Pango-WARNING **: Invalid UTF-8 string passed to pango_layout_set_text() in GTK C

Question

I am getting above mentioned warning in my gtk application. I know this question is already been discussed but the problem with me is that I am not even using this funciton.

All I am doing is reading a text string from a file and then changing its font type and font size using pango and then applying the result in gtk label, Here is the code:

 FILE *fp;
 long lSize;
 char *buffer;

 fp = fopen ( "/home/user/file.txt" , "rb" );
 if( !fp ) perror("file.txt"),exit(1);

 fseek( fp , 0L , SEEK_END);
 lSize = ftell( fp );
 rewind( fp );

 buffer = calloc( 1, lSize+1 );
 if( !buffer ) fclose(fp),fputs("memory alloc fails",stderr),exit(1);


 if( 1!=fread( buffer , lSize, 1 , fp) )
   fclose(fp),free(buffer),fputs("entire read fails",stderr),exit(1);

 buffer[lSize+2]='\0';

 PangoFontDescription *font = pango_font_description_new ();    //NEW PANGO FONT
 pango_font_description_set_family (font,"Arial Rounded MT Bold");          //FONT FAMILY
 pango_font_description_set_size(font,60*PANGO_SCALE);  //FONT SIZE
 gtk_widget_override_font(GTK_WIDGET(label), font);         //APPLYING THE NEW FONT

 gtk_label_set_text(GTK_LABEL(label),buffer);

How can I remove this error?

Edit:

I removed the pango code and used gtk_set_markup

char *str = g_strdup_printf ("<span font=\"20\" color=\"white\">" "%s""</span>",buffer);
gtk_label_set_markup (GTK_LABEL (label), str);

The problem is if the font size is 20 or low then it displays fine with fullscreen but if I increase the font size to 30 or 40, then it gives same warning and window also resizes like below:

In normal with low font size, it looks like below :

Please use something like g_file_get_contents() to read a file -- I don't think your code is safe, at the very least you write the terminator after the end of buffer. — Jussi Kukkonen
– Jussi Kukkonen, Commented May 3, 2017 at 8:57
@jku I didnt knew about g_file_contents(). I am using it now but the problem remains same as per my edit. — S Andrew
– S Andrew, Commented May 3, 2017 at 9:10
@JoséFonte Its not about file. I tried this too char *str = g_strdup_printf ("<span font=\"20\" color=\"white\">" "%s""</span>","Text which I want to display"); it still gives the error — S Andrew
– S Andrew, Commented May 3, 2017 at 11:05
You dont use it but gtk uses it, gtk.label is using it so that means there are utf8 erros on your files content — José Fonte
– José Fonte, Commented May 3, 2017 at 11:08

ebassi · Accepted Answer · 2017-05-03 13:24:15Z

6

GTK+ widgets expect UTF-8 encoded text for all the user visible strings.

You must ensure that the contents of the file you are loading are encoded using UTF-8 before loading them into any GTK+ widget. You can use the character set conversion API provided by GLib, like g_convert() or g_locale_to_utf8().

I'd also recommend using the GIO API for loading the file contents, i.e. g_file_load_contents_async(), as it won't block the UI while loading arbitrarily sized files from arbitrarily slow storage.

answered May 3, 2017 at 13:24

ebassi

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