Re: Why can't I pass a char* in gtk_signal_connect!

["Brian J. Tarricone" <bjt23 cornell edu>]

sreekant kodela wrote:

> Hi folks
>
> I am trying to make a small toolbar app for my
> purposes. I suppose I can always use someone elses
> work but I thought I will give it a try. The program
> is supposed to start, find the user home dir, parse
> the config file, and create buttons with icons as a
> button bar. As part of that it links the button to the
> callback run_event which accepts the widget and data.
> I used the command string eg: xterm , gimp what ever
> in the data section of params for callback. But if you
> try and compile the bummer it seem to get the string
> completely mixed up. Some times it sends the same
> string or null or partial string. If I use a string in
> "" directly it accepts but otherwise if I use char*
> parsed from config file, it gets the strings wrong as
> above.
>  
[snip]

You can't rely on strings returned by strtok() to be around later.  You 
need to pass a heap-allocated copy to g_signal_connect().  I'd recommend 
using g_strdup() for this purpose.  Note that you'll need to free this 
string when you're done using it, otherwise you'll end up with a memory 
leak.  I'd suggest you read the man page for strtok() while you're at it.

   -brian

> Full source code below. [ Not very big ]
> =================================
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> #include <gtk/gtk.h>
> #include <sys/types.h>
> #include <unistd.h>
> #include <pwd.h>
> #include <sys/stat.h>
>
>
> #define SZ_LINES 512
> #define SZ_PARSE 128
> #define SZ_WIDTH 128
>
> void delete_event (GtkWidget *widget, gpointer data)
> {
>  gtk_main_quit ();
> }
>
> //whether data is char* or gpointer it still doesnot
> work.
> void run_event(GtkWidget *widget,gpointer data)
> {
>  printf("%s",data);
>  //   pid_t id;
>  /*  id=fork();
>  if (id==0)
>  {system(data); exit(0);}*/
> }
>
> int main (int argc, char *argv[])
> {
>  uid_t userid;
>  struct passwd *user;
>  FILE* fin;
>  char *buf,*cnfname;
>  char *title,*cmd,*pixmap;
>  int cnt=0;
>  size_t len=0;
>  ssize_t read;
>  GtkWidget* win;
>  GtkWidget * btnbox;
>  GtkWidget * iconw[SZ_WIDTH];
>  GtkWidget* button[SZ_WIDTH];
>  GtkWidget* xpmbox[SZ_WIDTH];
>  GtkWidget *cbtn;
>  GtkTooltips *tooltips;
>
>  //Start UI
>  gtk_init (&argc, &argv);
>  tooltips=gtk_tooltips_new();
>  win = gtk_window_new (GTK_WINDOW_POPUP);
>  gtk_window_set_decorated (GTK_WINDOW (win), FALSE);
>  gtk_window_set_skip_pager_hint (GTK_WINDOW (win),
> TRUE);
>  g_signal_connect (G_OBJECT (win),
> "delete_event",G_CALLBACK (delete_event), NULL);
>  gtk_widget_realize (win);
>  btnbox=gtk_hbox_new(FALSE,0);
>  gtk_container_add (GTK_CONTAINER (win), btnbox);
>  //Create the first button, for closing the app
>  cbtn=gtk_button_new_from_stock("gtk-stop");
>
> g_signal_connect(G_OBJECT(cbtn),"clicked",G_CALLBACK(delete_event),NULL);
>
> gtk_box_pack_start(GTK_BOX(btnbox),cbtn,FALSE,FALSE,0);
>  gtk_widget_show(cbtn);
>  //Findout home dir and read conf
>  //TODO: error checking in conf reading
>  //TODO: Deal better with empty new lines etc.
>  userid=getuid();
>  user=getpwuid(userid);
>  cnfname=(char *)malloc(SZ_LINES);
>  strcpy(cnfname,user->pw_dir);
>  strcat(cnfname,"/.mybar/config");
>  //  fin=fopen(cnfname,"r"); //dbg
>  fin=fopen(argv[1],"r");
>  if (fin==NULL) exit(1);
>  //Get some memory
>  buf=(char *)calloc(SZ_LINES,sizeof(char));
>  title=(char *)calloc(SZ_PARSE,sizeof(char));
>  cmd=(char *)calloc(SZ_PARSE,sizeof(char));
>  pixmap=(char *)calloc(SZ_PARSE,sizeof(char));
>  //TODO : check memory has been alloced.
>
>  //Now create the buttons
>  while ((read=getline(&buf,&len,fin))!= -1)
>    {
>      // parse lines
>      title=strtok(buf,",");
>      cmd=strtok(NULL,",");
>      pixmap=strtok(NULL,",");
>      pixmap[strlen(pixmap)-1]='\0';
>      button[cnt]=gtk_button_new();
>      iconw[cnt] = gtk_image_new_from_file (pixmap);
>     
> gtk_container_add(GTK_CONTAINER(button[cnt]),iconw[cnt]);
>      //The one below works but the one further down
> doesnot. Why!!!
>      //     
> g_signal_connect(G_OBJECT(button[cnt]),"clicked",G_CALLBACK(run_event),(gpointer)"hi
> there");
>     
> g_signal_connect(G_OBJECT(button[cnt]),"clicked",G_CALLBACK(run_event),(gpointer)cmd);
>      gtk_tooltips_set_tip (tooltips,
> button[cnt],title, NULL);
>     
> gtk_box_pack_start(GTK_BOX(btnbox),button[cnt],FALSE,FALSE,0);
>      gtk_widget_show(button[cnt]);
>      gtk_widget_show(iconw[cnt]);
>      memset(buf,sizeof(buf),'\0');
>      memset(title,sizeof(title),'\0');
>      memset(pixmap,sizeof(pixmap),'\0');
>      memset(cmd,SZ_PARSE,'\0');
>      ++cnt;
>    }
>  gtk_widget_show (btnbox);
>  gtk_widget_show (win);
>
>  gtk_main ();
>  return 0;
> }
>
>
> // CONF FILE BELOW
> /*
> Terminal,xterm,kterm.xpm
> Gimp,gimp,xpaint.xpm
> Gimp,gimp,xpaint.xpm
> Terminal,xterm,kterm.xpm
> */
> //END CONF FILE
>
>
>
>                 
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