Re: GTK app to change pic on click

[Tomas Carnecky <tom dbservice com>]

Midhun A wrote:
> Hi All,
>
>   I am very new to GTK+ (started out yesterday). I am writing a simple
> application which will show pictures one by one on button click.
> Although I am able to get my first picture, the picture does not
> change on click of the button (next or previous). The full code is as
> below.
>
> #include <stdio.h>
> #include <gtk/gtk.h>
> #include <string.h>
> #include <unistd.h>
> #include </usr/include/stdio.h>
> #include <glib.h>
>
> GtkWidget *image2;
> GtkWidget *window;
> GtkWidget *vbox;
> GtkWidget *prev_button, *next_button;
>
>
>
> gchar *files[6] =
> {
> "/home/pics/1.jpg",
> "/home/pics/2.jpg",
> "/home/pics/3.jpg",
> "/home/pics/4.jpg",
> "/home/pics/5.jpg",
> "/home/pics/6.jpg"
> };
>
> typedef struct{
> gint data;
> } data;
>
> void prev_callback (GtkWidget *widget, data *v )
> {
>         gint cnt = v->data;
>         if (cnt == 0)
>                 cnt = 5;        
>         else
>                 cnt = cnt - 1;
>                         
>         image2 = gtk_image_new_from_file (files[cnt]);
> }

This callback only creates the new image, it doesn't display it in the 
window. You seem to lack basic C understanding, especially about pointers.

To replace the current image, you have to remove the image widget from 
the vbox and replace it with the new image. Like this:

> void next_callback (GtkWidget *widget, data *v)
> {
>         int cnt = v->data;
>         if (cnt == 5)
>                 cnt = 0;        
>         else
>                 cnt = cnt + 1;
>                         
        gtk_container_remove(GTK_CONTAINER(vbox), image2);
>         image2 = gtk_image_new_from_file (files[cnt]);
        gtk_container_add(GTK_CONTAINER(vbox), image2);
> }
>
>
> int main (int argc, char *argv[])
> {
>
>         data *w = g_slice_new(data);
>         w->data = 0;
>
>         gtk_init(&argc,&argv);
>         window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
>         gtk_window_maximize (window);
>         
>         vbox = gtk_vbox_new(FALSE, 1);
>
>         image2 = gtk_image_new_from_file (files[w->data]);
>         gtk_container_add(GTK_CONTAINER(vbox), image2);
>                                 
>         prev_button = gtk_button_new_with_mnemonic ("Previous");
>         next_button = gtk_button_new_with_mnemonic ("Next");
>
>         gtk_widget_set_name(prev_button,"prev_button");
>         gtk_widget_set_name(next_button,"next_button");       
>
>         gtk_container_add(GTK_CONTAINER(vbox), prev_button);
>         gtk_container_add(GTK_CONTAINER(vbox), next_button);            
>         gtk_container_add(GTK_CONTAINER(window), vbox); 
>
>         g_signal_connect (G_OBJECT (prev_button), "clicked", G_CALLBACK
> (prev_callback),(gpointer)w);
>         g_signal_connect (G_OBJECT (next_button), "clicked", G_CALLBACK
> (next_callback),(gpointer)w);
>
>         gtk_widget_show (image2);
>         gtk_widget_show (prev_button);
>         gtk_widget_show (next_button);          
>         gtk_widget_show (vbox); 
>         gtk_widget_show (window);
>         
>         gtk_main();
>         return 0;
> }
>
>
> This is very primitive code to test the functionality.  Whats wrong
> with the code? I would like to see the previous picture on click of
> previous button and the next picture on click of next button.

tom