Question

I have pretty simple application with text entry and button.

When user press on button , the application downloads file (in other thread) from URL and on success opens dialog message that all done. During downloading i activate spinner (like busy)

Since I don’t know how long will take connect to download file I use separate thread for that purpose. But on “dialog show” my application fails and I get followed error:

(enter_license.exe:210232): Gdk-WARNING **: gdkdrawable-win32.c:1873: GetDC failed: Invalid window handle.

(enter_license.exe:210232): Gdk-WARNING **: gdkgc-win32.c:968: GetCurrentObject failed: The handle is invalid.

(enter_license.exe:210232): Gdk-WARNING **: gdkgc-win32.c:970: RestoreDC failed: The handle is invalid.

(enter_license.exe:210232): Gdk-CRITICAL **: _gdk_win32_drawable_release_dc: assertion `impl->hdc_count > 0' failed

(enter_license.exe:210232): Gdk-WARNING **: gdkwindow-win32.c:2216: SetWindowLongPtr failed: Invalid window handle.

Sounds like something wrong when I try to call GTK object from separate thread.
Maybe somehow I need call handle (callback) to implement “show_dialog” in main thread?

Compile:

 gcc -IC:/MinGW/include -o enter_license enter_license.c  `pkg-config --libs --cflags gtk+-2.0 gthread-2.0``

Flow: main -> call “do_something” -> create thread and call “argument_thread” ->

Here is a snippets of code:

typedef struct _Data
{
 GtkWidget *win; 
 } Data;

main

int main(int argc, char **argv)
{
 GtkWidget *window;

 gtk_init(&argc, &argv);
 window = do_something(NULL, argv);
 g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);
 gtk_main();    

return 0;
}

do_something

GtkWidget * do_something(GtkWidget *do_widget, char **argv){
  ....
 GtkWidget *window;

if (!window){
window = gtk_dialog_new_with_buttons ("GtkSpinner",
                                      GTK_WINDOW (do_widget),
                                      0,
                                      GTK_STOCK_CLOSE,
                                      GTK_RESPONSE_NONE,
                                      NULL);
gtk_window_set_resizable (GTK_WINDOW (window), FALSE);

g_signal_connect (window, "response", G_CALLBACK (gtk_widget_destroy), NULL);
g_signal_connect (window, "destroy",  G_CALLBACK (gtk_widget_destroyed), &window);


 ....

if (!gtk_widget_get_visible (window)){
 gtk_widget_show_all (window);
}
else{
 gtk_widget_destroy (window);
}

    // define thread
    GThread*  thread;
    GError*   err;  
    Data data;

data.win = window;

     thread = g_thread_create((GThreadFunc)argument_thread,&data,FALSE, &err);
 return window;
}

show_dialog

gboolean show_dialog( GtkWidget* mw)
{
 GtkWidget *dialog;

  printf("BOO: \n");

  // here all works fine
  sleep(3000);
  gtk_widget_show(spinner_sensitive);
  gtk_spinner_start (GTK_SPINNER (spinner_sensitive));
  sleep(3000);
  gtk_spinner_stop (GTK_SPINNER (spinner_sensitive));
  sleep(3000);
  gtk_widget_hide(spinner_sensitive);

  printf("BOO\n");
  // here dialog is shown for 1-10 milisec and get error.

     dialog = gtk_message_dialog_new (GTK_WINDOW(mw),
                     GTK_DIALOG_DESTROY_WITH_PARENT,
                     GTK_MESSAGE_INFO,
                     GTK_BUTTONS_CLOSE,
                     "Downloaded successfully");

             g_signal_connect_swapped (G_OBJECT (dialog), "response",
                     G_CALLBACK (gtk_widget_destroy),
                     G_OBJECT (dialog));
             gtk_widget_show(dialog);
printf("BOO\n");

}

argument_thread

void *argument_thread( gpointer ptr ) {
  Data *data = (Data*)ptr;
gdk_threads_enter();
 show_dialog (data->win);
 gdk_threads_leave();
  return( NULL );
}

Please help me,

Any and all suggestions would be greatly appreciated

Answer 1

GTK is not thread-safe so anything that interacts with the GUI will have to run on the main thread.

Use the g_idle_add function to notify your main thread when the download has finished.