Bugzilla

Possible in theory, yes; but that comes with significant downsides too: we'd then have to rebuild the platform font list (we can't gradually mutate it -- when the set of available fonts changes, we throw it away and start again), and that in turn means we have to completely reflow everything in all processes (because all the font references hanging off the textruns in the frame tree etc will become invalid).

On the whole I don't think we want to be doing that; at whatever point we decide to add Twemoji to the available fonts, we're liable to end up janking all processes because changing the font list disrupts everything. (Normally, we don't expect the available font collection to bechanging while we're running, or at least not while the user is actively using the browser -- if they've clicked over to Windows Explorer to install a new font, the browser is in the background and it probably doesn't matter so much if it momentarily janks when the font gets activated.)

Possible in theory, yes; but that comes with significant downsides too: we'd then have to rebuild the platform font list (we can't gradually mutate it -- when the set of available fonts changes, we throw it away and start again), and that in turn means we have to completely reflow everything in all processes (because all the font references hanging off the textruns in the frame tree etc will become invalid).

On the whole I don't think we want to be doing that; at whatever point we decide to add Twemoji to the available fonts, we're liable to end up janking all processes because changing the font list disrupts everything. (Normally, we don't expect the available font collection to be changing while we're running, or at least not while the user is actively using the browser -- if they've clicked over to Windows Explorer to install a new font, the browser is in the background and it probably doesn't matter so much if it momentarily janks when the font gets activated.)