Bug 1826645 Part 2: Make Document hold fullscreen requests while an exit is being processed. r=edgar

This change makes the parent process delay a fullscreen request if there
is a pending fullscreen exit. It also changes the DOMFullscreenParent
actor listener lifecycle. Once it has started handling a fullscreen
request, it will remain a listener to the Document until it receives an
exit event when the manager is out of fullscreen.

Differential Revision: https://phabricator.services.mozilla.com/D175186

browser/actors/DOMFullscreenParent.sys.mjs

@@ -239,7 +239,12 @@ export class DOMFullscreenParent extends JSWindowActorParent {
         }
         this.cleanupDomFullscreen(window);
         this.updateFullscreenWindowReference(window);
+
+        // If the document is supposed to be in fullscreen, keep the listener to wait for
+        // further events.
+        if (!this.manager.fullscreen) {
           this.removeListeners(window);
+        }
         break;
       }
     }

dom/base/Document.cpp

@@ -14467,11 +14467,14 @@ class ExitFullscreenScriptRunnable : public Runnable {
     nsContentUtils::DispatchEventOnlyToChrome(
         mLeaf, ToSupports(mLeaf), u"MozDOMFullscreen:Exited"_ns,
         CanBubble::eYes, Cancelable::eNo, /* DefaultAction */ nullptr);
-    // Ensure the window exits fullscreen.
+    // Ensure the window exits fullscreen, as long as we don't have
+    // pending fullscreen requests.
     if (nsPIDOMWindowOuter* win = mRoot->GetWindow()) {
+      if (!mRoot->HasPendingFullscreenRequests()) {
         win->SetFullscreenInternal(FullscreenReason::ForForceExitFullscreen,
                                    false);
       }
+    }
     return NS_OK;
   }
 
@@ -15262,6 +15265,15 @@ static bool ShouldApplyFullscreenDirectly(Document* aDoc,
   if (!iter.AtEnd()) {
     return false;
   }
+
+  // Same thing for exits. If we have any pending, we have to push
+  // to the pending queue.
+  PendingFullscreenChangeList::Iterator<FullscreenExit> iterExit(
+      aDoc, PendingFullscreenChangeList::eDocumentsWithSameRoot);
+  if (!iterExit.AtEnd()) {
+    return false;
+  }
+
   // We have to apply the fullscreen state directly in this case,
   // because nsGlobalWindow::SetFullscreenInternal() will do nothing
   // if it is already in fullscreen. If we do not apply the state but
@@ -15341,6 +15353,15 @@ void Document::RequestFullscreenInParentProcess(
     return;
   }
 
+  // See if we're waiting on an exit. If so, just make this one pending.
+  PendingFullscreenChangeList::Iterator<FullscreenExit> iter(
+      this, PendingFullscreenChangeList::eDocumentsWithSameRoot);
+  if (!iter.AtEnd()) {
+    PendingFullscreenChangeList::Add(std::move(aRequest));
+    rootWin->SetFullscreenInternal(FullscreenReason::ForFullscreenAPI, true);
+    return;
+  }
+
   // We don't need to check element ready before this point, because
   // if we called ApplyFullscreen, it would check that for us.
   if (!FullscreenElementReadyCheck(*aRequest)) {

xpfe/appshell/AppWindow.cpp

@@ -1977,7 +1977,7 @@ nsresult AppWindow::SetPersistentValue(const nsAtom* aAttr,
 void AppWindow::MaybeSavePersistentPositionAndSize(
     PersistentAttributes aAttributes, Element& aRootElement,
     const nsAString& aPersistString, bool aShouldPersist) {
-  if ((aAttributes & PersistentAttributes{PersistentAttribute::Position,
+  if ((aAttributes& PersistentAttributes{PersistentAttribute::Position,
                                          PersistentAttribute::Size})
           .isEmpty()) {
     return;
@@ -2915,24 +2915,7 @@ void AppWindow::SizeModeChanged(nsSizeMode aSizeMode) {
   nsCOMPtr<nsPIDOMWindowOuter> ourWindow =
       mDocShell ? mDocShell->GetWindow() : nullptr;
   if (ourWindow) {
-    // Ensure that the fullscreen state is synchronized between
-    // the widget and the outer window object.
-    if (aSizeMode != nsSizeMode_Fullscreen &&
-        aSizeMode != nsSizeMode_Minimized) {
-      if (ourWindow->GetFullScreen()) {
-        // The first SetFullscreenInternal call below ensures that we do
-        // not trigger any fullscreen transition even if the window was
-        // put in fullscreen only for the Fullscreen API. The second
-        // SetFullScreen call ensures that the window really exit from
-        // fullscreen even if it entered fullscreen for both Fullscreen
-        // Mode and Fullscreen API.
-        ourWindow->SetFullscreenInternal(
-            FullscreenReason::ForForceExitFullscreen, false);
-        ourWindow->SetFullScreen(false);
-      }
-    }
-
-    // And always fire a user-defined sizemodechange event on the window
+    // Always fire a user-defined sizemodechange event on the window
     ourWindow->DispatchCustomEvent(u"sizemodechange"_ns);
   }