Ligature subtables use virtual links to enforce an ordering constraint between the subtables and the coverage table. Unfortunately this has the sideeffect of prevent the subtables from being shared by another Ligature with a different coverage table since object equality compares all links real and virtual. This change makes virtual links stored separately from real links and updates the equality check to only check real links. If an object is de-duped any virtual links it has are merged into the object that replaces it.
Assign each connected component that is underneath one or more 32 bit offsets into a unique space. This ensures that 32 bit subgraphs which are connected are packed into the same space.
Prior to this fix id remapping at the end of the isolation operation was fed the old subgraph instead of the new one. Which results in object indices being remapped for the nodes outside of the new subgraph. Adds a test which detects this problem.
Each subgraph pointed to by a 32 bit offset should be packed into it's own space. This adds a space property to vertices which affects the distance calculation. This effectively places the distances for all of the nodes of a 32 bit subgraph into a distinct range. Thus all of the nodes of the subgraph will be packed together.
Vertices can now be prioritized to force them to sort closer to their parent. The resolver will attempt to use this for overflows on non-shared vertices.
Garret Rieger
Behdad Esfahbod