindow.h"
+#include "nsIWidget.h"
+#include "nsIObserverService.h"
+#include "nsISimpleEnumerator.h"
+#include "nsAppShellWindowEnumerator.h"
+#include "nsWindowMediator.h"
+#include "nsIWindowMediatorListener.h"
+#include "nsGlobalWindow.h"
+
+#include "nsIDocShell.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIAppWindow.h"
+
+using namespace mozilla;
+
+nsresult nsWindowMediator::GetDOMWindow(
+    nsIAppWindow* inWindow, nsCOMPtr<nsPIDOMWindowOuter>& outDOMWindow) {
+  nsCOMPtr<nsIDocShell> docShell;
+
+  outDOMWindow = nullptr;
+  inWindow->GetDocShell(getter_AddRefs(docShell));
+  NS_ENSURE_TRUE(docShell, NS_ERROR_FAILURE);
+
+  outDOMWindow = docShell->GetWindow();
+  return outDOMWindow ? NS_OK : NS_ERROR_FAILURE;
+}
+
+nsWindowMediator::nsWindowMediator()
+    : mEnumeratorList(),
+      mOldestWindow(nullptr),
+      mTopmostWindow(nullptr),
+      mTimeStamp(0),
+      mSortingZOrder(false),
+      mReady(false) {}
+
+nsWindowMediator::~nsWindowMediator() {
+  while (mOldestWindow) UnregisterWindow(mOldestWindow);
+}
+
+nsresult nsWindowMediator::Init() {
+  nsresult rv;
+  nsCOMPtr<nsIObserverService> obsSvc =
+      do_GetService("@mozilla.org/observer-service;1", &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = obsSvc->AddObserver(this, "xpcom-shutdown", true);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mReady = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsWindowMediator::RegisterWindow(nsIAppWindow* inWindow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+
+  if (!mReady) {
+    NS_ERROR("Mediator is not initialized or about to die.");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (GetInfoFor(inWindow)) {
+    NS_ERROR("multiple window registration");
+    return NS_ERROR_FAILURE;
+  }
+
+  mTimeStamp++;
+
+  // Create window info struct and add to list of windows
+  nsWindowInfo* windowInfo = new nsWindowInfo(inWindow, mTimeStamp);
+
+  for (const auto& listener : mListeners.ForwardRange()) {
+    listener->OnOpenWindow(inWindow);
+  }
+
+  if (mOldestWindow)
+    windowInfo->InsertAfter(mOldestWindow->mOlder, nullptr);
+  else
+    mOldestWindow = windowInfo;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::UnregisterWindow(nsIAppWindow* inWindow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mReady);
+  NS_ENSURE_STATE(mReady);
+  nsWindowInfo* info = GetInfoFor(inWindow);
+  if (info) return UnregisterWindow(info);
+  return NS_ERROR_INVALID_ARG;
+}
+
+nsresult nsWindowMediator::UnregisterWindow(nsWindowInfo* inInfo) {
+  // Inform the iterators
+  uint32_t index = 0;
+  while (index < mEnumeratorList.Length()) {
+    mEnumeratorList[index]->WindowRemoved(inInfo);
+    index++;
+  }
+
+  nsIAppWindow* window = inInfo->mWindow.get();
+  for (const auto& listener : mListeners.ForwardRange()) {
+    listener->OnCloseWindow(window);
+  }
+
+  // Remove from the lists and free up
+  if (inInfo == mOldestWindow) mOldestWindow = inInfo->mYounger;
+  if (inInfo == mTopmostWindow) mTopmostWindow = inInfo->mLower;
+  inInfo->Unlink(true, true);
+  if (inInfo == mOldestWindow) mOldestWindow = nullptr;
+  if (inInfo == mTopmostWindow) mTopmostWindow = nullptr;
+  delete inInfo;
+
+  return NS_OK;
+}
+
+nsWindowInfo* nsWindowMediator::GetInfoFor(nsIAppWindow* aWindow) {
+  nsWindowInfo *info, *listEnd;
+
+  if (!aWindow) return nullptr;
+
+  info = mOldestWindow;
+  listEnd = nullptr;
+  while (info != listEnd) {
+    if (info->mWindow.get() == aWindow) return info;
+    info = info->mYounger;
+    listEnd = mOldestWindow;
+  }
+  return nullptr;
+}
+
+nsWindowInfo* nsWindowMediator::GetInfoFor(nsIWidget* aWindow) {
+  nsWindowInfo *info, *listEnd;
+
+  if (!aWindow) return nullptr;
+
+  info = mOldestWindow;
+  listEnd = nullptr;
+
+  nsCOMPtr<nsIWidget> scanWidget;
+  while (info != listEnd) {
+    nsCOMPtr<nsIBaseWindow> base(do_QueryInterface(info->mWindow));
+    if (base) base->GetMainWidget(getter_AddRefs(scanWidget));
+    if (aWindow == scanWidget.get()) return info;
+    info = info->mYounger;
+    listEnd = mOldestWindow;
+  }
+  return nullptr;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetEnumerator(const char16_t* inType,
+                                nsISimpleEnumerator** outEnumerator) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(outEnumerator);
+  if (!mReady) {
+    // If we get here with mReady false, we most likely did observe
+    // xpcom-shutdown. We will return an empty enumerator such that
+    // we make happy Javascripts calling late without throwing.
