opencv trackbar not showing at all

edit

Example:

#include <opencv2/opencv.hpp>
#include <opencv/highgui.h>
#include <iostream>

using namespace std;
using namespace cv;

Mat srimg, deimg;
int max_brightness = 100;
int slider_b = (max_brightness / 2);

void on_change_brightness(int, void*)
{
    int brightness = slider_b - (max_brightness / 2);

    deimg = srimg + Scalar::all(brightness);
    imshow("Girl", deimg);
}

int main()
{
    srimg = imread("lenna.PNG");
    imshow("girl", srimg);
    createTrackbar("Track", "Window", &slider_b, max_brightness,on_change_brightness);
    waitKey();
    return EXIT_SUCCESS;
}

Note: when i run the code it works well no error but the track bar does not show up, and to my knowledge everything should be fine any help pls .. Thanks in advance