Bug 1688004 - Build top layer items for XUL documents that don't have scrollframes. r=miko

This will allow the browser chrome to use `<dialog>` etc, see
bug 1685313.

Tweak the check to support scrolling="false" on reftests, so that we can
test this.

Differential Revision: https://phabricator.services.mozilla.com/D102623

layout/base/nsCSSFrameConstructor.cpp

@@ -2565,7 +2565,7 @@ void nsCSSFrameConstructor::SetUpDocElementContainingBlock(
     isScrollable = presContext->HasPaginatedScrolling();
   } else if (isXUL) {
     isScrollable = false;
-  } else if (nsContentUtils::IsInChromeDocshell(aDocElement->OwnerDoc()) &&
+  } else if (aDocElement->OwnerDoc()->AllowXULXBL() &&
              aDocElement->AsElement()->AttrValueIs(
                  kNameSpaceID_None, nsGkAtoms::scrolling, nsGkAtoms::_false,
                  eCaseMatters)) {

layout/generic/ViewportFrame.cpp

@@ -16,9 +16,10 @@
 #include "mozilla/RestyleManager.h"
 #include "nsGkAtoms.h"
 #include "nsIScrollableFrame.h"
-#include "nsSubDocumentFrame.h"
-#include "nsCanvasFrame.h"
 #include "nsAbsoluteContainingBlock.h"
+#include "nsCanvasFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsSubDocumentFrame.h"
 #include "GeckoProfiler.h"
 #include "nsIMozBrowserFrame.h"
 #include "nsPlaceholderFrame.h"
@@ -56,12 +57,27 @@ void ViewportFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
   AUTO_PROFILER_LABEL("ViewportFrame::BuildDisplayList",
                       GRAPHICS_DisplayListBuilding);
 
-  if (nsIFrame* kid = mFrames.FirstChild()) {
-    // make the kid's BorderBackground our own. This ensures that the canvas
-    // frame's background becomes our own background and therefore appears
-    // below negative z-index elements.
-    BuildDisplayListForChild(aBuilder, kid, aLists);
+  nsIFrame* kid = mFrames.FirstChild();
+  if (!kid) {
+    return;
   }
+
+  nsDisplayListCollection set(aBuilder);
+  BuildDisplayListForChild(aBuilder, kid, set);
+
+  // If we have a scrollframe then it takes care of creating the display list
+  // for the top layer, but otherwise we need to do it here.
+  if (!kid->IsScrollFrame()) {
+    bool isOpaque = false;
+    if (auto* list = BuildDisplayListForTopLayer(aBuilder, &isOpaque)) {
+      if (isOpaque) {
+        set.DeleteAll(aBuilder);
+      }
+      set.PositionedDescendants()->AppendToTop(list);
+    }
+  }
+
+  set.MoveTo(aLists);
 }
 
 #ifdef DEBUG
@@ -150,12 +166,16 @@ static bool BackdropListIsOpaque(ViewportFrame* aFrame,
   return opaque.Contains(aFrame->GetRect());
 }
 
-void ViewportFrame::BuildDisplayListForTopLayer(nsDisplayListBuilder* aBuilder,
-                                                nsDisplayList* aList,
-                                                bool* aIsOpaque) {
+nsDisplayWrapList* ViewportFrame::BuildDisplayListForTopLayer(
+    nsDisplayListBuilder* aBuilder, bool* aIsOpaque) {
+  nsDisplayList topLayerList;
+
   nsTArray<dom::Element*> topLayer = PresContext()->Document()->GetTopLayer();
   for (dom::Element* elem : topLayer) {
-    if (nsIFrame* frame = elem->GetPrimaryFrame()) {
+    nsIFrame* frame = elem->GetPrimaryFrame();
+    if (!frame) {
+      continue;
+    }
     // There are two cases where an element in fullscreen is not in
     // the top layer:
     // 1. When building display list for purpose other than painting,
@@ -187,14 +207,13 @@ void ViewportFrame::BuildDisplayListForTopLayer(nsDisplayListBuilder* aBuilder,
                  "did you intend to reflow ::backdrop placeholders?");
       nsIFrame* backdropFrame =
           nsPlaceholderFrame::GetRealFrameForPlaceholder(backdropPh);
-        BuildDisplayListForTopLayerFrame(aBuilder, backdropFrame, aList);
+      BuildDisplayListForTopLayerFrame(aBuilder, backdropFrame, &topLayerList);
 
       if (aIsOpaque) {
-          *aIsOpaque = BackdropListIsOpaque(this, aBuilder, aList);
+        *aIsOpaque = BackdropListIsOpaque(this, aBuilder, &topLayerList);
       }
     }
-      BuildDisplayListForTopLayerFrame(aBuilder, frame, aList);
-    }
+    BuildDisplayListForTopLayerFrame(aBuilder, frame, &topLayerList);
   }
 
