1743749 - Clean up use of atoms for cache keys

Status: NEW

(Core :: Disability Access APIs, task)

Description

[James Teh [:Jamie]]

We use AccAttributes for the CTW cache and AccAttributes is keyed by nsAtom. This has some advantages as compared to an enum: we don't need separate data structures for object/text attributes and the CTW cache and we get readable logging for the keys for free. However, a major disadvantage is that because we try to avoid polluting the nsGkAtoms namespace, we end up with some unclear/unintuitive keys; e.g. nsGkAtoms::line for text line start boundaries, nsGkAtoms::style for text attributes, etc.

We need to find a way to make this more obvious and readable. We can either alias the atoms in our own namespace or switch to using an enum after all.

I looked into various approaches of aliasing. We can't use an enum because enums have to be convertable to int. We can't use a using declaration because they only work for types, not values. What does work is this:

class CacheKey {
 public:
  static constexpr nsStaticAtom* TextLineStarts = nsGkAtoms::line;
};