On Tue, Jul 01, 2014 at 01:39:03AM -0700, Anoop Neem wrote:
> This application is intended to convert value entered in Text entry
> field (in Celcius) to Farenheit in label. I was having hard time in
> altering the properties of two widgets (other than calling widget) in
> the same callback, hence created a structure 'struct mulptr' for passing
> two widgets. But when i click on the button application closes giving me
> some error:
>
>
> xxx@ubuntu:~/gtk$ gcc `pkg-config --cflags gtk+-3.0` -o 4 4.c
> `pkg-config --libs gtk+-3.0`
> xxx@ubuntu:~/gtk$ ./4
>
> (4:4221): Gtk-CRITICAL **: gtk_entry_get_text: assertion 'GTK_IS_ENTRY
> (entry)' failed
> Segmentation fault (core dumped)
This basically means that the pointer that you passed to
gtk_entry_get_text was not pointing to a GtkEntry.
> ---------------------------------------------------------------------
> #include<gtk/gtk.h>
> #include<string.h>
> #include<stdlib.h>
>
> char a[15] = "Result here";
>
> struct mulptr
> {
> GtkWidget *one;
> GtkWidget *two;
> };
>
> int tofarenheit(int c)
> {
> return (c*1.8 + 32);
> }
>
> void calculate(GtkWidget *widget, gpointer data)
> {
> GtkWidget *textEntry = ((struct mulptr *)data)->one;
> GtkWidget *label = ((struct mulptr *)data)->two;
> int res = 0, F;
>
> res = atoi(gtk_entry_get_text(GTK_ENTRY(textEntry)));
> if(res)
> {
> F = tofarenheit(res);
> sprintf(a, "%d", F);
> }
> else
> strcpy(a, "Invalid Input!");
> gtk_label_set_text(GTK_LABEL(label), a);
> }
>
> int main(int argc, char *argv[])
> {
> //Decleration
> GtkWidget *window;
> GtkWidget *calButton;
> GtkWidget *textEntry;
> GtkWidget *label;
> GtkWidget *grid;
> struct mulptr *p = (struct mulptr *)malloc(sizeof(struct mulptr));
> p->one = textEntry;
At this point textEntry is still not initialized, so all this did was
copy the uninitialized value from textEntry to p->one.
> p->two = label;
>
> //Initilization
> gtk_init(&argc, &argv);
>
> window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
> //gtk_window_set_default_size(GTK_WINDOW(window), 480, 320);
> gtk_window_set_title(GTK_WINDOW(window), "Celcius to Ferenheit
> Converter");
> gtk_container_set_border_width(GTK_CONTAINER(window), 10);
> grid = gtk_grid_new();
>
> label = gtk_label_new(a);
> textEntry = gtk_entry_new();
And here you assign textEntry with the pointer to your new GtkEntry, but
p->one is not updated and sill contains the old value which is used in
calculate.
> calButton = gtk_button_new_with_label("Calculate");
>
> //Adding widget to frame
> gtk_container_add(GTK_CONTAINER(window), grid);
> gtk_grid_attach(GTK_GRID(grid), textEntry, 0, 0, 1, 1);
> gtk_grid_attach(GTK_GRID(grid), label, 1, 0, 1, 1);
> gtk_grid_attach(GTK_GRID(grid), calButton, 0, 1, 1, 1);
>
>
> //Signal Handlers
> g_signal_connect (window, "delete-event", G_CALLBACK (gtk_main_quit),
> NULL);
> g_signal_connect (calButton, "clicked", G_CALLBACK(calculate), p);
>
>
> //Essentials
> gtk_widget_show_all(window);
> gtk_main();
> return 0;
> }
> ---------------------------------------------------------------------
>
> Please help me with this piece of code?? Is it all right to use this
> kind of struct??
In a large application sure, it makes sense to bundle related things
together as a struct and passit around; but that's not really necessary
in a small application like this. Since you're using Gtk you might just
as well want to check out GObject which formalizes a lot of this stuff.
Marcus
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