[webkit-reviews] review requested: [Bug 33150] Do not render the full frame when there is some elements with fixed positioning : [Attachment 47957] Repaint only the invalidated area after scrolling

[bugzilla-daemon at webkit.org]

Benjamin Poulain <benjamin.poulain at nokia.com> has asked  for review:
Bug 33150: Do not render the full frame when there is some elements with fixed
positioning
https://bugs.webkit.org/show_bug.cgi?id=33150

Attachment 47957: Repaint only the invalidated area after scrolling
https://bugs.webkit.org/attachment.cgi?id=47957&action=review

------- Additional Comments from Benjamin Poulain <benjamin.poulain at nokia.com>
(In reply to comment #64)
> (From update of attachment 47844 [details])
> This is not quite right.  Both fixed and absolute positioned objects can be
> added to RenderView. so you can't just use the list as is like that.	I
wasn't
> suggesting that you change how you detected and added the objects.  The way
you
> did that in your old patch is still necessary.  The count just lets you not
> keep a whole separate list, since you can walk the RenderView's list and
check
> if the object is fixed positioned (and if so use it).

I did not get that difference "positioned = fixed | absolute". I have changed
FrameView::scrollContentsFastPath() to skip the RenderBox that are not in fixed
position.

For increasing m_fixedObjectCount, I have stayed with doing it in
RenderView::insertPositionedObject(). If I do it in
RenderBox::styleWillChange(), the counter of fix objects will not be decreased
when the parent get a transformation. As I understand, this is not a problem
with the current implementation (I have added "if (o->style()->position() ==
FixedPosition)" though). Your input is welcome on that issue.

> Rename the variable in ScrollView to m_fixedObjectCount rather than
> m_positionedObjectCount.

Fixed.

I have also removed the test. It is not longer relevant.