Seg fault and malloc() errors

[0x62]

There seems to be some issues with canvas on at least the Pi Zero 2 W. I didn't notice it in testing as it only seems to appear after a certain number of elements are added to the canvas. Each plugin prints successfully in isolation, but together we get errors.

Plan for now is to switch from using a shared canvas to each plugin managing its own canvas, then combining them together. Should also simplify render logic as you don't need to manage your Y offset.