That's why I said "entire browser". Page rendering, font rendering, <canvas>, et al, are the interesting bits. The use of XUL and the resulting UI clunkiness (

That's why I said "entire browser". Page rendering, font rendering, <canvas>, et al, are the interesting bits. The use of XUL and the resulting UI clunkiness (speed, responsiveness, nativeness) are pretty well known. A world in which only the vendor gets to write low-level code sounds is a terrible division of labor.