This doesn't seem to work. Neither does "p_anchor_legend". Am I missing something; is there a way to do it?
Again, I am going to answer my own question. Bruce, listen up, since I think you also ran into this problem on https://therion.speleo.sk/wiki/metapost (search for "not working"). It is a case of Therion not being as helpful as you might like. It would be great if it actually respected _legend macros for all points, lines and areas. It doesn't. Maybe someone can fix that? Pretty please? Anyway... With p_u_* and l_u_* and a_u_*, Therion creates a default p_u_*_legend macro, which you can choose to override with your own. When drawing the legend, it runs those macros. beginfig(164); clean_legend_box; p_u_foo_legend; draw_legend_box; endfig; With anything else, it does not work that way. Instead, the MetaPost contains hardcoded calls to the macros, with hardcoded points or paths defined inline, not via macros and variables. These points and paths can be seen in the binary source as being tied to the specific symbols (most symbols use the same few default values, but a few have their own special ones). It ends up looking like this: beginfig(161); clean_legend_box; drawoptions(); p_anchor((0.5,0.5) inscale,0.0,1.0,(0,0)); draw_legend_box; endfig; You can detect this default coordinate in your point/line symbol code, and respond differently. But it is entirely possible for a legitimate point in your survey to match "(0.5,0.5) inscale", and you will end up randomly converting a real point into a special legend version. Not good. There is no other way to ask "is this code running inside the legend" since there is no variable that says that the legend has started. But! You can rewrite the clean_legend_box macro to store a flag, which you can check in your point code to see if it is running inside one of those legend sections. Legends are always created as the last step, so even though that flag will get left forever, it will not be mistaken in non-legend code. boolean p_anchor_MY_inlegend; p_anchor_MY_inlegend:=false; % store the original clean_legend_box let p_anchor_MY_legend_box = clean_legend_box; % redefine clean_legend_box to store the flag, then run the original def clean_legend_box = p_anchor_MY_inlegend:=true; p_anchor_MY_legend_box; enddef; def p_anchor_MY (expr P,R,S,A)= if p_anchor_MY_inlegend: % this is the legend - make sure the function works normally again p_anchor_MY_inlegend:=false; % draw a pretty legend p_anchor_MY((.7,.3) inscale,270,1,(0,0)); else: % ... do the regular stuff fi; enddef; Hopefully someone else will find this useful, and with any luck, I will add it to the wiki soon. Along with all the other stuff I need to add to the wiki.