Bug 1800897 - Don't fire resize events along before/afterprint. r=dholbert, a=RyanVM

This partially backs out bug 774398.

This code was added to match what Chromium was doing, but it seems (per
discussions with Chromium engineers) that:

 * Resize event listener in Chromium never changed
   innerWidth/innerHeight. That doesn't match my recollection from bug
   774398, but it's true now in Chrome stable, at least.

 * Chromium canary no longer fires a resize event
   (https://crbug.com/1076867).

 * WebKit doesn't fire resize either.

So let's get rid of this, which also causes some correctness issues with
some iframes, and keep just the media query listeners firing.

Differential Revision: https://phabricator.services.mozilla.com/D185404

dom/base/AutoPrintEventDispatcher.h

@@ -18,9 +18,9 @@ class AutoPrintEventDispatcher {
   // NOTE(emilio): For fission iframes, we dispatch this event in
   // RecvCloneDocumentTreeIntoSelf.
   static void CollectInProcessSubdocuments(
-      Document& aDoc, nsTArray<std::pair<nsCOMPtr<Document>, bool>>& aDocs) {
+      Document& aDoc, nsTArray<nsCOMPtr<Document>>& aDocs) {
     auto recurse = [&aDocs](Document& aSubDoc) {
-      aDocs.AppendElement(std::make_pair(&aSubDoc, false));
+      aDocs.AppendElement(&aSubDoc);
       CollectInProcessSubdocuments(aSubDoc, aDocs);
       return CallState::Continue;
     };
@@ -28,69 +28,22 @@ class AutoPrintEventDispatcher {
   }
 
   MOZ_CAN_RUN_SCRIPT void DispatchEvent(bool aBefore) {
-    for (auto& [doc, isTop] : mDocuments) {
+    for (auto& doc : mDocuments) {
       nsContentUtils::DispatchTrustedEvent(
           doc, doc->GetWindow(), aBefore ? u"beforeprint"_ns : u"afterprint"_ns,
           CanBubble::eNo, Cancelable::eNo, nullptr);
       if (RefPtr<nsPresContext> presContext = doc->GetPresContext()) {
         presContext->EmulateMedium(aBefore ? nsGkAtoms::print : nullptr);
-        bool needResizeEvent = false;
-        if (isTop) {
-          // NOTE(emilio): Having this code here means that we only fire the
-          // resize on the initial document clone, not on any further print
-          // settings changes. This is an intentional trade-off.
-          //
-          // On a continuously changing document, we don't want to keep
-          // re-cloning every time the user changes the print settings, as it
-          // changes what you're printing.
-          if (aBefore) {
-            mVisibleAreaToRestore = presContext->GetVisibleArea();
-            presContext->SetVisibleArea(
-                nsRect(mVisibleAreaToRestore.TopLeft(), mPageSize));
-            needResizeEvent = mVisibleAreaToRestore.Size() != mPageSize;
-          } else {
-            if (presContext->GetVisibleArea().Size() == mPageSize) {
-              presContext->SetVisibleArea(mVisibleAreaToRestore);
-              needResizeEvent = mVisibleAreaToRestore.Size() != mPageSize;
-            } else {
-              // This shouldn't happen, but can if used by privileged script,
-              // like in test_printpreview.xhtml. It's ok to do nothing here
-              // tho, we just need to make sure that the mPageSize viewport size
-              // doesn't persist.
-              NS_WARNING(
-                  "Something changed our viewport size between firing "
-                  "before/afterprint?");
-            }
-          }
-        }
-
         // Ensure media query listeners fire.
         doc->FlushPendingNotifications(FlushType::Style);
-
-        if (needResizeEvent) {
-          if (RefPtr ps = presContext->GetPresShell()) {
-            ps->FireResizeEventSync();
-          }
-        }
       }
     }
   }
 
