Fixed width saver and loader don't round trip. (Columns expand with increasing number of spaces) about visidata HOT 6 CLOSED

Another example to consider is saving a frequency sheet as .fixed. For example, suppose you have colours.csv:

colours
blue
blue
blue
green
green
green
green
orange
purple
red
red

The Frequency sheet looks like this:

If you save it as fixed, you get:

colours   count   percent   histogram                                
green           4     36.36 ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇   
blue            3     27.27 ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇             
red             2     18.18 ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇                      
orange          1      9.09 ▇▇▇▇▇▇▇▇▇                                
purple          1      9.09 ▇▇▇▇▇▇▇▇▇                                

Once again, there are three extra spaces inserted. However, because the count and percent are numeric, they are right-aligned. Due to the right-alignment, the three extra spaces are added on the left side of the numeric values, which causes them to not be aligned with the column headers. This breaks the fixed loader:

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Most recent fixed width saver issue: #1849

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Hmm... I'm wondering if getMaxWidth is being used for conflicting purposes. Here, we want the max width of the data, but it looks like getMaxWidth is trying to get a max display width. Also, I'm wondering if this is where the extra spaces come from:

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I've added a draft PR with some experimentation. (#2257) It's a lot closer to what I expect. It separates columns by a single space. However, when reading, that space is still interpreted as data, so we still grow by a single space per round trip. I think the saver is good to go, but the loader needs some work to prevent it loading the column separation space as data. I also switched it to use the real max width, rather than the max width of the window. This will be slow, but I think it's OK, because it will only run when saving, and I think most people would want to save all the data without truncating it.

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The PR above is ready for initial review.

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