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96 lines
3.2 KiB
ObjectPascal
96 lines
3.2 KiB
ObjectPascal
program HelloWorld;
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{$mode objfpc}{$H+}
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uses
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Glib2, Gdk2, Gtk2;
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(* This is a callback function. The data arguments are ignored
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* in this example. More on callbacks below. *)
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procedure hello(Widget: PGtkWidget; Data: gpointer); cdecl;
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begin
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g_print ('Hello World'#13#10);
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end;
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function delete_event( Widget: PGtkWidget; Event: PGdkEvent; Data: gpointer):gint; cdecl;
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begin
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(* If you return FALSE in the "delete_event" signal handler,
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* GTK will emit the "destroy" signal. Returning TRUE means
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* you don't want the window to be destroyed.
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* This is useful for popping up 'are you sure you want to quit?'
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* type dialogs. *)
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g_print ('delete event occurred'#13#10);
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(* Change TRUE to FALSE and the main window will be destroyed with
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* a "delete_event". *)
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Result:=gTRUE;
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end;
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(* Another callback *)
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procedure destroy(Widget: PGtkWidget; Data: gpointer); cdecl;
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begin
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gtk_main_quit;
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end;
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var
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(* GtkWidget is the storage type for widgets *)
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Window: PGtkWidget;
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Button: PGtkWidget;
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begin
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(* This is called in all GTK applications. Arguments are parsed
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* from the command line and are returned to the application. *)
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gtk_init (@argc, @argv);
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(* create a new window *)
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window := gtk_window_new (GTK_WINDOW_TOPLEVEL);
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(* When the window is given the "delete_event" signal (this is given
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* by the window manager, usually by the "close" option, or on the
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* titlebar), we ask it to call the delete_event () function
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* as defined above. The data passed to the callback
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* function is NULL and is ignored in the callback function. *)
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g_signal_connect (G_OBJECT (window), 'delete_event',
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G_CALLBACK (@delete_event), NULL);
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(* Here we connect the "destroy" event to a signal handler.
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* This event occurs when we call gtk_widget_destroy() on the window,
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* or if we return FALSE in the "delete_event" callback. *)
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g_signal_connect (G_OBJECT (window), 'destroy',
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G_CALLBACK (@destroy), NULL);
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(* Sets the border width of the window. *)
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gtk_container_set_border_width (GTK_CONTAINER (window), 10);
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(* Creates a new button with the label "Hello World". *)
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button := gtk_button_new_with_label ('Hello World');
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(* When the button receives the "clicked" signal, it will call the
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* function hello() passing it NULL as its argument. The hello()
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* function is defined above. *)
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g_signal_connect (G_OBJECT (button), 'clicked',
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G_CALLBACK (@hello), NULL);
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(* This will cause the window to be destroyed by calling
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* gtk_widget_destroy(window) when "clicked". Again, the destroy
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* signal could come from here, or the window manager. *)
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g_signal_connect_swapped (G_OBJECT (button), 'clicked',
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G_CALLBACK (@gtk_widget_destroy), window);
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(* This packs the button into the window (a gtk container). *)
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gtk_container_add (GTK_CONTAINER (window), button);
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(* The final step is to display this newly created widget. *)
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gtk_widget_show (button);
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(* and the window *)
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gtk_widget_show (window);
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(* All GTK applications must have a gtk_main(). Control ends here
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* and waits for an event to occur (like a key press or
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* mouse event). *)
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gtk_main ();
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end.
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