A frameAnchor option for positioning otherwise position-less marks relative to the frame

[mbostock]

When marks don’t have a position, we currently default them to the center of the frame. For example:

plot/src/marks/dot.js

Lines 57 to 58 in 136fc2f

	const cx = (marginLeft + width - marginRight) / 2;
	const cy = (marginTop + height - marginBottom) / 2;

plot/src/marks/text.js

Lines 56 to 57 in 136fc2f

	const cx = (marginLeft + width - marginRight) / 2;
	const cy = (marginTop + height - marginBottom) / 2;

The frameAnchor option would allow more control over this behavior, for example when labeling facet frames. It would support nine possible values:

• top-left
• top
• top-right
• right
• bottom-right
• bottom
• bottom-left
• left
• middle (default)