355521 - Expose CSS visibility and CSS visibility changes properly

Status: RESOLVED FIXED

(Core :: Disability Access APIs, defect)

Description

[Aaron Leventhal]

When CSS visibility: visible is used, it overrides any visibility set in an ancestor.

Therefore, we need to fix several things:
1) It should not be like display: none, where we don't even bother walking the subtree looking to create accessible objects. We should continue to walk the subtree, but just don't create an object if (!frame->GetStyleVisibility()->IsVisible())
2) We should fire a different notification for visibility changes ( in nsFrameManager::ReResolveStyleContext) than we do for changes where something is being created or destroyed for another reason (in nsCSSFrameConstructor::RecreateFramesForContent).

The accessibility system should make sure that multiple changes are coallesced intelligently. For example:

<div style="visibility: visible">
  <div style="visibility: hidden">
    Content
  </div>
</div>

Reversing both visibility values actually makes "Content" become visible. We need to make sure that sane events are fired for that situation.

Comment 1

[David Bolter [:davidb] (NeedInfo me for attention)]

Mass un-assigning bugs assigned to Aaron.

Comment 2

[alexander :surkov (:asurkov)]

fixed by bug 606125

Comment 3

[Firefox Bug Husbandry Bot]

https://bugzilla.mozilla.org/show_bug.cgi?id=1527381