[singron]

This is a great idea. Actually drawing the glyphs can be computationally expensive too. I'm not sure what browsers do, but in the last game I made, it was an enormous win to have a glyph cache for the various combinations of (size,glyph,quantized pixel alignment) rather than rendering each glyph from scratch.

I could imagine quickly getting layout information, then asynchronously getting glyph drawing information and painting from the glyph cache when it becomes available. You could even paint a similar fallback font using the layout information of the real font to avoid redoing layout on the whole page while still being readable until it finishes.