Controls disappearing when a message box appears C++ GTK

Question

I have programed the GUI in C++.

#include <gtk/gtk.h>
#include <unistd.h>
#include <cstddef>
#include <iostream>
#include <string>
#include <stdio.h>
#include <stdlib.h>
int main(){
    GtkWidget *_LinuxWindow, *_Box, *_Button;
    int argC = 0;
    char** argV;
    // Setup the window and fixed grid
    gtk_init(&argC,&argV);
    _LinuxWindow = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    _Box = gtk_fixed_new();
    // Set the title
    gtk_window_set_title(GTK_WINDOW(_LinuxWindow),"Title");
    // Finish up
    gtk_widget_show(_LinuxWindow);
    g_signal_connect(G_OBJECT(_LinuxWindow),"destroy",G_CALLBACK(gtk_main_quit), NULL);
    // Add controls
    _Button = gtk_button_new_with_label("Click Me!");
    gtk_fixed_put(GTK_FIXED(_Box),_Button,20,20);
    gtk_fixed_move(GTK_FIXED(_Box),_Button,20,20);
    gtk_widget_show(_Box);
    gtk_widget_set_size_request(_Button,30,100);
    // Create a dialog
    GtkWidget *dialog;
    dialog =  gtk_message_dialog_new(GTK_WINDOW(_LinuxWindow), GTK_DIALOG_DESTROY_WITH_PARENT,GTK_MESSAGE_INFO,GTK_BUTTONS_OK_CANCEL,"OK or Cancel?",NULL,g_strerror(errno));
    gint ret = gtk_dialog_run(GTK_DIALOG(dialog));
    gtk_widget_destroy(GTK_WIDGET(dialog));
    printf("%i", ret);
    // Add the fixed grid and go the to the main window loop
    gtk_container_add(GTK_CONTAINER(_LinuxWindow),_Box);
    gtk_widget_show(_Box);
    gtk_widget_show_all(_LinuxWindow);
    gtk_main();


    return 0;
}

When I run it using

g++ -o out-withoutCross without-cross.cpp -lX11 `pkg-config --cflags gtk+-3.0`pkg-config --libs gtk+-3.0`

A message box and a window appears. The problem is the controls in the window do not appear while the message box is open. I think this may be because the message box is being ran on the same thread that the main window is. Is there any way to add multi-threading to GTK?

Also the return value of the message box printed to console is running after the main window is exited.

Unrelated to your problem, but please note that all symbols beginning with an underscore and followed by an upper-case letter (like e.g. `_LinuxWindow`) are *reserved* for the "implementation" (compiler and standard library). Please don't define your own symbols anywhere. See e.g. [What are the rules about using an underscore in a C++ identifier?](https://stackoverflow.com/questions/228783/what-are-the-rules-about-using-an-underscore-in-a-c-identifier) for more information. — Some programmer dude, Apr 23 '20 at 07:47
More related to your problem, you show your dialog and let it end before you run the main event loop (`gtk_main()`). Try adding a button in the window, and show the dialog when that button is pressed instead. — Some programmer dude, Apr 23 '20 at 07:50

score 0 · Accepted Answer · answered Apr 23 '20 at 10:23

The problem is the structure of your code..\

#include <gtk/gtk.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
int main() {
  GtkWidget *_LinuxWindow, *_Box, *_Button;
  int argC = 0;
  char **argV;
  // Setup the window and fixed grid
  gtk_init(&argC, &argV);
  _LinuxWindow = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  _Box = gtk_fixed_new();
  // Set the title
  gtk_window_set_title(GTK_WINDOW(_LinuxWindow), "Title");
  // Finish up
  gtk_widget_show_all(_LinuxWindow);
  g_signal_connect(G_OBJECT(_LinuxWindow), "destroy", G_CALLBACK(gtk_main_quit),
                   NULL);
  // Add controls
  _Button = gtk_button_new_with_label("Click Me!");
  gtk_fixed_put(GTK_FIXED(_Box), _Button, 20, 20);
  gtk_fixed_move(GTK_FIXED(_Box), _Button, 20, 20);
  gtk_widget_set_size_request(_Button, 30, 100);
  gtk_container_add(GTK_CONTAINER(_LinuxWindow), _Box);
  gtk_widget_show_all(_LinuxWindow);
  // Create a dialog
  GtkWidget *dialog;
  dialog = gtk_message_dialog_new(
      GTK_WINDOW(_LinuxWindow), GTK_DIALOG_DESTROY_WITH_PARENT,
      GTK_MESSAGE_INFO, GTK_BUTTONS_OK_CANCEL, "OK or Cancel?", NULL);
  gint ret = gtk_dialog_run(GTK_DIALOG(dialog));
  gtk_widget_destroy(GTK_WIDGET(dialog));
  printf("%i", ret);
  // Add the fixed grid and go the to the main window loop

  gtk_main();

  return 0;
}

gtk_dialog_run is a blocking function so it will wait until it gets a response from the dialog box.. to proceed further

In your code, you are adding the button to the window only after running the dialog box window (which is a blocking call) so after its execution, the button is being added to the window

Controls disappearing when a message box appears C++ GTK

1 Answers1