By default, flexbox items have a min size of -webkit-min-content in the
the flex axis. I previously switched the pane item-views to flex
horizontally for performance reasons (preventing over-aggressive
repaints), but forgot to change min-height to min-width.
For some reason, having flex-flow column on the pane item views
container was forcing the entire view to be repainted on cursor
movement and line edits. Allowing the container to flow row-wise and
setting the min-height to 0 instead of min-content-height achieves
the same layout effect without the huge repaint cost. Flexbox is a
fragile bitch.
