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printoperation: fix another case where operation may complete twice

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This is a little tricky. At first, I thought we had a codepath where we
fail to schedule the idle that completes the print operation: if we take
the gtk_print_backend_printer_list_is_done path for each printer
backend, then printer_list_done_cb() is never executed and we never
schedule the idle. But in fact, in this case, then backends == NULL at
the bottom of find_printer(), and we'll schedule the idle there, so it's
OK. Except it's not really OK, because we'll schedule it even if a
printer was already found, resulting in the callback completing twice
and a double free.

Simplify this. Schedule the idle in find_printer() only if there are
*initially* no backends, not also if all backends are immediately ready
and already removed from consideration. Instead, always call
printer_list_done_cb() for every backend in find_printer_init(). After
the previous commit, printer_list_done_cb() will schedule the idle when
appropriate.

printer_list_done_cb() additionally disconnects signals that we did not
connect in this codepath, but it does so using
g_signal_handlers_disconnect_by_func, which is harmless. Otherwise, the
only extra work it's doing is scheduling the idle, and that's exactly
what find_printer_init() is missing.
This commit is contained in:
Michael Catanzaro 2023-09-26 18:52:37 -05:00
parent d8c821a851
commit dfbafdf047
1 changed files with 7 additions and 6 deletions
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13
gtk/print/gtkprintoperation-unix.c
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@ -1165,9 +1165,7 @@ find_printer_init (PrinterFinder *finder,
if (gtk_print_backend_printer_list_is_done (backend)) if (gtk_print_backend_printer_list_is_done (backend))
{ {
finder->backends = g_list_remove (finder->backends, backend); printer_list_done_cb (backend, finder);
gtk_print_backend_destroy (backend);
g_object_unref (backend);
} }
else else
{ {
@ -1229,14 +1227,17 @@ find_printer (const char *printer,
if (g_module_supported ()) if (g_module_supported ())
finder->backends = gtk_print_backend_load_modules (); finder->backends = gtk_print_backend_load_modules ();
if (finder->backends == NULL)
{
g_idle_add (find_printer_idle, finder);
return;
}
for (node = finder->backends; !finder->found_printer && node != NULL; node = next) for (node = finder->backends; !finder->found_printer && node != NULL; node = next)
{ {
next = node->next; next = node->next;
find_printer_init (finder, GTK_PRINT_BACKEND (node->data)); find_printer_init (finder, GTK_PRINT_BACKEND (node->data));
} }
if (finder->backends == NULL)
g_idle_add (find_printer_idle, finder);
} }