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15.4 Document History protocol

The Document History protocol (DHST) serves to provide a global list of the last-used documents, similar to the Recall menu in Texel. Start-Me-Up makes use of this by enabling files to be retrieved from just one place.

Here is a short version of the structure in C-notation:

 #define DHST_ADD 0xdadd
 #define DHST_ACK 0xdade

typedef struct
{
   int8_t *appname,
          *apppath,
          *docname,
          *docpath;
} DHSTINFO;

Every time the user opens a file, it searches the application for the cookie 'DHST'. The AES ID of the DHST-Server informs other programs where they should send DHST messages using the DHST_ADD message. The application then sends the information down to the global DHSTINFO- structure and adds the corresponding information depending upon:

 appname:     Name of the application
              (e.g. "Texel")

 apppath:     Absolute path of the application
              (e.g. "c:\program\texel.app")

 docname:     Name of the document
              (e.g. "balmer.txl")

 docpath:     Absolute path of the document
              (e.g. "d:\Data\balmer.txl")

Then the DHST-Server sends the following message:

 msg[0]    DHST_ADD (0xdadd)
 msg[1]    ap_id
 msg[2]    0
 msg[3]    and
 msg[4]    Pointer to DHSTINFO-structure (how DHST_ADD passed)
 msg[5]    0
 msg[6]    0
 msg[7]    0

When an answer is received, the application sends the following message:

 msg[0]    DHST_ACK (0xdade)
 msg[1]    ap_id
 msg[2]    0
 msg[3]    and
 msg[4]    Pointer to DHSTINFO structure (how passed with DHST_ADD)
 msg[5]    0
 msg[6]    0
 msg[7]    0=error(s), else: OK

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