Reading help file into textview

roger.matthews · May 30, 2020, 10:03am

Hi,
I’m using Gtk 3.2 on Ubuntu 18.04.1 LTS with C language. I have GtkMenuItem ‘Help’, with submenu ‘contents’, this calls ‘callback_contents()’ as shown below. The included comments describe the problems in reading a textfile into a textview buffer to create help documentation. The textfile was created in another part of the program using other menuitems ‘file/new’ ‘file/save’ as per modified versions of Andrew Krauses Gtk 2 book. It compiles with no warnings (other than a couple of unused variables) and when the submenuitem ‘help/contents’ is clicked the contents of the .txt file are displayed in the transient window as desired, but the runtime message:

(myexec:3474): Gtk-CRITICAL **: 19:26:32.147: gtk_text_buffer_emit_insert: assertion 'g_utf8_validate (text, len, NULL)' failed

is displayed at the terminal, once for each character in the file. How do I stop this? It seems to me that by writing and reading from the same system would mean that it would naturally be UTF8 coded. I have had previous version built with ui manager that included <?xml version="1.0" encoding="UTF-8"?> command at the start of the ui file, but the current version is fully coded.
Also included below are the help_file.txt contents as well as other failed and commented attempts in the callback_contents() function.

  void callback_contents(GtkMenuItem *contents, struct main_struct *stuff)
  {
  printf("Hello from callback_contents()\n");
    int i = 0;
    int count = 0;

    GtkWidget *window_help = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW(window_help), "Help");
    gtk_container_set_border_width(GTK_CONTAINER(window_help), 5);
    gtk_window_set_default_size(GTK_WINDOW(window_help), 600, 250);
    gtk_window_set_position(GTK_WINDOW(window_help), GTK_WIN_POS_CENTER);
    gtk_window_set_resizable(GTK_WINDOW(window_help), TRUE);

    GtkTextBuffer *buffer_textview_help;
    GtkWidget *textview_help;
    GtkWidget *entry_help;

    textview_help = gtk_text_view_new();
    gtk_text_view_set_editable(GTK_TEXT_VIEW(textview_help), FALSE);
    gtk_text_view_set_cursor_visible(GTK_TEXT_VIEW(textview_help), TRUE);
    gtk_text_view_set_wrap_mode(GTK_TEXT_VIEW(textview_help), GTK_WRAP_WORD);
    gtk_text_view_set_pixels_above_lines(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_pixels_below_lines(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_pixels_inside_wrap(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_left_margin(GTK_TEXT_VIEW(textview_help), 10);
    gtk_text_view_set_right_margin(GTK_TEXT_VIEW(textview_help), 10);

    entry_help = gtk_entry_new();
    gtk_entry_set_text(GTK_ENTRY(entry_help), "Search for ...");

    buffer_textview_help = gtk_text_view_get_buffer(GTK_TEXT_VIEW(textview_help));

    // This works but I want to read it from file:
    /*gtk_text_buffer_set_text(buffer_textview_help,
 "Hello,\nhow\n are\n you? textview_help\n***********************\n\n\n\n\n\n\n** **\n\n\n\n\n\n\n** **\n\n\n\n\n\n\n** **\n\n\n\n\n\n\n** **\n\n\nroger1\n\n\n\n** **\n\n\nroger2\n\n\n\n** **\n\n\n\nroger3\n\n\n** **\n\n\n\nroger4\n\n\n** **\n\n\nroger5\n\n\n\n** **\n\n\n\nroger6\n\n\n** ****\n\n\n\nroger7\n\n\n** ***\n\n\n\nroger8\n\n\n** **\n\n\nroger9\n\n\n\n** **\n\n\n\nroger10\n\n\n** **\n\n\nroger11\n\n\n\n** **\nend\n", -1);*/

    char line[82];
    char string[303];

    // Compiles but get segmentation fault when run
    /*char help_contents;
    FILE* infile_help_contents = fopen("help_file.txt", "r");
    fscanf(infile_help_contents, "%s\n", &help_contents);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) &help_contents, -1);
    fclose(infile_help_contents);*/


    FILE* infile_help_contents = fopen("help_file.txt", "r");

    // This works but only shows the first line (81 characters)
    /*fgets(string, 166, infile_help_contents);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);*/

    // This works but also only shows the first line (81 characters)
    /*fscanf(infile_help_contents, "%s\n", (char *) &string);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);*/

/*******************************************************************************************/
    // Here is the relevant bit:
    // This shows all in the file, but get this run-time message:
    // (myexec:3474): Gtk-CRITICAL **: 19:26:32.147: gtk_text_buffer_emit_insert:
    // assertion 'g_utf8_validate (text, len, NULL)' failed
    for (i=0; i<303; i++)
    {
    string[i] = fgetc(infile_help_contents);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);
    }
/*******************************************************************************************/

