New to Bangle.js and Espruino. Need help with graphics

Hi - yes, this is something that came up before with your UI code, and after making some changes to fillPoly at that point I unfortunately ended up having to revert to a more standard polygon fill implementation to make vector fonts work correctly (otherwise the ended up getting filled in when they were small).

It seems like a pretty normal thing to have to do with polygon fills. Basically:

     A
B
                          C
             D

If you're drawing a polygon between point ABC, and another between BCD, you don't want to be drawing the pixels along the line BC twice - and to do that the main way is to not completely cover one side of the poly. It's actually documented in the fillPoly reference: http://www.espruino.com/Reference#l_Graphics_fillPoly

This fills from the top left hand side of the polygon (low X, low Y) down to but not including the bottom right. When placed together polygons will align perfectly without overdraw - but this will not fill the same pixels as drawPoly (drawing a line around the edge of the polygon).