MJ already pillarboxes video if the window is wider than they are. The aspect ratio code should just modify the existing calculations so this should work fine.
Of course then you are on the slippery slope as some of the market share of TT and ZP are running 2.35 screens etc so it gets messy from then on in !!
The only 1:2.35 monitors I've ever seen have been very specialist ones for high end film work, and they didn't catch on. I've never seen a 1:2.0 monitor. Can you give me any references for these?
Also having a way to crop and stretch letterbox movies is vital...
Very few video files are letterboxed as this is a real waste of file space. I wouldn't worry too much about this. The exceptions are 2.35 movies ripped from DVD, but they are already formatted for 16:9, which is the widest common monitor format (see above). You could always implement Zoom's "Restrict Aspect Ratio Adjustments to Height in Zoom Mode". It provides for exacly this problem.
Thinking further about this, a couple of tweaks would make MC even better at this than Zoom.
- Anamorphic should be a check box, separate from the other ratios. It should apply the 1.33333 vertical stretch on top of any other stretches you have asked for
- Anamorphic on/off should be preserved as a system setting, but the aspect ratio of the video file should be saved as a tag.
- Allow the user to set the background colour for letterboxed video. 50% grey is usually considered the best option for plasmas and projectors as it minimises burn-in