Bug 1795139 - Show fullscreen notification as soon as browser window goes into fullscreen mode; r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D159383

browser/actors/DOMFullscreenParent.sys.mjs

@@ -197,6 +197,12 @@ export class DOMFullscreenParent extends JSWindowActorParent {
         TelemetryStopwatch.start("FULLSCREEN_CHANGE_MS");
         window.FullScreen.enterDomFullscreen(browser, this);
         this.updateFullscreenWindowReference(window);
+
+        if (!this.hasBeenDestroyed() && this.requestOrigin) {
+          window.PointerlockFsWarning.showFullScreen(
+            this.requestOrigin.manager.documentPrincipal.originNoSuffix
+          );
+        }
         break;
       }
       case "MozDOMFullscreen:Exited": {

dom/base/Document.cpp

@@ -15069,12 +15069,12 @@ bool Document::ApplyFullscreen(UniquePtr<FullscreenRequest> aRequest) {
 
   // The origin which is fullscreen gets changed. Trigger an event so
   // that the chrome knows to pop up a warning UI. Note that
-  // previousFullscreenDoc == nullptr upon first entry, so we always
-  // take this path on the first entry. Also note that, in a multi-
-  // process browser, the code in content process is responsible for
-  // sending message with the origin to its parent, and the parent
-  // shouldn't rely on this event itself.
-  if (aRequest->mShouldNotifyNewOrigin &&
+  // previousFullscreenDoc == nullptr upon first entry, we show the warning UI
+  // directly as soon as chrome document goes into fullscreen state. Also note
+  // that, in a multi-process browser, the code in content process is
+  // responsible for sending message with the origin to its parent, and the
+  // parent shouldn't rely on this event itself.
+  if (aRequest->mShouldNotifyNewOrigin && previousFullscreenDoc &&
       !nsContentUtils::HaveEqualPrincipals(previousFullscreenDoc, this)) {
     DispatchFullscreenNewOriginEvent(this);
   }

dom/tests/mochitest/chrome/MozDomFullscreen_chrome.xhtml

@@ -38,28 +38,26 @@ var gOuterDoc = null;
 var gInnerDoc = null;
 
 var gReceivedFullscreenEnteredEvent = false;
-var gReceivedNewOriginEvent = false;
 function firstEntry(event) {
-  if (event.type == "MozDOMFullscreen:Entered") {
-    window.removeEventListener("MozDOMFullscreen:Entered", firstEntry, false);
-    ok(!gReceivedFullscreenEnteredEvent, "MozDOMFullscreen:Entered shouldn't have been triggered twice");
-    is(event.target, gOuterDoc.body, "First MozDOMFullscreen:Entered should be targeted at outer body");
-    gReceivedFullscreenEnteredEvent = true;
-  } else if (event.type == "MozDOMFullscreen:NewOrigin") {
-    window.removeEventListener("MozDOMFullscreen:NewOrigin", firstEntry, false);
-    ok(!gReceivedNewOriginEvent, "MozDOMFullscreen:NewOrigin shouldn't have been triggered twice");
-    is(event.target, gOuterDoc, "First MozDOMFullscreen:NewOrigin should be targeted at outer doc");
-    gReceivedNewOriginEvent = true;
-  } else {
-    ok(false, "Unknown event received");
+  if (event.type == "MozDOMFullscreen:NewOrigin") {
+    ok(false, "MozDOMFullscreen:NewOrigin shouldn't be triggered at first entry");
+    return;
   }
-  if (!gReceivedFullscreenEnteredEvent || !gReceivedNewOriginEvent) {
+
+  if (event.type != "MozDOMFullscreen:Entered") {
+    ok(false, "Unknown event received");
     return;
   }
 
   ok(gOuterDoc.fullscreenElement != null, "Outer doc should be in fullscreen");
+  is(event.target, gOuterDoc.body, "First MozDOMFullscreen:Entered should be targeted at outer body");
+  ok(!gReceivedFullscreenEnteredEvent, "MozDOMFullscreen:Entered shouldn't have been triggered twice");
+  gReceivedFullscreenEnteredEvent = true;
+  window.removeEventListener("MozDOMFullscreen:Entered", firstEntry);
+  window.removeEventListener("MozDOMFullscreen:NewOrigin", firstEntry);
+
+  window.addEventListener("MozDOMFullscreen:NewOrigin", secondEntry);
   gInnerDoc = gOuterDoc.getElementById("innerFrame").contentDocument;
-  window.addEventListener("MozDOMFullscreen:NewOrigin", secondEntry, false);
   gInnerDoc.defaultView.focus();
   gInnerDoc.body.requestFullscreen();
 }