Formatting usage messages

Question

If you take a look at the Combinatorica package in Mathematica8 in (mathematicapath)/AddOns/LegacyPackages/DiscreteMath/Combinatorica.m you wi

Answer 1

I will answer on how the link in the Message is generated. Tracing Message printing shows a call to undocumented Documentation`CreateMessageLink function which returns the URL to the corresponding Documentation page if this page exists:

Trace[Information[Sin], Documentation`CreateMessageLink]

In[32]:= Documentation`CreateMessageLink["System", "Sin", "argx", "English"]

Out[32]= "paclet:ref/message/General/argx"

In some cases we can also see calls to Internal`MessageButtonHandler which further calls Documentation`CreateMessageLink:

Trace[Message[Sin::argx, 1, 1], 
 Internal`MessageButtonHandler | Documentation`CreateMessageLink, 
 TraceInternal -> True]