+    return NS_NewEmptyEnumerator(outEnumerator);
+  }
+  RefPtr<nsAppShellWindowEnumerator> enumerator =
+      new nsASDOMWindowEarlyToLateEnumerator(inType, *this);
+  enumerator.forget(outEnumerator);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetAppWindowEnumerator(const char16_t* inType,
+                                         nsISimpleEnumerator** outEnumerator) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(outEnumerator);
+  if (!mReady) {
+    // If we get here with mReady false, we most likely did observe
+    // xpcom-shutdown. We will return an empty enumerator such that
+    // we make happy Javascripts calling late without throwing.
+    return NS_NewEmptyEnumerator(outEnumerator);
+  }
+  RefPtr<nsAppShellWindowEnumerator> enumerator =
+      new nsASAppWindowEarlyToLateEnumerator(inType, *this);
+  enumerator.forget(outEnumerator);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetZOrderAppWindowEnumerator(const char16_t* aWindowType,
+                                               bool aFrontToBack,
+                                               nsISimpleEnumerator** _retval) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(_retval);
+  if (!mReady) {
+    // If we get here with mReady false, we most likely did observe
+    // xpcom-shutdown. We will return an empty enumerator such that
+    // we make happy Javascripts calling late without throwing.
+    return NS_NewEmptyEnumerator(_retval);
+  }
+  RefPtr<nsAppShellWindowEnumerator> enumerator;
+  if (aFrontToBack)
+    enumerator = new nsASAppWindowFrontToBackEnumerator(aWindowType, *this);
+  else
+    enumerator = new nsASAppWindowBackToFrontEnumerator(aWindowType, *this);
+
+  enumerator.forget(_retval);
+  return NS_OK;
+}
+
+void nsWindowMediator::AddEnumerator(nsAppShellWindowEnumerator* inEnumerator) {
+  mEnumeratorList.AppendElement(inEnumerator);
+}
+
+int32_t nsWindowMediator::RemoveEnumerator(
+    nsAppShellWindowEnumerator* inEnumerator) {
+  return mEnumeratorList.RemoveElement(inEnumerator);
+}
+
+// Returns the window of type inType ( if null return any window type ) which
+// has the most recent time stamp
+NS_IMETHODIMP
+nsWindowMediator::GetMostRecentWindow(const char16_t* inType,
+                                      mozIDOMWindowProxy** outWindow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(outWindow);
+  *outWindow = nullptr;
+  if (!mReady) return NS_OK;
+
+  // Find the most window with the highest time stamp that matches
+  // the requested type
+  nsWindowInfo* info = MostRecentWindowInfo(inType, false);
+  if (info && info->mWindow) {
+    nsCOMPtr<nsPIDOMWindowOuter> DOMWindow;
+    if (NS_SUCCEEDED(GetDOMWindow(info->mWindow, DOMWindow))) {
+      DOMWindow.forget(outWindow);
+      return NS_OK;
+    }
+    return NS_ERROR_FAILURE;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetMostRecentBrowserWindow(mozIDOMWindowProxy** outWindow) {
+  nsresult rv = GetMostRecentWindow(u"navigator:browser", outWindow);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+#ifdef MOZ_WIDGET_ANDROID
+  if (!*outWindow) {
+    rv = GetMostRecentWindow(u"navigator:geckoview", outWindow);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+#endif
+
+#ifdef MOZ_THUNDERBIRD
+  if (!*outWindow) {
+    rv = GetMostRecentWindow(u"mail:3pane", outWindow);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+#endif
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetMostRecentNonPBWindow(const char16_t* aType,
+                                           mozIDOMWindowProxy** aWindow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(aWindow);
+  *aWindow = nullptr;
+
+  nsWindowInfo* info = MostRecentWindowInfo(aType, true);
+  nsCOMPtr<nsPIDOMWindowOuter> domWindow;
+  if (info && info->mWindow) {
+    GetDOMWindow(info->mWindow, domWindow);
+  }
+
+  if (!domWindow) {
+    return NS_ERROR_FAILURE;
+  }
+
+  domWindow.forget(aWindow);
+  return NS_OK;
+}
+
+nsWindowInfo* nsWindowMediator::MostRecentWindowInfo(
+    const char16_t* inType, bool aSkipPrivateBrowsingOrClosed) {
+  int32_t lastTimeStamp = -1;
+  nsAutoString typeString(inType);
+  bool allWindows = !inType || typeString.IsEmpty();
+
+  // Find the most recent window with the highest time stamp that matches
+  // the requested type and has the correct browsing mode.
