I'm trying to pass an object to the callback of a "clicked" event in order to set the text of the target label.
Here's my code so far:
#include <gtk/gtk.h>
typedef struct {
int i;
GtkWidget *target;
} Data;
void change( GtkWidget *widget,
Data *data )
{
gtk_label_set_text(GTK_LABEL(data->target), "it did!");
}
int main( int argc,
char* argv[] )
{
gtk_init(&argc, &argv);
GtkWidget *window, *label, *button;
Data data;
data.i = 0;
data.target = label;
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(window), "GTKdemo");
g_signal_connect(window, "delete-event", G_CALLBACK(gtk_main_quit), NULL);
GtkGrid *grid = gtk_grid_new();
button = gtk_button_new_with_label("Click here");
g_signal_connect(button, "clicked", G_CALLBACK(change), &data);
gtk_grid_attach(grid, button, 0,0,1,1);
label = gtk_label_new("this will change");
gtk_grid_attach(grid, label, 0,1,1,1);
gtk_container_add(GTK_CONTAINER(window), GTK_WIDGET(grid));
gtk_widget_show_all(window);
gtk_main();
return 0;
}
I'm trying to set the text of label when button is clicked.
I tried gtk callback multiple arguments but no dice. Help?
Okay, I fixed it by moving data.target = label to execute after the g_signal_connect of the button.
Perhaps the problem arose from using the pointer address before the object variables were defined.
Related
I am trying to make UI using GTK in c for raspberry pi 4. I want to change the visibility of different widgets based on button click just to simulate a new page. I have tried everything available on the internet but as I am not that good at coding I cant figure out what is wrong.
can someone please help ?
This program compiles but when I press the button it gives error " assertion failed on gtk_widget_show " and also on widget hide. Also a segmentation fault occurs and the program crashes.
I am using cmake to compile my code. I have attached the error screen shot.
#include <gtk/gtk.h>
typedef struct AppData
{
GtkWidget *label1;
GtkWidget *label2;
} AppData;
static void button1 (gpointer data)
{
AppData *data2 = (AppData*)data;
gtk_widget_hide(data2->label1);
gtk_widget_show(data2->label2);
}
static void button2 ( gpointer data)
{
AppData *data2 = (AppData*)data;
gtk_widget_show(data2->label1);
gtk_widget_hide(data2->label2);
}
int main(int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *fixed;
GtkWidget *btn1;
GtkWidget *btn2;
GtkWidget *box1;
GtkWidget *box2;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(window), "ethercat test 1");
gtk_window_set_default_size(GTK_WINDOW(window), 1000,500);
fixed = gtk_fixed_new();
gtk_container_add(GTK_CONTAINER(window), fixed);
box1 = gtk_box_new(GTK_ORIENTATION_VERTICAL, 1);
gtk_fixed_put(GTK_FIXED(fixed), box1, 0,0);
box2 = gtk_box_new(GTK_ORIENTATION_VERTICAL, 1);
gtk_fixed_put(GTK_FIXED(fixed), box2, 100,100);
AppData *app_data = g_new0 (AppData, 2);
app_data->label1 = gtk_label_new("label1");
gtk_box_pack_start(GTK_BOX(box1),app_data->label1, TRUE,TRUE,0);
app_data->label2 = gtk_label_new("label2");
gtk_box_pack_start(GTK_BOX(box2),app_data->label2, TRUE,TRUE,0);
btn1 = gtk_button_new_with_label("ethercat 1");
gtk_fixed_put(GTK_FIXED(fixed), btn1, 10, 450);
gtk_widget_set_size_request(btn1, 80,30);
btn2 = gtk_button_new_with_label("ethercat 2");
gtk_fixed_put(GTK_FIXED(fixed), btn2, 110, 450);
gtk_widget_set_size_request(btn2, 80,30);
gtk_widget_show_all(window);
g_signal_connect(G_OBJECT(btn1), "clicked", G_CALLBACK(button1), app_data);
g_signal_connect(G_OBJECT(btn2), "clicked", G_CALLBACK(button2), app_data);
g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
gtk_main();
printf("program end\n");
return (0);
}
enter image description here
The function signature of your "clicked" callbacks is wrong. It should be of the form as described in the documentation:
void on_clicked(
GtkButton* self,
gpointer user_data
)
So for example, your button2() function becomes
static void button2 (GtkButton *btn2, gpointer data)
{
AppData *data2 = (AppData*)data;
gtk_widget_show(data2->label1);
gtk_widget_hide(data2->label2);
}
I am a new C programmer coming from Java. After reading some old books and articles, I've written the following code:
#include <gtk/gtk.h>
static void activate(GtkApplication* app, gpointer user_data) {
GtkWidget *window;
GtkWidget *button1;
GtkWidget *box;
box = gtk_alignment_new(0, 0, 0, 0);
window = gtk_application_window_new(app);
gtk_window_set_title(GTK_WINDOW(window), "Calculator");
gtk_window_set_default_size(GTK_WINDOW(window), 300, 400);
gtk_container_add(GTK_CONTAINER(window), box);
button1 = gtk_button_new();
gtk_button_set_label(GTK_BUTTON(button1), "1");
gtk_widget_set_size_request(button1, 40, 30);
gtk_container_add(GTK_CONTAINER(box), button1);
gtk_widget_show_all(window);
}
int main(int argc, char **argv) {
GtkApplication *app;
int status;
app = gtk_application_new("me.test.calculator", G_APPLICATION_FLAGS_NONE);
g_signal_connect(app, "activate", G_CALLBACK(activate), NULL);
status = g_application_run(G_APPLICATION(app), argc, argv);
g_object_unref(app);
return status;
}
The code compiles and runs correctly. The problem is that gtk_alignment_new is deprecated and I want to get rid of it.
