Hi Jonathan, For Stylo to compute values for 'ex' and 'ch' units, it needs access to font metrics from the parallel worker threads. I've heard that font metrics are generally not thread-safe in Gecko, so I'm trying to figure out next steps, and have a few questions:
(1) How not-thread-safe is the font metric stuff? If we just need trivial stuff like the things mentioned above, will we still run into problems? (2) Assuming that the information we need does indeed require non-threadsafe calls, can you tell us whether those calls are strictly main-thread-only, or whether it's enough to simply avoid concurrency? We block the main thread during style traversal, so we could stick a mutex around the font metrics stuff and only acquire that mutex during parallel traversal (leaving main-thread callpaths untouched). We could then also cache the metrics we need in TLS to further-reduce the synchronization cost. Thanks, bholley _______________________________________________ dev-tech-layout mailing list [email protected] https://lists.mozilla.org/listinfo/dev-tech-layout