+  nsWindowInfo* searchInfo = mOldestWindow;
+  nsWindowInfo* listEnd = nullptr;
+  nsWindowInfo* foundInfo = nullptr;
+  for (; searchInfo != listEnd; searchInfo = searchInfo->mYounger) {
+    listEnd = mOldestWindow;
+
+    if (!allWindows && !searchInfo->TypeEquals(typeString)) {
+      continue;
+    }
+    if (searchInfo->mTimeStamp < lastTimeStamp) {
+      continue;
+    }
+    if (!searchInfo->mWindow) {
+      continue;
+    }
+    if (aSkipPrivateBrowsingOrClosed) {
+      nsCOMPtr<nsIDocShell> docShell;
+      searchInfo->mWindow->GetDocShell(getter_AddRefs(docShell));
+      nsCOMPtr<nsILoadContext> loadContext = do_QueryInterface(docShell);
+      if (!loadContext || loadContext->UsePrivateBrowsing()) {
+        continue;
+      }
+
+      nsCOMPtr<nsPIDOMWindowOuter> piwindow = docShell->GetWindow();
+      if (!piwindow || piwindow->Closed()) {
+        continue;
+      }
+    }
+
+    foundInfo = searchInfo;
+    lastTimeStamp = searchInfo->mTimeStamp;
+  }
+
+  return foundInfo;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetOuterWindowWithId(uint64_t aWindowID,
+                                       mozIDOMWindowProxy** aWindow) {
+  RefPtr<nsGlobalWindowOuter> window =
+      nsGlobalWindowOuter::GetOuterWindowWithId(aWindowID);
+  window.forget(aWindow);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetCurrentInnerWindowWithId(uint64_t aWindowID,
+                                              mozIDOMWindow** aWindow) {
+  RefPtr<nsGlobalWindowInner> window =
+      nsGlobalWindowInner::GetInnerWindowWithId(aWindowID);
+
+  // not found
+  if (!window) return NS_OK;
+
+  nsCOMPtr<nsPIDOMWindowOuter> outer = window->GetOuterWindow();
+  NS_ENSURE_TRUE(outer, NS_ERROR_UNEXPECTED);
+
+  // outer is already using another inner, so it's same as not found
+  if (outer->GetCurrentInnerWindow() != window) return NS_OK;
+
+  window.forget(aWindow);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::UpdateWindowTimeStamp(nsIAppWindow* inWindow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mReady);
+  NS_ENSURE_STATE(mReady);
+  nsWindowInfo* info = GetInfoFor(inWindow);
+  if (info) {
+    // increment the window's time stamp
+    info->mTimeStamp = ++mTimeStamp;
+    return NS_OK;
+  }
+  return NS_ERROR_FAILURE;
+}
+
+/* This method's plan is to intervene only when absolutely necessary.
+   We will get requests to place our windows behind unknown windows.
+   For the most part, we need to leave those alone (turning them into
+   explicit requests to be on top breaks Windows.) So generally we
+   calculate a change as seldom as possible.
