[regression] #10644 iframe stacking issue

[paulrouget]

The progressbar doesn't show up anymore in browserhtml.

Regression introduced by #10644

This might need a reduced test case, but in the meantime, if anybody has an idea…

[paulrouget]

Not a P1 anymore (there was an easy work around in bhtml).
Here is a test case showing the stacking issue with non-display:block iframes:

<style>
  iframe, div {
    position: absolute;
    width: 200px;
    height: 200px;
    border-width: 0px; 
  }
  iframe {
    top: 50px;
    left: 50px;
    background-color: blue;
  }
  div {
    top: 100px;
    left: 100px;
    background-color: red;
  }
</style>

<iframe></iframe>
<div></iframe>

[mrobinson]

This seems to be an issue with layout. The iframe, as an inline is added to the end of the list of Flow children. This means that when it is promoted to a pseudo-stackingcontext during display list construction, it is positioned after the div. Going to unassign this from myself, since it's unrelated to display list construction.

[mrobinson]

This flow tree dump shows the iframe as last child of the shared ancestor of the div and the iframe.

│  ├─ Block(7f8a440ea390) sc=StackingContextId(0) pos=LogicalRect(H LTR, i1024px×b740px, @ (i0px,b0px)),  floatspec-in=L 0px R 0px, floatspec-out=L 0px R 0px, overflow=Overflow { scroll: TypedRect(1024px×740px at (0px,0px)), paint: TypedRect(1024px×740px at (0px,0px)) } children=1 abs-descendents=2
│  │  ├─ ↑↑ Fragment for block: SpecificFragmentInfo::Generic(10) [] border_box=LogicalRect(H LTR, i1024px×b740px, @ (i0px,b0px))
│  │  ├─ Block(7f8a440ea110) sc=StackingContextId(0) pos=LogicalRect(H LTR, i1024px×b0px, @ (i0px,b8px)),  floatspec-in=L 0px R 0px, floatspec-out=L 0px R 0px, overflow=Overflow { scroll: TypedRect(1008px×300px at (8px,0px)), paint: TypedRect(1008px×300px at (8px,0px)) } children=2
│  │  │  ├─ ↑↑ Fragment for block: SpecificFragmentInfo::Generic(8) [] border_box=LogicalRect(H LTR, i1008px×b0px, @ (i8px,b0px)) margin=LogicalMargin(H LTR, i:8px..8px b:8px..8px)
│  │  │  ├─ Block(7f8a440e8f90) sc=StackingContextId(1) pos=LogicalRect(H LTR, i200px×b200px, @ (i100px,b100px)),  floatspec-in=L 0px R 0px, floatspec-out=L 0px R 0px, overflow=Overflow { scroll: TypedRect(200px×200px at (0px,0px)), paint: TypedRect(200px×200px at (0px,0px)) }
│  │  │  │  └─ ↑↑ Fragment for block: SpecificFragmentInfo::Generic(2) [] border_box=LogicalRect(H LTR, i200px×b200px, @ (i0px,b0px)) damage=REPOSITION | STORE_OVERFLOW
│  │  │  ├─ Inline(7f8a44015550) sc=StackingContextId(0) pos=LogicalRect(H LTR, i1008px×b0px, @ (i8px,b0px)),  floatspec-in=L 0px R 0px, floatspec-out=L 0px R 0px, overflow=Overflow { scroll: TypedRect(0px×0px at (0px,0px)), paint: TypedRect(0px×0px at (0px,0px)) } children=1
│  │  │  │  ├─ SpecificFragmentInfo::InlineAbsoluteHypothetical(7) [] border_box=LogicalRect(H LTR, i0px×b0px, @ (i0px,b0px)) damage=REPOSITION | STORE_OVERFLOW
│  │  │  │  ├─ Block(7f8a440e9e90) sc=StackingContextId(2) pos=LogicalRect(H LTR, i200px×b200px, @ (i50px,b50px)),  floatspec-in=L 0px R 0px, floatspec-out=L 0px R 0px, overflow=Overflow { scroll: TypedRect(200px×200px at (0px,0px)), paint: TypedRect(200px×200px at (0px,0px)) }
│  │  │  │  │  └─ ↑↑ Fragment for block: SpecificFragmentInfo::Iframe(6) [] border_box=LogicalRect(H LTR, i200px×b200px, @ (i0px,b0px)) damage=REPOSITION | STORE_OVERFLOW