From 1986ba6f20787606184aeb25a2358a1bcc899b0f Mon Sep 17 00:00:00 2001
From: Robert O'Callahan <roc@ocallahan.org>
Date: Fri, 27 Aug 2010 18:15:08 -0500
Subject: [PATCH] Bug 590468. Part 1: Add support for XUL 'layer' attribute.
 r=tnikkel sr=vlad

---
 layout/xul/base/src/nsBoxFrame.cpp | 39 +++++++++++++++++++++++++-----
 1 file changed, 33 insertions(+), 6 deletions(-)

diff --git a/layout/xul/base/src/nsBoxFrame.cpp b/layout/xul/base/src/nsBoxFrame.cpp
index f464abfe603..2c3bfb67f60 100644
--- a/layout/xul/base/src/nsBoxFrame.cpp
+++ b/layout/xul/base/src/nsBoxFrame.cpp
@@ -1307,27 +1307,54 @@ nsBoxFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
                              const nsRect&           aDirtyRect,
                              const nsDisplayListSet& aLists)
 {
-  nsresult rv = DisplayBorderBackgroundOutline(aBuilder, aLists);
+  // forcelayer is only supported on XUL elements with box layout
+  PRBool forceLayer =
+    GetContent()->HasAttr(kNameSpaceID_None, nsGkAtoms::layer) &&
+    GetContent()->IsXUL();
+
+  nsDisplayListCollection tempLists;
+  const nsDisplayListSet& destination = forceLayer ? tempLists : aLists;
+
+  nsresult rv = DisplayBorderBackgroundOutline(aBuilder, destination);
   NS_ENSURE_SUCCESS(rv, rv);
 
 #ifdef DEBUG_LAYOUT
-  // REVIEW: From GetFrameForPoint
   if (mState & NS_STATE_CURRENTLY_IN_DEBUG) {
-    rv = aLists.BorderBackground()->AppendNewToTop(new (aBuilder)
+    rv = destination.BorderBackground()->AppendNewToTop(new (aBuilder)
         nsDisplayGeneric(aBuilder, this, PaintXULDebugBackground,
                          "XULDebugBackground"));
     NS_ENSURE_SUCCESS(rv, rv);
-    rv = aLists.Outlines()->AppendNewToTop(new (aBuilder)
+    rv = destination.Outlines()->AppendNewToTop(new (aBuilder)
         nsDisplayXULDebug(aBuilder, this));
     NS_ENSURE_SUCCESS(rv, rv);
   }
 #endif
 
-  rv = BuildDisplayListForChildren(aBuilder, aDirtyRect, aLists);
+  rv = BuildDisplayListForChildren(aBuilder, aDirtyRect, destination);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // see if we have to draw a selection frame around this container
-  return DisplaySelectionOverlay(aBuilder, aLists);
+  rv = DisplaySelectionOverlay(aBuilder, destination);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (forceLayer) {
+    // This is a bit of a hack. Collect up all descendant display items
+    // and merge them into a single Content() list. This can cause us
+    // to violate CSS stacking order, but forceLayer is a magic
+    // XUL-only extension anyway.
+    nsDisplayList masterList;
+    masterList.AppendToTop(tempLists.BorderBackground());
+    masterList.AppendToTop(tempLists.BlockBorderBackgrounds());
+    masterList.AppendToTop(tempLists.Floats());
+    masterList.AppendToTop(tempLists.Content());
+    masterList.AppendToTop(tempLists.PositionedDescendants());
+    masterList.AppendToTop(tempLists.Outlines());
+    // Wrap the list to make it its own layer
+    rv = aLists.Content()->AppendNewToTop(new (aBuilder)
+        nsDisplayOwnLayer(aBuilder, this, &masterList));
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+  return NS_OK;
 }
 
 NS_IMETHODIMP