[Therion] Sketches on doesn't work / legacy survey

[Bruce Mutton]

> As you may see, your .th2 file include only those three stations (and
sketch). Probably it is bug in Therion that it not allows to hide stations
from the final output. I may imagine the reason - MetaPost works with one
scrap in time to interpret and draw that particular scrap. When it has
nothing in scrap it will produce error.

 

> symbol-hide group cave-centerline will cause an error, because there is
then no scrap to draw (Therion must have at least a scrap or a centreline to
draw - seems that scrap station points and images don't count).

 

I think it is a bug.  If the user hides all of the centreline objects, and
also hides all scrap objects (or something like that), then Therion should
trap the error and exit in a controlled manner, rather than letting metapost
get in a tangle and produce a mess of messages until it finally crashes.

 

Thanks for your insights Benoit, I had not thought of your approaches and
they helped me make some mental connections.  I guess redefining metapost
for 'area dimensions' is the same as specifying 'walls off' in the survey
file.

 

Bruce

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