UFO feature compiler needs to catch and report errors

[justvanrossum]

UFO feature compiler needs to catch and report errors

[justvanrossum]

There are two steps:

1. create ttf with cmap
2. compile features into OTL tables

If step 1 fails we're doomed (should be extremely rare), but if step 2 fails we still want to deliver the result of step 1 and report the error of step 2.

[justvanrossum]

The two-step idea is hard to impossible to implement with the multiprocessing module. We may have to create our own process pool using subprocess, and implement communication. May not be worth it.

[justvanrossum]

My thoughts were garbled: doing the two-step thing is actually easy, (and has been implemented with d0e73d0).

What is hard (and perhaps not worth it) is to have font loading/compiling be executed as two async steps, so that we quickly get rendered text without features, and get an update once the features have been compiled.

[justvanrossum]

Catching has been implemented, reporting now goes to stderr, so won't reach the user properly yet. Closing this in favor of #24.