CSS Box Alignment says:
multi-column containers [...] row-gap does not currently apply.
https://drafts.csswg.org/css-align-3/#gap-multicol
I think it should apply to multi-column containers too, specifically between column-span elements and the set of columns above/below. I'm working on a prototype implementation of gap decorations in Gecko, which adds row-rule properties, which will render between the "rows" created by spanners. So it's reasonable to change row-gap so that it applies to multi-column containers too. (I'll file a separate issue on the gap decorations proposal.)
Like for Grid and Flexbox gaps, the row-gap should be applied between margin-boxes, and it doesn't collapse or merge with any margins. It creates space in addition to any margins on the spanner.
Here's an example multi-column container with row-gap and (purple) row-rules:
CSS Box Alignment says:
I think it should apply to multi-column containers too, specifically between
column-spanelements and the set of columns above/below. I'm working on a prototype implementation of gap decorations in Gecko, which addsrow-ruleproperties, which will render between the "rows" created by spanners. So it's reasonable to changerow-gapso that it applies to multi-column containers too. (I'll file a separate issue on the gap decorations proposal.)Like for Grid and Flexbox gaps, the row-gap should be applied between margin-boxes, and it doesn't collapse or merge with any margins. It creates space in addition to any margins on the spanner.
Here's an example multi-column container with
row-gapand (purple)row-rules: