Add a `ColumnWidth.Contents`

[sschuberth]

I'm proposing to add a Contents mode to ColumnWidth that works similar to Fixed, but automatically sets the width to the maximum length of text in any row of that column.

My use-case is very much related to #13: The cell contents of the grid I'm using get truncated as the terminal width is detected incorrectly, see https://github.com/ajalt/mordant/issues/67#issuecomment-1658341307. So I'd like to force the contents of some important cells to be fully shown nonetheless.

[ajalt]

It sounds like what you're asking for is already how ColumnWidth.Auto works: it tries to be as wide as its widest cell. Mordant will never create a table wider than the terminal width; even Fixed columns will shrink if they can't fit.

[sschuberth]

Actually, I tried ColumnWidth.Auto already (as it's the default), but if the terminal is too narrow to show all cell contents in full width, what happens is that contents of all cells get truncated. But I want some cells to not be truncated under any circumstances (and rather truncate some other cells earlier).

I also tried to achieve that via ColumnWidth.Expand(...), but I failed.

[ajalt]

I think I'd want to implement that as something like WeightedAuto(weight: Int), which would behave like Auto when there's enough space to fit the table, and would behave like Expand when columns need to be shrunk, but it would get priority over Auto and Expand columns if they exist. Or maybe it would be simpler to make Auto equivalent to WeightedAuto(1) and avoid adding another tier of priority. Then you could use something like WeightedAuto(99) to allocate everything to a column.

For now, the easiest way to get what you want is to probably pick a width for those columns you want to keep and use Fixed for them.

[sschuberth]

For now, the easiest way to get what you want is to probably pick a width for those columns you want to keep and use Fixed for them.

Yeah, that's what I did 👍🏻

[ajalt]

After working on the design some more, I ended up generalizing all the width behaviors into a new ColumnWidth.Custom class. This enables more types of behavior than adding another special case, and ended up simplifying the implementation by removing some branches.

You can get the behavior asked for in this issue with ColumnWidth.Custom(width=null, expandWeight=null, priority=4)

[sschuberth]

You can get the behavior asked for in this issue with ColumnWidth.Custom(width=null, expandWeight=null, priority=4)

Thanks for this! However, could we get a constant for the highest priority now? It seems a bit unclean to hard-code it to 4 here.

[sschuberth]

On a related note, maybe it makes sense to turn priority into an abstract property of ColumnWidth now? That way one could easily get the highest priority by max'ing over the sealed subclasses.

[ajalt]

In the next major version I'll get rid of all the subclasses and have them all be instances of Custom so you'll be able to do Fixed.priority etc. But that's a breaking change, so I'm holding off for now.