Below is a list of groups of signs that are translated to atomic glyphs in the font upon rendering. The motivation is that the standard interpretation of the controls is sometimes unsatisfactory. This corresponds to ligatures.json. At present, all ligatures are overlays, but later we may consider insertions as well.
One challenge is to translate any shading of the constituent signs to areas in the ligature. For this reason, each constituent sign comes with its bounding box.
For an overlay with a single sign as first argument and a single sign as second argument, the rendering will be the same regardless of the order of the two signs. There is a proposal to normalize such overlays to have the code points in numerical order.