GTK+ программа не изменяет стиль

На Debian 9.8 c Gnome GTK+ программа не изменяет стиль

main.cpp

#include <gtk/gtk.h>
void myStyleCss(void);
void createWind(GtkWidget **window, gint width, gint height);
void createGrid(GtkWidget **grid, GtkWidget **window, const gchar *name);
void chngBkgrd(gpointer *data);
int main(int argc, char *argv[]){
  GtkWidget *window;
  GtkWidget *grid;
  GtkWidget *button;
  gtk_init(&argc, &argv);
  myStyleCss();
  createWind(&window, 350, 250);
  createGrid(&grid, &window, "myGrid");
  button = gtk_toggle_button_new_with_label("tgl_btn");
  g_signal_connect (button, "toggled", G_CALLBACK(chngBkgrd),(gpointer 
    *)button);
  gtk_grid_attach (GTK_GRID (grid), button, 0 , 0, 1, 1);

  gtk_widget_show_all(window);
  gtk_main();
}   
void myStyleCss(void){
  GtkCssProvider *provider;
  GdkDisplay *display;
  GdkScreen *screen;
  provider = gtk_css_provider_new ();
  display = gdk_display_get_default ();
  screen = gdk_display_get_default_screen (display);
  gtk_style_context_add_provider_for_screen (screen,
                                           GTK_STYLE_PROVIDER(provider),
  GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
  const gchar *myCssFile = "style.css";
  GError *error = 0;
  gtk_css_provider_load_from_file(provider,
                                g_file_new_for_path(myCssFile), &error);
                                g_object_unref (provider);
}
void createWind(GtkWidget **window, gint width, gint height){
  *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title(GTK_WINDOW(*window), "MyApp");
  gtk_window_set_default_size(GTK_WINDOW(*window), width, height);
  gtk_window_set_resizable (GTK_WINDOW(*window), TRUE);
  gtk_container_set_border_width(GTK_CONTAINER(*window), 5);
  g_signal_connect(*window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
}
void createGrid(GtkWidget **grid, GtkWidget **window, const gchar *name){
  *grid = gtk_grid_new ();
  gtk_grid_set_row_homogeneous(GTK_GRID(*grid), TRUE);
  gtk_grid_set_column_homogeneous(GTK_GRID(*grid), TRUE);
  gtk_widget_set_name(*grid, name);
  gtk_container_set_border_width(GTK_CONTAINER (*grid), 50);
  g_object_set (*grid, "margin", 0, NULL);
  gtk_container_add (GTK_CONTAINER (*window), *grid);
}
void chngBkgrd(gpointer *data){
  if(gtk_toggle_button_get_active(GTK_TOGGLE_BUTTON(data))){
    g_print("On\n");
  }
  else{
    g_print("Off\n");
  }
}

style.css

GtkWindow {
  background-color: red;
  color: cyan;
  border-width: 3px;
  border-color: blue;
};
#myGrid {
  background-color: white;
  border-style: solid;
  border-width: 3px;
  border-radius: 15px;
  border-color: grey;
};
#myChild {
  background-color: red;
  border-style: solid;
  border-width: 3px;
  border-radius: 15px;
  border-color: grey;
};
#tgl_btn{
  background-color: red;
  color: red;
};

GtkButton {
  background-image: none;
  background-color: blue;
};
GtkButton:active {
  background-color: #00FF00;
};
GtkButton:checked{
  background-color: #000000;
};