don’t allow margins or insets to invert range

[mbostock]

Alternative to #618. Fixes #616. This behavior is more consistent with how rects treat insets, e.g.,

plot/src/marks/rect.js

Lines 57 to 60 in 72b2adb

	.attr("x", X1 && X2 && !isCollapsed(x) ? i => Math.min(X1[i], X2[i]) + insetLeft : marginLeft + insetLeft)
	.attr("y", Y1 && Y2 && !isCollapsed(y) ? i => Math.min(Y1[i], Y2[i]) + insetTop : marginTop + insetTop)
	.attr("width", X1 && X2 && !isCollapsed(x) ? i => Math.max(0, Math.abs(X2[i] - X1[i]) - insetLeft - insetRight) : width - marginRight - marginLeft - insetRight - insetLeft)
	.attr("height", Y1 && Y2 && !isCollapsed(y) ? i => Math.max(0, Math.abs(Y1[i] - Y2[i]) - insetTop - insetBottom) : height - marginTop - marginBottom - insetTop - insetBottom)

I’d slightly prefer using the midpoint here, something like:

if (right >= left) {
  scale.range = [left, right];
} else {
  const center = (right + left) / 2;
  scale.range = [center, center];
}

But then I’d want rects to behave similarly, and I don’t think it’s really worth the trouble for such a rare thing. Mostly I just want to avoid the surprising (to me) behavior of the scale’s range getting inverted when the insets or margins are too big, and I think a collapsed range is a sufficient indication of a misconfiguration and we don’t need to do more.