Compute the margin boundary of a polygon for the simple cases where the polygon is either convex, or the margin boundary has the same shape as the original polygon boundary. This simplification is a first provisional step, similar to the one introduced for shape-padding. See https://bugs.webkit.org/show_bug.cgi?id=112592.
Created attachment 196433 [details] Polygonal shape-margin illustration. The attached screenshot illustrates the margin-polygon for a polygonal shape. The edges of the (larger outer) margin-polygon are separated from the polygon by a shape-margin value of about 100px. Linear approximations to circular arcs join adjacent margin-polygon offset edges when the corresponding polygon edges do not meet at a reflex vertex.
Created attachment 196685 [details] Patch
Comment on attachment 196685 [details] Patch LGTM. r=me.
Comment on attachment 196685 [details] Patch Clearing flags on attachment: 196685 Committed r147831: <http://trac.webkit.org/changeset/147831>
All reviewed patches have been landed. Closing bug.