Macro explanation?

[Randy Kramer]

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I'm (finally) trying to work my way through some of the nedit code in hopes of 
someday adding folding capability.  Up to this point, I've been mostly 
browsing through the code, using comments to get a general idea of what's 
going on.  I'm currently in textDisp.c, and I have a lot more of that kind of 
browsing to do.  But I'm also trying to see if I can understand some of the 
code.  I can understand some, but I'm not there with macros yet (by any 
means).  I've done some googling re macros, and I'm now working my way 
through a document named "The C 
Preprocessor" (http://developer.apple.com/documentation/DeveloperTools/gcc-4.0.1/cpp/Diagnostics.html#Diagnostics).
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But, if anybody feels like helping, I think it would help me to understand the 
following macro (from textDisp.c).   Maybe somebody could show me what it 
looks like expanded?  Or provide (or point me to) an explanation.

/* Macro for getting the TextPart from a  textD */
#define TEXT_OF_TEXTD(t) (((TextWidget)((t)->w))->text)

Also, I have a vague understanding of the "->" operator--iiuc (google isn't a 
whole lot of help here it doesn't want to search for a "->", and I don't know 
the name of it).  IIUC, it is used to select an element of a struct, and is 
an alternate to the "." operator.  Further (iiuc), the "." operator is used 
in "normal" circumstances, while the "->" is used when a pointer is involved?

Randy Kramer

(Sorry, I woke up with a headache today, and I'm finding it hard to 
concentrate--I know that I could do more googling, and may, but help would be 
appreciated.)