XPAConvert: Converting the XPA API to 2.0

Summary

This document describes tips for converting from xpa 1.0 (Xt-based xpa) to xpa 2.0 (socket-based xpa).

Description

The following are tips for converting from xpa 1.0 (Xt-based xpa) to xpa 2.0 (socket-based xpa). The changes are straight-forward and almost can be done automatically (we used editor macros for most of the conversion).

• The existence of the cpp XPA_VERSION directive to distinguish between 1.0 (where it is not defined) and 2.0 (where it is defined).

• Remove the first widget argument from all send and receive server callbacks. Also change first 2 arguments from XtPointer to void *. For example:

  #ifdef XPA_VERSION
  static void XPAReceiveFile(client_data, call_data, paramlist, buf, len)
       void *client_data;
       void *call_data;
       char *paramlist;
       char *buf;
       int len;
  #else
  static void XPAReceiveFile(w, client_data, call_data, paramlist, buf, len)
       Widget w;
       XtPointer client_data;
       XtPointer call_data;
       char *paramlist;
       char *buf;
       int len;
  #endif
  

• Server callbacks should be declared as returning int instead of void. They now should return 0 for no errors, -1 for error.

• The mode flags have changed when defining XPA server callbacks. The old S flag (save buffer) is replaced by freebuf=false. The old E flag (empty buffer is OK) is no longer used (it was an artifact of the X implementation).

• Change NewXPACommand() to XPAcmdNew(), with the new calling sequence:

    xpa = NewXPACommand(toplevel, NULL, prefix, NULL);
  

  is changed to:

    xpa = XPACmdNew(xclass, name);
  

• Change the AddXPACommand() subroutine name to XPACmdAdd (with the same calling sequence):

    AddXPACommand(xpa, "file",
      "\tdisplay a new file\n\t\t  requires: filename",
      NULL, NULL, NULL, XPAReceiveFile, text, NULL);
  

  is changed to:

    XPACmdAdd(xpa, "file",
      "\tdisplay a new file\n\t\t  requires: filename",
      NULL, NULL, NULL, XPAReceiveFile, text, NULL);
  

• The XPAXtAppInput() routine should be called just before XtAppMainLoop() to add xpa fds to the Xt event loop:

    /* add the xpas to the Xt loop */
    XPAXtAddInput(app, NULL);
  
    /* process events */
    XtAppMainLoop(app);
  

• Change NewXPA() to XPANew() and call XPAXtAddInput() if the XtAppMainLoop routine already has been entered:

    xpa = NewXPA(saotng->xim->toplevel, prefix, xparoot,
                 "FITS data or image filename\n\t\t  options: file type",
                 XPASendData, new, NULL,
                 XPAReceiveData, new, "SE");
  

  is changed to:

    sprintf(tbuf, "%s.%s", prefix, xparoot);
    xpa = XPANew("SAOTNG", tbuf,
                 "FITS data or image filename\n\t\t  options: file type",
                 XPASendData, new, NULL,
                 XPAReceiveData, new, "SE");
    XPAXtAddInput(XtWidgetToApplicationContext(saotng->xim->toplevel), xpa);
  

• Change XPAInternalReceiveCommand() to XPACmdInternalReceive() remove first argument in the calling sequence):

    XPAInternalReceiveCommand(im->saotng->xim->toplevel,
  			    im->saotng, im->saotng->commands,
  			    "zoom reset", NULL, 0);
  

  is changed to:

    XPACmdInternalReceive(im->saotng, im->saotng->commands,
  			"zoom reset", NULL, 0);
  

• Change DestroyXPA to XPAFree:

    DestroyXPA(im->dataxpa);
  

  is changed to:

    XPAFree(im->dataxpa);
  

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Last updated: September 10, 2003