+*/
+NS_IMETHODIMP
+nsWindowMediator::CalculateZPosition(nsIAppWindow* inWindow,
+                                     uint32_t inPosition, nsIWidget* inBelow,
+                                     uint32_t* outPosition,
+                                     nsIWidget** outBelow, bool* outAltered) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(outBelow);
+  MOZ_ASSERT(mReady);
+  NS_ENSURE_STATE(mReady);
+
+  *outBelow = nullptr;
+
+  if (!inWindow || !outPosition || !outAltered) return NS_ERROR_NULL_POINTER;
+
+  if (inPosition != nsIWindowMediator::zLevelTop &&
+      inPosition != nsIWindowMediator::zLevelBottom &&
+      inPosition != nsIWindowMediator::zLevelBelow)
+    return NS_ERROR_INVALID_ARG;
+
+  nsWindowInfo* info = mTopmostWindow;
+  nsIAppWindow* belowWindow = nullptr;
+  bool found = false;
+  nsresult result = NS_OK;
+
+  *outPosition = inPosition;
+  *outAltered = false;
+
+  if (mSortingZOrder) {  // don't fight SortZOrder()
+    *outBelow = inBelow;
+    NS_IF_ADDREF(*outBelow);
+    return NS_OK;
+  }
+
+  uint32_t inZ;
+  GetZLevel(inWindow, &inZ);
+
+  if (inPosition == nsIWindowMediator::zLevelBelow) {
+    // locate inBelow. use topmost if it can't be found or isn't in the
+    // z-order list
+    info = GetInfoFor(inBelow);
+    if (!info || (info->mYounger != info && info->mLower == info))
+      info = mTopmostWindow;
+    else
+      found = true;
+
+    if (!found) {
+      /* Treat unknown windows as a request to be on top.
+         Not as it should be, but that's what Windows gives us.
+         Note we change inPosition, but not *outPosition. This forces
+         us to go through the "on top" calculation just below, without
+         necessarily changing the output parameters. */
+      inPosition = nsIWindowMediator::zLevelTop;
+    }
+  }
+
+  if (inPosition == nsIWindowMediator::zLevelTop) {
+    if (mTopmostWindow && mTopmostWindow->mZLevel > inZ) {
+      // asked for topmost, can't have it. locate highest allowed position.
+      do {
+        if (info->mZLevel <= inZ) break;
+        info = info->mLower;
+      } while (info != mTopmostWindow);
+
+      *outPosition = nsIWindowMediator::zLevelBelow;
+      belowWindow = info->mHigher->mWindow;
+      *outAltered = true;
+    }
+  } else if (inPosition == nsIWindowMediator::zLevelBottom) {
+    if (mTopmostWindow && mTopmostWindow->mHigher->mZLevel < inZ) {
+      // asked for bottommost, can't have it. locate lowest allowed position.
+      do {
+        info = info->mHigher;
+        if (info->mZLevel >= inZ) break;
+      } while (info != mTopmostWindow);
+
+      *outPosition = nsIWindowMediator::zLevelBelow;
+      belowWindow = info->mWindow;
+      *outAltered = true;
+    }
+  } else {
+    unsigned long relativeZ;
+
+    // check that we're in the right z-plane
+    if (found) {
+      belowWindow = info->mWindow;
+      relativeZ = info->mZLevel;
+      if (relativeZ > inZ) {
+        // might be OK. is lower window, if any, lower?
+        if (info->mLower != info && info->mLower->mZLevel > inZ) {
+          do {
+            if (info->mZLevel <= inZ) break;
+            info = info->mLower;
+          } while (info != mTopmostWindow);
+
+          belowWindow = info->mHigher->mWindow;
+          *outAltered = true;
+        }
+      } else if (relativeZ < inZ) {
+        // nope. look for a higher window to be behind.
+        do {
+          info = info->mHigher;
+          if (info->mZLevel >= inZ) break;
+        } while (info != mTopmostWindow);
+
+        if (info->mZLevel >= inZ)
+          belowWindow = info->mWindow;
+        else
+          *outPosition = nsIWindowMediator::zLevelTop;
+        *outAltered = true;
+      }  // else they're equal, so it's OK
+    }
+  }
+
+  if (NS_SUCCEEDED(result) && belowWindow) {
+    nsCOMPtr<nsIBaseWindow> base(do_QueryInterface(belowWindow));
+    if (base)
+      base->GetMainWidget(outBelow);
+    else
+      result = NS_ERROR_NO_INTERFACE;
+  }
+
+  return result;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::SetZPosition(nsIAppWindow* inWindow, uint32_t inPosition,
+                               nsIAppWindow* inBelow) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  nsWindowInfo *inInfo, *belowInfo;
+
+  if ((inPosition != nsIWindowMediator::zLevelTop &&
+       inPosition != nsIWindowMediator::zLevelBottom &&
+       inPosition != nsIWindowMediator::zLevelBelow) ||
+      !inWindow) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  if (mSortingZOrder)  // don't fight SortZOrder()
+    return NS_OK;
+
+  MOZ_ASSERT(mReady);
+  NS_ENSURE_STATE(mReady);
+
+  /* Locate inWindow and unlink it from the z-order list.