    // No messages, but shows last line only
    /*for (i=0; i<303; i++)
    {
    fgets(string, 303*sizeof(char *), infile_help_contents);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);
    }*/

    // Only shows the last line
    /*while (fgets(line, 82, infile_help_contents) != NULL)
    {
    fgets(line, 82, infile_help_contents);
    gtk_text_buffer_set_text(buffer_textview_help, (char *) line, -1);
    printf("%s\n", line);
    count = count +1;
    printf("count = %d\n", count);
    i++;
    }*/

    // Only shows part of last line
    /*while ((i = fgetc(infile_help_contents)) != EOF)
    {
      fgets(line, 82, infile_help_contents);
      gtk_text_buffer_set_text(buffer_textview_help, (char *) line, -1);
      printf("%s\n", line);

    count = count +1;

    printf("count = %d\n", count);
    i++;
    }*/

    fclose(infile_help_contents);

    GtkWidget *grid_help = gtk_grid_new();

    GtkWidget *swin_textview_help = gtk_scrolled_window_new(NULL, NULL);
    gtk_widget_set_size_request (swin_textview_help, 300, 200);
    gtk_widget_set_hexpand(swin_textview_help, TRUE);
    gtk_widget_set_vexpand(swin_textview_help, TRUE);

    gtk_container_add (GTK_CONTAINER (swin_textview_help), textview_help);

    gtk_grid_attach(GTK_GRID(grid_help), entry_help, 0, 0, 10, 1);
    gtk_grid_attach(GTK_GRID(grid_help), swin_textview_help, 0, 2, 10, 1);

    gtk_container_add (GTK_CONTAINER (window_help), grid_help);
    gtk_widget_show_all(window_help);
  }

The contents of file ‘help_file.txt’:

 help_file.txt line1 nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn81
 help_file.txt line2 nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn81
 help_file.txt line3 nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn81
line4
line5
line6
line7
line8
line9
line10
last line (11)

fmuellner · May 30, 2020, 11:29am

roger.matthews:

// Compiles but get segmentation fault when run
char help_contents;
FILE* infile_help_contents = fopen("help_file.txt", "r");
fscanf(infile_help_contents, "%s\n", &help_contents);

From the fscanf man page:

the next pointer must be a pointer to the initial element of a character array that is long enough to hold the input sequence and the terminating null byte

You are passing a pointer to a single char, which is only big enough to hold the terminating nul byte.

From the fgets man page:

Reading stops after an EOF or a newline.

You only see a single line because you only read a single line.

Mmh, that one’s a bit surprising. s “Matches a sequence of non-white-space characters”, so I would expect the output to be the first word rather than the first line.

roger.matthews:

// No messages, but shows last line only
for (i=0; i<303; i++)
{
  fgets(string, 303*sizeof(char *), infile_help_contents);
  gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);
}

On each iteration, you read one line and set the text buffer’s text to that line, until you get to the last line that sticks.

Same with the while loop.

roger.matthews:

// Here is the relevant bit:0
// This shows all in the file, but get this run-time message:
// (myexec:3474): Gtk-CRITICAL **: 19:26:32.147: gtk_text_buffer_emit_insert:
// assertion 'g_utf8_validate (text, len, NULL)' failed
for (i=0; i<303; i++) {
  string[i] = fgetc(infile_help_contents);
  gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);
}

Passing -1 as length parameter means that the string is expected to be \0-terminated, but you are passing the partially-read contents plus uninitialized (read: random) memory in each iteration.

The following should work:

for (i = 0; i < 303; i++)
    string[i] = fgetc(infile_help_contents);
string[i] = '\0';

gtk_text_buffer_set_text (buffer_textview_help, (char *) string, -1);

However I strongly recomment that you use glib or gio instead of stdio, as it reduces significantly the number of ways you can shoot yourself in the foot:

g_autofree char *contents = NULL;

if (g_file_get_contents ("help_file.txt", &contents, NULL, NULL))
  gtk_text_buffer_set_text (buffer_textview_help, contents, -1);

roger.matthews · May 31, 2020, 4:49am

Hi Florian,
here is my solution, thanks for your help, the solution lay in the \0 as you suggested. Will have a look at:

g_autofree char *contents = NULL;

if (g_file_get_contents ("help_file.txt", &contents, NULL, NULL))
  gtk_text_buffer_set_text (buffer_textview_help, contents, -1);

also,
Cheers,
Roger

void callback_contents(GtkMenuItem *contents, struct main_struct *stuff)
  {
  printf("Hello from callback_contents()\n");
    int i = 0;
    int cha_count = 0;

