help with `gtkmm' needed

Aidin_36 · 03-19-2009, 01:41 AM

I'm trying to write a GUI for one of my projects using `gtkmm'. I'm not a GUI programmer, so I've got some problems with this. Let me explain more:

The program itself provide a TCP/IP connection for the GUIs, and every GUI should connect to it via this protocol. Then, program send them information about objects, and GUI draw them on the screen. I use a `drawable area' widget to handle this.

I put all of the code about connecting to the server, getting information and updating the drawable area into the `on_expose_event'. But it dosen't works correctly.

If I had an option to put whole GUI code (drawing into screen) on a separate class, and then call it whenever a update required, every thing would be OK. But the only way I know for creating a GUI is the one explained in the gtkmm's tutorials: to create a Gtk::Main and call .run()

Here is the part of the code:

Main.cpp:

Code:

int main(){
   Gtk::Main kit(argc, argv);
   Gtk::Window win;

   Drawer d;
   win.add(d);
   d.show();

   Gtk::Main::run(win);
}

Drawer class:

Code:

class Drawer : public Gtk::DrawingArea {

public:
   Drawer();
   virtual ~Drawer();

protected:
   //Override default signal handler:
   virtual bool on_expose_event(GdkEventExpose* event);
}

And in the `on_expose_event' are the codes about connecting to the server using sockets, and so on. Anyone have any suggestion?

jiml8 · 03-19-2009, 10:50 AM

Your event handlers can't be part of a C++ class. In fact, you have to link them as C code since this is what gtk expects.

Best thing to do is put event handlers in their own file, and compile that file as a C file, and refer to it from C++ using the extern "C" macro.

Thus, create a file sighandlers.c which contains, for instance,

Code:

G_MODULE_EXPORT void on_drawingarea1_expose_event( GtkWidget *widget, GdkEventExpose *event )
{
	drawarea_expose_event(widget,event);
}

Then in the sighandlers.h file, put this code:

Code:

 extern "C" {
	void on_drawingarea1_expose_event( GtkWidget *widget, GdkEventExpose *event );
}

and include sighandlers.h in your main file.

I should note that you'll probably also need an on_configure_event handler as well as the on_expose_event handler for your drawing area updates.

Now, in the particular example I just gave, the function drawarea_expose_event() is another C function, kept in another C file (which I call cmd_button_handlers.c), and it looks like this:

Code:

gboolean drawarea_expose_event(GtkWidget *widget, GdkEventExpose *event)
{
	draw_drawingarea_drawable(widget,event);
	return FALSE;
}

and draw_drawingarea_drawable() is a routine kept in a C++ file that looks like this:

Code:

void draw_drawingarea_drawable(GtkWidget *object,GdkEventExpose *event)
{
	drawing_area* da=get_drawing_area_object(object);
	da->draw_drawable(event);
}

which is obviously C++ code referring to the drawing_area class which I wrote for this application.

When you make this, you need something that looks like this (only a partial makefile):

Code:

GTKLIBS= -export-dynamic -lgthread-2.0 `pkg-config --libs gtkmm-2.4` `pkg-config --libs gtk+-2.0`

OBJFILES= commander.o cmd_parser.o main_window.o requesters.o requester_base.o sighandlers.o tcp_connect.o cmd_button_handlers.o commander_classes.o drawing_area.o libunp.a

commander: $(OBJFILES) 
	$(CXX) -o commander $(GTKLIBS) $(OBJFILES)

sighandlers.o:
	$(CC) -o $@ $(CFLAGS) -c sighandlers.c

tcp_connect.o:
	$(CC) -o $@ $(CFLAGS) -c tcp_connect.c

cmd_button_handlers.o
	$(CC) -o $@ $(CFLAGS) -c cmd_button_handlers.c

jiml8 · 03-19-2009, 11:00 AM

Oh, also...

You really should investigate glade for writing a gui using gtk. It makes life a lot simpler.

Aidin_36 · 03-20-2009, 12:11 AM

Thanks for you complete answer!
I will try that as soon as I get back home!