docs: def arc(self, x, y, width, height, start, end, color, thick=1, _=None):
          """
          This is different than the Processing function arc():
          https://processing.org/reference/arc_.html
  
          Use the Cairo arc() function to draw an arc with a given line thickness.
          """
          thick *= 4
          self.context.set_source_rgb(*color)
          self.context.save()
          self.context.translate(self.tx(x+(width/2)), self.ty(y+(height/2)))
          self.context.scale(self.tx(width/2), self.ty(height/2))
          self.context.arc(0.0, 0.0, 1.0 - (self.tx(thick)/2),
              (2*math.pi*start)/360,
              (2*math.pi*end)/360
          )
          self.context.set_line_width(self.tx(thick))
          self.context.stroke()
          self.context.restore()