Animation on linechart enter

[schirrel]

in my old morris fork (moved to https://github.com/schirrel/morris.js) i had add someanimation online chart enter
alsoby that time i have made and formater for the value to show only inlegend, as far as i saw its similar to you hover callback, thus i dont think still interesting

great job done there pierre

[pierresh]

Hi Alan,

thanks a lot for this pull request and sorry for my late reply. Your "in-line" animation is very interesting and definitively makes sense. Nevertheless, as it is mostly done of CSS (and therefore not really configurable), I suppose it is better to give flexibility, which CSS class has to be used per chart. That is why I just added new 2 options extraClassLine and extraClassCircle to define the extra class to be used.