-  static nsSize ComputePrintPageSize(nsIPrintSettings* aPrintSettings) {
-    double pageWidth = 0;
-    double pageHeight = 0;
-    aPrintSettings->GetEffectivePageSize(&pageWidth, &pageHeight);
-    return nsSize(nsPresContext::CSSTwipsToAppUnits(NSToIntFloor(pageWidth)),
-                  nsPresContext::CSSTwipsToAppUnits(NSToIntFloor(pageHeight)));
-  }
-
  public:
-  MOZ_CAN_RUN_SCRIPT AutoPrintEventDispatcher(Document& aDoc,
-                                              nsIPrintSettings* aPrintSettings,
-                                              bool aIsTop)
-      : mPageSize(ComputePrintPageSize(aPrintSettings)) {
+  MOZ_CAN_RUN_SCRIPT explicit AutoPrintEventDispatcher(Document& aDoc) {
     if (!aDoc.IsStaticDocument()) {
-      mDocuments.AppendElement(std::make_pair(&aDoc, aIsTop));
+      mDocuments.AppendElement(&aDoc);
       CollectInProcessSubdocuments(aDoc, mDocuments);
     }
 
@@ -99,8 +52,7 @@ class AutoPrintEventDispatcher {
 
   MOZ_CAN_RUN_SCRIPT ~AutoPrintEventDispatcher() { DispatchEvent(false); }
 
-  // The bool represents whether this is the top-level paginated document.
-  AutoTArray<std::pair<nsCOMPtr<Document>, bool>, 8> mDocuments;
+  AutoTArray<nsCOMPtr<Document>, 8> mDocuments;
   const nsSize mPageSize;
   nsRect mVisibleAreaToRestore;
 };

dom/base/nsGlobalWindowOuter.cpp

@@ -5284,7 +5284,7 @@ Nullable<WindowProxyHolder> nsGlobalWindowOuter::Print(
       }
     }
 
-    AutoPrintEventDispatcher dispatcher(*docToPrint, ps, /* aIsTop = */ true);
+    AutoPrintEventDispatcher dispatcher(*docToPrint);
 
     nsAutoScriptBlocker blockScripts;
     RefPtr<Document> clone = docToPrint->CreateStaticClone(

dom/ipc/BrowserChild.cpp

@@ -935,8 +935,7 @@ nsresult BrowserChild::CloneDocumentTreeIntoSelf(
 
   RefPtr<Document> clone;
   {
-    AutoPrintEventDispatcher dispatcher(*sourceDocument, printSettings,
-                                        /* aIsTop = */ false);
+    AutoPrintEventDispatcher dispatcher(*sourceDocument);
     nsAutoScriptBlocker scriptBlocker;
     bool hasInProcessCallbacks = false;
     clone = sourceDocument->CreateStaticClone(ourDocShell, cv, printSettings,

testing/web-platform/mozilla/tests/css/cssom/size-change-print-notref.html

@@ -1,5 +0,0 @@
-<!doctype html>
-<div id="target">FAIL</div>
-<script>
-  document.getElementById("target").innerHTML = `${window.innerWidth}x${window.innerHeight}`;
-</script>

testing/web-platform/mozilla/tests/css/cssom/size-change-print.html

@@ -1,10 +0,0 @@
-<!doctype html>
-<link rel="mismatch" href="size-change-print-notref.html">
-<div id="target">FAIL</div>
-<script>
-function update() {
-  document.getElementById("target").innerHTML = `${window.innerWidth}x${window.innerHeight}`;
-}
-update();
-window.addEventListener("resize", update);
-</script>

testing/web-platform/tests/css/printing/no-resize-event-print.html

@@ -0,0 +1,10 @@
+<!doctype html>
+<title>No resize event on the original page when printing</title>
+<link rel="help" href="https://drafts.csswg.org/mediaqueries-4/#valdef-media-print">
+<link rel="match" href="no-resize-event-ref.html">
+<div id="target">PASS</div>
+<script>
+window.addEventListener("resize", function() {
+  document.getElementById("target").innerHTML = `FAIL: ${window.innerWidth}x${window.innerHeight}`;
+})
+</script>

testing/web-platform/tests/css/printing/no-resize-event-ref.html

@@ -0,0 +1,2 @@
+<!doctype html>
+<div>PASS</div>