GUI development

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Foreword

Almost everything in NavIt works as a plugin, and so do the guis.

Initializing your gui

You have to provide a function plugin_init in your plugin.

This function should call plugin_register_gui_type("gui-name",function)

The function has the following parameters: struct gui_methods *meth, int w, int h

  • meth is a structure with gui-functions you have to fill
  • w is the expected width
  • h is the expected height of the gui.

But you might ignore w and h, they are only recommendations.

meth should be filled with the following data:

  • menubar_new
  • toolbar_new
  • statusbar_new
  • popup_new
  • set_graphics

You can probably implement menubar_new, toolbar_new, statusbar_new and popup_new as a dummy, since it is rather GTK-specific, but set_graphics is required. It connects the graphics to the gui.

 struct gui_methods gui_<plugin>_methods = {
 	gui_<plugin>_menubar_new,
 	gui_<plugin>_toolbar_new,
 	gui_<plugin>_statusbar_new,
 	gui_<plugin>_popup_new,
 	gui_<plugin>_set_graphics,
 	gui_<plugin>_main_loop,
 };
 
 
Here is a code sample :
<source lang="c">
 void
 plugin_init(void)
 {
 	dbg(1,"registering <your plugin>\n");
 	plugin_register_gui_type("<your plugin>", <your init function>);
 }


Now, here is a sample of the init function :

 static struct gui_priv *
 gui_<plugin>_new(struct navit *nav, struct gui_methods *meth, struct attr **attrs) 
 {
 	dbg(1,"Begin initialization of <your plugin>\n");
 	struct gui_priv *this_;
        *meth=gui_<plugin>_methods;
 
 	this_=g_new0(struct gui_priv, 1);
 
 	// Perform initializations specific to your gui
 	// ...
 
 	// If you want to register a callback function for the vehicle, you can do it so:
 	struct callback *cb=callback_new_0(callback_cast(vehicle_callback_handler));
 
 	navit_add_vehicle_cb(nav,cb);
 	this_->nav=nav;
 
 	return this_;
}

And you plugin (gui) should initialize. Now, you need somme dummy functions (for now). Thoses are requested for GTK.

 static struct menu_priv *
 gui_<plugin>_toolbar_new(struct gui_priv *this_, struct menu_methods *meth)
 {
 	return NULL;
 }
 
 static struct statusbar_priv *
 gui_<plugin>_statusbar_new(struct gui_priv *gui, struct statusbar_methods *meth)
 {
 	return NULL;
 }
 
 static struct menu_priv *
 gui_<plugin>_popup_new(struct gui_priv *this_, struct menu_methods *meth)
 {
 	return NULL;
 }


The following function allows to get menu entries for bookmarks

 static struct menu_priv *
 gui_<plugin>_menubar_new(struct gui_priv *this_, struct menu_methods *meth)
 {
 	*meth=menu_methods;
 	return (struct menu_priv *) 1;
 }

The plugin main()

And, last but not least :

 static int gui_run_main_loop(struct gui_priv *this_)
 {
        // Whatever needs to be done right before beginning the navigation
 
        // Define your viewport
 	struct map_selection sel;
 
 	memset(&sel, 0, sizeof(sel));
 	sel.u.c_rect.rl.x=800;
 	sel.u.c_rect.rl.y=600;
 
 	transform_set_screen_selection(navit_get_trans(this_->nav), &sel);
 
 
 	navit_draw(this_->nav);
 
        // Register the callback to handle navigation instructions updates
 	struct navigation *navig;
 	navig=navit_get_navigation(navit);
 
 	navigation_register_callback(navig,
 		attr_navigation_long,
 		callback_new_0((void (*)())update_roadbook)
 	);
 
 	timeout = g_timeout_source_new(100);
 	g_source_set_callback(timeout, gui_timeout_cb, NULL, NULL);
 	g_source_attach(timeout, NULL);
 	while (!must_quit)
 	{
        //Poll event, process them
 
        // Call update of gps
        g_main_context_iteration (NULL, TRUE);
 
        // Any other task you may need
 
        }
        g_source_destroy(timeout);
 
 }