+     It's important we look for it in the age list, not the z-order list.
+     This is because the former is guaranteed complete, while
+     now may be this window's first exposure to the latter. */
+  inInfo = GetInfoFor(inWindow);
+  if (!inInfo) return NS_ERROR_INVALID_ARG;
+
+  // locate inBelow, place inWindow behind it
+  if (inPosition == nsIWindowMediator::zLevelBelow) {
+    belowInfo = GetInfoFor(inBelow);
+    // it had better also be in the z-order list
+    if (belowInfo && belowInfo->mYounger != belowInfo &&
+        belowInfo->mLower == belowInfo) {
+      belowInfo = nullptr;
+    }
+    if (!belowInfo) {
+      if (inBelow)
+        return NS_ERROR_INVALID_ARG;
+      else
+        inPosition = nsIWindowMediator::zLevelTop;
+    }
+  }
+  if (inPosition == nsIWindowMediator::zLevelTop ||
+      inPosition == nsIWindowMediator::zLevelBottom)
+    belowInfo = mTopmostWindow ? mTopmostWindow->mHigher : nullptr;
+
+  if (inInfo != belowInfo) {
+    inInfo->Unlink(false, true);
+    inInfo->InsertAfter(nullptr, belowInfo);
+  }
+  if (inPosition == nsIWindowMediator::zLevelTop) mTopmostWindow = inInfo;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::GetZLevel(nsIAppWindow* aWindow, uint32_t* _retval) {
+  NS_ENSURE_ARG_POINTER(_retval);
+  *_retval = nsIAppWindow::normalZ;
+  // This can fail during window destruction.
+  nsWindowInfo* info = GetInfoFor(aWindow);
+  if (info) {
+    *_retval = info->mZLevel;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::SetZLevel(nsIAppWindow* aWindow, uint32_t aZLevel) {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mReady);
+  NS_ENSURE_STATE(mReady);
+
+  nsWindowInfo* info = GetInfoFor(aWindow);
+  NS_ASSERTION(info, "setting z level of unregistered window");
+  if (!info) return NS_ERROR_FAILURE;
+
+  if (info->mZLevel != aZLevel) {
+    bool lowered = info->mZLevel > aZLevel;
+    info->mZLevel = aZLevel;
+    if (lowered)
+      SortZOrderFrontToBack();
+    else
+      SortZOrderBackToFront();
+  }
+  return NS_OK;
+}
+
+/*   Fix potentially out-of-order windows by performing an insertion sort
+   on the z-order list. The method will work no matter how broken the
+   list, but its assumed usage is immediately after one window's z level
+   has been changed, so one window is potentially out of place. Such a sort
+   is most efficiently done in a particular direction. Use this one
+   if a window's z level has just been reduced, so the sort is most efficiently
+   done front to back.
+     Note it's hardly worth going to all the trouble to write two versions
+   of this method except that if we choose the inefficient sorting direction,
+   on slow systems windows could visibly bubble around the window that
+   was moved.