    GtkWidget *window_help = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title(GTK_WINDOW(window_help), "Help");
    gtk_container_set_border_width(GTK_CONTAINER(window_help), 5);
    gtk_window_set_default_size(GTK_WINDOW(window_help), 600, 250);
    gtk_window_set_position(GTK_WINDOW(window_help), GTK_WIN_POS_CENTER);
    gtk_window_set_resizable(GTK_WINDOW(window_help), TRUE);

    GtkTextBuffer *buffer_textview_help;
    GtkWidget *textview_help;
    GtkWidget *entry_help;

    textview_help = gtk_text_view_new();
    gtk_text_view_set_editable(GTK_TEXT_VIEW(textview_help), FALSE);
    gtk_text_view_set_cursor_visible(GTK_TEXT_VIEW(textview_help), TRUE);
    gtk_text_view_set_wrap_mode(GTK_TEXT_VIEW(textview_help), GTK_WRAP_WORD);
    gtk_text_view_set_pixels_above_lines(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_pixels_below_lines(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_pixels_inside_wrap(GTK_TEXT_VIEW(textview_help), 5);
    gtk_text_view_set_left_margin(GTK_TEXT_VIEW(textview_help), 10);
    gtk_text_view_set_right_margin(GTK_TEXT_VIEW(textview_help), 10);

    entry_help = gtk_entry_new();
    gtk_entry_set_text(GTK_ENTRY(entry_help), "Search for ...");
    GtkWidget *find_help = gtk_button_new_with_label("Find");
    g_signal_connect(G_OBJECT(find_help), "clicked", G_CALLBACK(search_help), stuff);

    buffer_textview_help = gtk_text_view_get_buffer(GTK_TEXT_VIEW(textview_help));

    stuff->findstring_help = 1;
    GtkAdjustment *findstring_help_adj=gtk_adjustment_new(stuff->findstring_help,
          1, 2001, 1, 1, 1);
    GtkWidget *findstring_help_label=gtk_label_new("FindString");
    GtkWidget *findstring_help_spin=gtk_spin_button_new(findstring_help_adj, 1, 0);
    g_signal_connect(findstring_help_spin, "value-changed",
    G_CALLBACK(findstring_help_spin_changed), stuff);
    g_signal_connect(findstring_help_spin, "scroll-event", G_CALLBACK(gtk_true), NULL);

    FILE* infile_help_contents0 = fopen("help_file.txt", "r");
    while ((i = fgetc(infile_help_contents0)) != EOF)
    {
    cha_count = cha_count + 1;
    i++;
    }
    printf("cha_count = %d\n", cha_count);
    fclose(infile_help_contents0);

    char *string = malloc(cha_count*sizeof(char));

    FILE* infile_help_contents = fopen("help_file.txt", "r");

    for (i=0; i<=cha_count-1; i++)
    {
      if (i <= cha_count-2)
      {
      string[i] = fgetc(infile_help_contents);
      }
      else if (i == cha_count-1)
      {
      string[i] = '\0';
      }
      else
      {
      break;
      }
    }
    gtk_text_buffer_set_text(buffer_textview_help, (char *) string, -1);

    fclose(infile_help_contents);

    stuff->entry_help = entry_help;
    stuff->textview_help = textview_help;
    stuff->findstring_help_label = findstring_help_label;
    stuff->findstring_help_spin = findstring_help_spin;

    GtkWidget *grid_help = gtk_grid_new();

    GtkWidget *swin_textview_help = gtk_scrolled_window_new(NULL, NULL);
    gtk_widget_set_size_request (swin_textview_help, 300, 200);
    gtk_widget_set_hexpand(swin_textview_help, TRUE);
    gtk_widget_set_vexpand(swin_textview_help, TRUE);

    gtk_container_add (GTK_CONTAINER (swin_textview_help), textview_help);

    gtk_grid_attach(GTK_GRID(grid_help), entry_help, 0, 0, 5, 1);
    gtk_grid_attach(GTK_GRID(grid_help), find_help, 6, 0, 1, 1);
    gtk_grid_attach(GTK_GRID(grid_help), stuff->findstring_help_label, 7, 0, 1, 1);
    gtk_grid_attach(GTK_GRID(grid_help), stuff->findstring_help_spin, 8, 0, 1, 1);

    gtk_grid_attach(GTK_GRID(grid_help), swin_textview_help, 0, 2, 10, 1);

    gtk_container_add (GTK_CONTAINER (window_help), grid_help);

    gtk_widget_show_all(window_help);

    free(string);
  }

system · June 14, 2020, 4:49am

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