Pending background jobs

1. Leave a visible note about pending work done in the background for up to five seconds
2. Avoid raising signal if control is not available any longer, avoids rare crashes
3. Some minor formatting

Author: jenshannoschwalm

src/control/control.c

@@ -302,17 +302,27 @@ void dt_control_quit()
   if(dt_atomic_exch_int(&dc->quitting, 1) == 1) return;
 
 #ifdef HAVE_PRINT
-    dt_printers_abort_discovery();
-    // Cups timeout could be pretty long, at least 30seconds
-    // but don't rely on cups returning correctly so a timeout
-    for(int i = 0; i < 40000 && !dc->cups_started; i++)
-      g_usleep(1000);
+  dt_printers_abort_discovery();
+  // Cups timeout could be pretty long, at least 30seconds
+  // but don't rely on cups returning correctly so a timeout
+  for(int i = 0; i < 40000 && !dc->cups_started; i++)
+    g_usleep(1000);
 #endif
 
-    dt_pthread_mutex_lock(&dc->cond_mutex);
-    // set the "pending cleanup work" flag to be handled in dt_control_shutdown()
-    dt_atomic_set_int(&dc->running, DT_CONTROL_STATE_CLEANUP);
-    dt_pthread_mutex_unlock(&dc->cond_mutex);
+  if(dt_control_jobs_pending())
+     dt_control_log(_("<span foreground='#FF0000' background='#000000'>"
+                      "darktable will be locked until background work has been done"
+                      "</span>"));
+  for(int i = 0; i < 50 && dt_control_jobs_pending(); i++)
+  {
+    g_usleep(100000);
+    dt_gui_process_events();
+  }
+
+  dt_pthread_mutex_lock(&dc->cond_mutex);
+  // set the "pending cleanup work" flag to be handled in dt_control_shutdown()
+  dt_atomic_set_int(&dc->running, DT_CONTROL_STATE_CLEANUP);
+  dt_pthread_mutex_unlock(&dc->cond_mutex);
 
   if(g_atomic_int_get(&darktable.gui_running))
   {
@@ -760,12 +770,14 @@ void dt_control_navigation_redraw()
 
 void dt_control_log_redraw()
 {
-  DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_CONTROL_LOG_REDRAW);
+  if(dt_control_running())
+    DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_CONTROL_LOG_REDRAW);
 }
 
 void dt_control_toast_redraw()
 {
-  DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_CONTROL_TOAST_REDRAW);
+  if(dt_control_running())
+    DT_CONTROL_SIGNAL_RAISE(DT_SIGNAL_CONTROL_TOAST_REDRAW);
 }
 
 static int _widget_queue_draw(void *widget)
@@ -893,6 +905,8 @@ gboolean dt_control_key_pressed_override(guint key, guint state)
 
 void dt_control_hinter_message(const char *message)
 {
+  if(!dt_control_running())
+    return;
   dt_control_t *s = darktable.control;
   if(s && s->proxy.hinter.module)
     return s->proxy.hinter.set_message(s->proxy.hinter.module, message);