~jaro/balkon

ref: 3e3fef4440b5d982144bdb4b13a3d784ba686233 balkon/src/Data/Text/ParagraphLayout/Internal/ProtoLine.hs -rw-r--r-- 3.7 KiB 
Allow explicit control of box collapsing.

Add extensible filter for invisible lines.

Handle ancestor boxes in rich layout.