Am 22.11.2014 um 21:32 schrieb John Kitzmiller:

...

Given rectangles with text:

\starttext Before:\\ \startMPcode draw unitsquare xscaled 2cm yscaled 1cm; \stopMPcode \\ After:\\ \startMPcode for i=0 upto 1: draw unitsquare scaled 1cm xshifted i*cm; endfor; \stopMPcode \stoptext

How can a line be drawn connecting the right edges of the rectangles? I have played with:

\startuniqueMPgraphic{line} path a; a:=(0,0)--(0,3cm); draw a withpen pencircle scaled 3pt withcolor green; \stopuniqueMPgraphic

\defineoverlay[line][{\uniqueMPgraphic{line}}]

and using it in \framed, but placing the line correctly is elusive.

Just a quick and dirty solution. The trick is to draw the extra line as part of the graphic and then fake the boundingbox. This is also limited to a few centimeter, objects are cut off after you reach that 'invisible' border around the boundingbox.

I would use uniqueMPgraphic with proper parameters for the graphics. Using overlays is also possible (urcorner OverlayBox), but I see no real need or benefit to do so.

HTH, Peter

Yes it helped Peter, thank you. Interesting moves with the mpost bounding box. I thought I might need more flexibility—overlays—but it has turned out that single mp graphic with labels for the commentary will work for the task. Thanks again, John