GtkToolButton with custom icon but of stock icon size

Question

I've a GtkToolBar which has say 3 GtkToolButtons with each of these having a stock icon value, and hence they all appear in the same size; now I added a 4th GtkToolButton with a custom image (.png), which was of an arbitrary dimension and only this button ended up looking huge (since the image was of higher resolution). What do I do to scale this GtkToolButton to match the other 3 buttons?

Here's the code which does what I briefed about:

GtkWidget *custom_icon = gtk_image_new_from_file(path);
GtkToolItem *toolbar_item = gtk_toggle_tool_button_new();
gtk_tool_button_set_icon_widget(GTK_TOOL_BUTTON(toolbar_item), custom_icon);
gtk_tool_button_set_label(GTK_TOOL_BUTTON(toolbar_item), "Custom Item");
gtk_toolbar_insert(toolbar, toolbar_item, -1);

Answer 1

Here is another solution.

GdkPixbuf *pixbuf = gdk_pixbuf_new_from_file(icon_file_path, NULL);
int width, height;
gdk_pixbuf_get_file_info (icon_file_path, &width, &height);
gtk_icon_theme_add_builtin_icon ("custom_icon", width, pixbuf);
g_object_unref (G_OBJECT (pixbuf)); 

GtkToolItem *toolbar_item = gtk_toggle_tool_button_new();
gtk_tool_button_set_icon_name (GTK_TOOL_BUTTON(toolbar_item), "custom_icon");

If you have the image in different sizes, you can add them all and let Gtk choose the one of the correct size (or resize if not found): Just repeat the first five lines for each of the image files.

You can use your icon anywhere else and its size will also be adjusted automatically. For example, to use it for your main window:

gtk_window_set_icon_name(GTK_WINDOW(main_window), "custom_icon");