Ability to only extend-horizontally for window-padding-color

[zuqini]

Sometimes setting window-padding-color = extend will extend the padding colors vertically which (in my opinion) looks off, but extending horizontally looks fine. See below examples.
Example of padding extended both vertically and horizontally:

Example of padding only extended horizontally:

I think adding an option to only extend horizontally might be worthwhile!

[00-kat]

I'm certain someone will want to only extend it vertically but not horizontally, so I think that window-padding-color should accept both extend-horizontal/extend-horizontal-always and extend-vertical/extend-vertical-always.

[pluiedev]

Perhaps we should split window-padding-color into horizontal and vertical variants? (Or, go down the theme route and support horizontal: and vertical: prefixes) Need more design passes on that idea.

[00-kat]

I'm for splitting the option.

Or, go down the theme route and support horizontal: and vertical: prefixes

Most other similar options split it or use prefixes on the values (as I had suggested); in fact theme is the only option which uses that syntax right now. Whether newer configuration options should be changed over to the theme syntax sounds like it would be outside the scope of this discussion and perhaps warrants a discussion of its own (discussion on this option could maybe be paused until a hypothetical new discussion is closed?).