vcs.Canvas.setantialiasing unusable

[alliepiper]

vtkRenderWindow needs to have multisampling settings specified before the first render, but currently setantialiasing can only be used before the window is created (which triggers an error) or after initialization (which has no effect).

The easy fix would be to make an antialiasing ivar in the canvas or backend that can be set between calls to vcs.init and Canvas.plot, and warns if called after the window is already initialized.

[aashish24]

@dlonie I would assign it to @sankhesh

[alliepiper]

@sankhesh Grab me if you want to go over this -- this one should be higher priority than the other issues.

[alliepiper]

@sankhesh The code of interest is in Packages/vcs/Lib/VTKPlots.py, the setantialiasing and getantialiasing methods.

To visually determine whether or not antialiasing is working the following command line can be used to produce a line plot with aliasing artifacts:

[build dir]/install/bin/runtest [source dir]/testing/vcs/test_vcs_basic_gms.py --gm_type=yxvsx --show

[sankhesh]

Fixed and merged