I've tried replacing gtk_alignment_new with:
gtk_widget_set_halign(box, GTK_ALIGN_START);
gtk_widget_set_valign(box, GTK_ALIGN_START);
but the window does not show up when using this method. Thanks.
You want to set the halign/valign properties of the button (and then add the button straight into the window) to achieve the same functional results as your original code. 'box' is no longer needed at all.
Note that a GtkWindow is a GtkBin so only takes a single child: you will need to add additional containers in between to actually make a calculator. Maybe start by adding a GtkGrid as the sole window child and then attach all your buttons into the grid.
Using jku's advice I've written the following code which compiles and runs correctly without using gtk_alignment_new:
#include <gtk/gtk.h>
static void activate(GtkApplication* app, gpointer user_data) {
GtkWidget *window;
GtkWidget *button1;
GtkWidget *fixed;
fixed = gtk_fixed_new();
window = gtk_application_window_new(app);
gtk_window_set_title(GTK_WINDOW(window), "Calculator");
gtk_window_set_default_size(GTK_WINDOW(window), 300, 400);
gtk_container_add(GTK_CONTAINER(window), fixed);
button1 = gtk_button_new();
gtk_button_set_label(GTK_BUTTON(button1), "1");
gtk_widget_set_size_request(button1, 45, 35);
gtk_fixed_put(GTK_FIXED(fixed), button1, 5, 200);
gtk_widget_show_all(window);
}
int main(int argc, char **argv) {
GtkApplication *app;
int status;
app = gtk_application_new("me.test.calculator", G_APPLICATION_FLAGS_NONE);
g_signal_connect(app, "activate", G_CALLBACK(activate), NULL);
status = g_application_run(G_APPLICATION(app), argc, argv);
g_object_unref(app);
return status;
}
NOTE: I ended up using GtxFixed because the size of the window will be fixed as well.
#include <gtk/gtk.h>
GtkBuilder *builder;
GtkWidget *window;
GtkImage *image;
GtkButton *but;
char s[1000];
void on_button1_button_press_event(GtkWidget *but, gpointer data)
{
strcpy(s, "/home/linux/testing2.png");
gtk_widget_queue_draw (image);
}
int main(void)
{
gtk_init(NULL, NULL);
builder = gtk_builder_new();
gtk_builder_add_from_file(builder, "/home/linux/gui.xml", NULL);
window = (GtkWidget *) gtk_builder_get_object(builder, "window1");
image = (GtkImage *) gtk_builder_get_object(builder, "image1");
but = (GtkButton *) gtk_builder_get_object(builder, "button1");
gtk_image_set_from_file(image, strcpy(s, "/home/linux/testing1.png"));
g_signal_connect(but, "clicked", G_CALLBACK(on_button1_button_press_event), NULL);
gtk_widget_show(window);
gtk_main();
return 0;
}
When I click on "button1", "callback" function called, and it updates string s then I want gtk refresh "image1" with gtk_widget_queue_draw. But "image1" have not changed.
gtk_widget_queue_draw() takes a string with the filename of the image. But it does not keep the string you pass. Instead the widget stores the whole loaded image.
So your s variable is useless, and changing it does nothing. You should do instead, in main():
gtk_image_set_from_file(image, "/home/linux/testing1.png");
and in the event callback:
gtk_image_set_from_file(image, "/home/linux/testing2.png");
There is no need to call gtk_widget_queue_draw() because changing the image does that automatically.