+*/
+void nsWindowMediator::SortZOrderFrontToBack() {
+  nsWindowInfo *scan,  // scans list looking for problems
+      *search,         // searches for correct placement for scan window
+      *prev,           // previous search element
+      *lowest;         // bottom-most window in list
+  bool finished;
+
+  if (!mTopmostWindow)  // early during program execution there's no z list yet
+    return;  // there's also only one window, so this is not dangerous
+
+  mSortingZOrder = true;
+
+  /* Step through the list from top to bottom. If we find a window which
+     should be moved down in the list, move it to its highest legal position. */
+  do {
+    finished = true;
+    lowest = mTopmostWindow->mHigher;
+    scan = mTopmostWindow;
+    while (scan != lowest) {
+      uint32_t scanZ = scan->mZLevel;
+      if (scanZ < scan->mLower->mZLevel) {  // out of order
+        search = scan->mLower;
+        do {
+          prev = search;
+          search = search->mLower;
+        } while (prev != lowest && scanZ < search->mZLevel);
+
+        // reposition |scan| within the list
+        if (scan == mTopmostWindow) mTopmostWindow = scan->mLower;
+        scan->Unlink(false, true);
+        scan->InsertAfter(nullptr, prev);
+
+        // fix actual window order
+        nsCOMPtr<nsIBaseWindow> base;
+        nsCOMPtr<nsIWidget> scanWidget;
+        nsCOMPtr<nsIWidget> prevWidget;
+        base = do_QueryInterface(scan->mWindow);
+        if (base) base->GetMainWidget(getter_AddRefs(scanWidget));
+        base = do_QueryInterface(prev->mWindow);
+        if (base) base->GetMainWidget(getter_AddRefs(prevWidget));
+        if (scanWidget)
+          scanWidget->PlaceBehind(eZPlacementBelow, prevWidget, false);
+
+        finished = false;
+        break;
+      }
+      scan = scan->mLower;
+    }
+  } while (!finished);
+
+  mSortingZOrder = false;
+}
+
+// see comment for SortZOrderFrontToBack
+void nsWindowMediator::SortZOrderBackToFront() {
+  nsWindowInfo *scan,  // scans list looking for problems
+      *search,         // searches for correct placement for scan window
+      *lowest;         // bottom-most window in list
+  bool finished;
+
+  if (!mTopmostWindow)  // early during program execution there's no z list yet
+    return;  // there's also only one window, so this is not dangerous
+
+  mSortingZOrder = true;
+
+  /* Step through the list from bottom to top. If we find a window which
+     should be moved up in the list, move it to its lowest legal position. */
+  do {
+    finished = true;
+    lowest = mTopmostWindow->mHigher;
+    scan = lowest;
+    while (scan != mTopmostWindow) {
+      uint32_t scanZ = scan->mZLevel;
+      if (scanZ > scan->mHigher->mZLevel) {  // out of order
+        search = scan;
+        do {
+          search = search->mHigher;
+        } while (search != lowest && scanZ > search->mZLevel);
+
+        // reposition |scan| within the list
+        if (scan != search && scan != search->mLower) {
+          scan->Unlink(false, true);
+          scan->InsertAfter(nullptr, search);
+        }
+        if (search == lowest) mTopmostWindow = scan;
+
+        // fix actual window order
+        nsCOMPtr<nsIBaseWindow> base;
+        nsCOMPtr<nsIWidget> scanWidget;
+        nsCOMPtr<nsIWidget> searchWidget;
+        base = do_QueryInterface(scan->mWindow);
+        if (base) base->GetMainWidget(getter_AddRefs(scanWidget));
+        if (mTopmostWindow != scan) {
+          base = do_QueryInterface(search->mWindow);
+          if (base) base->GetMainWidget(getter_AddRefs(searchWidget));
+        }
+        if (scanWidget)
+          scanWidget->PlaceBehind(eZPlacementBelow, searchWidget, false);
+        finished = false;
+        break;
+      }
+      scan = scan->mHigher;
+    }
+  } while (!finished);
+
+  mSortingZOrder = false;
+}
+
+NS_IMPL_ISUPPORTS(nsWindowMediator, nsIWindowMediator, nsIObserver,
+                  nsISupportsWeakReference)
+
+NS_IMETHODIMP
+nsWindowMediator::AddListener(nsIWindowMediatorListener* aListener) {
+  NS_ENSURE_ARG_POINTER(aListener);
+
+  mListeners.AppendElement(aListener);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::RemoveListener(nsIWindowMediatorListener* aListener) {
+  NS_ENSURE_ARG_POINTER(aListener);
+
+  mListeners.RemoveElement(aListener);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsWindowMediator::Observe(nsISupports* aSubject, const char* aTopic,
+                          const char16_t* aData) {
+  if (!strcmp(aTopic, "xpcom-shutdown") && mReady) {
+    MOZ_RELEASE_ASSERT(NS_IsMainThread());
+    while (mOldestWindow) UnregisterWindow(mOldestWindow);
+    mReady = false;
+  }
+  return NS_OK;
+}