   if (nsCanvasFrame* canvasFrame = PresShell()->GetCanvasFrame()) {
@@ -203,10 +222,26 @@ void ViewportFrame::BuildDisplayListForTopLayer(nsDisplayListBuilder* aBuilder,
         MOZ_ASSERT(frame->StyleDisplay()->mTopLayer != StyleTopLayer::None,
                    "ua.css should ensure this");
         MOZ_ASSERT(frame->HasAnyStateBits(NS_FRAME_OUT_OF_FLOW));
-        BuildDisplayListForTopLayerFrame(aBuilder, frame, aList);
+        BuildDisplayListForTopLayerFrame(aBuilder, frame, &topLayerList);
       }
     }
   }
+  if (topLayerList.IsEmpty()) {
+    return nullptr;
+  }
+  nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(aBuilder,
+                                                                    this);
+  // Wrap the whole top layer in a single item with maximum z-index,
+  // and append it at the very end, so that it stays at the topmost.
+  nsDisplayWrapList* wrapList = MakeDisplayItemWithIndex<nsDisplayWrapList>(
+      aBuilder, this, 2, &topLayerList, aBuilder->CurrentActiveScrolledRoot(),
+      false);
+  if (!wrapList) {
+    return nullptr;
+  }
+  wrapList->SetOverrideZIndex(
+      std::numeric_limits<decltype(wrapList->ZIndex())>::max());
+  return wrapList;
 }
 
 #ifdef DEBUG

layout/generic/ViewportFrame.h

@@ -15,6 +15,7 @@
 #include "mozilla/Attributes.h"
 #include "nsContainerFrame.h"
 
+class nsDisplayWrapList;
 class nsPresContext;
 
 namespace mozilla {
@@ -51,8 +52,7 @@ class ViewportFrame : public nsContainerFrame {
   virtual void BuildDisplayList(nsDisplayListBuilder* aBuilder,
                                 const nsDisplayListSet& aLists) override;
 
-  void BuildDisplayListForTopLayer(nsDisplayListBuilder* aBuilder,
-                                   nsDisplayList* aList,
+  nsDisplayWrapList* BuildDisplayListForTopLayer(nsDisplayListBuilder* aBuilder,
                                                  bool* aIsOpaque = nullptr);
 
   virtual nscoord GetMinISize(gfxContext* aRenderingContext) override;

layout/generic/nsGfxScrollFrame.cpp

@@ -4117,30 +4117,16 @@ void ScrollFrameHelper::BuildDisplayList(nsDisplayListBuilder* aBuilder,
 
 nsDisplayWrapList* ScrollFrameHelper::MaybeCreateTopLayerItems(
     nsDisplayListBuilder* aBuilder, bool* aIsOpaque) {
-  if (mIsRoot) {
-    if (ViewportFrame* viewportFrame = do_QueryFrame(mOuter->GetParent())) {
-      nsDisplayList topLayerList;
-      viewportFrame->BuildDisplayListForTopLayer(aBuilder, &topLayerList,
-                                                 aIsOpaque);
-      if (!topLayerList.IsEmpty()) {
-        nsDisplayListBuilder::AutoBuildingDisplayList buildingDisplayList(
-            aBuilder, viewportFrame);
-
-        // Wrap the whole top layer in a single item with maximum z-index,
-        // and append it at the very end, so that it stays at the topmost.
-        nsDisplayWrapList* wrapList =
-            MakeDisplayItemWithIndex<nsDisplayWrapList>(
-                aBuilder, viewportFrame, 2, &topLayerList,
-                aBuilder->CurrentActiveScrolledRoot(), false);
-        if (wrapList) {
-          wrapList->SetOverrideZIndex(
-              std::numeric_limits<decltype(wrapList->ZIndex())>::max());
-          return wrapList;
-        }
-      }
-    }
-  }
+  if (!mIsRoot) {
     return nullptr;
+  }
+
+  ViewportFrame* viewport = do_QueryFrame(mOuter->GetParent());
+  if (!viewport) {
+    return nullptr;
+  }
+
+  return viewport->BuildDisplayListForTopLayer(aBuilder, aIsOpaque);
 }
 
 nsRect ScrollFrameHelper::RestrictToRootDisplayPort(

layout/reftests/bugs/1688004.xhtml

@@ -0,0 +1,9 @@
+<html xmlns="http://www.w3.org/1999/xhtml" scrolling="false" class="reftest-wait">
+  <body>
+    <dialog>ABC</dialog>
+    <script><![CDATA[
+      document.querySelector("dialog").showModal();
+      document.documentElement.className = "";
+    ]]></script>
+  </body>
+</html>

layout/reftests/bugs/reftest.list

@@ -2111,3 +2111,4 @@ fuzzy(0-2,0-96600) == 1648282-1a.html 1648282-1-ref.html
 fuzzy(0-2,0-96600) == 1648282-1b.html 1648282-1-ref.html
 != 1672137-1.html 1672137-1-notref.html
 == 1686729-1.html 1686729-1-ref.html
+!= chrome://reftest/content/bugs/1688004.xhtml about:blank