Attempt to refactor scrolling in FileMenu2D

[devmodi154]

PR against the issue viz.ui.FileMenu2D #16. To improve scrolling in FileMenu2D that was already done in ListBox2D component.

[pep8speaks]

Hello @devmodi154! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers:

Comment last updated at 2020-05-12 12:14:34 UTC

[codecov[bot]]

Codecov Report

Merging #222 (77f3058) into master (78310d8) will increase coverage by 0.01%. The diff coverage is 87.30%.

@@            Coverage Diff             @@
##           master     #222      +/-   ##
==========================================
+ Coverage   88.65%   88.67%   +0.01%     
==========================================
  Files          17       17              
  Lines        4356     4398      +42     
  Branches      548      555       +7     
==========================================
+ Hits         3862     3900      +38     
- Misses        354      356       +2     
- Partials      140      142       +2     

Impacted Files	Coverage Δ
fury/window.py	83.37% <28.57%> (-1.14%)	:arrow_down:
fury/ui.py	86.26% <88.88%> (-0.03%)	:arrow_down:
fury/primitive.py	85.71% <100.00%> (+2.19%)	:arrow_up:
fury/utils.py	90.02% <100.00%> (+0.24%)	:arrow_up:
fury/actor.py	92.76% <0.00%> (+0.13%)	:arrow_up:
fury/colormap.py	93.91% <0.00%> (+0.14%)	:arrow_up:
fury/testing.py	90.90% <0.00%> (+1.62%)	:arrow_up:

[skoudoro]

Thank you for doing this @devmodi154,

Can you have a look at this PR @MarcCote? Thank you

[ganimtron-10]

Closing with reference to #816.