Charts fill their column and sit centred. A spec that sizes itself — a
projection, an hconcat, a repeat — is centred too, rather than hanging off
the left margin.
Set width when a chart should be narrower than the column:
width takes any plain CSS length, so a chart can be sized against the browser
window rather than the column:
55% of the viewport width
The same chart at a third of the viewport:
33vw
vw, vh, %, px, rem, em and ch are accepted; a bare number means
pixels. A value with any other unit, or anything that is not a number and a
unit, is dropped — the string reaches a style attribute, so the filter is
strict rather than escaped.
A width is capped at the column, so width=90vw inside a narrow column will not
force the page to scroll sideways. It is also floored at 24rem, so a small width
never collapses into an unreadable sliver — the floor reacts to the column the
chart is in rather than to the size of the window.
No !important is used anywhere in the chart stylesheet, so a width= you
write always wins.
Set width in the spec itself
(as the map on vega-remote does) when the chart
needs fixed pixels — a projection cannot be fluid.