261605 - Fixed-pos kids of fixed-pos elements precede them in viewport's framelist

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Boris Zbarsky [:bzbarsky]]

The basic issue is that we process child frames before adding the fixed-pos
frame to aState.mFixedItems.  Since mFixedItems is effectively global, this
means that descendant fixed frames will get added before their ancestors.

I think we should be adding frames to aState.whateverItems before processing
children (not just for fixed, but in general, for consistency).  In some cases
this is pretty easy to do; in others it seems to be painful due to the way
codepaths split up.  I'm tempted to factor this code out into a helper function,
basically.

The question is whether we care.  I don't think this issue can arise with floats
or abs pos elements (since those push new float and abs pos containing blocks
respectively), so this is only a problem for fixed frames.  Since we order views
based on content order anyway, maybe this is a non-issue?

Comment 1

[Boris Zbarsky [:bzbarsky]]

Note: see bug 256108 for more background on this.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Helper function is happening in bug 263406, and I suspect this will get fixed by
it, since proper cleanup requires adding the frame before processing kids.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Fixed by checkin for bug 263406