TermBuf::StyleTable

Stability: internal

Interns styles so a Cell can carry a four byte id rather than the whole struct.

Two cells with equal styles always get the same id, which turns the paint diff's style comparison into an integer compare and lets the encoder cache one SGR byte string per id.

The table only grows. An application cycling through distinct styles — an animated colour gradient, say — accumulates entries at roughly 32 bytes each; a hundred thousand of them costs a few megabytes. Real applications use tens.