Distance functions gravity

Boxes are place at the smalles possible value of a user supplied distance function. This means that you can make clouds of different shapes. Distance functions currently implemented are:

• radial_center (makes a circular cloud)
• radial_ll (makes a pie chaped cloud, i.e. a quater circle centered in the lower left corner of the canvas)
• x-dist (makes a horizontal band of words)
• ellipse (makes an elliptical cloud, currently it is not possible to specify the degree of ellipticity).

I think of these functions as a gravitational field and they describe the points of attraction for the word boxes. In the circle, the boxes are attracted to the center, in the horizontal band, the boxes are attracted to the x-axis. It would be awesome to have a bunch of different shapes, so please experiment and share your results.

Currently the first box is placed in the middle of the canvas, but I plan to change that.