| How can I use functions in textedit.h to edit a text variable?

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Q: | I don't understand how I can use functions from textedit.h header file to edit a text variable. When I tried to open a blank editor everything seems OK, but when I tried to edit an existing text variable, I got a crash...

A:

I must admit that the problem is not so easy. The problem is, in fact, caused by severe error in my documentation in releases of TIGCCLIB prior to 2.2 (it is corrected now). Namely, I was wrong when I told that a handle passed as a parameter to TE_open function may be a handle of a text variable. In fact, text variables have another extra data at the begining (one word for the length, and one word for the cursor position). But, the editor expects a raw data. I inspected what TIOS does exactly during opening a text variable. Then I concluded: there is no any other solutions than striping out extra data (this is a little play with memmove). Of course, after the editing is finished, it is necessary to reconstruct again the proper structure of the text variable (this is possible using some informations presented in TEXT_EDIT structure after the editing is finished).
After this theoretical elaboration, I will be much more concrete. Here is a complete code example (called "Text Editor") which edits the text variable named "mytext". Due to simplicity, it is assumed that this variable really exists and that it is not archived:

    // A simple text editor example

    #define USE_TI89              // Compile for TI-89
    #define USE_TI92PLUS          // Compile for TI-92 Plus
    #define USE_V200              // Compile for V200

    #define OPTIMIZE_ROM_CALLS    // Use ROM Call Optimization
    #define MIN_AMS 100           // Compile for AMS 1.00 or higher
    #define SAVE_SCREEN           // Save/Restore LCD Contents

    #include <tigcclib.h>         // Include All Header Files

    TEXT_EDIT te;

    // Typical event handler for text editing
    CALLBACK void EventHandler(EVENT *ev)
    {
      if (ev->Type == CM_KEYPRESS && ev->extra.Key.Code == KEY_ESC)
        ER_throw (1);
      if (!TE_handleEvent (&te, ev))
        EV_defaultHandler (ev);
    }

    // Main Function
    void _main(void)
    {
      char *base_addr;
      SYM_ENTRY *sym = SymFindPtr (SYMSTR ("mytext"), 0);

      if (!sym) return;  // Exit if file not found...

      // First, you need to remove the garbage data at the begining of
      // the text variable, because the text editor expects raw data:

      base_addr = HeapDeref (sym->handle);
      memmove (base_addr, base_addr + 4, peek_w(base_addr));

      // Now, do the editing. This is straightforward...

      WinClr (DeskTop);
      TE_open (&te, DeskTop, MakeWinRect (0, 16, 159, 92), sym->handle, 1, 0, 7);
      CU_start ();
      EV_captureEvents (EventHandler);
      TRY
         EV_eventLoop ();
      ONERR
         EV_captureEvents (NULL);
      ENDTRY

      // Finally, you must transform raw editor data into the proper
      // format of the text variable. This is not so straightforward:

      base_addr = HeapDeref (HeapRealloc (sym->handle, te.CurSize + 10));
      memmove (base_addr + 4, base_addr, te.CurSize);
      poke_w (base_addr, te.CurSize + 4);
      poke_w (base_addr + 2, te.CursorOffset);
      poke (base_addr + te.CurSize + 4, 0);
      poke (base_addr + te.CurSize + 5, TEXT_TAG);
    }

It is important to understand how this program works if you plan to do any serious application of text editing functions.