C and libappindicator - Creating multiple indicators - c

Question

I'm programming a simple indicator that is supposed to show an icon for each CPU Core in the Unity panel, that will change color depending on the temperature range.
That would require me to have more than one AppIndicator on the same program, since I think there's no way to have one AppIndicator with multiple icons or use a gtk_container to hold those and append it to the AppIndicator. I'm actually trying to use 1 AppIndicator for the menu (with the "Quit" option) and 1 AppIndicator for each CPU Core.
The program had no Gtk warnings with just one AppIndicator (the main one), but after I added the code for creating the other 2 AppIndicators for each CPU Core (both with different unique id's) Gtk started throwing some warnings and critical messages. The indicators show up in the panel just like they are supposed to, but I don't want to simply ignore those messages, as they could be hiding some real issues under the curtains.
Checking the code, the only thing I think could be triggering those warnings and critical messages is app_indicator_new() being called more than once, I actually removed all the menu and menu_item's creation routines for those extra indicators, leaving only the app_indicator_new() call and I still get those messages (one for each extra app_indicator_new() call after the first):
(process:8040): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8040): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8040): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
When I add the code with the menu being created and associated with the extra AppIndicator's some extra errors show up:
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_settings_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8681): GLib-GObject-CRITICAL **: g_object_ref: assertion 'G_IS_OBJECT (object)' failed
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_settings_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_icon_theme_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_settings_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(process:8681): GLib-GObject-CRITICAL **: g_object_ref: assertion 'G_IS_OBJECT (object)' failed
(process:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(process:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(process:8681): Gtk-CRITICAL **: IA__gtk_settings_get_for_screen: assertion 'GDK_IS_SCREEN (screen)' failed
(TempI:8681): Gtk-WARNING **: Screen for GtkWindow not set; you must always set
a screen for a GtkWindow before using the window
(TempI:8681): Gdk-CRITICAL **: IA__gdk_screen_get_display: assertion 'GDK_IS_SCREEN (screen)' failed
(TempI:8681): Gdk-CRITICAL **: IA__gdk_keymap_get_for_display: assertion 'GDK_IS_DISPLAY (display)' failed
(TempI:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(TempI:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
(TempI:8681): Gtk-WARNING **: Screen for GtkWindow not set; you must always set
a screen for a GtkWindow before using the window
(TempI:8681): Gdk-CRITICAL **: IA__gdk_screen_get_display: assertion 'GDK_IS_SCREEN (screen)' failed
(TempI:8681): Gdk-CRITICAL **: IA__gdk_keymap_get_for_display: assertion 'GDK_IS_DISPLAY (display)' failed
(TempI:8681): GLib-GObject-WARNING **: invalid (NULL) pointer instance
(TempI:8681): GLib-GObject-CRITICAL **: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed
I can post the code of the program if necessary, just didn't do it because it would make the question even larger. That's the block where I'm creating the extra AppIndicators though:
for(int i=0; i<TempI_Main.Cores_Counter; i++){
TempI_Main.Core[i].Gtk_Menu_Root=gtk_menu_new();
//The core name ("Core " + number)
char IndicatorName[TEMPI_MAX_CHARS];
snprintf(IndicatorName, TEMPI_MAX_CHARS,"TempI_Core %u",i);
TempI_Main.Core[i].Gtk_Menu_Root_Description=gtk_menu_item_new_with_label(IndicatorName);
gtk_menu_append(GTK_MENU(TempI_Main.Core[i].Gtk_Menu_Root),TempI_Main.Core[i].Gtk_Menu_Root_Description);
gtk_widget_set_sensitive(GTK_WIDGET(TempI_Main.Core[i].Gtk_Menu_Root_Description),FALSE);
gtk_widget_show(TempI_Main.Core[i].Gtk_Menu_Root_Description);
TempI_Main.Core[i].Gtk_Indicator=app_indicator_new(IndicatorName,"indicator-messages",APP_INDICATOR_CATEGORY_APPLICATION_STATUS);
app_indicator_set_status(TempI_Main.Core[i].Gtk_Indicator, APP_INDICATOR_STATUS_ACTIVE);
//Need to set icon
//Need to set attention icon
app_indicator_set_menu(TempI_Main.Core[i].Gtk_Indicator,GTK_MENU(TempI_Main.Core[i].Gtk_Menu_Root));
}
Any clues what could be the cause? Are multiple AppIndicators per program not supported?
EDIT:
Corrected code after #Jean-François Fabre answer.
for(int i=0; i<TempI_Main.Cores_Counter; i++){
TempI_Main.Core[i].Gtk_Menu_Root=gtk_menu_new();
//The core name ("Core " + number)
char IndicatorName[TEMPI_MAX_CHARS];
//MAX_CHARS - 6 ("Core "+'\0') is the limit for appending
snprintf(IndicatorName, TEMPI_MAX_CHARS,"TempI_Core %u",i);
TempI_Main.Core[i].Gtk_Indicator_Name=strdup(IndicatorName);
TempI_Main.Core[i].Gtk_Menu_Root_Description=gtk_menu_item_new_with_label(TempI_Main.Core[i].Gtk_Indicator_Name);
gtk_menu_append(GTK_MENU(TempI_Main.Core[i].Gtk_Menu_Root),TempI_Main.Core[i].Gtk_Menu_Root_Description);
gtk_widget_set_sensitive(GTK_WIDGET(TempI_Main.Core[i].Gtk_Menu_Root_Description),FALSE);
gtk_widget_show(TempI_Main.Core[i].Gtk_Menu_Root_Description);
TempI_Main.Core[i].Gtk_Indicator=app_indicator_new(TempI_Main.Core[i].Gtk_Indicator_Name,"indicator-messages",APP_INDICATOR_CATEGORY_APPLICATION_STATUS);
app_indicator_set_status(TempI_Main.Core[i].Gtk_Indicator, APP_INDICATOR_STATUS_ACTIVE);
//Need to set icon
//Need to set attention icon
app_indicator_set_menu(TempI_Main.Core[i].Gtk_Indicator,GTK_MENU(TempI_Main.Core[i].Gtk_Menu_Root));
}
EDIT2:
Code for creating a single Core indicator explicitely. Still throwing warnings and critical messages:
TempI_Main.Core[0].Gtk_Menu_Root=gtk_menu_new();
TempI_Main.Core[0].Gtk_Menu_Root_Description=gtk_menu_item_new_with_label("Core1");
gtk_menu_append(GTK_MENU(TempI_Main.Core[0].Gtk_Menu_Root),TempI_Main.Core[0].Gtk_Menu_Root_Description);
gtk_widget_set_sensitive(GTK_WIDGET(TempI_Main.Core[0].Gtk_Menu_Root_Description),FALSE);
gtk_widget_show(TempI_Main.Core[0].Gtk_Menu_Root_Description);
TempI_Main.Core[0].Gtk_Indicator=app_indicator_new("Core1","indicator-messages",APP_INDICATOR_CATEGORY_APPLICATION_STATUS);
app_indicator_set_status(TempI_Main.Core[0].Gtk_Indicator, APP_INDICATOR_STATUS_ACTIVE);
//Need to set icon
//Need to set attention icon
app_indicator_set_menu(TempI_Main.Core[0].Gtk_Indicator,GTK_MENU(TempI_Main.Core[0].Gtk_Menu_Root));

