Use the new lifetime bounds feature of Rust to enforce that the
RootCollection field of Root outlives the jsref field. This still
doesn't enforce that the Root itself outlives the jsref field, and
doing this would require some sort of init dance.
formatting contexts.
The widths of block formatting contexts depend on the floats prior to
them. To avoid a circular dependency between width assignment and height
assignment, we must guess their widths during the assign-widths pass.
The old code simply used the size of the last float, whether
left-floated or right-floated, but this proved insufficient to handle
layouts like those seen on Reddit. The new heuristic keeps track of both
left and right floats independently and sums the width of all left and
right floats to determine the width of a block formatting context. This
is still insufficient to properly lay out Reddit, but the results are
much more acceptable.
A fully correct approach will require that blocks be laid out again if
the initial guess proved to be incorrect. A `TODO` is in the code to
handle this case.
The float code was old and did not support most of CSS 2.1. So unifying
the two paths both simplifies code and improves functionality.
Improves the Reddit sidebar.
wrapper around them.
Fixes Wikipedia tables leaking out.
Along the way, I refactored tables' width calculation significantly.
This was necessary in order to properly handle floated tables, as some
of the logic had to be ported over from block flows.
When traversing the layer tree to assign content offset, the new offset
needs to take into account any additional offset from children that are
also scrolling roots. This means that when you scroll a parent frame, it
doesn't override the scroll position of its children, but adds to it.
Base layers (the background layer of each frame) shouldn't override the
size of their root layers. This allows base layers to scroll inside
root layer frames. This does mean that when determining the maximum
scroll position, we need to look at the size of scrolling root children
though.
Root layers should be sized to their frame rectangles and the root of
the root layers should track the window size. This is important because
layers need to be properly sized to scroll.
This allows iframe layers to move properly when their parents scroll
and is necessary to properly track their masking rects as their
children move and to draw their backgrounds in the proper position.
Instead of sneakily setting the content offset and not the transform on
scrolling roots, let scrolling roots specify their scroll offset
directly and separately. This will also be important when adding proper
scrolling support for iframes.
