As the following simple example creates a button in a window and 2 seconds later a timer replaces it with a bigger button.
import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, GLib
class ButtonWindow(Gtk.Window):
def __init__(self):
super().__init__()
self.set_default_size(500, 200)
button = Gtk.Button.new_with_label("one")
button.set_size_request(100, 50)
button.set_halign(Gtk.Align.CENTER)
button.set_valign(Gtk.Align.CENTER)
self.add(button)
self.timeout_id = GLib.timeout_add(2000, self.on_timeout, button)
def on_timeout(self, button):
rect, _ = button.get_allocated_size()
print(rect.x, rect.y, rect.width, rect.height)
self.remove(button)
button = Gtk.Button.new_with_label("two")
button.set_size_request(200, 100)
button.set_halign(Gtk.Align.CENTER)
button.set_valign(Gtk.Align.CENTER)
self.add(button)
self.show_all()
rect, _ = button.get_allocated_size()
print(rect.x, rect.y, rect.width, rect.height)
win = ButtonWindow()
win.connect("destroy", Gtk.main_quit)
win.show_all()
Gtk.main()
Unfortunately get_allocated_size returns a zero rect for the larger button after it has been added to the Window even thought show_all is called and the new button is visible.
Also the allocated size returned is the size of the Window not the button, as the console output shows:
0 0 500 200
0 0 0 0
Update
The behaviour is identical in the native GTK3 API
#include <gtk/gtk.h>
guint timeout_id;
GtkWidget *window;
GtkWidget *button;
static gboolean on_timeout(gpointer user_data)
{
int baseline;
GtkAllocation rect;
GtkWidget *button2;
gtk_widget_get_allocated_size(button, &rect, &baseline);
printf("x: %i y: %i width: %i height: %i\n", rect.x, rect.y, rect.width, rect.height);
gtk_container_remove(GTK_CONTAINER(window), button);
//g_object_unref (button); // segfault???
button2 = gtk_button_new_with_label ("two");
gtk_widget_set_size_request (button2, 200, 100);
gtk_widget_set_halign (button2, GTK_ALIGN_CENTER);
gtk_widget_set_valign (button2, GTK_ALIGN_CENTER);
gtk_container_add (GTK_CONTAINER(window), button2);
gtk_widget_show_all (window);
gtk_widget_get_allocated_size(button2, &rect, &baseline);
printf("x: %i y: %i width: %i height: %i\n", rect.x, rect.y, rect.width, rect.height);
g_source_remove(timeout_id);
return 0;
}
static void activate(GtkApplication* app, gpointer user_data)
{
window = gtk_application_window_new (app);
gtk_window_set_default_size (GTK_WINDOW (window), 500, 200);
button = gtk_button_new_with_label ("one");
gtk_widget_set_size_request (button, 100, 50);
gtk_widget_set_halign (button, GTK_ALIGN_CENTER);
gtk_widget_set_valign (button, GTK_ALIGN_CENTER);
gtk_container_add (GTK_CONTAINER(window), button);
gtk_widget_show_all (window);
timeout_id = g_timeout_add(2000, on_timeout, NULL);
}
int main(int argc, char **argv)
{
GtkApplication *app;
int status;
app = gtk_application_new ("org.gtk.example", G_APPLICATION_DEFAULT_FLAGS);
g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);
status = g_application_run (G_APPLICATION (app), argc, argv);
g_object_unref (app);
return status;
}
Output:
x: 0 y: 0 width: 500 height: 200
x: 0 y: 0 width: 0 height: 0
Update 2
Here is the Python version of the correct program
import gi
import time
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk, GLib
class MyButton(Gtk.Button):
def __init__(self, label, width, height):
Gtk.Button.__init__(self)
self.set_label(label)
self.connect("size-allocate", self.my_size)
self.set_size_request(width, height)
self.set_halign(Gtk.Align.CENTER)
self.set_valign(Gtk.Align.CENTER)
def my_size(self, obj, rect):
print("Button dimensions", rect.x, rect.y, rect.width, rect.height)
class ButtonWindow(Gtk.Window):
def __init__(self):
Gtk.Window.__init__(self)
self.set_default_size(500, 200)
button = MyButton("one", 100, 50)
self.add(button)
self.timeout_id = GLib.timeout_add(2000, self.on_timeout, button)
def on_timeout(self, button):
self.remove(button)
button = MyButton("two", 200, 100)
self.add(button)
self.show_all()
win = ButtonWindow()
win.connect("destroy", Gtk.main_quit)
win.show_all()
Gtk.main()
To solve this issue, connect to the "size-allocate" signal. This will be called when a new region has actually been allocated to the widget. From the handler, you can get that information:
#include <gtk/gtk.h>
guint timeout_id;
GtkWidget *window;
GtkWidget *button;
// Called when dimensions is actually allocated to widget.
void on_size_allocate(GtkWidget *widget, GtkAllocation *allocation, void *data)
{
printf("x: %i y: %i width: %i, height: %i\n", allocation->x, allocation->y, allocation->width, allocation->height);
}
static gboolean on_timeout(gpointer user_data)
{
int baseline;
GtkAllocation rect;
GtkWidget *button2;
gtk_container_remove(GTK_CONTAINER(window), button);
button2 = gtk_button_new_with_label("two");
g_signal_connect(button2, "size-allocate", G_CALLBACK(on_size_allocate), NULL);
gtk_widget_set_size_request(button2, 200, 100);
gtk_widget_set_halign(button2, GTK_ALIGN_CENTER);
gtk_widget_set_valign(button2, GTK_ALIGN_CENTER);
gtk_container_add(GTK_CONTAINER(window), button2);
gtk_widget_show(button2);
g_source_remove(timeout_id);
return 0;
}
static void activate(GtkApplication* app, gpointer user_data)
{
window = gtk_application_window_new(app);
gtk_window_set_default_size(GTK_WINDOW (window), 500, 200);
button = gtk_button_new_with_label("one");
g_signal_connect(button, "size-allocate", G_CALLBACK(on_size_allocate), NULL);
gtk_widget_set_size_request(button, 100, 50);
gtk_widget_set_halign(button, GTK_ALIGN_CENTER);
gtk_widget_set_valign(button, GTK_ALIGN_CENTER);
gtk_container_add(GTK_CONTAINER(window), button);
gtk_widget_show_all(window);
timeout_id = g_timeout_add(2000, on_timeout, NULL);
}
int main(int argc, char **argv)
{
GtkApplication *app;
int status;
app = gtk_application_new("org.gtk.example", 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;
}
Here is the output I get from this code:
x: 200 y: 75 width: 100, height: 50
x: 150 y: 50 width: 200, height: 100
which I think is what you were looking for. From what I understand, the problem with calling gtk_widget_set_size_request and then calling gtk_widget_get_allocated_size is that the size request may not happen immediately. If it has not happened, the values returned by gtk_widget_get_allocated_size are invalid, hence your weird output. By connecting to the signal, you let GTK notify you when the size has actually been allocated, hence the valid values.