Created attachment 206272 [details]
reftest for Roman writing mode
If a polygon is defined to have a zero-width segment - such as polygon(0% 0%, 0% 51%, 100% 100%, 0 100%) - then content that intersects with that segment wraps around the bounding box of the shape instead of up against the shape segment.
Created attachment 206284 [details]
The latest nightly appears to ignore empty shape segments, so the original reftest now passes. I've attached a new reftest that moves the empty segment to the midpoint of the float. Here I'd expect the inline content to start at that midline.
What's the latest on this?
We're discussing whether this is a bug in the implementation or a bug in the spec. In either case, I think it's very low-priority - you have to create a fairly degenerate polygon in order to reproduce the problem.
As of the patch for https://bugs.webkit.org/show_bug.cgi?id=130975 we've addressed this issue. More about the zero-width segment case and the semantics of self-intersecting polygonal shapes can be found here: http://hansmuller-webkit.blogspot.com/2014/03/a-simpler-algorithm-for-css-shapes.html