Write text to the information bar of a dwg file

[fly-sure]

My goal is to write text in the red box in the picture through C language programming. Under the Linux system, I have installed libredwg0.13.3, but I can't find the relevant API documentation. I don't know what API this library provides. If you can help me, I will be very grateful.

[rurban]

Search for add_TEXT in
examples/load_dwg.c

[fly-sure]

I tried to write text to the dwg file using dwg_add_TEXT, but it didn't work and the dwg file didn't seem to change. Could you please help me figure out what went wrong?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dwg.h>
#include <time.h>
#include "dwg_api.h"

static int add_text(Dwg_Data *dwg, dwg_point_3d *pt)
{
  int error = 0;
  char text[128];
  double height = dwg->header_vars.TEXTSIZE;
  time_t t = time (NULL);
  Dwg_Object_BLOCK_HEADER *hdr = dwg_get_block_header (dwg, &error);
  Dwg_Entity_TEXT *ent;

  strftime (text, sizeof (text), "Last updated: %c", localtime (&t));

  if ((ent = dwg_add_TEXT (hdr, text, pt, height)))
    {
      ent->horiz_alignment = HORIZ_ALIGNMENT_RIGHT;
      return 0;
    }

    return 1;
}

int main() {
    int result=0;
    const char *filename = "test.dwg"; 
    Dwg_Data dwg;
    dwg_point_3d pt;

    memset (&dwg, 0, sizeof (Dwg_Data));

    result = dwg_read_file(filename, &dwg); 

    if (result != 0) {  
        fprintf(stderr, "Failed to open DWG file: %s\n", filename);
        return 1; 
    }
    printf("Successfully opened DWG file: %s\n", filename);

    // get the insertion point for text
    //pt.x = dwg.header_vars.LIMMAX.x;
    //pt.y = dwg.header_vars.LIMMAX.y;
    pt.x = 100;
    pt.y = 100;
    pt.z = 0.0;

    if (1)
    {
      add_text (&dwg, &pt);
      fprintf (stderr, "text added at (%f, %f)\n", pt.x, pt.y);
    }
    dwg.header.version = R_2000;
    result = dwg_write_file (filename, &dwg);

    dwg_free(&dwg); 
    printf("Successfully closed DWG file: %s\n", filename);

    return 0; 
}