I created a filechooser dialog in Glade. I placed OK and Cancel buttons in it. After that I set the clicked handler of the GtkButton to be open_clicked or whatever; also I have a button which displays the filechooser dialog. Its signal handler is cb_show_filed. Here is my code:
#include <gtk/gtk.h>
typedef struct _Data Data;
struct _Data
{
GtkWidget *file;
};
G_MODULE_EXPORT void cb_show_filed(GtkButton *button, Data *data)
{
gtk_dialog_run(GTK_DIALOG(data->file));
gtk_widget_hide(data->file);
}
int main(int argc, char **argv)
{
GtkBuilder *builder;
GtkWidget *window;
GtkWidget *filechooserdialog1;
gtk_init(&argc, &argv);
builder = gtk_builder_new();
gtk_builder_add_from_file(builder, "ui.glade", NULL);
window = GTK_WIDGET(gtk_builder_get_object(builder, "window1"));
g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
filechooser =
GTK_WIDGET(gtk_builder_get_object(builder, "filechooserdialog1"));
gtk_builder_connect_signals(builder, &data);
g_object_unref(G_OBJECT(builder));
gtk_widget_show(window);
gtk_main();
return (0);
}
Now, how can I get path and filename from filechooserdialog1?
Use gtk_file_chooser_get_file() and friends:
GFile *chosen_file = gtk_file_chooser_get_file(GTK_FILE_CHOOSER(filechooser));
I am developing an application that has a numeric keypad and a text box when clicked on a button, text box shows the number.
I need to write a function to each button? Or you can pass a text and a widget as parameter?
#include <stdio.h>
#include <stdlib.h>
#include <gtk/gtk.h>
void callback( GtkWidget *widget,
gpointer data )
{
gtk_entry_append_text(entry, text);
}
void create_button(GtkWidget* table,GtkWidget* entry,
int start_r,int end_r,
int start_c,int end_c,
char* label)
{
GtkWidget *button;
button = gtk_button_new_with_label (label);
g_object_set_data( G_OBJECT( button ),
"char", (gpointer)label );
g_signal_connect (button, "clicked",
G_CALLBACK (callback), entry);
gtk_table_attach_defaults (GTK_TABLE(table), button, start_c, end_c, start_r, end_r);
gtk_widget_show (button);
}
gint delete_event( GtkWidget *widget,
GdkEvent *event,
gpointer data )
{
gtk_main_quit ();
return(FALSE);
}
int main(int argc,char* argv[]){
GtkWidget *window;
//GtkWidget *button;
GtkWidget *table;
GtkWidget *entry;
//GtkWidget *label;
gtk_init (&argc, &argv);
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Armario");
g_signal_connect (GTK_OBJECT (window), "delete_event",
G_CALLBACK (delete_event), NULL);
gtk_container_set_border_width (GTK_CONTAINER (window), 20);
table = gtk_table_new (2, 2, TRUE);
gtk_container_add (GTK_CONTAINER (window), table);
entry = gtk_entry_new();
gtk_entry_set_max_length(GTK_ENTRY(entry),10);
gtk_entry_set_placeholder_text(GTK_ENTRY(entry),"Teste");
gtk_table_attach_defaults (GTK_TABLE(table), entry, 0, 2, 1, 2);
gtk_widget_show(entry);
create_button(table,entry,0,1,0,1,"Botao");
gtk_widget_show (table);
gtk_widget_show (window);
gtk_main ();
return 0;
}
The answer to your question is yes, you can pass a widget in Gtk+ to a callback. Actually, the first parameter of the callback for the clicked signal is the button which received the signal (ie. usually the button that was clicked). As you can see in the sample code below, you can extract from the button its label and use it as text.
[...] /* In create_button... */
/* Make your buttons be notified when they are clicked */
g_signal_connect (button, "clicked", G_CALLBACK (on_button_clicked), entry);
[...]
/* Append the text in the button to the text entry */
void on_button_clicked (GtkButton *button, gpointer user_data)
{
GtkEntry *entry = user_data;
const gchar *text = gtk_button_get_label (button);
gint position = 0;
gtk_editable_insert_text (GTK_EDITABLE (entry), text, -1, &position);
}
I'm using gtk_editable_insert_text because gtk_entry_append_text has been deprecated for a long time. Passing the "entry" parameter to the callback is possible by using the last parameter of g_signal_connect which allows you to specify some data that you need to access in your callback. This info is then made available to the callback in the "user_data" parameter.
Your exemple could also be improved by using gtk_widget_show_all, and I also don't see the point in calling g_object_set_data on the "char" property, as the text is already set in the label property (and retrieved with gtk_button_get_label).
Two options, that I can think of:
GTK widgets are really GObjects, so you can attach to them arbitrary pieces of data. See the functions g_object_set_data/g_object_set_data_full/g_object_get_data. So you can just add the text to the button as an attached data and retrieve it when needed.
You can pass any data you need to a callback by defining a struct with all the fields, and passing a pointer to it. If the struct cannot be declared statically, you can malloc it and use g_signal_connect_data to specify the function to release the data:
For example:
struct entry_and_text;
{
GtkWidget *w;
char *text;
};
void free_data(gpointer data, GClosure *closure)
{
free(data);
}
entry_and_text *data = (entry_and_text *)malloc(sizeof(entry_and_text));
data->w = entry;
data->text = label;
g_signal_connect_data (button, "clicked",
G_CALLBACK (callback), data, free_data, 0);