--textmode and signing/clearsigning

[Dirk Traulsen]

Hi,

after reading the gpg man page, I have four questions
concerning --textmode and signing.

A citation from the gpg man-page:
 -t, --textmode
       Use  canonical  text  mode.   If  -t  (but   not
       --textmode)  is  used together with armoring and
       signing,  this  enables  clearsigned   messages.
       This  kludge  is  needed  for PGP compatibility;
       normally you would use --sign or --clearsign  to
       selected the type of the signature.
    
1. What is a cannonical text mode? 
   I found no explanation in the man page or the gnu gpg handbook. 
   I only found in an introduction to gpg from Brian Hatch:
      --text 
            Using --text tells GPG that the file is ASCII text.
            When the file is decrypted on the other end, 
            end-of-line sequences (CR/LF vs CR, etc) will be
            automatically converted, which is convenient. 
   I assume, --text is the short of --textmode.
   Is his explanation correct and complete?

2. Why is there a difference between -t and --textmode? 
   Why should it matter to pgp, whether gpg accepts a -t as a 
   short form for --textmode?
   
3. Does this mean 
   (gpg -seat) is clearsigning the message, but
   (gpg -sea --textmode) is signing it?

4. The difference between signing and clearsigning is that with 
   clearsigning, the original text is preserved and fully readable
   even without a public key of the author and with 
   signing, it gets compressed and safed in binary form.
   When I encrypt a text, it gets compressed anyway.
   Why does it make a difference, whether I use signing or
   clearsigning on a compressed text?

Dirk