Different font on dialog?

I’m creating a few widgets to use on a custom canvas on a dialog and I want to use the Aseprite Mini font in those widgets. The API lists functions GraphicsContext:fillText() and GraphicsContext:measureText(), even using the specific words using the current font, but I can’t find any way to change the font used on the graphics context.

How can I change the font used by GraphicsContext:fillText() when drawing text on a canvas on a dialog?