Answer 1

That in a loop is just bad:
char IndicatorName[TEMPI_MAX_CHARS];
snprintf(IndicatorName, TEMPI_MAX_CHARS,"TempI_Core %u",i);
TempI_Main.Core[i].Gtk_Menu_Root_Description=gtk_menu_item_new_with_label(IndicatorName);
...
TempI_Main.Core[i].Gtk_Indicator=app_indicator_new(IndicatorName, ...
You are declaring IndicatorName as an auto variable in the loop but pass it to gtk_menu_item_new_with_label which expects a const char *, means: it will just store the address of the string.
Not only the memory will be reused for further iterations and all menus will have the same indicator name within the loop, but exiting the loop the memory will be allocated to some other variable and the names will be trashed => undefined behaviour
You should make a copy of the string like this:
TempI_Main.Core[i].Gtk_Menu_Root_Description=gtk_menu_item_new_with_label(strdup(IndicatorName));
(of course a better way would be to store the copied string to be able to deallocate them if needed)

Answer 2

I found the root of the issue and it's embarassing to say, but I just misplaced the function that created the AppIndicator. It was being called before gtk_init() so that's where all those errors were coming from. First I had:
TempI_Set_Core_Indicator();
//Starts gtk
gtk_init(&argc,&argv);
TempI_Set_Main_Indicator();
and simply replacing it by:
//Starts gtk
gtk_init(&argc,&argv);
TempI_Set_Main_Indicator();
TempI_Set_Core_Indicator();
was enough to solve the problem. I was focusing so much on the function itself that I didn't stop to look where it was being called.