1144905 - Update comment on SortByZOrder to reflect the code

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Mats Palmgren (inactive)]

This comment is from nsFrame.cpp:

  // This z-order sort also sorts secondarily by content order. We need to do
  // this so that boxes produced by the same element are placed together
  // in the sort. Consider a position:relative inline element that breaks
  // across lines and has absolutely positioned children; all the abs-pos
  // children should be z-ordered after all the boxes for the position:relative
  // element itself.
  set.PositionedDescendants()->SortByZOrder(aBuilder, GetContent());

The SortByZOrder code from nsDisplayList.cpp:

static bool IsZOrderLEQ(nsDisplayItem* aItem1, nsDisplayItem* aItem2,
                        void* aClosure) {
  // Note that we can't just take the difference of the two
  // z-indices here, because that might overflow a 32-bit int.
  return aItem1->ZIndex() <= aItem2->ZIndex();
}

void nsDisplayList::SortByZOrder(nsDisplayListBuilder* aBuilder,
                                 nsIContent* aCommonAncestor) {
  Sort(aBuilder, IsZOrderLEQ, aCommonAncestor);
}

so I think the comment is obsolete and that we now assume that
the PositionedDescendants list is already sorted in content
document order, right?

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Yes.

Comment 2

[Mats Palmgren (inactive)]

Attachment: fix

Fixed the documentation and removed the unused param.

Comment 3

[Mats Palmgren (inactive)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/df0b52334a1d

Comment 4

[Phil Ringnalda (:philor)]

https://hg.mozilla.org/mozilla-central/rev/df0b52334a1d