Re: [libcvd-members] GVars3 example

[Edward Rosten]

On Tue, 3 Jun 2008, Pablo Barrera Gonz?lez wrote:

> Hello everyone,
>
> I am new in the mailing list and I would like to introduce me. My name is 
> Pablo Barrera and I am working as teaching assistant at Rey Juan Carlos 
> University, where I have just finished my PhD in Computer Science. I am 
> interested in use CVD in some projects for object tracking. So far no 
> problem, however I am not able to understand how GVars3 works.
>
> Is there any example or small tutorial about how to use GVars3?

No, so here's a basic example:

#include <gvars3/instances.h>
#include <iostream>
using namespace GVars3;
using namespace std;

int main(int argc, char** argv)
{
        GUI.LoadFile("autoexec.cfg");      //Read a configuration file.
        GUI.parseArguments(argc, argv);    //Read command line argments.

        //Read an integer from the database, and display it.
        //This is probably the most common use of GVars.
        int i = GV3::get<int>("an_integer");
        cout << i << endl;

        //get also returns writeable values
        GV3::get<int>("an_integer") = -10;
        cout <<   GV3::get<int>("an_integer")  << endl;

        //You can also have a variable type which is linked
        //to the database:
        gvar3<int> an_integer("an_integer");
        cout << *an_integer << endl;

        //Now change the value
        GV3::get<int>("an_integer") = 200;

        //The new value is reflected here:
        cout << *an_integer << endl;
}

The configuration file contains lines like:
varname=value
an_integer=10

Any line which doesn't look like that is a command. The command
commandlist

lists all commands currently registered (you can also add your own).


Commandline arguments are of the form
--var value
and can only be used to set variables. The one exception is
--exec file
which will load a configuration file.


There are quite a lot more features. There is a very basic scripting 
language, and you can bind GUI toolkit elements to database entries, if 
you have compiled it with a GUI toolkit (one of Motif, FLTK or FLTK2). 
Here is an example of how to bind a slider bar to a float, in a window. 
All interaction on the C++ side is the same as before. The GUI is written 
in the configuration file.

#include <gvars3/instances.h>
#include <iostream>
#include <sstream>
using namespace GVars3;
using namespace std;

//Inline a configuration file
string conf_file=
"keep_running=1                           \n"
"a_float=7                                \n"
"                                         \n"
"GUI.InitXInterface                       \n"
"                                         \n"
"GUI.AddWindow ex Example                 \n"
"ex.AddSlider a_float -10 10              \n"
"ex.AddPushButton \"Quit\" keep_running=0 \n";


int main(int argc, char** argv)
{
        istringstream file_stream(conf_file);
        GUI.ParseStream(file_stream);

        gvar3<int> keep_running("keep_running");
        gvar3<float> a_float("a_float");

        while(*keep_running)
        {
                GUI_Widgets.process_in_crnt_thread();
                cout << *a_float << endl;
        }
}


As you slide the bar, the number printed should change. Press the button 
to quit.

Hope this helps

-Ed