Hans Hagen wrote:

Peter Rolf wrote:

...

Hi all,

I pass a string to a MP graphic using \setMPtext{LABEL}{TEXT}. The string can also be empty, and then no action (for the text) is taken. How can I test in MP, if the given \MPstring{LABEL} is empty?

I have tried everything I can imagine in the last one hour, but no success. Not my day...

This is the old, not working version

if not(\MPstring{LABEL}="") : % is always true.

unless to set it to nothign (currently you don't assign it at all)

yes and no. I had an older macro \XXmacro[#1]#2{% ... \ifsecondargument\setMPtext{XX}{\SomeFontsettings\strut#2}\else\setMPtext{XX}{}\fi which is naturally always true. I replaced it with a \doiftextelse and now everything is working as expected. Thanks for the enlightenment and the nice example :) Peter

take this:

\setupcolors[state=start]

\starttext

\startuseMPgraphic{test} fill fullcircle scaled 1cm withcolor if not(\MPstring{XX}="") : red else : green fi ; \stopuseMPgraphic

\useMPgraphic{test} \start \setMPtext{XX}{} \useMPgraphic{test} \stop

\unprotect

\def\MPtext #1{\executeifdefined{\@@MPT#1}\empty} \def\MPstring #1{"\executeifdefined{\@@MPT#1}\empty"} \def\MPbetex #1{btex \executeifdefined{\@@MPT#1}\empty etex}

\protect

\useMPgraphic{test} \start \setMPtext{XX}{} \useMPgraphic{test} \stop

\stoptext

the current definitions return "\relax" when a text is not defined; i'll change the definitions

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