> Sure, you can ask!
> I play 4:3 games exclusively. And most of those are, technically, 3:4
> (vertically-oriented) games.
> 3:4 games on a 16:9 screen leaves a -huge- amount of blank space on the left and
> right. Accurate bezel artwork wouldn't fill it properly, and I tend to find that
> stuff a distraction anyway. So I feel like a vertically mounted 43" HD screen will
> give me the size I want with the minimum amount of wasted (visible) display space.
I think that's perfectly fair, and thank you for the explanation! I tend to agree, since when doing development I don't really have time to go tracking down all the various artwork and such. I just didn't want to miss a chance to plug the MAME Artwork subforum.
You can probably use the artwork/bgfx/border_blur/default.lay file as reference, as it's a layout I came up with for this one shader. Some background:
.lay files are essentially XML files which define the layout of MAME's output relative to the dimensions of the host screen, in units of your choosing.
In the most basic sense, they consist of one or more "view" tags, which then contain one or more "screen" tags, which then have a "bounds" tag which defines the borders of that emulated screen's output.
In the case of the specific .lay file that I mentioned, I use it to fill out the blank border space when showing a 4:3 game on an un-rotated 16:9 screen (the "Horizontal" view), or when showing a 3:4 game on an un-rotated 16:9 screen (the "Vertical" view), then at runtime, there's a shader which applies a desaturate/zoom/blur filter to the left and right strips on either side of the main screen. The idea is that combined with the shader, you get the sort of effect that you often see on YouTube or news broadcasts when they want to display a vertical video without having a bunch of blank space on either side of it.
As you can see based on the differences between the Horizontal and Vertical bounds tags, the units really are arbitrary, they just need to ultimately divide down to match the aspect ratio of the output screen. That's obvious in the Horizontal view, and in the Vertical view, the overall bounds of 64:36 divides by 4 to give 16:9 as well.
Supposing I wanted to simply left-justify the Vertical view on an un-rotated 16:9 screen and not duplicate it on either side, I would simply have one "screen" tag, and its bounds would be 0, 0, 27, 36 for left, top, right, and bottom. Or, if you wanted to divide out the common factor (9), you would go with 0, 0, 3, 4, which shows more clearly that the source screen has an aspect ratio of 3:4 (i.e. a vertical game).
Hopefully this should be enough information to help get you going in the right direction. Cheers!