Hey billconan, great question! Right now we are using Text renderer provided by Pixi.js, which uses browser api to render font to canvas and then stores the outcome as texture.

We are working towards integrating C / Rust libraries for font rendering in a nearby future to increase performance and decrease memory usage.

If you are looking for libraries you might want to check harfbuzz / freefont, cosmic-text, swash or fontations project.